CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   CFX (http://www.cfd-online.com/Forums/cfx/)
-   -   aspect ratio vs. y+ (http://www.cfd-online.com/Forums/cfx/24358-aspect-ratio-vs-y.html)

hammam August 5, 2007 08:31

aspect ratio vs. y+
 
Hi all

iam simulating 2d airfoil using c-grid topology , i want to trade off between y+ and aspect ratio , i use sst & ( Gamma-Theta) trnsition model which needs y+<1 , i meshed my domain by hex mesh using pre-mesh>edge meshing parameter tool.

i decrease the y+ by decreasing the edge spacing from the airfoil and i increase the number of nodes by using low edge ratio at the airfoil surface.

when i used a hyperbolic mesh with spacing 1e-4 it gives me a maximum aspect ratio of about 17000 .

and the convergence was unstable.

so what is the solution for that problem?

& what is the acceptable value for aspect ratio to use?

thanks Hammam

johnny August 6, 2007 09:19

Re: aspect ratio vs. y+
 
did you try running in double precision?

hammam August 6, 2007 10:27

Re: aspect ratio vs. y+
 
hello

excuse me would you please explain what is double precision, and how to use it?

regards

Gui August 6, 2007 10:41

Re: aspect ratio vs. y+
 
double precision is a more precise calculation (the values are represented with more digits).

you can get it before starting you run in the solver, where you can specify initial value file, you can click on "show advanced control" and there you can specify double precision


All times are GMT -4. The time now is 01:27.