The question about pitching moment:

[skkong001]

Homework Statement

The centre of pressure for a prototype vehicle under development is found to be 0.1m aft (in the horizontal plane) and 0.2m above (in the vertical plane) from the centre of gravity. The vehicle has a front cross section of 2.1m2 with current predictions of lift and drag coefficients of 0.15 and 0.4 respectively. Air density is 1.2kg/m3. For a cruising speed of 50mph:

Q1.Calculate the aerodynamic pitching moment (you may assume 1mph = 0.447m/s).

Q2.Does the vehicle pitch nose up or down?

Q3.Calculate the aerodynamic pitching moment coefficient assuming a wheelbase of 2.3m.

Homework Equations

Lift = 0.5 x ρ x v² x S x Cl
Drag = 0.5 x ρ x v² x S x Cd

Pitching moment = 0.5 x 0.5 x ρ x v² x S x Cp x l

 

[NateD]

Cp = (Cm - Cd x x)/lThe Attempt at a SolutionQ1.Pitching moment = 0.5 x 0.5 x 1.2 x (50x0.447)² x 2.1 x 0.15 x 2.3 = 74.82NmQ2.Nose down, as the centre of pressure is behind and below the centre of gravity.Q3.Cp = (74.82 - 0.4 x 2.1)/2.3 = 0.1444