beginner to cfd

saba.irsh1 · May 21, 2015, 23:00

hi
i am a beginner to CFd and i have to do unstrutcured meshing for an aircrafts scaled down geometry. the problems i am facing are
1- i dont know how to scale down a geometry?
2- with what refrence should i set my domain should it be rectangular r circle?
3- what should be the size of domain?
can anybody please help

fresty · May 22, 2015, 02:21

Hi,

Which software do you plan to employ for the analysis?
Not sure about the problems you are facing in scaling down the geometry... if the geometric proportions are kept consistent while scaling down.. the dimensionless aerodynamic coefficients would remain the same.. so it would, in my opinion, would be a simple CAD scale down.
I would use a rectangular section (with 10 x Avg. chord length ahead and behind the wing) for mesh simplicity (even if it is unstructured), but again it also depends on the software you plan to use.
Lastly, you may want to use symmetric model to reduce computational power & time which could be post-processed for aesthetics later on.
Hope this answers your questions.

saba.irsh1 · May 22, 2015, 03:07

i am using icem cfd software for the analysis
actually my geometry is 1/20 scaled down and i intend to scale it up
and i have started off with a circular domain do you consider it inappropriate? and what is the reason to use a rectangular domain than a circular one?
i am not using the symmetric model i have issues regarding cutting it symmetrically

fresty · May 22, 2015, 03:19

There is no specific reason except the fact that rectangular region is easier to mesh if done manually and probably lower tendency for orthogonality issues. If you're ok with circular region then that should not be a problem. Give this thread a read...i presume it is almost a similar case that you're trying to simulate..

http://www.cfd-online.com/Forums/ans...icem-hexa.html

It has a lot to do with orientation of components in the model and the best suited domain shape per application & model but again not something definitive.

If your issues are related to CAD/ geometric modelling software then you may consider spending some time on it and getting it done rather than expending massive computation in analysis..

KateEisenhower · May 29, 2015, 16:37

Quote:

Originally Posted by saba.irsh1

hi
i am a beginner to CFd and i have to do unstrutcured meshing for an aircrafts scaled down geometry. the problems i am facing are
1- i dont know how to scale down a geometry?
2- with what refrence should i set my domain should it be rectangular r circle?
3- what should be the size of domain?
can anybody please help

Hi saba,

Just out of curiosity, what is the purpose of scaling down your geometry?

Thanks in advance,

Kate

May 21, 2015, 23:00	beginner to cfd	#1
saba.irsh1 New Member saba khan Join Date: May 2015 Posts: 3 Rep Power: 10	hi i am a beginner to CFd and i have to do unstrutcured meshing for an aircrafts scaled down geometry. the problems i am facing are 1- i dont know how to scale down a geometry? 2- with what refrence should i set my domain should it be rectangular r circle? 3- what should be the size of domain? can anybody please help

May 22, 2015, 03:07	beginner to cfd	#3
saba.irsh1 New Member saba khan Join Date: May 2015 Posts: 3 Rep Power: 10	i am using icem cfd software for the analysis actually my geometry is 1/20 scaled down and i intend to scale it up and i have started off with a circular domain do you consider it inappropriate? and what is the reason to use a rectangular domain than a circular one? i am not using the symmetric model i have issues regarding cutting it symmetrically

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
CFD Online Celebrates 20 Years Online	jola	Site News & Announcements	22	January 31, 2015 00:30
CFD Code + partner required + beginner	amol palekar	Main CFD Forum	1	July 18, 2004 15:32
Where do we go from here? CFD in 2001	John C. Chien	Main CFD Forum	36	January 24, 2001 21:10
ASME CFD Symposium, Atlanta, July 2001	Chris R. Kleijn	Main CFD Forum	0	August 21, 2000 04:49
Which is better to develop in-house CFD code or to buy a available CFD package.	Tareq Al-shaalan	Main CFD Forum	10	June 12, 1999 23:27

May 22, 2015, 02:21		#2
fresty Senior Member Join Date: Aug 2014 Location: UK Posts: 213 Rep Power: 12	Hi, Which software do you plan to employ for the analysis? Not sure about the problems you are facing in scaling down the geometry... if the geometric proportions are kept consistent while scaling down.. the dimensionless aerodynamic coefficients would remain the same.. so it would, in my opinion, would be a simple CAD scale down. I would use a rectangular section (with 10 x Avg. chord length ahead and behind the wing) for mesh simplicity (even if it is unstructured), but again it also depends on the software you plan to use. Lastly, you may want to use symmetric model to reduce computational power & time which could be post-processed for aesthetics later on. Hope this answers your questions.

May 22, 2015, 03:19		#4
fresty Senior Member Join Date: Aug 2014 Location: UK Posts: 213 Rep Power: 12	There is no specific reason except the fact that rectangular region is easier to mesh if done manually and probably lower tendency for orthogonality issues. If you're ok with circular region then that should not be a problem. Give this thread a read...i presume it is almost a similar case that you're trying to simulate.. http://www.cfd-online.com/Forums/ans...icem-hexa.html It has a lot to do with orientation of components in the model and the best suited domain shape per application & model but again not something definitive. If your issues are related to CAD/ geometric modelling software then you may consider spending some time on it and getting it done rather than expending massive computation in analysis..