# computing boundary layer thickness

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 August 8, 2013, 06:37 computing boundary layer thickness #1 Member   Liam Join Date: Aug 2013 Posts: 40 Rep Power: 6 Hi people, Anyone knows how can I compute boundary layer thickness for an arbitrary geometry? I have seen some theoretical formulas for flat plates, but I am not sure if there exists a formula for any kind of problem... Thank you so much

 August 12, 2013, 06:29 #2 New Member     Fateme Sh Join Date: Jul 2013 Location: Tehran Posts: 8 Rep Power: 6 first you need to find the first row height regarding to your flow condition you can find your first row height with the help of yplus calculations in here: http://geolab.larc.nasa.gov/APPS/YPlus/ then i think 12 rows is enough (base on my experiments and studies) for the boundary layer mesh

 August 12, 2013, 06:47 #3 Member   Liam Join Date: Aug 2013 Posts: 40 Rep Power: 6 Hi aeroAngel, I am seeing that those calculations are for a flat plate. Are the values computed here valid for an arbitrary geometry? Thanks for your reply!

 August 12, 2013, 07:24 #4 New Member     Fateme Sh Join Date: Jul 2013 Location: Tehran Posts: 8 Rep Power: 6 the nasa calculator is based on yplus calculations which is for any wall-bounded flow, I've used it in my calculations for any shape ,like other engineers that i know and I haven't seen something about not using it in my studies. I asked other engineers and they agreed

 August 12, 2013, 09:22 #5 Senior Member   James Join Date: May 2013 Posts: 111 Rep Power: 6 Thank you so much! I will have to make several aproximations because freestream velocity is not given, I only know pressure values at inlet/outlet and I guess this info is not enough for the calculator...

August 12, 2013, 09:32
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 Originally Posted by Tensian Thank you so much! I will have to make several aproximations because freestream velocity is not given, I only know pressure values at inlet/outlet and I guess this info is not enough for the calculator...
Although it is true the inlet/outlet pressure is not enough, you can certainly have an initial guess for your reference velocity (which depends on your case)