How to know the know the Boundary Layer thickness and the edge velocity on a 3D wing?
 

Hi guys,
My questions are simple...Using CFD ( especially CFX)...
1-How to know the Boundary Layer thickness and the edge velocity on a 3D wing( blade)?...
2- Think that I have determined the BL thickness everywhere on the blade surface....Then how to save the geometry[ x,y,z=(thickness)] of the BL on the whole wing in a Text file or Excel file?

Regards

Please...help me ...TNX :)

to get the bl thickness you can create an isosurface of veocity = 99% free stream velocity. then the distanche between the isosurface and the wing is your thickness

you will also need a very fine mesh at the surface to get an accurate measurement of the leading edge boundary layer thickness.

Dear Andrew, dear Sail,
Thanks for your answers.
one other question : if I want to plot the velocity profile inside the BL , I must use some other isodurfaces between wall( zero velocity) to 0.99V and then plot the velocity profiles inside the BL, isn't it?

Regards

what you would do in Fluent is create a plane perpendicular to surface, and then plot the velocity in that plane. You can do it as a contour plot. Or, you can get the values at each grid from the plane and determine the thickness from there. That is why you need a fine grid towards the surface. That is how I would do it. But, setting a criteria for .99V would be the fastest

to get the bl Vprofile, if you need the plot for the whole section you can simply create a plane and then plot the velocity contours on it, as mettler said.

else, if you need the profile at vairous chord coordinates, make a line normal to the foil surface at each station you need to investigate and just plot the velocities on those lines.

Hi everybody,
A new question arises; when the blade is rotary( in Wind turbine) which speed should i work with when i want to calculate 0.99V? with Local( roartion+ axial for any radial station) ,with Average speed ( at mid-radial station) or just with axial wind speed?

Use the rotational+axial velocity as reference for rotary surfaces.