An air at 3 ms free stream velocity flows past a horizontal

An air at 3 m/s free stream velocity flows past a horizontal flat plate with 3 m long. The kinematic viscosity of air is 1.46 times 10^-5 m^2/s. The air density is 1.23 kg/m^3. Assume the flat plate has a depth (out of the page\'s direction) of 50 cm. Determine the total drag and lift forces, in N, applied by the air onto both the top and bottom surfaces of the horizontal flat plate.

Solution

Given data, air free stream velocity = 3 m/s =V ,lenght of plate = 3 m =L

Re of flow = V*L/kinematic viscosity = 3*3/1.46*10^-5 = 616438.3562 = 6.16*10⁵

Drag force on plate = C_D *0.5*row*V²*A , row = fluid density = 1.23 kg/m3,

A=  area projected on a plane parallel to the direction of flow = 0.5*3*2 = 3 m2 (considering both sides of plate)

for Re = 6.16*10⁵ and for horizontal flat plate , C_D = 0.005 (from chart)

drag force on plate (on two sides) =0.005*0.5*1.23*9*2*0.5*3 = 0.083 N

similarly for calculating lift force on plate = C_L *0.5*row*V²*A .row,V,A are same as in above answer.

C_L = Lift coefficient