Dan Ruggirello wrote:

Hi Paul,
Here is profile R7.  My rational here was to use your concave wedge since it seems like it does a
good job of evening out the pressures across the radiator.  Also, in order to get a bit more flow

>from the left of the radiator, the opening behind the vent takes advantage of the vaccuum

developed from the air flow around the cowling, drawing more air through the left of the
radiator.  Actually, it looks like a bit too much air!  This configuration leaves the question of
how and where to install cowl flaps.  I think I will try a run with a full vent to see how that
differs from this one.

Dan

I am a bit suspicious of that velocity data under the aircraft. I think the boundaries
are too close or the overall flow field is not correctly modeled.
Try increasing the over all length of the model and moving the lower boundary
further away from the bottom of the aircraft. Twice as far. In fact I still
don't think it is velocity at all. I still think those plots are pressures.
Something wrong there. Makes good sense if you consider these plots pressure.
The pressure plots are believable on the other hand.

Also try the flaps at a
15 degree angle instead of 30 degrees as I initially drew. I can revise
the drawing if necessary. The concave diffuser shape was recommended
by Kay's & London. I also did some full scale test with that configuration with
good results several years ago.

If you can scan that paper and send it to me perhaps we can get it translated.

Paul Lamar

I hate to ask dumb questions about this stuff since all I know about it
is what I've 'read in the papers' (to mis-quote a dead humorist), but
here goes:

First, all the versions so far seem to have more or less parallel walls
on the duct which would not give any pressure recovery. The velocity &
pressure representations both seem to confirm this as there is no
slowing in the duct and no pressure increase.  Shouldn't the duct be
tapered for pressure recovery?

The wedge over the rad  takes the place of the classic diffuser. PL

Second, the simulations show an obvious increase in speed & decrease in
pressure above  the pinched trailing end of the duct over the radiator.
 Bernie Kerr has built & tested a duct without the pinched area at the
trailing edge of the duct. It showed equal flow from one end of the
radiator to the other. Are we missing something here?

That's strange.  Kays & London, Kuchemann & Weber, Dan  and me all found
the opposite effect.   PL

Third, it's been well documented on air cooled planes that the lip at
the bottom of the firewall (right edge of the radiator in these images)
should be given a generous radius to help the air transition from
downward to rearward direction. Wouldn't it be worthwhile to move the
trailing (right) edge of the radiator up a few inches & radius the
'firewall'  corner?

Fourth, if you rotate these images 180 degrees, they look like the
airspeed/pressure representations of the top of a stalled wing. It looks
like a very high drag & even inverse lift situation to my untrained eye.
 The air flowing past the exit duct seems to be working like a venturi
creating a large low pressure area below & behind the duct. Shouldn't
the exit air be re-accelerated by the duct to slipstream speed to reduce
this drag?

'I am only an egg', so please enlighten me.

Charlie England

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