DeltaT dependency of solution in chtMultiRegionSimpleFoam

aat74 · August 18, 2020, 09:29

Hello Everybody,

I've a case: a room filled with air, adiabatic round & bottom walls and free atmosphere on top (p_rgh as totalPressure and U as pressureInletOutletVelocity). in the middle of the room is a solid that represents a constant heat source(fvoption asscalarSemiImplicitSource).

Ignoring the cooling with convection the solid temperature should rise up 6 degree celsius in 1 sec (1 unit of time).

When I run chtMultiRegionsSimpleFoam for 1 time unit with different DeltaT I get different temperature for solid. I tries from 0.5-0.001.

The smaller is the time step the higher is the end Temperature after 1 time unit, and it differs very much.

I doub't that I have problem with interpretation of entTime and deltaT.
do they have absolute meanings(like 1 means 1 sec and 0.001 means 1 msec) or they are relative(endTime is interpreted according to DeltaT).

Thank you in advance for your advice(s).

All the best

Amirali

wanghongjie · August 18, 2020, 14:15

I initially coupled cht and interPhaseChangeFoam together, but there are problems that I can't solve. Please help me to see if there is a solution. I have declared these parameters in createFluidFields.H, but after compilation, it shows that these parameters in setRegionFluidFields.H are not declared. I am not very clear about that. Thanks!

./fluid/setRegionFluidFields.H:15:25: error: ‘UFluid’ was not declared in this scope 15 | volVectorField& U = UFluid[i]; | ^~~~~~ ./fluid/setRegionFluidFields.H:16:31: error: ‘phiFluid’ was not declared in this scope 16 | surfaceScalarField& phi = phiFluid[i]; | ^~~~~~~~ ./fluid/setRegionFluidFields.H:17:27: error: ‘rhoFluid’ was not declared in this scope 17 | volScalarField& rho = rhoFluid[i]; | ^~~~~~~~ ./fluid/setRegionFluidFields.H:18:36: error: ‘interfaceFluid’ was not declared in this scope; did you mean ‘interface’? 18 | interfaceProperties& interface=interfaceFluid[i]; | ^~~~~~~~~~~~~~ | interface ./fluid/setRegionFluidFields.H:19:32: error: ‘rhoPhiFluid’ was not declared in this scope 19 | surfaceScalarField& rhoPhi=rhoPhiFluid[i];
and others
(I am very sorry that I can not upload pictures to the web page, which will cause reading inconvenience. I can only paste part of the wrong text.)

August 18, 2020, 09:29	DeltaT dependency of solution in chtMultiRegionSimpleFoam	#1
aat74 New Member Join Date: Aug 2020 Posts: 1 Rep Power: 0	Hello Everybody, I've a case: a room filled with air, adiabatic round & bottom walls and free atmosphere on top (p_rgh as totalPressure and U as pressureInletOutletVelocity). in the middle of the room is a solid that represents a constant heat source(fvoption asscalarSemiImplicitSource). Ignoring the cooling with convection the solid temperature should rise up 6 degree celsius in 1 sec (1 unit of time). When I run chtMultiRegionsSimpleFoam for 1 time unit with different DeltaT I get different temperature for solid. I tries from 0.5-0.001. The smaller is the time step the higher is the end Temperature after 1 time unit, and it differs very much. I doub't that I have problem with interpretation of entTime and deltaT. do they have absolute meanings(like 1 means 1 sec and 0.001 means 1 msec) or they are relative(endTime is interpreted according to DeltaT). Thank you in advance for your advice(s). All the best Amirali

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August 18, 2020, 14:15		#2
wanghongjie New Member wanghongjie Join Date: Apr 2020 Posts: 28 Rep Power: 6	I initially coupled cht and interPhaseChangeFoam together, but there are problems that I can't solve. Please help me to see if there is a solution. I have declared these parameters in createFluidFields.H, but after compilation, it shows that these parameters in setRegionFluidFields.H are not declared. I am not very clear about that. Thanks! ./fluid/setRegionFluidFields.H:15:25: error: ‘UFluid’ was not declared in this scope 15 \| volVectorField& U = UFluid[i]; \| ^~~~~~ ./fluid/setRegionFluidFields.H:16:31: error: ‘phiFluid’ was not declared in this scope 16 \| surfaceScalarField& phi = phiFluid[i]; \| ^~~~~~~~ ./fluid/setRegionFluidFields.H:17:27: error: ‘rhoFluid’ was not declared in this scope 17 \| volScalarField& rho = rhoFluid[i]; \| ^~~~~~~~ ./fluid/setRegionFluidFields.H:18:36: error: ‘interfaceFluid’ was not declared in this scope; did you mean ‘interface’? 18 \| interfaceProperties& interface=interfaceFluid[i]; \| ^~~~~~~~~~~~~~ \| interface ./fluid/setRegionFluidFields.H:19:32: error: ‘rhoPhiFluid’ was not declared in this scope 19 \| surfaceScalarField& rhoPhi=rhoPhiFluid[i]; and others (I am very sorry that I can not upload pictures to the web page, which will cause reading inconvenience. I can only paste part of the wrong text.)