I Lift Force of a Rotating Sphere in the Air

AI Thread Summary
The discussion centers on calculating the lift force of a rotating airsoft BB, with specific parameters provided, including mass, velocity, angular velocity, radius, and air density. The user has calculated the Reynolds number to be approximately 49182 and is seeking confirmation of its accuracy. There is a mention of the hop-up mechanism, which applies backspin to the BB, potentially affecting its linear velocity. Questions arise regarding the impact of backspin on muzzle velocity and whether CO2 discharge levels need adjustment to compensate for this loss. The focus remains on understanding the physics of the BB's behavior after it exits the barrel.
Ruda975
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Hello,
I would like to ask one question. What is the equation for the lift force of a rotating sphere when flying through the air:
m = 0.25 g
v = 130 m/s
angular velocity = 105 rad/s
radius = 3 mm
air density = 1.2292 kg/m^3
air pressure = 101200 Pa
air temperature = 15 °C = 288.15 K
If anyone is interested, it is an airsoft bb. I have also calculated the Reynolds number to be around 49182. I don´t know if that´s correct or not.
I have not yet measured the angular velocity of my airsoft gun, but there is a wikipedia article about hop up (the mechanism that applies backspin to the bb), that says that the backspin can exceed 1000 rpm which is about 105 rad/s, so I am using that value.
 
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What is the direction of that rotation?
 
Lnewqban said:
What is the direction of that rotation?
https://en.wikipedia.org/wiki/Hop-up_(airsoft)
There is an animation of the rotation of this webpage.
And here is a quick illustration I made.
 

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Ruda975 said:
I have not yet measured the angular velocity of my airsoft gun, but there is a wikipedia article about hop up (the mechanism that applies backspin to the bb), that says that the backspin can exceed 1000 rpm
Do you also increase the CO2 discharge level to compensate for the lost velocity in the barrel? If energy is being put into the backspin of the BB, then linear velocity will be lost in the process, it would seem...

https://en.wikipedia.org/wiki/Hop-up_(airsoft)

1644251955182.png
 
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I only consider the behavior of the bb after it leaves the barrel. I do this through measuring the velocity and angular velocity of the bb once it leaves the barrel.
 
Ruda975 said:
I only consider the behavior of the bb after it leaves the barrel. I do this through measuring the velocity and angular velocity of the bb once it leaves the barrel.
Whate decrease in muzzle velocity do you measure with the Hop-Up mechanism in place?
 
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