How many prism layers should be added in a pump simulation?

Jasmine · June 16, 2009, 16:27

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 · June 16, 2009, 19:34

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 · June 17, 2009, 17:02

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 · June 17, 2009, 17:05

Adendum

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

Best Regards,

Paulo Rocha

dileeps · April 3, 2020, 11:15

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

ghorrocks · April 3, 2020, 20:58

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.

June 16, 2009, 16:27	How many prism layers should be added in a pump simulation?	#1
Jasmine Member ^_^ Join Date: Mar 2009 Posts: 36 Rep Power: 17	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?

April 3, 2020, 20:58		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	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. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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June 16, 2009, 19:34		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	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

June 17, 2009, 17:02		#3
paulo Member Paulo Alexandre Costa Rocha Join Date: Mar 2009 Posts: 71 Rep Power: 17	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.

June 17, 2009, 17:05		#4
paulo Member Paulo Alexandre Costa Rocha Join Date: Mar 2009 Posts: 71 Rep Power: 17	Adendum It is better to use hex meshes at least in the boundary layer region. Avoid tetrahedrons there. Best Regards, Paulo Rocha

April 3, 2020, 11:15		#5
dileeps New Member Dileep S Join Date: Nov 2017 Posts: 7 Rep Power: 9	Hi, Is it the total layer thickness or first layer thickness more important?