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velocity cyclic BC-groovyBC

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Old   February 17, 2012, 11:51
Default velocity cyclic BC-groovyBC
  #1
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Jian Zhong
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Hi,

1 How to set a fixedvalue of velocity to the cyclic BC?
2 But the pressure is not cyclic, how to set a fixedgradient of pressure?

--> FOAM FATAL IO ERROR:
inconsistent patch and patchField types for

I want to set the following fixedvalue using groovyBC. How to do that?

inlet
{
type cyclic;
type groovyBC;
//type fixedValue
// log-law expression
uniform (0 0 0);
variables "u_f=0.23;z0=0.9;z_f=pos().z-10;vel=u_f*log(z_f/z0);";
valueExpression "vector (vel,0,0)";
}

outlet
{
type cyclic;
type groovyBC;
//type fixedValue
// log-law expression
uniform (0 0 0);
variables "u_f=0.23;z0=0.9;z_f=pos().z-10;vel=u_f*log(z_f/z0);";
valueExpression "vector (vel,0,0)";
}
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Old   February 18, 2012, 08:47
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Nima Sam
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i think its impossible, you should write your BC, with existing BC you can not!
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Old   February 18, 2012, 11:12
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Jian Zhong
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But I have installed the groovyBC. You mean I should write another BC? I donot know how to do that.

1 How to set a fixedvalue of velocity to the cyclic BC (inlet and outlet)?
2 But the pressure is not cyclic, how to set a fixedgradient of pressure?
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Old   February 18, 2012, 12:48
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Nima Sam
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i think you should write new BC
however try this, may be it works
1) use funkySetFields and define your velocity function in whole domain at time 0
2) uses a fan boundary condition with one constant ( constant value is the fixed pressure gradient * pipe length)
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Old   February 19, 2012, 19:40
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Bernhard Gschaider
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Quote:
Originally Posted by zxj160 View Post
Hi,

1 How to set a fixedvalue of velocity to the cyclic BC?
2 But the pressure is not cyclic, how to set a fixedgradient of pressure?

--> FOAM FATAL IO ERROR:
inconsistent patch and patchField types for

I want to set the following fixedvalue using groovyBC. How to do that?

inlet
{
type cyclic;
type groovyBC;
//type fixedValue
// log-law expression
uniform (0 0 0);
variables "u_f=0.23;z0=0.9;z_f=pos().z-10;vel=u_f*log(z_f/z0);";
valueExpression "vector (vel,0,0)";
}

outlet
{
type cyclic;
type groovyBC;
//type fixedValue
// log-law expression
uniform (0 0 0);
variables "u_f=0.23;z0=0.9;z_f=pos().z-10;vel=u_f*log(z_f/z0);";
valueExpression "vector (vel,0,0)";
}
Basically the problem is that a patch defined in the mesh as cyclic will accept no other boundary type than cyclic for fields (no groovyBC, no fixedValue, no ...).
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Old   July 2, 2012, 11:30
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Jian Zhong
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Quote:
Originally Posted by gschaider View Post
Basically the problem is that a patch defined in the mesh as cyclic will accept no other boundary type than cyclic for fields (no groovyBC, no fixedValue, no ...).
Hi gschaider,

Could you give me some idea of how to set fixedValue and zeroGradient for cyclic inlet and outlet patches respectively? Is it possible to achieve that?

Best regards,
Jian
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