[dennis.olivetree]

We are currently validating our simulation method, which uses the radiation model Surface-to-Surface, and we are looking at the wall radiative heat flux results.

Our simple 2D configuration represents an enclosure containing air and consisting of two parallel plates - a hot (Tc = 309.15 K) and a cold one (Tc = 293.15 K) - and two adiabatic sidewalls [please refer to the following Figure].



A structured mesh was used (10x10,000 = 100,000 elements) and view factors have been calculated using Resolution = 100 (Ray Tracing method) and 1 face per Surface Cluster (i.e., no clustering). Additionally, values for Energy Iterations per Radiation Iteration, Maximum Number of Radiation Iterations and Residual Convergence Criteria (for both radiosity and energy) were set to 1, 20 and 1e-6, respectively. Solution normally converged after 9 radiosity iterations.

Results for Wall Radiative Heat Flux along the hot wall (x-direction) are plotted in the following Figure.



Although the mean value of these data points is in good agreement with the theoretical value of 19.403 W.m-2, it is still noticeable an asymmetric oscillation around the mean value. Furthermore, this oscillation actually increases for denser grids.

We would therefore be thankful if you would please give us your hypothesis on what could be the cause of such odd oscillatory behaviour.

Thank you very much for your attention.

Cheers,
Dennis Olivetree

[sarathnjan007]

Originally Posted by dennis.olivetree

We are currently validating our simulation method, which uses the radiation model Surface-to-Surface, and we are looking at the wall radiative heat flux results.

Our simple 2D configuration represents an enclosure containing air and consisting of two parallel plates - a hot (Tc = 309.15 K) and a cold one (Tc = 293.15 K) - and two adiabatic sidewalls [please refer to the following Figure].



A structured mesh was used (10x10,000 = 100,000 elements) and view factors have been calculated using Resolution = 100 (Ray Tracing method) and 1 face per Surface Cluster (i.e., no clustering). Additionally, values for Energy Iterations per Radiation Iteration, Maximum Number of Radiation Iterations and Residual Convergence Criteria (for both radiosity and energy) were set to 1, 20 and 1e-6, respectively. Solution normally converged after 9 radiosity iterations.

Results for Wall Radiative Heat Flux along the hot wall (x-direction) are plotted in the following Figure.



Although the mean value of these data points is in good agreement with the theoretical value of 19.403 W.m-2, it is still noticeable an asymmetric oscillation around the mean value. Furthermore, this oscillation actually increases for denser grids.

We would therefore be thankful if you would please give us your hypothesis on what could be the cause of such odd oscillatory behaviour.

Thank you very much for your attention.

Cheers,
Dennis Olivetree

sir I am facing the same problem. Did you solve the issue??

[dennis.olivetree]

The problem only seems to happen on CFD-Post. No "noise" when exporting directly from Fluent.

Hoping this hint will help you,

Kind regards,
Dennis

[sarathnjan007]

Originally Posted by dennis.olivetree

The problem only seems to happen on CFD-Post. No "noise" when exporting directly from Fluent.

Hoping this hint will help you,

Kind regards,
Dennis

sorry. What do you mean by exporting