Originally Posted by mpierce
Nice, but I believe the holes will ADD wind resistance. Ever see the large pipes on a semi, with the tarp over the front end of them? With the tarp, they pull easier. A LOT easier. The wind going thru the pipes ADD wind resistance.
Other than than, nice mod.
Hmmm...interesting engineering problem!
In this pic it looks like the box is on the side of the trailer. So the air flow hitting the leading edge is going to be significant. So if the air flow through the box is faster than outside the box it's going to want to fly off (like a wing). My expertise is in hydraulic dynamics inside pipelines and not airfoils, but it seems to me that adding the holes will create a turbulent flow over the inside surface that would tend to equalize the air pressure.
Now if the box is on the back of the trailer (like mine) then we have a different situation. In that case the box is already in the vortex of a fairly low pressure turbulent flow anyway so the holes probably would make no difference.
It would be interesting to test these hypotheses in a wind tunnel!
An interesting counter-intuitive parallel (which has been tested in wind tunnels) is the question of whether leaving the tailgate of a pickup down reduces wind resistance. The proven scientific answer is no! If the tailgate is down the air passes over the cab and down over the bed surface (which has a lot of air resistance). And to make it worse, that air is like the top of a wing. With the faster air passing underneath the vehicle the truck wants to "take off" and can actually lose control at higher speeds. With the tailgate up, the air passes over the cab, hits the tailgate and then creates a bubble of turbulent air in the bed that actually creates a faster, more efficient airflow over the top of the vehicle.
In NASCAR truck racing they have to cover the beds to artificially enhance this effect and add spoilers front and rear to keep the trucks from going airborne at high speeds because even more so than race cars they are basically wings on wheels. If you have ever seen a major crash during a truck race you will see that they have a bad tendency to "take off" because at 200 mph they are literally just on the verge of taking flight.