While waiting for the real thing I've been designing a wind tunnel for future testing of different models. I've come up with most of the components ( some still need to be purchased ) but one thing I'm having a hard time finding is the inlet diffuser air straightner.
The air straightener is basically a honeycomb layout of about an inch or two thick and its only purpose is to straighten the air as it enters the contraction tube. So far I've found nothing that would work. Anyone have any ideas of where or what could be used for this purpose?
I've put together a couple of cardboard tunnels using house fans to watch the inlet air and how it flows through the tunnel, not pretty but great initial knowledge. Using some insense at the inlet tells the whole story of what is going on around the inlet as well as traveling through the test chamber. I'll bet I spent an hour of watching the smoke trails in various positions of the tunnel. It's quite surprising how clean you can make it.
In any case for the larger one I'll definately need some straighteners of some type...
So far the larger design has been down graded because of the space required to build it as it should be. The original design ended up being around 32 ft long to keep the diffuser angles below 6 degrees. I've reduced that to 14.5 ft and will have to change the inlet and outlet curves to make up the difference. It will be using 2 30 inch jet fans that are rated at 8550 cfm each at 600 rpm but I'll be running them up to 1100 rpm giving me about 35,000 cfm through the test area ( about 30 mph free flow ). With a 2x2 turbine inside it will most likely be go to 20+ mph.
I'm hoping to have this done shortly after the real wind tunnel tests to see how the results vary using the same machine. I should be able to come up with a reasonable "fudge" factor between the two.
My ideas on the "honeycomb" so far are few, as follows...
Box fan grates stacked making up the thickness
PVC tube cut to length and glued in place (expensive)
Sheet metal stips slotted to form the honeycomb
Brain lock - can't vision what something like that would be used for... any suggestions would be greatly appreciated...
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