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October 14, 2015, 03:51 |
Temperature BC - Constant heat flux
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#1 |
Member
Join Date: May 2015
Posts: 68
Rep Power: 10 |
Hi all,
I have some problems deciding which boundary condition to use to assign a constant heat flux to a wall in my specific problem. My geometry is a backward facing step (simulating generic ideal fluid flowing inside, incompressible, steady state), after the step I want to assign the given heat flux to the wall. I use turbulence modelling. Solver: buoyantBoussinesqSimpleFoam I can't use a fixedGradient-BC since the thermal conductivity of the wall is unknown and more important I need to calculate the gradient in the fluid not in the wall, right? So I found three avaiable options for doing this: 1) turbluentHeatFluxTemperature https://github.com/OpenFOAM/OpenFOAM...luxTemperature But it asks for alphaeff, and I am not sure what this parameter means? If alhaeff is a thermal diffusivity, as stated at some point, the dimension [kg/m/s] does not match. In the .C code I found : gradient() = q_/(Cp0*alphaEffp); Does that mean temperature gradient= sp heat flux/(thermal capacity*effective thermal diff coeff) ? 2) externalWallHeatFluxTemperature https://github.com/OpenFOAM/OpenFOAM...luxTemperature From the code I guess it use the conductivity to calculate the T-gradient which is not suitable for this case: this->refGrad()[i] = q[i]/KWall[i] 3) Using groovyBC http://www.cfd-online.com/Forums/ope...acianfoam.html Using type groovyBC; variables "htot=100.0;Tinf=298.15;rho=2700.0;cp=900.0;k=DT*r ho*cp;"; valueExpression "Tinf"; fractionExpression "1.0/(1.0 + k/(mag(delta())*htot))"; Which I do not really understand at all. Every help or advise is appreciated! If you need further information to give a good answer, do not hesitate to ask! Best |
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October 14, 2015, 04:16 |
More questions :D
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#2 |
Member
Join Date: May 2015
Posts: 68
Rep Power: 10 |
Is it also possible to sample the calculated heat transfer coefficient h?
I want to calculate the Stanton number using h. St(x) = h(x) / (uref*rhoinf*cpinf) |
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January 14, 2019, 03:26 |
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#3 |
Senior Member
Jianrui Zeng
Join Date: May 2018
Location: China
Posts: 157
Rep Power: 7 |
I am also intereted in these BCs, Have you found some ideas? Which one is more suitable? Thank you.
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