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-   -   Reynolds number and 1st cell height (http://www.cfd-online.com/Forums/main/119214-reynolds-number-1st-cell-height.html)

Frank_M June 12, 2013 07:10

Reynolds number and 1st cell height
 
I guess a really basic question but … :confused:
System:
* inflow speed: 50 m/s
* wind tunnel: 1m x 1m x 10m -> specific length = 2*a*b/(a+b) = 1m
* body (sphere): diamater 0.1 m -> specific length = d = 0.1m
* air -> 1.225 kg/m3 and eta = 1.781e-5 Pa*s

Reynolds
-> Re(tunnel) = 3.523301e+6 and Re(body) = 3.52330e+5

1st cell height
* tunnel: length scale = 1m, y+ = 1
-> ~1.4 e-5
* body: length scale = 0.1m, y+ = 1
-> ~1.1 e-5

Additionally: what happens if the body changes to a box with 0.1m x 0.1m x 0.2m … does the specific length and length scale for the box change to length of the box = 0.2m or still 2*a*b/(a+b) = 0.1m

Thanks for your feedback!


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