Nozzle flow

Figure: Flow rate as a function of the back pressure taken after Stodola 1927 Steam and Gas Turbines

Romer et al^1.38 analyzed the isothermal flow in a nozzle. It is remarkable that choking was found as $1/\sqrt{k}$ as opposed to one (1). In general when the model is assumed to be isothermal the choking occurs at $1/\sqrt{k}$ . The concept that the choking point can move from the throat introduced by^1.39 a researcher unknown to this author. It is very interesting that the isothermal nozzle was proposed by Romer at el 1955 (who was behind the adviser or the student?). These researchers were the first ones to realized that choking can occurs at different Mach number ( $1/\sqrt{k}$ other then the isothermal pipe.