# simpleFoam: switching flow direction with kOmegaSST RAS Model

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 September 2, 2014, 15:25 simpleFoam: switching flow direction with kOmegaSST RAS Model #1 Member   Jason G. Join Date: Sep 2009 Location: St. Louis, IL Posts: 89 Rep Power: 16 I have been looking at pressure drops for internally bounded, steady-state, incompressible fluid flow cases with the simpleFoam solver. Typically, I specify a velocity at the entrance to the fluid domain and a reference pressure of 0 at the exit of the fluid domain. A new case I am working on requires me to specify a velocity at the exit and a reference pressure at the entrance. I have been able to successfully do this with laminar assumptions, but as soon as I attempt to switch to the kOmegaSST turbulence solver I run into convergence issues. It appears the kinetic turbulence values become discontinuous near the entrance. Any help and/or recommendations are greatly appreciated. Below are the current BC's I am implementing: "intialConditions" Code: ```flowVelocity (0 0 165.760612715333); pressure 0; turbulentKE 194.091657099187; turbulentOmega 1731.03910939215; kinematicvis nu [ 0 2 -1 0 0 0 0 ] 0.0398447454916618; // in^2/s density 0.00007839; // Value of the density(sslug/in^3) pstatic = lbf/in^2 //RAS PROPERTIES RAS_MODEL kOmegaSST; //kOmegaSST; //laminar; turb_on_off on; //on #inputMode merge``` "p" Code: ```#include "initialConditions" dimensions [0 2 -2 0 0 0 0]; internalField uniform \$pressure; boundaryField { outlet_1 { type inletOutlet; inletValue \$internalField; value \$internalField; } inlet_1 { type fixedValue; value \$internalField; } boundary { type zeroGradient; } symmetry { type symmetryPlane; } }``` "u" Code: ```#include "initialConditions" dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { outlet_1 { type outletInlet; outletValue \$flowVelocity; value \$flowVelocity; } inlet_1 { type outletInlet; outletValue \$internalField; value \$internalField; } boundary { type fixedValue; value \$internalField; } symmetry { type symmetryPlane; } }``` "k" Code: ```#include "initialConditions" dimensions [0 2 -2 0 0 0 0]; internalField uniform \$turbulentKE; boundaryField { outlet_1 { type fixedValue; value \$internalField; } inlet_1 { type outletInlet; outletValue \$internalField; value \$internalField; } boundary { type kqRWallFunction; value \$internalField; } symmetry { type symmetryPlane; } }``` "nut" Code: ```dimensions [0 2 -1 0 0 0 0]; internalField uniform 0; boundaryField { inlet_1 { type calculated; value uniform 0; } outlet_1 { type calculated; value uniform 0; } boundary { type nutLowReWallFunction; value uniform 0; } symmetry { type symmetryPlane; } }``` "omega" Code: ``` #include "initialConditions" dimensions [0 0 -1 0 0 0 0]; internalField uniform \$turbulentOmega; boundaryField { outlet_1 { type fixedValue; value \$internalField; } inlet_1 { type outletInlet; outletValue \$internalField; value \$internalField; } boundary { type omegaWallFunction; value \$internalField; } symmetry { type symmetryPlane; } }```

 September 25, 2014, 07:26 #2 Senior Member   Joachim Herb Join Date: Sep 2010 Posts: 650 Rep Power: 21 You might try the fixedMean boundary condition for the velocity, k and omega at the outlet (assuming the the specified flow is going "outwards"). Then you do not enforce a constant value over the whole outlet but just the (area averaged) mean for the three quantities. So the turbulent block profile within your flow domain is not destroyed at the outlet.