Derive an expression for the total drag force for laminar flow over the wing dep

Question

Derive an expression for the total drag force for laminar flow over the wing depicted in the diagram below. Consider only skin friction drag on one side of the air-foil. Start with the expression for local shear stress in equation (1). Arrows indicate the direction of air-flow over the wing. tau_0 = Squareroot8/15Re_xPU^2_infinity/2 (b) Sketch the structure of the flow over a cylinder at high Reynolds number. Your sketch should show stream lines, pressure variation and the different regions of the boundary layer should be clearly labelled. (c) (i) Calculate the rise velocity of a spherical bubble of air, with diameter D=.05m, through water. (ii) Calculate the fall velocity of a spherical droplet of water, with diameter D=.0-5m, through air. (iii) Given that the density difference for (i) and (ii) above is the same, why is the velocity difference so large.

Explanation / Answer

The loaded four wheel trailer shown in Figure P8.10 has a total mass of 5t and is pulled along a level road. Average resistance to motion (friction and windage) is 2 per cent of the total weight and acts at the same horizontal level as the applied force P. Determine the normal reaction at each of the front and rear wheels when the trailer moves:

a) at constant velocity

b) with forward acceleration 1.5m/s².

(Average resistance to motion is 2% of total weight is not required.)

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