Difference between MRF and RBM

Clerk · January 11, 2012, 05:06

Hi Everyone, I am new to Star CCM+, What is the difference between moving reference frame and rigid body motion. Except the difference like moving mesh in RBM(unsteady), stationary in MRF(steady).May i know what are all the other difference.

Ladnam · January 12, 2012, 16:16

I will give this a try.
In MRF the different bodies are fixed in position but the fluid feels the forces as if the bodies were moving. This will often be good enough for axisymmetric geometry.

sail · January 12, 2012, 16:56

in rigid body motion the reference system stays still, and the domain/flow/mesh is moving.

in mrf, as the name suggest, the entire system is moving. because this method is less computationally expensive than the rbm, it is successfully used in, for example, rotating parts, turbiles, isolated propeller analysis (in case of a rotation)

saleh alsubari · August 12, 2012, 22:45

Quote:

Originally Posted by sail

in rigid body motion the reference system stays still, and the domain/flow/mesh is moving.

in mrf, as the name suggest, the entire system is moving. because this method is less computationally expensive than the rbm, it is successfully used in, for example, rotating parts, turbiles, isolated propeller analysis (in case of a rotation)

hi ...
do u know how to use reference frame in turbine analysis
need to know ,the turbine RPM given the mas flow rate as input

thanx

sail · August 21, 2012, 22:39

Quote:

Originally Posted by saleh alsubari

hi ...
do u know how to use reference frame in turbine analysis
need to know ,the turbine RPM given the mas flow rate as input

thanx

sorry to disappoint you, but I belive that to get the rpm you'll need to use the RBM tecnique

saleh alsubari · August 21, 2012, 22:45

Quote:

Originally Posted by sail

sorry to disappoint you, but I belive that to get the rpm you'll need to use the RBM tecnique

thanx for replying ...
can u plz elaborate ,about RBM techinqes cuz i have not used that one so far...
thanx a gain

abdul099 · August 28, 2012, 19:49

Quote:

Originally Posted by sail

sorry to disappoint you, but I belive that to get the rpm you'll need to use the RBM tecnique

I'm sorry I have to disagree. It's just a matter of accuracy and computing time whether to use RBM or MRF. You'll get a (less acurate) result using MRF, but it might still be better than a bad RBM result.

January 11, 2012, 05:06	Difference between MRF and RBM	#1
Clerk New Member Clerk Join Date: Jan 2012 Posts: 1 Rep Power: 0	Hi Everyone, I am new to Star CCM+, What is the difference between moving reference frame and rigid body motion. Except the difference like moving mesh in RBM(unsteady), stationary in MRF(steady).May i know what are all the other difference.

January 12, 2012, 16:56		#3
sail Senior Member Vieri Abolaffio Join Date: Jul 2010 Location: Always on the move. Posts: 308 Rep Power: 16	in rigid body motion the reference system stays still, and the domain/flow/mesh is moving. in mrf, as the name suggest, the entire system is moving. because this method is less computationally expensive than the rbm, it is successfully used in, for example, rotating parts, turbiles, isolated propeller analysis (in case of a rotation) saleh alsubari and ank86it like this. __________________ http://www.leadingedge.it/ Naval architecture and CFD consultancy

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January 12, 2012, 16:16		#2
Ladnam Member Join Date: May 2010 Posts: 40 Rep Power: 15	I will give this a try. In MRF the different bodies are fixed in position but the fluid feels the forces as if the bodies were moving. This will often be good enough for axisymmetric geometry.