How to find force from volumetric flow rate and pressure

[bl965]

1. Homework Statement
Hi. This is a problem related to designing a RC hover craft. We are given a datasheet for a fan used as thrust.
http://imgur.com/6liZSid Sorry image post no working, url: http://imgur.com/a/6XLwL
We have to approximate the equation to a straight line through the curve. Then relate it to F_thrust = F₀+ γ*v. We have to find γ and what F₀ represents.

Homework Equations

Q = velocity * Area
F = mass * acceleration

The Attempt at a Solution

I found that the slope is -0.285 [m³/s/mmH20]. To find F₀, I think the graph has to be turned on its side: pressure is the independent variable and volumetric flow is the dependent. If pressure is zero, I can find F₀ which is the y intercept. But how to relate force to volumetric flow or velocity.

 

[Chestermiller]

If P is the pressure and A is the area that the pressure acts on, what is the force?

 

[bl965]

If pressure is 0, volumetric flow is high, and small pressure * area is small force. As pressure increases, there will be more force with less flow. Makes sense. From start the fan is operating at atmosphere. I get high results when I search for one atmosphere in mm of water. Am I on the right track?

 

[Chestermiller]

If pressure is 0, volumetric flow is high, and small pressure * area is small force. As pressure increases, there will be more force with less flow. Makes sense. From start the fan is operating at atmosphere. I get high results when I search for one atmosphere in mm of water. Am I on the right track?

I have no idea. Can you please provide an exact problem statement?

 

[bl965]

(b) We can relate this linear relationship to F_thrust = F₀-γv [Note: γ is a constant representing the slope of the F(v) line]. For each fan, based on your approximation in (a), what are the values for F₀ and for γ?

 

[haruspex]

I think the graph has to be turned on its side:

No, it looks the right way around already, with pressure on the vertical axis. Seems to me you flipped it around in order to get:

I found that the slope is -0.285 [m3/s/mmH20].

how to relate force to volumetric flow or velocity.

What do you think relates volumetric flow through an aperture to the linear flow rate through it?
As Chester asks, what relates pressure to force?