Learning Forum

[csZY]

 

Hello,

In the transient calculation of moving grid, only the continuity does not converge in the middle of one time step, but the continuity converges immediately after the maximum number of iterations is calculated. Will this have any impact on the final calculation result?

Thanks.

 

 

[SRP]

Hi,

The continuity equation represents mass conservation and is a crucial equation in fluid dynamics simulations. When it fails to converge within a time step, it indicates that there is a violation of mass conservation, suggesting that the flow field is not accurately represented. This can lead to errors in the predicted flow patterns, pressures, velocities, and other flow properties.

[csZY]

Thank you sir. My calculation uses dynamic mesh method. Only the middle time step does not converge, but the other time steps converge.How should I modify my model.

Thanks.

 

[SRP]

 

Hi,

You can consider reducing the time step size. A smaller time step can help improve stability and convergence.  Ensure that the mesh quality is good throughout the simulation, especially in the regions where the dynamic mesh is deforming. Adjust parameters such as smoothing factors, remeshing criteria.

 

[csZY]

Thank you ,sir. What's the meaning of Maxium length scale? It means the scale of rigid body?Maxium cell Skewness? I hope my computation could be steady how should I modify Maxium length scale and  Maxium cell Skewness?

Thanks

[SRP]

Hi,

A good starting point for the length scales are 0.4Lmin, 1.4Lmax, where Lmin and Lmax are the maximum and minimum length scale whose details you can find in mesh scale info.

You can check fluent user's manual: 11.6. Using Dynamic Meshes (ansys.com)

Thank you.

[csZY]

I’ll try.Thank you, sir