Numerical Simulation Wind Analysis for Plate-cone

8/12/2019 Numerical Simulation Wind Analysis for Plate-cone

1/4

ABSTRACTPlate-cone reticulated shell is a new type of

space steel structures with good mechanical behavior and

technical economy. In this paper, by using the wave superposi-

tion method, the fluctuation wind loads are simulated. Accord-

ing to the structural behavior of plate-cone reticulated shell,

the structural shape factors of wind load for plate-cone reticu-

lated shell were gained with numerical wind tunnel simulationbased on Computational Fluid Dynamic(CFD) method

through simulating wind field variation around plate-cone re-

ticulated shell, and comprised with the common reticulated

shells shape factors of wind load suggested by the Code for

loads, some important conclusions for plate-cone reticulated

shell are obtained for practical design.

Keywords-Plate-cone reticulated shell; Numerical Simula-

tion;Wave superposition method; Fluctuation wind loads

I. INTRODUCTION

Plate-cone reticulated shell is a new type of space struc-tures, in which cone elements are composed of plates andmade up into a whole based on the surface shape of reticu-lated shell, then the tops of cones are connected by members(Fig. 1). Plate-cone reticulated shell has good mechanical

behavior, technical economy and architectural appearance. Itcan make full use of the strength and stiffness of plates andmake materials most effective, integrate bearing, surround-ing and decoration into a whole. Plate-cone reticulated shellis light and has high bearing capacity, it has been appliedwidely abroad but not applied in China yet. Research for

plate-cone reticulated shell in China and abroad is not verysufficient, the research of Gilkie(1967)[1] abroad focuses onstatic analysis and approximate equivalent method. In China,Wang(2000)[2] analyzed the static characteristics of plate-

cone reticulated shell with composite structures FEM. Thedynamic problem of plate-cone reticulated shell is also avery important problem in engineering design, but due tocomplexity of the structure, the wind vibration responseanalysis for plate-cone reticulated shell has not been seen athome and abroad yet, not adapting to the needs of engineer-ing application.

In this paper, according to the structural behavior ofplate-cone reticulated shell, the structural shape factors ofwind load for plate-cone reticulated shell were gained withnumerical wind tunnel tests based on Computational FluidDynamic(CFD) method though simulating wind fieldvariation around plate-cone reticulated shell, and comprised

with the common reticulated shells shape factors of windload suggested by the Code for loads.

II. NUMERICAL SIMULATION METHOD FORTURBULENT FLOW

Turbulent flow is a highly complex nonlinear flow, cur-rent numerical simulation method for turbulent flow can bedivided into direct numerical simulation method and thenon-direct numerical simulation method. Some feasible nu-merical simulation methods for turbulent flow are introducedand compared as following.

A. Double Equations Modelk Equation Model

Standard k equation modelDue to the Reynolds stress and turbulence viscosity coef-

ficient unknown, Reynolds equation is not sealed, Establish-ing the transporting equations associated with unknown

quantity is necessary. Currently using the k equationsreflecting confused kinetic energy and the equations re-

flecting dissipation of confused kinetic energy, Reynolds

equation is sealed. k equations, continuous equationand Reynolds equation form the completely sealed turbulentflow equations.

RNG k modelRenormalization Group (RNG) is a kind of common

method, used to construct the models of many physical phe-

nomena. RNG k model is an improved form of the

standard k model, its k equations are:kequation:

k

ik

t

ii

i Px

k

xx

k

ut

k

])[( (1)

equation:

kCP

kCR

xxxu

tk

i

t

ii

i

2

21])[(

(2)

B. Reynolds Stress ModelRSM

Reynolds stress models applied on engineering numeri-cal computation are the secondary moment model and thealgebra stress model simplified on the basis. Starting from

Numerical Simulation WindAnalysis for Plate-cone

Reticulated Shell

Wang XingFang Ji-gaoZhu Li-zhuangSchool of Architecture and Civil Engineering

Ningbo University of Technology

Ningbo , China

[email protected]

___________________________________

978-1-4244-9600-6/11/$26.00 2011IEEE


2/4

the pulsation velocity field, and the stress equations of tur-bulence flow are derived, the equations are sealed afteranalysis and simplifying. But it's simulation accuracy of

kequation and equation is not higher than the stan-dard k model, and the engineering applications areloaded down with trivial details.

C. Large Eddy Simulation MethodLES

The computer memory and CPU speed required by theLES method are still relatively high, but below the DNSmethod. At present, the LES work can been carried on theworkstation and high-grade PC, the commercial softwareFLUENT also provides the LES module. The LES method isone of the hotspots of currently CFD study and application.

D. Comparison of Numerical Simulation Method for Tur-bulent Flow

At present, the most famous turbulent flow models such

as Standard k model, RNG k model, Reynoldsstress modelRSMand large eddy simulation model

LESshowed no significant differences for prediction of

the wind pressure distributions on blunt body surface [3][4],but there are some problems in local place, especially in the

top front of the building using the standard k model.Large eddy simulation result is best, Reynolds stress model

take second place, RNG k model is close to Reynolds

stress model, Standard k model is not as good as Rey-nolds stress model[5]. Due to the large eddy simulation still at

the stage of studying and needing advanced computer tech-nology, the application on civil engineering problems are not

practical at present.

In short, all types of k model and algebra stressmodel are the most practical value of turbulent flow modelsfor engineering calculation of complex turbulent flow prob-lems at present.

III. NUMERICAL WIND TUNNEL TESTS FORPLATE-CONE RETICULATED SHELL

In the paper, the structural shape factors of wind load forplate-cone reticulated shell were gained with numerical windtunnel tests by using Computational Fluid Dynamic software

FLUENT though simulating wind field variation aroundplate-cone reticulated shell, and comprised with the commonreticulated shells shape factors of wind load suggested bythe Code for loads.

A. Choice of Flow Field

Referring to the related references[6], RNG k turbu-lence model is adopted on calculation of the example in this

paper.In order to calculating boundary conditions more accord-

ing with actual physical boundary conditions, the marginal-ity of Numerical wind tunnel from buildings must be largeenough. After trial, comprehensively considering precision

and computational resources, the scale of numerical windtunnel is 20 times of the models plane diameter in this ex-ample. The model is divided by using hybrid grids, comput-

ing model is selected as steady state, Computing method isSIMPLEC.

B. Initial Condition and Boundary Condition

According to the experimental data and relevant refer-ences[6], initial condition and boundary condition are as fol-lows:

Inlet flow surface: the inlet velocity boundary condi-

tions is the inlet wind velocity 26.833 /v m s (accord-ing to the conversion for Hangzhou area basic wind pres-sure value 0.45kPa at Hangzhou area with the conversion

formula2

0/1600v ). Considering the sufficient de-

velopment of the inlet airflows disorder degree, turbulence

intensity is taken as 10% in the example. Maximum eddysize is usually same as the obstacles in the fluid in the samescale, turbulent flow scale is taken as half of plane diameterconsidering the structural symmetry.

Outlet flow surface: because of the outlet flow nearcomplete development, pressure outlet boundary conditionis taken and the relative pressure value is taken as zero.

The top and sides of flow field: symmetrical boundaryconditions is taken, equivalent to the free sliding wall.

Building surface and ground: no sliding wall condition.

C. Numerical Wind Tunnel Tests for Plate-coneCylindrical Reticulated Shell with Quadrangular

Pyramids

The geometric parameters of plate-cone cylindrical re-ticulated shell with quadrangular pyramids are: span is 30m,length is 45m, vector height is 5m, thickness is 1.5 m, meshis divided into 1015, the top connecting members are takenas steel pipes of1085.0, the triangle plates of cones aretaken as steel plates of 3mm thickness, the reticulated shell is

put on the 10m high maintenance structure. The model isanalyzed with numerical wind tunnel by using softwareFLUENT. This paper mainly discusses the mechanical char-acteristics of plate-cone cylindrical reticulated shell underthe 0 wind direction angle.

Structural wind pressure distribution:


3/4

Figure. 1 shows the wind pressure distribution of struc-ture surface under 26.833 m/s, 0 wind. Positive pressure onthe windward side of entrance of the reticulated shell, ismainly concentrated on windward side of the first row cones,

the maximum wind pressure of local field is about 55Pa.Most of the structure surface area is under negative pressure,the biggest negative wind pressure appeared in the side offirst row of cones, the local biggest negative unpressured to -800Pa, the first row of cones stress is complex. Due to thespecial shape of plate-cone reticulated shells, vortex-inducedvibration produced in the back of sides of cones will be morecomplex, plates of cones will likely produce wider margin offlutter and buffeting, causing the plates fatigued.

Shape factors distributions for net wind pressure:The shape factors for net wind pressure of plate-cone

cylindrical reticulated shell with quadrangular pyramids inthis example can be gained from the calculated results of

wind pressure distributions. The shape factors for net windpressure are zoned, zoning map is Fig. 3 and partition tableis table 1. From Fig. 1 and table 1, we can see:

On the case of 0 wind direction angle, the pressure area

of plate-cone cylindrical reticulated shell mainly are near thewindward surface, the maximum pressure zone (1-1)concentrated in the support or the middle plates near thesupport, the wind pressure coefficients are small, the maxi-mum wind pressure coefficient is 0.15, The windward sideand leeward side of cones mainly is under the suction, thewind pressure of sides is larger than the wind pressure ofthe back , the biggest suction area (1-2) is in the sides of thefirst row of cones, wind pressure coefficient can reach - 1.5or more.

Comparison of shape factors between plate-cone reticu-lated shell and common cylindrical reticulated shell:

TABLE 1 Partition Table of Shape Factors for Net Wind Pressure

Zone number Shape factors Zone number Shape factors

1-1 -0.457265206 6-1 -0.863304256

1-2 -0.451487423 6-2 -0.930247904

1-3 -0.433718469 6-3 -0.660339915

2-1 -0.436698454 7-1 -0.949023371

2-2 -0.454528728 7-2 -0.965167087

2-3 -0.469401121 7-3 -0.583854202

3-1 -0.469945866 8-1 -0.933128977

3-2 -0.496919379 8-2 -0.975819573

3-3 -0.49737519 8-3 -0.539154605

4-1 -0.553638559 9-1 -0.914989911

4-2 -0.590486423 9-2 -0.926543664

4-3 -0.573388737 9-3 -0.573408793

5-1 -0.697830496 10-1 -1.065871879

5-2 -0.780780353 10-2 -1.516645002

5-3 -0.645515981 10-3 -0.329726364

Figure.1 Zones of shape factors for net wind pressure of plate-cone cylindrical reticulated shell


4/4

The shape factors for net wind pressure of common cy-lindrical reticulated shell can be taken as the shape factors ofclosed-end vaulted roof.

In this example, the vector height of common cylindri-cal reticulated shell is 5m, the span is 30m,

/ 0.1667f l , calculating by method of insertion, the

zoning shape factors1 -0.27s 2 -0.8s

3 -0.5s , the average shape factor -0.59s . The zon-

ing shape factors of plate-cone cylindrical reticulated shell

with the same ratio of rise to span1 -0.85s

2 -0.73s 3 -0.46s , the average shape factor

-0.69s .

Flow velocity distribution:Flow velocity distribution of the structure is shown as

Figure. 3. In Figure. 3, we can see that the phenomenon ofvortex shedding between cones is serious.

Figure.3 Flow velocity distribution

IV. CONCLUSIONS

In this paper, the feasibility of numerical wind tunnel testwith CFD method for plate-cone reticulated shells is dis-cussed. The change of wind field around plate-cone reticu-lated shell is simulated on the Computer, the structuralshape factors of wind load for plate-cone reticulated shell

were gained, and comprised with the common reticulatedshells shape factors of wind load suggested by the Code forloads, some useful conclusions are summarized as follows:

a) CFD method for numerical simulation of complexshape structure under the wind is practical and effective. It

provides a kind of non-experimental and low cost method,which determines wind pressure distribution and values ofcomplex shape structures, so it is valuable in the engineeringapplication.

b) There is bigger difference between shape factors ofplate-cone cylindrical reticulated shell and shape factors ofaverage cylindrical reticulated shell. Due to the existence ofcones, the turbulent wind is increased, to cause greater nega-tive pressure on the structure. Therefore, in the structural de-sign on plate-cone reticulated shell, we should pay attentionto the connections between middle plates under negative

pressure, in order to prevent the connecting bolts pulled,

middle plate edge torn etc.c) Plate-cone cylindrical reticulated shell in the example

bears negative pressure overall, partial plates bear weakpositive pressure, the largest negative pressure and the larg-est positive appear on the first row of cones of windwardside, therefore, the rigidity of first row of cones of windwardside should be reinforced mainly in the design of plate-conecylindrical reticulated shell.

V. REFERENCES[1] RC Gilkie, A comparison between the theoretical and experimental

analysis of stresed shin system of construction in plastics and alu-minium, Space Structures, Blackwell Scientific Publictions Ltd,1967

[2] Meroney B N, Leitl B M and Rafailidis S, Wind tunnel numerical

modeling of flow and dispersion about several building shapes.Journal of Wind Engineering and Industrial Aerodynamics,1999,(81)

[3] Wang Xing and Dong SL, A study on static characteristics for plate-cone reticulated shellBuilding Structure2000, 30(9)

[4] Kim SE and Boyisan F, Application of CFD to environmental flows.Journal of Wind Engineering and Industrial Aerodynamics,1999,(81)

[5] Murakami S, Comparison of various turbulence models applied to abluff body. Journal of Wind Engineering and Industrial Aerodynam-ics, 1999

[6] Yang Wei and Gu Ming, Numerical simulation of constant windfield for high building, Journal of Tongji University, Vol.31, 2003(6)

Fi ure.2 Com arison of sha e factors between late-cone reticulated shell and common reticulated shell

-1.52

-1.32

-1.12

-0.92

-0.72

-0.52

-0.32

-0.12

1-

1

1-

2

1-

3

2-

1

2-

2

2-

3

3-

1

3-

2

3-

3

4-

1

4-

2

4-

3

5-

1

5-

2

5-

3

6-

1

6-

2

6-

3

7-

1

7-

2

7-

3

8-

1

8-

2

8-

3

9-

1

9-

2

9-

3

1

0-

1

1

0-

2

1

0-

3structural zones

shape factors of plate-cone reticulated shell

shape factors of common reticulated shell

Documents

Numerical Simulation Wind Analysis for Plate-cone