Numerical analysis of the shock train evolution in planar nozzles with throat length

In the present investigation, the behavior of compressible flow in planar nozzles with throat length is analyzed to determine the flow velocity range and pressure fluctuations in the throat section. The flow field was simulated in 2D computational domains with the ANSYS-Fluent R16.2 code. The RANS model was applied for steady-state flow. The governing equations used are the conservation of mass, momentum, energy, and the ideal gas equation of state. The Sutherland equation was used for the viscosity as a function of temperature. The Spalart-Allmaras turbulence model was used to model the flow turbulence, which was validated with experimental pressure data. In the throat section, for the central region of the flow, as the throat length increases, the flow fluctuates and decelerates. Oblique shock waves are produced, and a shock train region is formed. The flow velocity is transonic and is in the Mach number range of 1 to 1.2, and the static pressure is in the range of 0.37 to 0.52. Therefore, as a result of flow fluctuations, throat length has a significant effect on flow development.