Impulse 4.0 Quick Start

8/10/2019 Impulse 4.0 Quick Start

1/79

AFT ImpulseTM

Quick Start Guide

AFT Impulse version 4.0

Waterhammer Modeling in Piping Systems

Applied Flow Technology


2/79

Information in this document is subject to change without notice. No part of this QuickStart Guide may be reproduced or transmitted in any form or by any means, electronic ormechanical, for any purpose, without the express written permission of Applied FlowTechnology.

2007 Applied Flow Technology Corporation. All rights reserved.

Printed in the United States of America.

"AFT Impulse", "AFT Fathom", "Applied Flow Technology", and the AFT logo aretrademarks of Applied Flow Technology Corporation.

Windows is a registered trademarks of Microsoft Corporation. CAESAR II is aregistered trademark of COADE, Inc.


3/79

Contents

1. Introducing AFT Impulse ............................................... 1

Designing for waterhammer ..................................................................... 1 Modeling capabilities ......................................................................... 2

The steady-state solver ............................................................................. 2 The transient solver .................................................................................. 2 Engineering assumptions in AFT Impulse ............................................... 3 AFT Impulse Primary Windows............................................................... 3

Input windows.................................................................................... 4 Output windows ................................................................................. 4

2. Valve Closure Example .................................................. 5 Topics covered.......................................................................................... 5 Required knowledge ................................................................................. 5 Model files................................................................................................ 5 Step 1. Start AFT Impulse ........................................................................ 6

The Workspace window..................................................................... 7

Step 2. Layout model................................................................................ 7 Step 3. Complete the first three checklist requirements........................... 8

A. Review the checklist...................................................................... 8 B. Specify system properties.............................................................. 9

Step 4. Define the model components (checklist item #4) ..................... 11 Object status..................................................................................... 11

A. Enter data for reservoirs .............................................................. 11 B. Enter branch data......................................................................... 12 C. Enter valve data ........................................................................... 12 D. Enter pipe data for P1.................................................................. 14 E. Enter data for other pipes ............................................................ 15

Step 5. Complete the last two checklist requirements ............................ 16

A. Specify pipe sectioning ............................................................... 16 B. Specify transient control.............................................................. 18


4/79

iv AFT Impulse 4.0 Quick Start Guide

C. Save the model ............................................................................ 20 Step 6. Run the solver............................................................................. 20

The two solvers ................................................................................ 20 The transient output file ................................................................... 21

Step 7. Review the output....................................................................... 21 A. The Output window..................................................................... 21 B. Graph the results.......................................................................... 23 C. View the Visual Report ............................................................... 25

Conclusion .............................................................................................. 27

3. Pump Startup With Event Transients ......................... 29

Topics covered........................................................................................ 29 Required knowledge ............................................................................... 29 Model files.............................................................................................. 30 Step 1. Start AFT Impulse ...................................................................... 30 Step 2. Specify system properties........................................................... 30 Step 3. Build the model .......................................................................... 30

A. Place the pipes and junctions ...................................................... 30 B. Enter the pipe and junction data.................................................. 31

C. Check if the pipe and junction data is complete.......................... 35 Step 4. Section the pipes......................................................................... 35 Step 5. Specify transient control............................................................. 36 Step 6. Create scenarios to model the three startup cases ...................... 37

A. Create scenarios .......................................................................... 37 B. Set up scenarios ........................................................................... 38

Step 7. Run the first scenario.................................................................. 39 Step 8. Graph the results......................................................................... 39 Step 9. Animate the results ..................................................................... 42 Step 10. Run the other scenarios and graph the results .......................... 44

4. Pump Trip Example...................................................... 47

Topics covered........................................................................................ 47 Required knowledge ............................................................................... 47


5/79

Table of Contents v

Model files.............................................................................................. 48 Step 1. Start AFT Impulse ...................................................................... 48

Step 2. Specify system properties........................................................... 48 Step 3. Build the model .......................................................................... 48

A. Place the pipes and junctions ...................................................... 48 B. Enter the pipe and junction data.................................................. 49 C. Check if the pipe and junction data is complete.......................... 52

Step 4. Section the pipes......................................................................... 53

Step 5. Specify transient control............................................................. 53 Step 6. Run the model............................................................................. 53 Step 7. Review results ............................................................................ 53

A. Graph the transient pressures at the pump .................................. 53 B. Graph the pipeline transient pressure profile .............................. 55 C. Graph the pump speed decay....................................................... 56

Step 8. Add accumulator ........................................................................ 60 A. Modify model........................................................................ 60 B. Enter pipe and junction data.................................................. 60 C. Check if the pipe and junction data is complete.......................... 62 D. Some commentary on accumulators............................................ 62

Step 9. Re-section pipes.......................................................................... 63 Step 10. Run the model........................................................................... 63 Step 11. Graph results............................................................................. 63

5. Other AFT Impulse Capabilities .................................. 67

Transient cavitation and liquid column separation................................. 67

Four quadrant pump modeling................................................................ 67 Positive displacement pumps.................................................................. 68 Pumps with viscosity corrections ........................................................... 68 Pumps with variable speed controllers ................................................... 68 Variable density and viscosity modeling................................................ 68 Vacuum breaker valves........................................................................... 68

Surge tanks.............................................................................................. 68 Flow and pressure control valve transients ............................................ 69


6/79

vi AFT Impulse 4.0 Quick Start Guide

Non-Newtonian fluid modeling.............................................................. 69 Pulp and paper modeling ........................................................................ 69

Infinite pipe boundaries .......................................................................... 69 Expanded fluid properties with Chempak .............................................. 69 Repeat transient feature for periodic transient behavior ........................ 69 Intermediate elevations for pipes............................................................ 70 Force file output for use with CAESAR II ............................................. 70 Fitting library.......................................................................................... 70

Design alerts ........................................................................................... 70 Network databases .................................................................................. 70


7/79

C H A P T E R 1

Introducing AFT Impulse

Welcome to AFT Impulse 4.0, Applied Flow Technology's powerfulwaterhammer modeling tool. With AFT Impulse you can modeltransients caused by a wide range of pipe system behavior. This will

allow you to understand transient pressure extremes and, whennecessary, size and locate surge suppression equipment.

AFT Impulse includes a steady-state solution engine which solves for thesystem initial conditions. These results are used to automaticallyinitialize the transient model. The engineer accesses these capabilitiesthrough an advanced graphical interface, which includes built-inexpertise to guide the engineer through the modeling process.

Designing for waterhammer

Waterhammer can cause catastrophic failure of pipe systems and damageexpensive equipment. Properly addressing such issues at the design stageis essential. An AFT Impulse model allows the engineer to better

understand and predict the dynamic behavior of the pipe system. Whenundesirable waterhammer transients are identified at the design stage,different strategies to reduce surge pressures can be evaluated. Thesemay include surge suppression equipment, modifying the design, ormodifying the system operation.

Sometimes the undesirable transients are not discovered until after thesystem is built. In such cases, AFT Impulse can provide critical insight

into the cause of the problem, and allow the engineer to assess designand/or operational modifications to resolve the issue.


8/79

2 AFT Impulse 4.0 Quick Start Guide

Modeling capabilities

AFT Impulse provides a broad array of features to model pipe systemtransients. These include: Transients in open and closed (recirculating) systems

Network systems that branch or loop

Systems with valve transients

Systems with pump transients

Systems with pressure or flow control valve transients

Systems with transient cavitation and liquid column separation

Systems with surge suppression devices such as accumulators, surgetanks and vacuum breaker valves

Systems with variable density and viscosity

Multiple design cases in a single model file Non-Newtonian fluid behavior

The steady-state solver

Before a waterhammer model can be run, the initial steady-stateconditions are required. AFT Impulse obtains the steady-state solutionusing a Newton-Raphson matrix solution algorithm to obtain a mass andmomentum balance. The algorithm is similar to that used in theacclaimed AFT Fathom .

If desired, AFT Impulse can be run in Steady Only mode, where onlythe steady flow pipe hydraulics are modeled. When run in Transientmode, the steady flow solution is used to automatically initialize thetransient solution. This convenience avoids the often error prone processof manually setting up the initial conditions, and allows the user toquickly and safely modify and rerun the model.

The transient solver

AFT Impulse employs the traditional Method of Characteristics (MOC)to solve the transient equations of pipe flow. A mass and momentum


9/79

Chapter 1 Introducing AFT Impulse 3

balance is performed at all computing stations in each pipe, accuratelyrepresenting the propagation of transient pressure waves throughout thesystem.

The MOC is an explicit solution technique, where the solver marches intime for a duration specified by the user.

Engineering assumptions in AFT Impulse

AFT Impulse is based on the following fundamental fluid mechanicsassumptions:

Liquid flow

One-dimensional flow

No chemical reactions

Wavespeed remains constant during transients

Non-condensable gas release is negligible

Bubbles that form during transient cavitation do not move

AFT Impulse Primary Windows

AFT Impulse has five subordinate windows that work in an integratedfashion. You work exclusively from one of these windows at all times.For this reason they are referred to as primary windows .

Graph Results

Visual Report

Workspace Output

Model Data

Figure 1.1 Primary window workflow in AFT Impulse


10/79


11/79

C H A P T E R 2

Valve Closure Example

Summary

This example is designed to give you the big picture of AFT Impulse'slayout and structure. Some of the more basic concepts will be used tobuild a four-pipe, five-junction model of the waterhammer transients thatresult when a valve is closed.

Topics covered

Model building basics

Entering pipe and junction data

Entering transient data

Sectioning pipes

Graphing output results

Required knowledgeNo prior knowledge is required for this example.

Model files

This example uses the following file, which is installed in the Examplesfolder as part of the AFT Impulse installation:


12/79


Valve Closure.imp

Step 1. Start AFT Impulse

To start AFT Impulse, click Start on the Windows taskbar, choosePrograms, then AFT Products then AFT Impulse. (This refers to thestandard menu items created by setup. You may have chosen to specify adifferent menu item).

When you start AFT Impulse, the Workspace window is always theactive (large) window. The Workspace window is one of five primarywindows.

After AFT Impulse loads, you will notice four windows in the lower partof the AFT Impulse window; these represent four of the five primarywindows that are currently minimized (see Figure 2.1). The AFTImpulse window acts as a container for the five primary windows.

Toolbars

Workspace

Toolbox

Minimizedprimary

windows

Status Bar

Figure 2.1 The Workspace window is where the model is built


13/79

Chapter 2 Valve Closure Example 7

The Workspace window

You will build your waterhammer model on the Workspace using the

Toolbox tools. At the top of the Toolbox are four drawing tools. TheSelection Drawing tool, on the upper left, is useful for selecting groupsof objects on the Workspace for editing or moving. The Pipe Drawingtool, on the upper right, is used to draw new pipes on the Workspace.Below these two tools are the Zoom Select tool and the Annotation tool.The Zoom Select tool allows you to draw a box on the Workspace zoomafter which AFT Impulse will zoom into that area. The Annotation tool

allows you to create annotations and auxiliary graphics.Below the four drawing tools are nineteen icons that represent thedifferent types of junctions available in AFT Impulse. Junctions arecomponents that connect pipes and also influence the pressure or flowbehavior of the pipe system. The junction icons can be dragged from theToolbox and dropped onto the Workspace.

When you pass your mouse pointer over any of the Toolbox tools, aToolTip identifies the tool's function.

Step 2. Layout model

Create a model as shown in Figure 2.2.

1. The five junctions, J1 though J5 can be dragged from the Toolbox atthe left and dropped on the Workspace.

2. The four pipes, P1 though P4, can be drawn on the Workspace byclicking the Pipe Drawing Tool at the upper right of the Toolbox andthen drawing lines on the Workspace. Make sure the directionalarrows point from J1 to J3, J2 to J3, J3 to J4 and J4 to J5. (The flowdirection can be reversed by use of the Reverse Direction tool on the

Arrange menu.)


14/79


Figure 2.2 Pipe system layout on Workspace.

Step 3. Complete the first three checklist requirements

A. Review the checklist

Next, click the checkmark on the Toolbar that runs across the top of theAFT Impulse window. This opens the Checklist window (see Figure2.3). The Checklist contains six items. Each item needs to be completedbefore AFT Impulse allows you to run the Solver.


15/79


Figure 2.3 The Checklist tracks the models status

The Status Bar at the bottom of the AFT Impulse window also reflectsthe state of each Checklist item (see Figure 2.1). Once the Checklist iscomplete, the Model Status light in the lower left corner turns from redto green. Click the Close button to close the Checklist.

The first item, Specify Steady Solution Control, is always checked whenyou start AFT Impulse because AFT Impulse assigns default solution

control parameters for the steady-state part of the analysis. In general,you do not need to adjust Steady Solution Control values. If necessary,you can make adjustments by opening the Steady Solution Controlwindow from the Analysis menu.

The second item on the Checklist is Specify Output Control. LikeSolution Control, this item is always checked when you start AFTImpulse. Default Output Control parameters and a default title are

assigned.You may want to add a descriptive title for the model. To do this, openthe Output Control window from the Analysis menu and enter a title onthe General tab.

B. Specify system properties

The third item on the Checklist is Specify System Properties. Tocomplete this item, you must open the System Properties window. This


16/79


window allows you to specify your fluid properties (density, dynamicviscosity, bulk modulus, and optional vapor pressure), viscosity model,gravitational acceleration and atmospheric pressure.

1. Open the System Properties window from the Analysis menu (seeFigure 2.4)

2. In the upper left select the "AFT Standard" option

3. In the "Fluids Available in Database" list, select "Water at 1 atm"

4. Click the "Add to Model" button

5. In the Temperature field type 70 deg. F

6. Click the "Calculate Properties" button (this obtains the density,viscosity, bulk modulus and vapor pressure)

7. Click the OK button to close the window and accept the fluid datafor the model

Figure 2.4 System Properties window is where you specify thefluid


17/79


Step 4. Define the model components (checklist item #4)

The fourth item on the Checklist, Define All Pipes and Junctions, is notas straightforward to satisfy as the first three. This item encompasses theproper input data and connectivity for all pipes and junctions.

Object status

Every pipe and junction has an object status. The object status tells youwhether the object is defined according to AFT Impulse's requirements.To see the status of the objects in your model, click the floodlight on theToolbar (alternatively, you could choose Show Object Status from theView menu). Each time you click the light bulb, Show Object Status istoggled on or off.

When Show Object Status is on, the ID numbers for all undefined pipesand junctions are displayed in red on the Workspace. Objects that arecompletely defined have their ID numbers displayed in black. (Thesecolors are configurable through Workspace Preferences from theOptions menu.)

If you have not done so, turn the Show Object Status on. Because youhave not yet defined the pipes and junctions in this sample problem, allthe objects' ID numbers will change to red when you turn on ShowObject Status.

A. Enter data for reservoirs

As shown in Figure 2.2, the J1 (Supply Tank A) junction is a Reservoir junction.

1. Double-click the J1 junction icon to open the ReservoirSpecifications window (see Figure 2.5)

2. Enter a Surface Elevation of 45 feet3. Enter a Surface Pressure of 1 atm

4. Select the "Pipe Depth and Loss Coefficients" tab

5. Enter a pipe depth of 10 feet

6. Click the OK button


18/79


Figure 2.5 Input for Reservoir junction J1

Repeat this process for junctions J2 (Supply Tank B) and J5 (Discharge

Tank) with the following data: For J2 use a Surface Elevation of 44 feet and a pipe depth of 10 feet.

For J5 use a Surface Elevation of 5 feet and a pipe depth of 5 feet.

B. Enter branch data

Open the J3 Branch Specifications window and enter an elevation of 0feet.

C. Enter valve data

The J4 junction is a Valve junction. This junction will be the initiator ofthe transient.

1. Double-click the J4 junction icon to open the Valve Specificationswindow (see Figure 2.6)


19/79


2. Enter an elevation of 0 feet.

3. Choose the Loss Model as Cv and enter a Cv of 50 (this is the

steady-state Cv).

Figure 2.6 Input data for Valve junction J4

4. Click the Transient Data tab and enter the data below for C v (seeFigure 2.7).

Time (sec) Cv0 50

0.25 200.5 5

1 02 0

The first data point (C v = 50 at time zero) must match the steady-state value (entered in Item 3 above). The transient data representsthe valve as initially open. The valve then closes over a period of


20/79


one second (a Cv of zero means the valve is closed). The valve thenstays closed.

When transient data is entered for a junction, a T symbol is shownnext to the junction number on the Workspace (see Figure 2.2).

5. Click the OK button.

Figure 2.7 Transient input data for Valve junction J4

D. Enter pipe data for P1

1. Double-click on the pipe P1 to open the Pipe Specifications window(see Figure 2.8)

2. In the "Size" area choose the "Pipe Material" as "Steel"

3. Choose the Size and Type as "2 inch" and "STD (schedule 40)"

4. Specify the length as 100 feet

5. Choose the Pipe Support as Thin-Walled Anchored Throughout

6. Click the OK button


21/79


Figure 2.8 Pipe Specifications window for pipe P1

The wavespeed is a very important parameter in waterhammer analysis.The wavespeed can be calculated with reasonable accuracy from fluidand pipe data, or it may be available from test data or industrypublications. If the wavespeed is not known (which is typical), then theCalculated Wavespeed option is the preferred option. In this case, data isrequired for pipe wall thickness, modulus of elasticity, Poisson Ratio,and pipe support details. Data for pipe wall thickness, modulus ofelasticity, Poisson Ratio are built into the pipe material databasessupplied with AFT Impulse, and was automatically obtained when theSteel, 2-inch schedule 40 option was chosen. The calculated wavespeedis 4433 feet/sec (Figure 2.8).

E. Enter data for other pipes

Similar to pipe P1, enter the following data for the other pipes:


22/79


Pipe Length(feet)

Nom. Diameter(inches)

Pipe Support

1 100 2 Thin-Walled Anchored Throughout2 75 2 Thin-Walled Anchored Throughout3 20 3 Thin-Walled Anchored Throughout4 25 3 Thin-Walled Anchored Throughout

After entering the data for all the pipes, the fourth Checklist item shouldbe completed. If it is not, see if the Show Object Status is on. If not,select Show Object Status from the View menu or toolbar. If the fourthChecklist item is not completed at this point, see if any of the pipes or

junctions have their number displayed in red. If so, you did not enter allthe data for that item.

Step 5. Complete the last two checklist requirements

After completing the first four Checklist items, sufficient informationexists to run the model in steady-state. The final two Checklist items arefor transient modeling. To run the model in steady-state, select AnalysisType from the Analysis menu and then choose Steady Only. If one doesthis, the final two Checklist items are grayed out and the model can berun.

In general it is a good idea to always run your model in steady-state firstbefore running the full transient analysis to make sure the model isgiving reasonable results.

A. Specify pipe sectioning

The fifth Checklist item is Section Pipes. This window cannot be openeduntil sufficient data is entered previously. First, the fluid must beselected (we did this Step 3B when we entered System Properties).Second, all pipes must have a length and wavespeed entered. After thisdata has been entered, the pipes can be sectioned. The Section Pipeswindow helps divide the pipes into computation sections in a mannerwhich is consistent with the Method of Characteristics (MOC).

Select Section Pipes on the Analysis menu to display the Section PipesWindow (Figure 2.9). For this model the controlling pipe is P3. This is


23/79


the pipe with the shortest end-to-end communication time (i.e., L/a thelength divided by the wavespeed). To satisfy the MOC, the followingequation must be applied:

n L

a t ii

i

=

where n is the number of sections in pipe i, L is the length, and a is thewavespeed. The t is the time step. Since all pipes in the network mustbe solved together, the same time step must be used for each pipe. With

a given length and wavespeed for each pipe, it can be seen from theabove equation that it is unlikely that the number of required sections, n,for each pipe will be a whole number.

Figure 2.9 The Section Pipes window automates the sectioningprocess and calculates the time step.

To address this situation, it is helpful to recognize that the wavespeed, a ,is the least certain input parameter. It is therefore acceptable to allow up

to a 15% uncertainty in wavespeed. By adjusting the wavespeed for eachpipe within this tolerance the sectioning can be made to come out as


24/79


whole numbers for each pipe. The Section Pipes window automates thisprocess by searching for sectioning which satisfies the requiredtolerance.

You can specify the tolerance on wavespeed by entering it into the Max.Percentage Error. The minimum and maximum allowable sections in thecontrolling pipe narrows the search space. Also, the PercentageIncrement directs the routine in how fine to search the search space.

For Min. and Max. Sections in Controlling Pipe enter 1 section foreach. Limit the Max Percentage Error to 10% for the search (usually 5 or10% is fine). Check the box for Sort Sectioning by Minimum Error.Then click the Search button.

A message is displayed to the effect that no valid sectioningcombinations could be found. At this point one has two choices. One canincrease the Max Sections in the Controlling Pipe, or increase theMax. Percentage Error allowed. Increasing the Max Sections willlead to models with increased run time. Increasing the Max PercentageError will lead to models with lower accuracy. Unless it results inexcessive model run times, it is usually preferred to increase the MaxSections entry. Change this from 1 to 2 and click the Search buttonagain.

This time a number of possible sectioning choices exist. When the SortSectioning by Minimum Error feature is checked, the first item in the

Search Results table will be the one with minimum error and is thusgenerally the preferred choice. The top line will be clickedautomatically, which will apply the sectioning choice to all pipes in themodel. This is shown in the Sectioning For Model table at the bottom.The resulting time step is shown at the right. It is 0.002057 seconds.

Note: The error in the Section Pipes window relates only to sectioningroundoff and not to overall model accuracy.

B. Specify transient control

The sixth and final Checklist item is Transient Control. This windowallows you to specify the time at which the transient starts and ends, aswell as how much data to include in the output file.


25/79


Select Transient Control on the Analysis menu to display the TransientControl window (Figure 2.10). Enter zero seconds for Start Time and 2for Stop Time.

The Transient Control window lets you enable or disable transientcavitation modeling. It also offers control over how AFT Impulse shouldrespond to artificial transients. Artificial transients are a problem thatcan sometimes occur when steady-state and transient conditions areinconsistent.

At the bottom of the window the projected output file size is shown. Youshould pay attention to this number, as the output file size can grow verylarge. In this case the output file will be 130 kB. If the output file doesbecome excessively large, you will want to limit the number of timesteps and pipe output written to disk.

Click OK to accept the current settings. The last Checklist item shouldbe completed. The model is ready to be solved.

Figure 2.10 The Transient Control window offers features tospecify the time span for the transient and whatoutput data is written


26/79


27/79

22 AFT Imp lse 4 0 Q ick Start G ide


28/79


Figure 2.12 The Output window displays steady and transientoutput in text form.

Figure 2.13 The Output window displays transient data for eachtime step.



29/79


The Output window allows you to review both the steady-state andtransient results. A summary of the maximum and minimum transientresults for each computing station is given on the Transient Max/Min tabin the pipe area. You can also review the solutions for each time step(i.e., a time history) for which data was written to file. These two datasets are located on the Transient Output tab and Transient Max/Min tabin the pipe area of the Output window (see Figures 2.13 and 2.14).

Figure 2.14 The Output window displays maximum and minimumtransient data.

B. Graph the results

For transient analyses, the Graph Results window will usually be more

helpful than the Output window because of the more voluminous data.Change to the Graph Results window by choosing it from the Windowsmenu, Toolbar, pressing Ctrl-G or clicking anywhere on the window.The Graph Results window offers full-featured Windows plotpreparation.

Choose Select Graph Data from the View menu or the Toolbar to openthe Select Graph Data window (see Figure 2.15). From the All PipeStations list, double-click pipe 3. Select the Outlet of pipe 3, the pipecomputing station at the valve inlet, and click the Add button. Also addthe inlet of Pipe 4 which is the valve exit. Select the Graph Parameter asPressure Static and set the unit to psig. A graph of these stations showsthe pressure history upstream and downstream of the valve.

Click the Show button to display the graph (Figure 2.16).

24 AFT Impulse 4 0 Quick Start Guide


30/79


Figure 2.15 The Select Graph Data window controls the GraphResults content

Figure 2.16 The Graph Results window offers full-featured plotgeneration. Here the pressure at valve inlet and outletof time are shown.



31/79

C apte Va ve C osu e a p e 5

Further review of the valve graph results in Figure 2.16 shows that attime zero the pressure difference between the top and bottom curves isabout 11 psid. This is the steady-state pressure difference across thevalve, which can also be found in the Output window to be 11.26 psid.

As time increases one sees that the two curves move further apart, whichrepresents the increased pressure drop across the valve as it closes.Finally at 1 second, the valve closes entirely and the pipes upstream anddownstream of the valve are isolated from each other and will decay tothe steady-state conditions which exist for a closed valve.

Choose Select Graph Data from the View menu or the Toolbar again toopen the Select Graph Data window. From the All Pipe Stations listclick the Clear button. Then double-click pipe 1. Select the inlet of pipe1 and click the Add button. This is the pipe computing station at thereservoir J1. Also add the inlet of Pipe 2 which is the reservoir J2. Selectthe Graph Parameter as Volumetric Flowrate Upstream and set the unitto gal/min. A graph of these stations shows the flowrates out of the twosupply reservoirs. Note that after the valve closes, the fluid in reservoirJ1 flows to reservoir J2 (see Figure 2.17).

Figure 2.17 Transient flowrates out of the reservoirs.

C. View the Visual Report

Change to the Visual Report window by choosing it from the Windowmenu, Toolbar, pressing Ctrl-I, clicking anywhere on the window if its



32/79

p Q

been restored or, if minimized, clicking on the minimized window at thebottom of the Workspace and restoring it. This window allows you tointegrate your text results with the graphic layout of your pipe network.

Click the Visual Report Control button on the Toolbar (or View menu)and open the Visual Report Control window, shown in Figure 2.18.Default parameters are already selected, but you can modify these asdesired. For now, select Max Pressure Stagnation and Min PressureStagnation in the Pipe Results area. Click the Show button. The VisualReport window graphic is generated (see Figure 2.19).

It is common for the text in the Visual Report window to overlap whenfirst generated. You can change this by selecting smaller fonts or bydragging the text to a new area to increase clarity (this has already beendone in Figure 2.19). This window can be printed or copied to theclipboard for import into other Windows graphics programs.

Figure 2.18 The Visual Report Control window specifies what data

to show on the Visual Report window.



33/79

Figure 2.19 The Visual Report window shows text output togetherwith the input schematic.

Conclusion

You have now used AFT Impulse's five primary windows to build asimple waterhammer model.



34/79


35/79



36/79

Model files

This example uses the following file, which is installed in the Examplesfolder as part of the AFT Impulse installation:

Pump Startup With Event Transient.imp


From the Start Menu choose AFT Products and AFT Impulse.

Step 2. Specify system properties

1. Open the System Properties window by selecting System Propertiesin the Analysis menu

2. On the Fluid Data Tab, select the AFT Standard database and thenselect "water at 1 atm" in the fluids available window

3. Click "Add to Model" to select water for use in this model

4. Type in 60 degrees F in the fluid temperature box

5. Click "Calculate Properties"

This calculates the fluid properties to use in the model.

Step 3. Build the model

A. Place the pipes and junctions

At this point, the first three items are completed on the Checklist. Thenext Checklist item is to "Define Pipes and Junctions". In the Workspacewindow, assemble the model as shown in Figure 3.1.


37/79



38/79

Pipe Length(feet)

Size Type Name

1 50 10 inch STD Suction Pipe Pump #12 20 10 inch STD Discharge Pipe Pump #13 20 10 inch STD Pipe4 60 10 inch STD Suction Pipe Pump #25 20 10 inch STD Discharge Pipe Pump #16 20 10 inch STD Pipe7 100 16 inch STD Pipe

8 250 12 inch STD Line to Process #1 Tank9 200 12 inch STD Line to Process #1 Tank

10 1200 12 inch STD Line to Process #1 Tank11 5000 12 inch STD Line to Process #2 Tank

2) Reservoir J1

a) Name = Supply Reservoirb) Surface elevation = 20 feet

c) Surface pressure = 1 atm

d) Pipe depth = 20 feet

3) Pumps J2 and J5

a) J2 is named Transfer Pump #1b) J5 is named Transfer Pump #2

c) Elevation = 0 feet

d) Click the Pump Configurations tab and enter the following data

Q (gpm) H (ft)0 150

1000 1402000 120

e) In the Curve Fitting area click the Generate Curve Fit nowbutton. Then click the OK button.

f) On the Transient Data tab: select Transient Model = WithoutInertia

Chapter 3 Pump Startup With Event Transients 33


39/79

g) Enter the following data for pump speed (the pumps will comeup to speed in two seconds.)

Time (sec) Speed (%)0 02 100

10 100

h) On the Optional tab select the Special Condition as Pump OffWith Through Flow. This says that initially the pump is turned

off, but flow can go through it during steady-state. We will usevalve junctions to prevent any steady-state flow.

4) Valves J3 and J6

a) J3 is named Valve #1

b) J6 is named Valve #2


d) Cv = 1000 (this value will actually not be used for this casebecause the valve is closed)

e) On the Transient tab enter the following data

Time (sec) Cv0 0

1 8002 1000

10 1000

f) On the Optional tab select the Special Condition as Closed.(When you close the valves, the adjacent pipes are displayedwith dashed lines to denote that the pipes are closed.)

5) Branch J4, J7 and J8

a) Elevation = 0 feet

6) Reservoir J10

a) Name = Process #1 Tank

b) Surface elevation = 100 feet



d) Pi D h 10 f


40/79

d) Pipe Depth = 10 feet

7) Reservoir J11

a) Name = Process #2 Tankb) Surface elevation = 10 feet


d) Pipe Depth = 10 feet

8) Valve J9

This valve will use what is called an event transient. This means thatthe time zero in the Transient Data table is with respect to somecondition occurring in the system. If the condition is never reached,the valve transient is never initiated. Here we want the valve to openwhen the pressure at junction J7 is sufficient to cause the water toflow into the J10 reservoir. Since the liquid height in J10 is 100 feet,forward flow will occur when the hydraulic gradeline (HGL) at J7 is

100 feet. The HGL at J7 is the same as that at the outlet of pipe P7,so we will use pipe P7 as the location of the event initiation.

a) Name = Valve to Process #1 Tank

b) Elevation = 0 feet

c) Cv = 500 (this value will actually not be used for this casebecause the valve is closed)

d) On the Transient Data tab enter the following data (see Figure3.2)

Time (sec) Cv0 02 4003 500

10 500

e) In the Initiation of Transient area select Single Event

f) Event Type = HGL at Pipe

g) Condition = Greater Than

h) Value = 100 feet

i) Pipe = 7, Outlet


j) O th O ti l t b l t th S i l C diti Cl d


41/79

j) On the Optional tab select the Special Condition as Closed.

Figure 3.2 Specifying an event transient for valve junction

C. Check if the pipe and junction data is complete

Turn on the Show Object Status from the View menu to verify if all datais entered. If so, the fourth Checklist item will have a check mark. If not,the uncompleted pipes or junctions will have their number shown in red.If this happens, go back to the uncompleted pipes or junctions and enterthe missing data.

Step 4. Section the pipes

Open the Section Pipes window from the Analysis menu. Choose theSearch button to find valid sectioning choices. Click OK to accept thedisplayed sectioning.


42/79


43/79



44/79

Figure 3.4 Scenario Manager window with three child scenarios

B. Set up scenarios

Since the Base Scenario already has been setup with two pumps starting,

we do not need to modify the Two Pump Start child. Select the OnePump Start scenario in the list and then click the Load As CurrentScenario button.

Here we want to start only pump J2 and keep pump J5 off. Since pumpJ5 and valve J6 are off during the transient, if we delete their transientinput data then they will stay turned off. Alternatively, we can specifythat their transient data be ignored. The second option is what we will

use here.Open the J5 Pump window and on the Transient Data tab choose theIgnore Transient Data option in the Transient Special Condition areaand click OK. Do the same with the J6 Valve. This scenario is nowcompleted.

Open Scenario Manager again. Select the One Pump Start With OneRunning scenario in the list and then click the Load As CurrentScenario button.


Here we want pump J2 to be running at 100% speed during the steady-


45/79

p p g p g ystate and transient, and to start pump J5. Open the J2 Pump window andselect the Optional tab. Set the Special Condition to None. This specifies

that during the steady-state the pump will be on and operate on its curve.Since this pump will run at 100% speed during the transient, select theTransient Data tab and set the Transient Special Condition to IgnoreTransient Data. Alternatively, the speed data could be deleted.

We also need to change the J3 Valve junction Special Condition toNone, and the Transient Special Condition to Ignore Transient Data.

The third scenario is now complete.

Step 7. Run the first scenario

Open Scenario Manager and select the Two Pump Start scenario in thelist and then click the Load As Current Scenario button. Select RunModel in the Analysis menu. After completion view the results bypressing View Output at the bottom of the window.

Step 8. Graph the results

Change to the Graph Results window from the Window menu. Open theSelect Graph Data window from the View menu or toolbar. First lets

look at a pressure profile.1. Select the Profile Along a Flow Path tab.

2. In the Pipes section click the None button.

3. Select pipes 1, 2, 3, 7 and 11.

4. Select Pressure Static in the Graph Parameters.

5. Select Maximum and Minimum in the Parameter Values area.6. Change the units to psig.

7. Click the Show button.

Results (shown in Figure 3.5) indicate that the peak pressure occurs atthe pump discharge, and that the minimum pressure is aboveatmospheric at all times.



46/79

Figure 3.5 Profile of the maximum and minimum pressuresthrough Pump #1 to Process #2 Tank for Two PumpStart scenario.

To easily recreate this graph for the other scenarios, open the SelectGraph Data window and click the Save Set As button in the lower partof the window. Give the set a name, perhaps Pressure Profile Pump #1to Process Tank #2.

The profile through the other flow paths (there are four paths altogether)can also be plotted, and similar conclusions are obtained. Create Graph

Sets for the other three paths.Since the maximum pressure is at the pump discharge, it is of interesthere to plot the pressure vs. time. Open the Select Graph Data windowagain and choose the Transient Pipe Data tab. Add the inlet station ofpipes 2 and 5 to the stations to be graphed (these represent the pumpdischarge points). Select the Graph Parameter as Pressure Static and setthe units to psig. Click the Show button. As would be expected, both

pressure transients are very similar. Results are shown in Figure 3.6.Open Select Graph Data and create a Graph Set for this as well.



47/79

Figure 3.6 Pressure transient at both pump discharge locationsfor Two Pump Start scenario.

The flowrates through the pumps are of general interest, and can also beplotted as shown in Figure 3.7. Open Select Graph Data and create aGraph Set for this plot.

Figure 3.7 Flowrate transient at both pump discharge locationsfor Two Pump Start scenario.

The flowrates into the two process tanks are of interest. On the Transient

Pipe Data tab click the Clear button in the Pipe Station Selection areaand add the outlet of pipes 10 and 11. Select to plot the flowrate and


create a Graph Set for this plot. Then click the OK button. Results areh i Fi 3 8


48/79

shown in Figure 3.8.

Figure 3.8 Flowrate transient at process tanks for Two Pump

Start scenario.

Step 9. Animate the results

Open the Select Graph Data window again from the View menu ortoolbar.

1. Select the Profile Along a Flow Path tab (see Figure 3.9).

2. Select pipes 1, 2, 3, 7 and 11.

3. Select Pressure Static in the Graph Parameters.

4. Select Animate Using Output File in the Parameter Values area.

5. Change the units to psig.



49/79

Figure 3.9 Selecting animation in Graph Results for Two PumpStart scenario.

To use the Animate With Output File option, which we are using here,all pipe stations need to be saved in Transient Control (Step 5). Inaddition, it frequently is best to save all time step data as well. Weselected both of these previously. This animation option has the mostflexibility to start, pause, and restart animation.

Another animation option in Figure 3.9 is Animate Using Solver. Thisoption actually reruns the Transient Solver to generate the data foranimation, and thus does not need to read it from file. Therefore, it doesnot require all of the data to be saved in Transient Control.

Click the Show button. Additional animation control features appear onthe Graph Results window (Figure 3.10). Press the Play button andwatch the pressure waves move.


50/79


Table 3.1 Summary of maximum static pressure for the threecases.


51/79

Case Max. StaticPressure (psig)

Two Pumps Start 72.8One Pump Start 71.5One Pump Start With One On 72.8


52/79


53/79


Model files


54/79

This example uses the following files, which are installed in the

Examples folder as part of the AFT Impulse installation:Pump Trip.imp

Pump Trip With Accumulator.imp


From the Start Menu choose AFT Products and AFT Impulse.

Step 2. Specify system properties

1. Open the System Properties window by selecting System Propertiesin the Analysis menu

2. On the Fluid Data Tab, select the AFT Standard database and thenselect "water at 1 atm" in the fluids available window

3. Click "Add to Model" to select water for use in this model

4. Type in 70 degrees F in the fluid temperature box

5. Click "Calculate Properties"

This calculates the fluid properties to use in the model.

Step 3. Build the model

A. Place the pipes and junctions

At this point, the first three items are completed on the analysisChecklist. The next Checklist item is to "Define Pipes and Junctions". Inthe Workspace window, use the Toolbox on the left to drag and drop tworeservoirs and a pump onto the Workspace window. Then connect thesewith the pipe drawing tool. The default flow direction will be from thefirst object you select to the second object. An arrow indicates thedefault flow direction. The Workspace should look like Figure 4.1.

Chapter 4 Pump Trip Example 49


55/79

Figure 4.1 Workspace for pump trip example.

B. Enter the pipe and junction data

The system is in place but now we need to enter the specifications of theobjects. Double-click each junction and enter the following data in theJunction Specifications window.

1) Reservoir J1

a) Name = Lower Reservoir


c) Surface pressure = 1 atm.d) Pipe depth = 10 feet (entered on the "Pipe Depth and Loss "

tab)

2) Reservoir J3

a) Name = Upper Reservoir




d) Pipe depth = 10 feet (entered on the "Pipe Depth and Loss "


56/79

) p p ( p ptab)

3) Pump J2

a) Elevation = 0 feet

b) Select Power in the Efficiency/Power area

c) Click the Pump Configurations tab and enter the following data(see Figure 4.2):

Q (gpm) H (feet) Power (hp)0 400 25

250 390 33500 380 60

1000 340 130

d) In the Curve Fitting area select the All button then click the

Generate Curve Fit now button. Then click the OK button.e) On the Transient Data tab select Transient Model = Trip With

Inertia and No Backflow or Reverse Speed (see Figure 4.3)

f) Pump Speed = 1760 rpm

g) Rotating Inertia = 25 lbm-ft2



57/79

Figure 4.2 Pump J2 performance data

4) The pipe specifications are as follows:

a) Pipe P1

i) Material = steel, size = 4 inch, type = schedule 40, standardroughness

ii) Length = 10 feet

b) Pipe P2

i) Material = steel, size = 4 inch, type = schedule 40, standardroughness

ii) Length = 990 feet

iii) The pipe model also allows for additional losses like valvesor elbows. Select the Additional Losses tab for P2 and type


in 25 for the Total K Factor. Now close the pipespecification window to accept your changes.


58/79

Figure 4.3 Transient input data for Pump J2

Note that unless specified otherwise, pipe elevation is assumed to varylinearly between junctions. Thus the pipe P2 inlet elevation is 0 feet, and

the exit elevation is 190 feet (because the J3 reservoir is 10 feet deep). Inbetween the elevation is linear. If another profile is desired, this can beentered on the pipes Optional tab.

To model the pump transient behavior in this example we are using thePump Trip With Inertia and No Backflow model. This is the preferredmodel to use when the pump has a check valve which does not allowbackflow. When backflow is possible, the Four Quadrant method must

be used. This method requires additional input data.

C. Check if the pipe and junction data is complete

Turn on the Show Object Status from the View menu to verify if all datais entered. If so, the fourth Checklist item will have a check mark. If not,the uncompleted pipes or junctions will have their number shown in red.


If this happens, go back to the uncompleted pipes or junctions and enterthe missing data.


59/79

Step 4. Section the pipes

Open the Section Pipes window from the Analysis menu. Choose theSearch button to find valid sectioning choices. Click OK to accept thedisplayed sectioning.

Step 5. Specify transient control

Open the Transient Control window from the Analysis menu.

1. Enter the Stop Time as 30 seconds.

2. Click the OK button.

Step 6. Run the model

The Checklist should now be complete and the model ready to run.Select Run Model in the Analysis menu. This will open the SolutionProgress window. This window allows you to watch the progress of theSteady-State and Transient Solvers. When complete press the View

Output button at the bottom of the window.

Step 7. Review results

Clicking View Output will take you to the Output window, which willdisplay any warnings if they exist. There should not be any warningshere. The Graph Results window will be more useful in understandingthe results

A. Graph the transient pressures at the pump

1. Open the Select Graph Data from the View menu or toolbar.


2. On the Transient Pipe Data tab, add the Pipe 1 Outlet and Pipe 2Inlet (see Figure 4.4). These represent the pump suction anddischarge locations.


60/79

g

3. In the Graph Parameters list choose Pressure Static.4. Set the units to psig.


The resulting pressure transients are shown in Figure 4.5. Here one cansee that the transient pressure at the pump discharge does not rise abovethe initial steady-state pressure. This is not always the case.

Figure 4.4 Data selection to view the transient pump suction anddischarge pressures



61/79

Figure 4.5 Predicted transient pump suction and dischargepressures

B. Graph the pipeline transient pressure profile

1. Open the Select Graph Data from the View menu or toolbar again.

2. Select the Profile Along a Flow Path tab (Figure 4.6).

3. In the Pipes area choose the Select All button to select both pipes 1and 2.

4. In the Graph Parameters list choose Pressure Static.5. In the Parameter Values options choose Maximum and Minimum.

6. Set the units to psig.


Profile type graphs that show maximum and minimum values can bevery helpful. Here we see that the maximum transient pressure occurs atthe pump discharge, and that the minimum pressure occurs 600-700 feetdownstream of the pump. Also note that minimum pressure goes belowatmospheric pressure for almost 400 feet of pipe. For some applicationsthis may not be acceptable.



62/79

Figure 4.6 Data selection to view the max/min pressure profile

Figure 4.7 Predicted max/min pressure profiles

C. Graph the pump speed decay

1. Open the Select Graph Data from the View menu or toolbar again.


2. Select the Transient Junction Data tab (Figure 4.8).

Here there should be a message that No Junction Data Saved: SeeTransient Control window. What this means is that AFT Impulse can


63/79

Transient Control window . What this means is that AFT Impulse can

only graph transient data for items that are saved to the output file. Andfor this run, the pump speed was not saved.

Figure 4.8 Data selection to view the pump speed decay. Cannotselect the pump speed here because it was not saved.

To save this data, do the following:

1. Open the Transient Control window from the Analysis menu.

2. Select the Junctions tab.

3. Check the box next to the J2 pump (Figure 4.9).4. Click OK.

5. Rerun the model (the output file needs to be generated again with thepump speed included).



64/79

Figure 4.9 The Transient Control window allows you to includeselected data for junctions. Here the pump data isbeing added.

1. Open the Select Graph Data from the View menu or toolbar.

2. On the Transient Junction Data tab, add Pump J2 (see Figure 4.10).

3. In the Graph Parameters list choose Pump Speed.


The predicted pump speed is then shown (Figure 4.11).



65/79

Figure 4.10 The pump speed is selected on the Junction TransientData tab.

Figure 4.11 The pump speed decay is shown. The speed decaysquickly at first, and then slows down after the checkvalve closes and the flow goes to zero.


Step 8. Add accumulator

Review of Figure 4.7 shows that the pressure drops below atmospheric


66/79

pressure along about 400 feet of pipe. In some design situations this isnot acceptable. One way to change the transient response and thusmaintain only positive pressure is with an accumulator. To do this theaccumulator will need to be properly size and located.

A. Modify model

We need to break the original pipe P2 into two pipes and insert theaccumulator junction between them. The modified model should appearas in Figure 4.12.

Figure 4.12 System with accumulator junction

B. Enter pipe and junction data

The data for this example is as follows:

1) Gas Accumulator J4 (see Figure 4.13)


a) Initial Gas Volume = 0.5 cubic feet

b) Polytropic constant = 1.2 (conventional assumption for air,halfway between 1 and 1.4)


67/79


d) A short vertical connector pipe is used with the following data

e) Connector pipe diameter = 4 inches

f) Connector pipe area = 12.57 square inches (i.e., it is round)

g) Connector pipe length = 2 feet

h) Connector pipe elevation change = 2 feet (i.e., it is vertical)

i) Connector pipe friction factor = 0.018

Figure 4.13 Gas Accumulator Specifications window


2) Pipe P2

a) Length = 50 feet

b) Additional loss K factor = 0


68/79

)

3) Pipe P3

a) Length = 940 feet

b) Additional loss K factor = 25 (the K factor from the originalmodel is now in P3)

C. Check if the pipe and junction data is completeTurn on the Show Object Status from the View menu to verify if all datais entered. If so, the fourth Checklist item will have a check mark. If not,the uncompleted pipes or junctions will have their number shown in red.If this happens, go back to the uncompleted pipes or junctions and enterthe missing data.

D. Some commentary on accumulators

Sizing and locating accumulators is very much a cut and try method. Thetypical assumption is that the accumulator should be located as near thesource of the transient as possible. In developing this example, theaccumulator was first placed ten feet from the pump suction. Initial gasvolumes of 0.25 cubic feet up to 10 cubic feet were used. The

accumulator was effective in keeping the pressures in the discharge pipeabove atmospheric, but the suction pipe, which previously had allpositive pressures, now had sub-atmospheric pressure.

Therefore the accumulator was moved further away from the pump tosee if this could be avoided. It was therefore first located at 700 feetalong pipe P2 because that was the point of minimum pressure in Figure4.7. Thus pipe P2 was 700 feet long and P3 was 290 feet. This yielded

acceptable positive pressures. The accumulator was then moved closer tothe pump, and ultimately it was discovered that placing the accumulator50 feet downstream of the pump gave acceptable pressures on both thepump suction and discharge piping. If this were a real system, this wouldhave the added benefit of locating the accumulator near the pump,supposedly an accessible location rather than halfway up the side of ahill.


Step 9. Re-section pipes

Since a pipe was added, the previous sectioning is no longer valid. Open


69/79

the Section Pipes window from the Analysis menu. Choose the Searchbutton to find valid sectioning choices. Click OK to accept the displayedsectioning.

Step 10. Run the model

The Checklist should now be complete and the model ready to run.Select Run Model in the Analysis menu. View the results by pressingView Output at the bottom of the window.

Step 11. Graph results

As compared to Figure 4.7, the pressure profile is shown in Figure 4.14.As compared to Figure 4.5, the pressure transient at the pump suctionand discharge are shown in Figure 4.15. Note that the maximum pumpdischarge pressure has increased slightly above 170 psig, the valuewithout the accumulator.

Figure 4.14 Maximum and minimum pressure profile with theaccumulator



70/79

Figure 4.15 Transient pressures at pump suction and dischargewith accumulator

For interest, it should be mentioned that an initial accumulator volume of0.25 cubic feet was also used. It successfully kept all minimum pressuresabove atmospheric, but caused the pump discharge pressure to rise up toalmost 250 psig. Although accumulators are often thought to be pressurereduction devises, they can also increase peak pressures.

The pump speed decay is shown in Figure 4.16. Note how the pumpspeed does not decrease as quickly as before (Figure 4.11). The gasvolume in the accumulator is shown in Figure 4.17. (To be able to graphthe accumulator data, it must first be added in the Transient Controlwindow and the model rerun.)


71/79



72/79

C H A P T E R 5


73/79

C H A P T E R 5

Other AFT Impulse Capabilities

This Quick Start Guide necessarily omitted coverage of a number ofAFT Impulse capabilities. This chapter briefly describes some of theimportant capabilities not covered.

Transient cavitation and liquid column separation

AFT Impulse offers the Discrete Vapor Cavity model for modelingtransient cavitation (also known as liquid column separation). Thismodel calculates vapor volume size over time and accounts for pressurespikes when cavities collapse. Vapor volume can be plotted in the GraphResults window.

Four quadrant pump modeling

When pumps can flow backwards, then four quadrant modeling isneeded. AFT Impulse offers four quadrant models using the popularSuter method. Twenty-one sets of four quadrant data are provided.


74/79


75/79


Intermediate elevations for pipes

Typically, elevation changes along pipes do not affect the steady ortransient behavior of the system. Exceptions are high points whichcavitate If desired AFT Impulse can model varying elevations along a


76/79

cavitate. If desired, AFT Impulse can model varying elevations along apipe.

Force file output for use with CAESAR II

AFT Impulse can create force files for use with CAESAR II pipe stressmodeling software.

Fitting library

AFT Impulse offers a library of about 400 fitting losses which can beadded to pipes.

Design alerts

Design alerts can be entered for pipes and then cross-plotted vs. systembehavior. A common use is maximum and minimum allowed operatingpressure. These can be entered as design alerts for pipes and then plotted

against predicted pressure transients.

Network databases

Junction components and pipe materials can be saved to databases forlater reuse. Databases can be located on local PC's or deployed acrosslocal or wide area networks. The Database Manager allows users toconnect to relevant databases for their specific pipe system design.

Index

A

Checklist 8

Chempak fluid database 69

controlling pipe 16


77/79

A accumulator 2, See Gas Accumulator

junction

AFT Fathom 2

AFT Impulse

engineering assumptions 3

Overview 3

summary of capabilities 2

AFT Impulse window 6

animation 29, 42

Annotation

on Workspace 7

Assigned Flow junction

infinite pipe boundaries 69

Assigned Pressure junction

infinite pipe boundaries 69

B Bingham Plastic See Non-Newtonian

fluid

Brecht & Heller method See Pulp and

paper modelingbulk modulus 10

C CAESAR II Force Files 70

cavitation See transient cavitation

D Database Manager 70

Databases 70

Duffy method See Pulp and paper

modeling

E Event transient specification 34

F Flow control valves 69

Force files 70

G Gas Accumulator junction 60

Gas Accumulators

comments on use 62

Graph Results window 4, 23, 39, 53,63

design alerts 70

Graph Sets

creating 40

I Infinite pipe boundaries 69


L liquid column separation See transient

cavitation

Pump junction 32

entering pump curves 32, 50

four quadrant modeling 67

positive displacement pump modeling


78/79

M Method of Characteristics 2, 16

Model Data window 4

modulus of elasticity 15

N Newton-Raphson method 2

Non-Newtonian fluid 2, 69

O Output Control window 9, 21

output file See transient output file

Output window 4, 21, 53

Overview of AFT Impulse 3

P Pipe Drawing Tool 7

Pipe Specifications window 14

design alerts 70

intermediate elevations 70

Poisson Ratio 15

Power Law See Non-Newtonian fluid

pressure control valves 69

Primary windows 3

Pulp and paper modeling 69

positive displacement pump modeling68

Special Condition 33

transient data entry 32, 50

variable speed controllers 68

viscosity corrections 68

R Reservoir junction 11, 32

S Scenario Manager 37

Section Pipes window 16, 35, 53, 63

Select Graph Data window 23, 39, 42,53

Show Object Status 11

Solution Progress window 20, 53

Special Condition 33

Steady Solution Control 9

steady-state solver 2, 20

surge tank 2, 68

System Properties window 9, 10, 30,48

T Toolbox 7

transient cavitation 2, 67


79/79

Documents

Impulse 4.0 Quick Start