Question

HW#4 (Due 3/14/2019) Problem 1: (10pts) Consider a wing is mounted in a subsonic wind tunnel, where the airflow velocity is 50 m/s. If the velocity at a point on the wing is 60 m/s, what is the pressure coefficient at this point? Problem 2: (1Opts) In Problem 1, if the test section air temperature is 280 K, and if the flow velocity is increased point? to 200 m/s, what is the pressure coefficient at the same

Answer 1

Given that air force velocity is = 50m/s and velocity of air at thta point where we wont to determine pressure coefficient is given by c_p = p - p_infinity/1/2 s_infinity v^2_infinty = D - p_infinity/p_0 - p_infinity where p rightarrow static pressure p_8 rightarrow staic pressure in the free stream p_0 rightarrow stagnation in the free stream s_infinity rightarrow air density v_infinity rightarrow free stream velocity of air but we just velocity of air general and at abservation point so we are using here Bernoulli equation (li be as motion of fulid) c_p = 1 - (u/u_infinity)^2 u rightarrow airflow speed at observation point u_infinity airflow speed at in general = > c_p = (1 - (60/50)^2 = 1 - 36/25 = -0.36 c_P is negative c_p = -0.36 (iii) if the test section air temperature is 280 k and flow velocity is = 200 m/s (general) Now the u = 200m/s = > c_p = 1 - (200/50)^2 = 1 - 16 = 15