garygph wrote:olefud wrote:It’s been awhile but I did a boundary layer literature search for another concern. As I recall, a 300 micron “rough” surface produced a boundary layer 300% thicker than a “smooth” surface under more or less standard conditions.
My objective was different, but the boundary layer is sort of a glue that sticks the slipstream to the aero surface. At high velocities and with scouring vortices, a better attached and thicker boundary layer can maintain attachment –which is pretty much what is said above.
This makes the observation make sense then as maintaining attachment under the wing is where the challenge is and if it assists in wet weather as well, as mentioned in a previous post, then that is an added bonus. To me the reason air follows ,the designers hope, the contour under the wing is in part a contribution by the coanda effect. This then brings me back to one of my original querie/thoughts, would a "rough" surface aid the coanda effect elsewhere? A thicker boundary layer due to slowing the air down close to the surface and aiding attachment just screams out counda effect aid to me. In fact where there is a need to guide the air stream/flow or help initiate a vortice I could imagine areas of smooth and rough surfaces strategically placed could help to a small extent....but that is F1 isn't it? Every little bit adds up
Been thinking on this. My empirical data are concerned with viscosity which influences Candela most significantly. Just a guess, but modest surface roughness could cut two ways – a thicker boundary layer could assist in attachment, but at a critical air foil area could change the airfoil dimension and lead to detachment. I understand that vortex generators are employed on a wing to –among other things-scour down an over thick boundary layer.
Water in this example would seem to be a means of visualizing a phenomenon. Humidity relates to water as a gas while an aerosol is very small droplets of liquid water. High humidity diminishes the density of air while aerosols increase the density and also wet a solid such as a wing.
viewtopic.php?f=6&t=881&hilit=golf
