Quote:
Originally Posted by CFECO
Here are some pictures to ponder. On the flat shape, the Corvette headlight, the air does not create it's own "Streamlined path" and follow the hood, as in ChazInMT's drawing, "What the air is doing". The air is shown to be coming back down to the hood at a fairly large distance back of the headlight. The other page shows the "template" does not perform to it's potential, without the front streamlining also. Just my humble opinion.
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I'm not going to speak for Chaz,but if you'll look at the smoke,you'll notice that the air stream is deforming quite a bit ahead of the headlight housing.Dr.Prandtl called this a 'line of discontinuity.'
Air will avoid extreme accelerations and instead,warp its path around an object.
Certainly,any leading edge will require a minimum radius to enable attached flow,however,once attached flow is accomplished,very little drag reduction is realized from increasing the radius.I think this is inferred in Chaz'z illustration.
With respect to the second thumbnail.I don't think this is 3-dimensional flow being illustrated.I think the word 'sphere' should be replaced with the word 'cylinder.'
The flows are not correct for 3-D flow.
The 'pointed' nose of the 4th image is never used for sub-sonic design.In non-zero yaw it would actually have higher drag.Instability.
Not even the X-15 uses such a nose.
If you haven't seen the thread 'Flow-Images' you might want to check it out.
As to the 'Template',it's based on science.Below 250 mph,the semi-hemispherical nose is recommended for lowest drag.