Assignment 1 CFD with OpenSource Software

Assignment 1CFD with OpenSource Software

Shayan Rahat

Applied Mechanics/Fluid Dynamics,Chalmers University of Technology,

Gothenburg, Sweden

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cavity

Solver:icoFoam

Utilities used:

blockMesh

checkMesh

+ paraFoam for every case

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The threshold and glyph filters are used to produce the figure below. Ascan be seen, the flow-field is almost symmetric. This was expected as thevelocities are low.

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The dynamic pressure can be calculated easily as was done here. Since theabsolute pressure is irrelevant in incompressible flow, the ”dynamicpressure” here is only meaningful in a relative sense.

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cavityFine

Solver:icoFoam

Utilities used:

blockMesh

checkMesh

mapFields

foamCalc

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Here, both Ux and mag(U) have been plotted along a vertical line in thecenter of the cavity using Plot Over Line.

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The y component of the velocity field is plotted using foamCalc and theClip filter. Turning of the fluid in the corners can be seen.

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cavityGrade

Solver:icoFoam

Utilities used:

blockMesh

checkMesh

mapFields

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The mesh in this case set-up was graded to allocate more cells to theregions with the highest gradients. But since the flow is laminar andincompressible, the results do not show significant changes.

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cavityHighRe

Solver:icoFoam

Utilities used:

blockMesh

checkMesh

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As the Reynolds number is increased the flow becomes asymmetric. ASlice filter coloured according to Uy clearly shows this.

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A combination of Slice, Stream Tracer and Tube filters are used tovisualise the flow.

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cavityClipped

Solver:icoFoam

Utilities used:

blockMesh

checkMesh

mapFields

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In case cavityClipped the lower right part of the cavity is removed, whichcauses a recirculation region in the flow-field. Here, a transparent Slicefilter has been combined with Stream Tracer and Glyph to capture thebehaviour of the fluid.

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damBreak

Solver:interFoam

Utilities used:

blockMesh

setFields

checkMesh

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A simple model of a dam breaking is calculated using interFoam. Theevolution of phase fraction with time is captured using Slice and Glyph.

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damBreakFine

Solver:interFoam

Utilities used:

blockMesh

setFields

checkMesh

decomposePar

reconstructPar

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Increasing the mesh resolution improves the results. e.g. artificialtransition interface between water and air becomes thinner, smallerfeatures become visible, etc.

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Below, we can see velocity vectors plotted with the phase contour in thebackground. The higher velocities in the air phase are notable.

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pitzDaily

Solver:simpleFoam

Utilities used:

blockMesh

checkMesh

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In the PitzDaily tutorial, turbulent flow over a backward facing step wascalculated using the standard k-ε model. The figure shows the velocityfield after the solution has reached steady-state.

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Variables solved for in the turbulence model can be extracted andvisualized just as easily as the physical variables. The figure shows νtwhich is used in RANS turbulence models to account for turbulentconvection in the averaged equations.

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