def sigma_out(self):
        lambda_c_out = self.last_stage.lambda_c_3

        k = self.first_stage.k

        eps_out = gdf.epsilon(lambda_c_out, k)

        return 1 - self.dzeta_out * k / (k + 1) * eps_out * lambda_c_out ** 2
    def get_outlet_density(self, h_rel):
        triangle = self.get_outlet_triangle(h_rel)
        total_velocity = triangle.c_total
        density_stag = self.stage_model.thermal_info.density_stag_3
        a_crit = self.stage_model.thermal_info.a_crit_3
        lambda_ = total_velocity / a_crit

        return density_stag * gdf.epsilon(lambda_, self.stage_model.k)
    def sigma_in(self):
        lambda_c_in = self.first_stage.lambda_c_1
        k = self.first_stage.k
        eps_in = gdf.epsilon(lambda_c_in, k)

        return 1 / (1 + self.dzeta_in * k / (k + 1) * eps_in * lambda_c_in ** 2)