MRF query
 

I have one basic doubt for rotating flows. let's say I have to doflow analysis of a turbine. I will be having one stationary domain (stator) and one rotating domain(rotor). I am using MRF Suppose my rotor is rotating at 50000 rpm. Then am I required to apply rotation to walls of blade . My doubt is whether blade walls remain stationary or not? Is it stationary wrt rotating region? So, I can do two things. (1) Apply 0 rpm in relative frame. (2) Apply 50000 rpm in absolute frame. Which one is right?

Kindly let me know the answer.

Re: MRF query
 

Specify fluid domain as MRF. Leave all rotating walls as stationary relative to this rotating fluid domain. Moving walls only does not account for body forces though in many cases differences can be small. Also changing speed is much easier using 0 relative as only one bc needs changing for the fluid zone. However either approach will be correct whether 0 relative or 5000rpm absolute just as long as the fluid is still an MRF zone.

Re: MRF query
 

Hi, you can refer to the centrifugal blower tutorial in the Fluent tutorial manual. You can set the blades as 0 RPM relative or 5000 RPM abs.

Re: MRF query
 

The advantage of using relative is that you dont need to chanage the setting with the change in the rotational speed but in absolute you will need to change for every rotational speed. Hope that make it easier for you and have a good day