[Jasmine]

How much influence will the number of cells inside Boudary layers influence the final flow field inside a centrifugal pump. usually how many layers should be used? Is 5 enough?

[ghorrocks]

Hi,

This is problem dependant. Some designs will require more, some will require less. Also it will depend on the level of accuracy you want in the simulation - is an error of 30% acceptable? Then don't bother about inflation layers at all. Do you need 5% error - then you will need accurate boundary layer modelling.

You will have to figure it out for your design and for the level of accuracy you want. The documentation has some good guides as to general principles but you have to adapt it to your circumstance.

Glenn Horrocks

[paulo]

Hi,

Just to be more precise, under my experience.

You have to run your problem until convergence, and evaluate the y+ over the wing.

It must be at least less than 100, if your problem is incompressible.

If it is more than 100, you will have to put more layers in a way that the domain gets more refined.

Best Regards,

Paulo Rocha.

[paulo]

Adendum

It is better to use hex meshes at least in the boundary layer region. Avoid tetrahedrons there.

Best Regards,

Paulo Rocha

[dileeps]

Hi, Is it the total layer thickness or first layer thickness more
important?

[ghorrocks]

They are both important. You need the first layer fine enough that you are using a suitable y+, and you need enough total thickness to cover the entire high gradient region in the boundary layer. Both need to be acceptable for the simulated boundary layer to be accurate.