What psi can be achieved from a 60mph wind

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In summary, the conversation discussed the possibility of achieving psi through the use of vents on a car's hood at a speed of 60mph. The formula for wind pressure was mentioned, with a result of 0.06 psi. Further calculations were also provided, along with an explanation for the small pressure per unit area in relation to atmospheric pressure. The use of turbo-chargers and super-chargers were also mentioned as more effective options for achieving a significant charge boost.
  • #1
Cyclonus
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If I put vents on the hood of my car and drove at 60mph what kind of psi could be achieved? I don't care about what kind of technique is used just curious about what kind psi could be created. I apologize if I'm not asking this correctly but I have no background in fluid dynamics.
 
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  • #3
The wind pressure is proportional to the air density multiplied by the speed squared.
My very old engineering text gives pressure due to wind as; p = 0.0032 * v^2
where pressure p is in pounds per square foot and v is miles per hour.
For pressure in psi divide by 144 to get; p = .00002222 * v^2
So if v = 60 mph, then p = 0.08 psi.
This estimate agrees reasonably well with russ_watters result of 0.06 psi.
 
  • #4
The rolled-up constant I used was 4005, which inverted is .000250. Not sure where the discrepancy comes from. But not a big deal.
 
  • #5
I based my computation on an old formula to confirm the order of magnitude of russ_watters result. We agreed.

The coefficient should really be 0.00255646, not the 0.0032 as obtained from my 1938 engineering text that used a coefficient recommended by a paper published in 1911. I believe the result discrepancy comes about because Engineers are conservative and so overestimate the effect of wind on their structural designs. Standards have also been redefined during the last 102 years.

Further examination of the “rolled up” constant k based on;
dynamic pressure = half * density * velocity^2
Assuming air at 15°C and sea level, the density is 1.225 kg/m3
and knowing that 1 psi = 6.8948*10^3 Pa

k = (0.5 * 1.225 * 1609.344^2) / (6894.8 * 3600^2)
So k = 17.7532e-6
And 1 / k = 56327.87
Then psi = mph^2 * 17.7532e-6
Or psi = mph^2 / 56327.87

At 60 mph the theoretical dynamic pressure will be 0.0639115 psi

What the computation does confirm is that at the speed of road vehicles, the force of the wind on a large exposed surface can be very great, but the pressure per unit area is small when compared to atmospheric pressure. This limits the utility of ram air intakes and explains why a turbo-charger or super-charger must be used to get a significant charge boost. Fundamentally, a turbo-charger gives a greater pressure boost than a ram air intake because the blades of the compressor can move significantly faster than the vehicle.
 
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FAQ: What psi can be achieved from a 60mph wind

1. What is the relationship between wind speed and air pressure?

The higher the wind speed, the lower the air pressure. This is because fast-moving air molecules exert less pressure on their surroundings.

2. Is there a maximum psi that can be achieved from a 60mph wind?

Yes, there is a limit to how much pressure can be generated by a 60mph wind. The maximum psi will depend on various factors such as the atmospheric conditions and the surface area and shape of the object being hit by the wind.

3. Can a 60mph wind reach tornado-level psi?

No, a 60mph wind cannot reach the same psi as a tornado. Tornadoes are classified as having wind speeds of 65mph or higher, and can generate pressures of over 100 psi.

4. How do you calculate the psi from a given wind speed?

To calculate the psi from a given wind speed, you can use the formula: psi = 0.00256 x (wind speed in mph)^2. Keep in mind that this is a rough estimate and the actual psi may vary depending on the factors mentioned earlier.

5. What are the potential dangers of high psi generated by wind?

High psi generated by wind can cause structural damage to buildings, trees, and other objects. It can also create hazards such as flying debris and dangerous wind gusts, which can pose a threat to people and animals.

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