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Solution processSolution process

( ) 0=⎟⎠⎞

⎜⎝⎛ ⋅∇+∂∂

∫∫∫V t

uρρGeometryGeometry

CAD, GambitCAD, Gambit

PhysicsFluent

PhysicsFluent

Mesh generationMesh generationGambitGambit

VisualizationVisualizationFluentFluent

MathematicsMathematicsFluentFluent

• Convection• Conduction• Turbulence• Transient flow• Combustion• Radiation• Rotation• Multiphase• Chemical

reactions• Phase change• Acoustics• Deforming

mesh• EMC• Plasma flows• ...

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Introductory FLUENT NotesFLUENT v6.1 Feb 2003

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CFD Analysis: Basic Steps

Problem Identification and Pre-Processing1. Define your modeling goals.2. Identify the domain you will model.3. Design and create the grid.Solver Execution4. Set up the numerical model.5. Compute and monitor the solution.Post-Processing6. Examine the results.7. Consider revisions to the model.

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Tools for Post-ProcessingMany post-processing tools are available.Post-Processing functions typically operate on surfaces.

Surfaces are automatically created from zones.Additional surfaces can be created by user.

Example: an Iso-Surface of a constant grid coordinate can be created for viewing data within a plane.

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Tools for Post-Processing: Graphics (1)Display/Grid...

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Tools for Post-Processing: Graphics (2)Display/Contours...

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Post-Processing: Node vs Cell ValuesFluent calculates field variable data at cell centers.Node values of the grid are either:

calculated as the average of neighboring cell data, or,defined explicitly (when available) with boundary condition data.

Node values on surfaces are interpolated from grid node data.Data files store:

data at cell centersnode value data for primitive variables at boundary nodes.

Enable Node Values to interpolate field data to nodes.

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Tools for Post-Processing: Graphics (3)Display/Vectors...

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Tools for Post-Processing: Graphics (4)Display/Pathlines...

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Tools for Post-Processing: Graphics (5)Plot/XY Plot...

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Tools for Post-Processing: Graphics (6)Plot/Residuals...

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Tools for post-processing: Reports (1)Report/Flux Reports…

Net flux is calculated.Total Heat Transfer Rate includes radiation.

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Tools for post-processing: Reports (2)Report/Surface Integrals…

slightly less accurate on user-generated surfaces due to interpolation error.

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Tools for post-processing: Reports (3)Report/Volume Integrals…

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When can we trust in our Solution?When it is convereged!

All discrete conservation equations (momentum, energy, etc.) are obeyed in all cells to a specified tolerance (Residuals).

Overall mass, momentum, energy, and scalar balances are achieved.(Reports)

Solution no longer changes with more iterations.(Monitors)

All equations converged.

10-3

10-6

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When can we trust in our Solution?

AND...

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When can we trust in our Solution?

When it is accurate!Use the second-order upwind discretization scheme for final results.Solve/Controls/Solution…

Ensure that solution is grid-independent:

Use adaption to modify the grid or create additional meshes for the grid-independence study.Adapt/Region…Adapt/Gradient…Adapt/Iso-Value