How can we effciently mesh for these type of geometries?

arunraj · September 6, 2011, 01:51

Hi all,

I have attached a picture of a screen geometry with this ..I want to know whats the efficient way for meshing this?...Also I want to know which type of meshing (Structured grid or Unstructured grid) I need to use ..

ghorrocks · September 6, 2011, 19:01

The type of mesh which is approriate also depends on the type of model you plan to do. If this is a 1mm wide liquid stirrer you would mesh it entirely differently to a 1km across wind turbine.

arunraj · September 6, 2011, 23:06

Hi I have attached the Image of geometry which I want to analyze....Have a look at it ..It is the distrtion screen which they will keep in-front of axial compressor to produce distortion

ghorrocks · September 7, 2011, 07:51

You still have not answered the critical question - how big is the object, or what Re number does it run at?

Also, why are you modelling this rather than imposing its effect as a momentum sink term?

arunraj · September 7, 2011, 08:25

how big is the object? 40 CM OUTER DIA AND 6 CM INNER DIA, 3 CM THICK

what Re number does it run at-- velocity -- 50 m/s
reynolds n0:1235500

Also, why are you modelling this rather than imposing its effect as a momentum sink term?
I don understand this question..

The main thing why am i simulating is i need to find the exit velocity components of this geometry and have to give that as entry velocity components for full rotor geometry?.. I have created the complete rotor geometry ..but i am struck with this ..I am not able to get result for this geometry..Since we don have enough computational facility we are simulating rotor and this distortion screen separately...

arunraj · September 7, 2011, 08:38

I have meshed this geometries in Icem cfd with volume mesh option and then i have imported in cfx...When i run this case solver shows it has isolated volumes because of domain interface not properly designed... I DON KNOW WHAT AM I DOING WRONG...

Inlet boundary condition is Cartesian velocity components

u=50 m/s
v=0m/s w=om/s

Outlet boundary condition is :: static pressure :: 101667 pa

inteface as :: GGI inteface

REMAINING FACES :: WALL :: FREE SHEAR WALL

I HAVE ATTACHED THE GEOMETRY OF THE ROTOR ALSO

arunraj · September 7, 2011, 08:47

i HAVE CREATED THIS SCREEN GEOMETRY IN ICEM CFD..i HAVE CREATED IT AS A PART ...i WANT TO KNOW WHETHER I HAVE TO CREATE IT AS A PART OR AN ASSEMBLY TO AVOID THESE KIND OF ISOLATED VOLUME PROBLEMS..yOUR HELP IS MUCH NEEDED HERE..

ghorrocks · September 7, 2011, 18:56

Quote:

Since we don have enough computational facility we are simulating rotor and this distortion screen separately...

In that case forget about meshing this feature and impose its pressure drop as a momentum source term. This will be much easier and just as accurate (maybe more so). The only reason to directly model this feature is if you want the detailed flow off it, but that does not seem to be what you want.

Quote:

reynolds n0:1235500

OK, so it is high Re number, so turbulent flow with very thin boundary layers. If you wish to model this you need to do a mesh to capture this very thin boundary layer. But as I said above, I would not bother.

arunraj · September 7, 2011, 23:23

I don no how to impose its pressure drop as a momentum source term?
Could you explain in detail...

Also if I wants to know if we do like that then whether we will get the exit velocity components as a file so that it will be easier for me to give it as an input for complete rotor

ghorrocks · September 8, 2011, 07:53

Work out a function for the drag of your body versus velocity. You should be able to do by assuming it is a cylinder and using the well known cylinder drag for this Re range. Then read the documentation about source terms and impose the drag on the flow as a momentum source term.

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September 6, 2011, 19:01		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The type of mesh which is approriate also depends on the type of model you plan to do. If this is a 1mm wide liquid stirrer you would mesh it entirely differently to a 1km across wind turbine.

September 7, 2011, 07:51		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You still have not answered the critical question - how big is the object, or what Re number does it run at? Also, why are you modelling this rather than imposing its effect as a momentum sink term?

September 7, 2011, 08:25		#5
arunraj Senior Member Arun raj.S Join Date: Jul 2011 Posts: 194 Rep Power: 14	how big is the object? 40 CM OUTER DIA AND 6 CM INNER DIA, 3 CM THICK what Re number does it run at-- velocity -- 50 m/s reynolds n0:1235500 Also, why are you modelling this rather than imposing its effect as a momentum sink term? I don understand this question.. The main thing why am i simulating is i need to find the exit velocity components of this geometry and have to give that as entry velocity components for full rotor geometry?.. I have created the complete rotor geometry ..but i am struck with this ..I am not able to get result for this geometry..Since we don have enough computational facility we are simulating rotor and this distortion screen separately...

September 7, 2011, 08:47		#7
arunraj Senior Member Arun raj.S Join Date: Jul 2011 Posts: 194 Rep Power: 14	i HAVE CREATED THIS SCREEN GEOMETRY IN ICEM CFD..i HAVE CREATED IT AS A PART ...i WANT TO KNOW WHETHER I HAVE TO CREATE IT AS A PART OR AN ASSEMBLY TO AVOID THESE KIND OF ISOLATED VOLUME PROBLEMS..yOUR HELP IS MUCH NEEDED HERE..

September 7, 2011, 23:23		#9
arunraj Senior Member Arun raj.S Join Date: Jul 2011 Posts: 194 Rep Power: 14	I don no how to impose its pressure drop as a momentum source term? Could you explain in detail... Also if I wants to know if we do like that then whether we will get the exit velocity components as a file so that it will be easier for me to give it as an input for complete rotor

September 8, 2011, 07:53		#10
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Work out a function for the drag of your body versus velocity. You should be able to do by assuming it is a cylinder and using the well known cylinder drag for this Re range. Then read the documentation about source terms and impose the drag on the flow as a momentum source term.