Mesh Quality
Hi,
What are the parameters used to test the mesh quality: I know a few such as aspect ration, expansion ratio, orthogonality angle. There is also this parameter CGI, kindly explain it. Add any other parameters that are important when reporting a mesh. Thank you Regards Hamed 
topic about mesh quality is discussed multiple time in this forum try searching the forum i'm sure you will find a lot.
Don't know much about cgi parameters, hope someone else can explain it. 
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There is very nice explanation of these parameters by Simon on this forum, search is the key;) 
I think its GCI not CGI ;)

The Help documentation should also include something for each metric, but I am not sure what metric you are asking about (GCI or CGI, I don't know of either). What tool are you looking in?

Hi,
It is the grid convergence index GCI. It is a factor to estimate discretization error based on Richardson extrapolation principle 
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Hi,
thnx for reply. I have another question. We place the 1st node from the wall based on y+ value and the formula 1st node distance is delta y = sqrt(74)*Re^(13/14)*L*y+*L The value of y+ in above formula depends on the turbulence model used. My question is: Once 1st node distance is specified using above formula, what are the parameters that govern the selection of expansion ratio applied to the mesh. I mean what should the increasing gap of node be starting from the 1st node 
Usually a ratio of 1.2 is used. But you could go higher or lower if you want the total height of your boundary layer to be less or greater.
The point is just to have enough mesh discretization to capture the boundary layer profile. That profile is changing faster near the wall and reduces as you move away. The ratio is just to reduce the number of nodes so you are not using the same resolution to capture less change. 
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1. Use expansion ratio 1.2 at max and for transition critical flows lower values to 1.15 or 1.1 2. For fully turbulent flows you can use the Y+ upto 10, in that case you will have the 1015 nodes in the whole boundary layer. You can find the boundary layer total thickness from the turbulent flat plate boundary layer formulae 3. Boundary layer gets thinner as Reynolds number increases and viceversa 
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:)  For transitional flows (laminar to turbulent), you need Y+ less than 1 with other constraints. 
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