[Vijay_01]

Hello! This is my first thread in CFD Online. I'm working on the design of a pressure-fed LO2 and LNG rocket engine. I've been using Fluent to estimate the heat flux for an ablative-cooled engine. I was able to solve all the compilation errors for my UDF.

I'm attaching my boundary conditions and mesh. My model is axisymmetric and I have a fluid-solid domain in my problem, so all my methods are second order. But I keep getting this error whenever I run my calculations.

"Divergence detected in AMG solver. temporarily reducing Courant number to 0.5 and trying again..."

Is there a problem with my mesh? I've used a multi-zone and face mesh with 15 inflation layers.

I've tried all the methods I know to simplify the problem. I still keep getting the same error.

[hasnaaoub]

I am doing a CFD study on an electric car.
Currently, I am in the setup phase. I tried to integrate solar radiation using a function in the "User Defined" interface with C code. I tried to use the "Interpreted" extension, but I still encounter an error. When I try to use the "Compiled" extension, another error occurs.

Can you send me an example of a udf function that you have already used in your studies and that can be used in ansys?

Thank you in advance for your help.

[Vijay_01]

Heat flux estimation for a liquid rocket engine - UDF
Check this out.
Can you add some images of the error that you face?

[hasnaaoub]

thank you for your response. here there is the picture of error.

[Martin_Sz]

The "Divergence detected in AMG solver" error in ANSYS Fluent indicates that the Algebraic Multigrid (AMG) solver is struggling to converge. This can arise from several factors, including:
* Mesh quality: Ensure your mesh is well-defined, with good aspect ratios and minimal skewness. Consider refining the mesh, particularly in areas with high gradients or complex geometry.
* Under-relaxation factors (URFs): URFs control the rate at which solution values are updated between iterations. Excessive URFs can lead to divergence. Try reducing the URFs, especially for the temperature equation.
* Boundary conditions: Double-check that your boundary conditions are defined correctly and consistent with the physics of your problem. Inaccurate boundary conditions can lead to the solver struggling to find a solution.
* Solver settings: Experiment with different AMG solver settings, such as the coarsening scheme or relaxation method. You might also consider switching to a different solver, such as SIMPLE or PISO.
If you've already tried simplifying the problem and the error persists, consider sharing your mesh and boundary condition details on the CFD Online forum for more specific guidance from experienced users.

[hasnaaoub]

hi Martin, sorry but i didn't understand what did you meant. we are in the setup stage, not the solution stage. and I want to integrate the udf equation of solar radiation written in C language?? can you explain more plz