[MNMK]

Hi Everybody,

I have 2 questions:

1.How should I write exactly an expression to calculate the heat flux on a wall in post?

For example:

Ave(Heat Flux) @ Location
Sum(Heat Flux) @ Location
AreaAvg(Heat Flux) @ Location?

2. I have simulated a model, therefore I know the Heat flux through a Wall in my model. When I want use the amount of Heat Flux (W/m2) through the mentioned Wall in the next Simulation, how can I definde for the same wall, the Heat flux amount as a Boundary condition?
my Purpose is an optimization and considering a part of my first model to prevent calculating my whole model every time.

Best regards

[Opaque]

Originally Posted by MNMK

Hi Everybody,

I have 2 questions:

1.How should I write exactly an expression to calculate the heat flux on a wall in post?

For example:

Ave(Heat Flux) @ Location
Sum(Heat Flux) @ Location
AreaAvg(Heat Flux) @ Location?

2. I have simulated a model, therefore I know the Heat flux through a Wall in my model. When I want use the amount of Heat Flux (W/m2) through the mentioned Wall in the next Simulation, how can I definde for the same wall, the Heat flux amount as a Boundary condition?
my Purpose is an optimization and considering a part of my first model to prevent calculating my whole model every time.

Best regards

Neither of them. If you want the same amount of the energy between two models, you must first compute the total heat FLOW across the boundary, i.e.

areaInt(Heat Flux)@Location.

Then, if you want to assume uniform heat flux for that total amount in your next model, you do

MyNewHeatFlux = areaInt(Heat Flux)@Location / area()@Location

The closest of the 3 proposed formulas is the last one, but using the proper syntax areaAve instead of areaAvg

areaAve( Variable )@Location = areaInt( Variable )@Location / area()@Location

Hope the above helps,

[MNMK]

Originally Posted by Opaque

Neither of them. If you want the same amount of the energy between two models, you must first compute the total heat FLOW across the boundary, i.e.

areaInt(Heat Flux)@Location.

Then, if you want to assume uniform heat flux for that total amount in your next model, you do

MyNewHeatFlux = areaInt(Heat Flux)@Location / area()@Location

The closest of the 3 proposed formulas is the last one, but using the proper syntax areaAve instead of areaAvg

areaAve( Variable )@Location = areaInt( Variable )@Location / area()@Location

Hope the above helps,

I appreciate your answer.

I have calculated the Heat Flux (W/m2)from the first result in Post through the Expression Areave( Heat Flux) @ Location. The new Problem is my new calculation after the first iteration will be diverged. and I got the Error attached.

Wishes

[Opaque]

You got a value for the new simulation, but you did not say how much that value was, and most importantly, its sign.

[ghorrocks]

This FAQ is the starting point for the convergence problem: https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F

[MNMK]

Originally Posted by Opaque

You got a value for the new simulation, but you did not say how much that value was, and most importantly, its sign.

Hi again,

The amount of Heat flux is -22000 (W/m2). It means I lose from the Wall 22000 W/m2. I defined this amount(-22000) in my new simulation as a boundary condition for this wall.

I hope I could answer your question.