def set_NPR(self, NPR): """ Define Nozzle Pressure Ratio (inlet Ptot over outlet Ps) for this case Define Nozzle pressure ratio and compute Mach number, Ptot and Ps according to nozzle regime :param NPR: NPR value (>1) """ self._Pt = np.ones_like(self.AxoAc) if NPR < self.NPR0: _Ms = Is.Mach_PtPs(NPR, gamma=self.gamma) self._M = mf.MachSub_Sigma(self.AxoAc / self.AsoAc * mf.Sigma_Mach(_Ms), gamma=self.gamma) self._Ps = self._Pt / Is.PtPs_Mach(self._M, gamma=self.gamma) else: self._M = np.ones_like(self.AxoAc) self._M[:self.ithroat + 1] = mf.MachSub_Sigma( self.AxoAc[:self.ithroat + 1], gamma=self.gamma) self._M[self.ithroat + 1:] = mf.MachSup_Sigma( self.AxoAc[self.ithroat + 1:], gamma=self.gamma) if NPR < self.NPRsw: # analytical solution for Ms, losses and upstream Mach number of shock wave Ms = Ms_from_AsAc_NPR(self.AsoAc, NPR) Ptloss = Is.PtPs_Mach(Ms) / NPR Msh = sw.Mn_Pi_ratio(Ptloss) # redefine curves starting from 'ish' index (closest value of Msh in supersonic flow) ish = np.abs(self._M - Msh).argmin() self._M[ish:] = mf.MachSub_Sigma( self.AxoAc[ish:] * mf.Sigma_Mach(Ms) / self.AsoAc) self._Pt[ish:] = Ptloss self._Ps = self._Pt / Is.PtPs_Mach(self._M)
def NPR_choked_supersonic(AsAc): """Compute Nozzle Pressure Ratio to get a choked supersonic regime 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) """ return Is.PtPs_Mach(mf.MachSup_Sigma(AsAc))
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
def test_MachSup_Sigma(AsAc): mach = mf.MachSup_Sigma(AsAc) assert (mach > 1) assert mf.Sigma_Mach(mach) == pytest.approx(AsAc, rel=1.e-6)