def f2(z, t):
"""4x4 system for golf ball with drag in two directions."""
zout = np.zeros_like(z)
C = 3.0 * rho_f / (4.0 * rho_s * d)
vrx = z[2] - vfx
vry = z[3] - vfy
vr = np.sqrt(vrx**2 + vry**2)
Re = vr * d / nu
CD, CL = cdcl(vr, nrpm)
zout[:] = [z[2], z[3], -C * vr * (CD * vrx), C * vr * (-CD * vry) - g]
return zout
def f3(z, t):
"""4x4 system for golf ball with drag and lift in two directions."""
zout = np.zeros_like(z)
C = 3.0*rho_f/(4.0*rho_s*d)
vrx = z[2] - vfx
vry = z[3] - vfy
vr = np.sqrt(vrx**2 + vry**2)
Re = vr*d/nu
CD, CL = cdcl(vr, nrpm)
zout[:] = [z[2], z[3], -C*vr*(CD*vrx + CL*vry), C*vr*(CL*vrx - CD*vry) - g]
return zout