#### Re: Sparrow strainer stall conundrum

Brian Larick

I’m on pins and needles for the magic solution.  Question would a longer arm with a better angle of attack have the same negative aerodynamics or would they improve on the negative airflow due to the longer angle?

Brian

On Feb 22, 2022, at 20:12, Jay Scheevel <jay@...> wrote:

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Here is the basic problem and I am not sure if vg’s on the sparrow strainer can fully solve it:  The first picture below is the streamline flow-field around the LS1 airfoil, with the standard sparrow strainer position depicted with the red outline.

Zooming in on the sparrow strainer and flipping it over, you can see the relative wind (AOA) of the sparrow “Clark Y” airfoil to the streamlines is 27 degrees (the green angle). This is way beyond the stall angle of that airfoil, which is why is appears to be stalled at all airspeeds in my videos.

Maybe sparrow strainers can allow the Clark Y to reach that AOA before fully stalling, but I doubt it.  Another option to give the sparrow strainer the same aerodynamic effect, is to move it farther back from the trailing edge and lower its angle of attack, thereby giving it the same moment relative to the elevator pivot point, of course this would require longer arms. It needs to have a certain amount of lift, but it certainly is not producing a lot of lift when fully stalled. Maybe just lowering the angle to below the stall point would do the trick, because it would pick up more lift in the process.

I have modeled the combination of the two airfoils (LS1 and sparrow strainer) in a single flow field and here is that result.  You can see the result below and it shows the same flow that is demonstrated by the tufts in my video. Now I will scratch my head and see if the vg’s may do the trick.

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