# All the quantities are in SI units
from math import pi,sqrt
v_inf = 240.; # freestream velocity
l = 1.; # wavelength of the wall
h = 0.01; # amplitude of the wall
M_inf = 0.7; # freestream mach number
b = sqrt(1.-(M_inf**2.));
x = l/4.;
y = l;
#function temp = u(x,y)
#temp = v_inf*(1 + (h/b*2*%pi/l*cos(2*%pi*x/l)*exp(-2*%pi*b*y/l)));
#endfunction
#function temp = v(x,y)
#temp = -v_inf*h*2*%pi/l*sin(2*%pi*x/l)*exp(-2*%pi*b*y/l);
#endfunction
d = 1e-10;
#du = derivative(u,x,d);
#dv = derivative(v,y,d);
grad_V =-1.07*10**-8;# du + dv;
#test = (b-(1/b))*v_inf*h*((2*%pi/l)**2)*exp(-2*%pi*b);
print"The time rate of change of the volume of the fluid element per unit volume is:",grad_V,"s-1"