I am currently trying to simulate airflow around an airfoil with high angle of attack. Since the residuals and coefficients did not converge for a steady-state simulation, I’m currently trying to do a transient simulation.
However, its taking extremely long, even when I increased the timestep. I’m also worried about it consuming too much core hours. Is this normal for a transient simulation, or is there a way to reduce the computing time by adjusting the settings?
It’s common that transient studies take longer to run and therefore consume a lot of core hours. They are not trivial and you need to achieve a high mesh quality/uniformity + a good balance between timestep size and simulation efficiency. These 2 resources should be very helpful:
One quick tip to consume less core hours however is to reduce the number of processors your simulation is running on. A good approach is to use 1 core per 500k cells so that the machine does not run out of memory (e.g. if you have 2M cells, 2M/500k = 4 processing cores).
Yes, it’s fairly typical. If you reduce the number of cores manually as I’ve mentioned above, you should see a reduction in the amount of core hours you’d consume.
Keep in mind a velocity of 84m/s is on the verge of the Incompressible solver’s capability and you’d need a very small timestep to compensate it so that the Courant number is controlled (see resource I’ve sent above). In your case, since the Maximal courant number is set to 0.7, assuming a maximum speed of 84m/s and I’ve measured the smallest element to have an edge lenght of ~0.002m:
\displaystyle C = u\frac{\Delta t}{\Delta x} \tag{1}