# time varying velocity outlet boundary condition

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 September 11, 2014, 16:11 time varying velocity outlet boundary condition #1 New Member   simin Join Date: Apr 2012 Posts: 13 Rep Power: 7 Dear all, I am simulating flow inside the pipe considering time varying decrease of outlet velocity. for decreasing outlet velocity by time I used the groovy BC boundary condition for velocity as follows: velocity:::: boundaryField { inlet { type zeroGradient; } outlet { type groovyBC; variables "U0=0.13;T1=3754;Uout=U0*(1-pow((time()/T1),3));"; valueExpression "(time() FOAM Warning : From function groovyBCFvPatchField::groovyBCFvPatchField(c onst fvPatch& p,const DimensionedField& iF,const dictionary& dict) in file groovyBCFvPatchField.C at line 131 No value defined for U on outlet therefore using 30{(0 0 0)} I think it means that the groovy BC is not defined for outlet condition. But as I have to reduce the outlet velocity by time could any one help me for finding a proper boundary condition. Many thanks for the help, Simin

 September 12, 2014, 01:42 #2 New Member   simin Join Date: Apr 2012 Posts: 13 Rep Power: 7 any idea????

 September 12, 2014, 02:09 #3 Senior Member   Mohammad Shakil Ahmmed Join Date: Oct 2012 Location: AUS Posts: 132 Rep Power: 7 Hi, From the error message, "No value defined for U on outlet therefore using 30{(0 0 0)}". So, you haven't defined any value,i.e. initial, at the boundary and it's taking some default value. What you can do is that, outlet { type groovyBC; variables "U0=0.13;T1=3754;Uout=U0*(1-pow((time()/T1),3));"; valueExpression "(time()

 September 12, 2014, 02:13 #4 New Member   simin Join Date: Apr 2012 Posts: 13 Rep Power: 7 Hi Ahmmed, Many thanks for your help

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