def NPR_shock_at_exit(AsAc):
"""Compute Nozzle Pressure Ratio to get a choked, supersonic regime but shock at exit in a nozzle with As/Ac diffuser
Args:
AsAc ([real]): ratio of exit over throat surfaces
Returns:
[real]: Nozzle Pressure ratio (inlet total pressure over exit static pressure)
"""
Msup = mf.MachSup_Sigma(AsAc)
Msh = sw.downstream_Mn(Msup)
return Is.PtPs_Mach(Msh) / sw.Pi_ratio(Msup)
def _NPR_Ms_list(AsAc):
"""
Computes all NPR limits and associated exit Mach number
internal function
:param AsAc: ratio of section at exit over throat
:return: result NPR and Mach numbers
:Example:
>>> import aerokit.aero.MassFlow as mf ; mf.Sigma_Mach(Is.Mach_PtPs(np.array(_NPR_Ms_list(2.)[:3:2])))
array([ 2., 2.])
.. seealso:: NPR_choked_subsonic(), NPR_choked_supersonic(), NPR_shock_at_exit()
.. note:: available for scalar or array (numpy) computations
"""
Msub = mf.MachSub_Sigma(AsAc)
NPR0 = Is.PtPs_Mach(Msub)
Msup = mf.MachSup_Sigma(AsAc)
Msh = sw.downstream_Mn(Msup)
NPRsw = Is.PtPs_Mach(Msh) / sw.Pi_ratio(Msup)
NPR1 = Is.PtPs_Mach(Msup)
return NPR0, NPRsw, NPR1, Msub, Msh, Msup
ax[2].plot(CWalpha, CWm3, '-', color='#bb0000')
# --- (UC) unstarted channel (A8 is sonic)
alphamax = 1.1 * alphamax
# M8 is sonic so M4 is known
UCm4 = mf.Mach_Sigma(A3A2 / A8A2, .1, gam) # look for subsonic value
UCm3low = mf.Mach_Sigma(A3A2, .1, gam) # look for subsonic value
alphamin = ray.Ti_Ticri(UCm4, gam) / ray.Ti_Ticri(UCm3low, gam)
print(" (restart) choked throat for Ti4/Ti0 = %6.3f" % (alphamin))
A1A2 = mf.Sigma_Mach(sw.downstream_Mn(M0, gam), gam)
print(" critical flow for unstart condition if A1/A2 = %6.3f" % (A1A2))
print(" A1/A0 = %6.3f" % (A1A2 * A2A0))
UCalpha = np.log10(np.logspace(alphamin, alphamax, npts + 1))
UCpi0 = sw.Pi_ratio(M0)
UCm3 = ray.SubMach_TiTicri(ray.Ti_Ticri(UCm4, gam) / UCalpha, gam)
UCpi3 = UCpi0 * np.ones(npts + 1)
UCpi4 = UCpi3 * ray.Pi_Picri(UCm4, gam) / ray.Pi_Picri(UCm3, gam)
UCm4 = np.ones(npts + 1) * UCm4
ax[0].plot(UCalpha, UCpi3, '-', color='#990000')
ax[1].plot(UCalpha, UCpi4, '-', color='#990000')
ax[2].plot(UCalpha, UCm3, '-', color='#990000')
# --- (RC) unstarted but choked channel (A2 and A8 are sonic)
alphamax = alphamin
RCm4 = mf.Mach_Sigma(A3A2 / A8A2, .1, gam) # look for subsonic value
RCm3low = mf.Mach_Sigma(A3A2, 2., gam) # look for supersonic value
alphamin = ray.Ti_Ticri(RCm4, gam) / ray.Ti_Ticri(RCm3low, gam)
def test_Ptshock():
assert sw.Pt_ratio(2.) == sw.Pi_ratio(2.)