A Numerical Analysis of Hydrogen Underexpanded Jets

The aim of this work is the study of the fluid dynamic structure of underexpanded hydrogen jets by using a High Performance Computing (HPC) methodology. An axial symmetric two-dimensional turbulent flow model, which solves the Favre-averaged Navier-Stokes equations for a multicomponent gas mixture, has been implemented and validated. In order to predict the decrease in spreading rate with increasing Mach number, a compressibility correction has been added to the turbulence closure model. The flow model has been assessed by comparing spreading and centerline property decay rates of subsonic jets at different Mach numbers with those obtained both by theoretical considerations and experimental measurements. Besides, the Mach disk structure of an underexpanded jet has been analysed, thus confirming the suitability of the computational model. To take into account the effects of real gases, both van der Waals and Redlich-Kwong equations of state have been implemented. The computations performed under ICEs conditions show that the values of Mach number and pressure just behind the Mach disk are affected by the use of real gas equations