Calculate pressure from vehicle moving through air

AI Thread Summary
To calculate the air pressure generated against a vehicle moving through air, the discussion emphasizes using stagnation pressure, which applies to any moving fluid, not just pipes. The user seeks to estimate the drag on a flat surface of one square meter at a speed of 90 kph, while also trying to transition these calculations for varying speeds. While drag coefficients typically account for the entire vehicle, a focus on stagnation pressure can provide a rough estimate for the specific flat area. The conversation highlights the importance of understanding drag equations and stagnation flow for more accurate calculations. Overall, the key takeaway is that stagnation pressure is a relevant concept for estimating pressure on a flat surface of a moving vehicle.
Cbrown92
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Alright, I've been looking everywhere, and tried to use a few formulas but they don't answer what I'm trying to find. Let's say I have a car that weighs 1815kg )4000 pounds) and its traveling at 90kph (roughly 56 mph) with a flat one square meter (10.76 sq ft.) grill facing the wind as it travels. What is the air pressure (In pascals and psi) I can expect to generate against the vehicle as it moves? Though providing me the answer in Newtons wouldn't hurt either.Also, the vehicle is moving at a constant rate assuming a flat road surface. I'm trying to invent a new kind of engine based on relatively low air pressures
 
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What formulae did you try? It's not to hard to find one.
 
I tried F=MA in relation to P=F/A but the vehicle isn't accelerating, its moving at a constant rate. Unless I'm confused about the definition of acceleration itself? Is there anything I'm missing?
 
You need to look at drag equations...

http://en.wikipedia.org/wiki/Drag_(physics)

eg..

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If the front is flat, he doesn't even need to concern himself with the drag equation. He can get a good enough estimate just using the concept of stagnation pressure.

So, in short, just look up "stagnation pressure."

You might also look up "stagnation flow" if you want a more accurate estimate. That would require an integral of the pressure distribution over your flat surface, but that's pretty trivial.
 
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Sorry for having taken so long to reply, but if I use a drag coefficient, that accounts for the drag in its entirety not a specific sectional area. Stagnation pressure, from what I understand applies to pressure in pipes. I guess what I'm trying to find out is the amount of drag on that single plate of which measures 1sq meter in area at speed, and then how to transition that into pressure and calculate for higher and lower speeds. Think of something about the shape of a Cadillac grille in the front (Similar size even) while ignoring the drag/pressure on the windshield, sides of the car, etc.
 
Stagnation pressure applies to any moving fluid, not just pipes. I wouldn't have suggested it if it didn't make sense to use it. Stagnation pressure is just the pressure that results from isentropically slowing the flow to zero velocity. Just calculating the stagnation pressure at the front of a car moving a given speed is going to be a rough estimate of the pressure on the given size of plate. If you want a better estimate, then like I said before, stagnation flow would give you a more accurate estimate.
 
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Sorry for having taken so long to reply, but if I use a drag coefficient, that accounts for the drag in its entirety not a specific sectional area.

Not sure what you mean but I was proposing to use the drag coefficient for a flat plate not the whole car (I agree that using the drag coefficient for a flat plate would probably give an over estimate).
 

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