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clc
// Example 3.3.py
// Return to Example 1.1, calculate the percentage density change between the given point
// on the wing and the free-stream, assuming compressible flow.
// Variable declaration from example 1.1
rho_1 = 0.002377 // density at sea level (slug/ft^3)
T_1 = 519.0 // temperature at sea level (R)
v_1 = 100.0 // velocity far ahead of the wing (mi/h)
v_2 = 150.0 // velocity at some point on the wing (mi/h)
gamma1 = 1.4 // ratio of specific heat capacity for air
R = 1716.0 // gas constant (ft lbf/slug/R)
// Calculations
cp = gamma1*R/(gamma1-1) // specific heat capacity at constant pressure (ft lb/ slug / R)
u_1 = v_1 * 88.0/60.0 // converting v_1 in ft/s
u_2 = v_2 * 88.0/60.0 // converting v_2 in ft/s
T_2 = T_1 + (u_1*u_1 - u_2*u_2)/cp/2.0 // temperature at a point from energy equation (R)
rho_2_by_rho_1 = ((T_2/T_1)** 1/(gamma1-1))// density ratio from isentropic flow relation
rho_2 = rho_2_by_rho_1 * rho_1 // density at the point (slug/ ft^3)
delrho = rho_1 - rho_2 // change in density (slug/ ft^3)
fracrho = delrho/rho_1 // fractional change in density
// Result
printf("\n Percentage change in density is %.1f",(fracrho*100))
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