- May 26, 2017
- Merrill, Wisconsin, USA
Looking at this pictures of this 120 MPH Aircraft. Hard to tell exactly but if I have to guess opening of the air scoop is approximately 2 1/2 inches tall and about the same distance from fuselage.You need to reference a fluid mechanics text or other docs on how to calculate the boundary layer thickness at that point. Air will be flowing from the nose of the airplane all the way to the inlet. Once you know how thick that boundary layer is, make the bottom of the scoop a little higher above the rest of the fuselage.
Yes, and the cheap, good light digital cameras available now really help. Eugene has apparently made good use of these.The best tool to optimize those things, in my view, for those mere mortals that neither have hi-end CFD software in their computer nor have a wind tunnel at home, is experimenting with wool strands.
Thank you! Makes perfect sense and corresponding what I am hearing from my Russian friend about not to increase 8° because after that you most likely going to see separation.No corners on the inside either. You can have flat walls that diverge from the free stream by 7 degrees but any more than that and there will probably be separation from the walls with recirculation (drag and loss of cooling) near the walls. If you want to get really anal about internal drag I'd use a model airplane airfoil for the whole cross section from the lip clear back to the face of the radiator.
Yes in the real world one would only use the turbulent calculation as if it really did have much laminar flow, one would be running CFD anyway. It is only to give an indicative depth, I would be making sure there is a good margin over and above the calculated depth.Very interesting paper, Mad MAC. One basic rule is undeniable: as the formula in the paper shows for both laminar and turbulent flows, the further aft it is the thicker the boundary layer becomes. However in the real world the boundary layer change from laminar to turbulent depends on quite a few factors: if it is a tractor or a pusher engine, the shape of the windshield, type of finishing, you name it.
Correct. With a good duct and properly matched rad, I didn't see any inlet spillage until the outlet to inlet ratio was below 0.5 in my flight testing.In this situation presumably your outlet is mostly open, so you'd not be spilling air over the inlet lip anyway, right?
I understand what you're trying to show me, but my real situation not corresponding to your picture at all. I will try to come up with a little sketch tonight. Oil cooler is position right behind water cooler. This installation was approved by Rotax and they actually like it this way because oil will be a little bit warmer than water. And this is what they want. But thank you for trying to straighten me out!!!How about something like this, Eugene?