In some numerical and practical situations, the nozzle inlet boundary quantities p_{in} T_{in}, ρ_{in}, and win (the pressure, temperature, density, and axial velocity at the nozzle inlet) are utilized to define the jet flow instead of the stagnation quantities p_{s}, T_{s} and ρ_{s} (the stagnation pressure, temperature, and density). In this short note, for given stagnation quantities p_{s}, T_{s}, and ρs, the inlet boundary conditions p_{in} T_{in}, ρ_{in}, and win are algebraically represented based on a local sonic assumption together with the isentropic expansion and adiabatic flow assumptions by employing three different gas models: the ideal gas model, the Abel-Noble gas model, and the Soave-Redlich-Kwong (SRK) real gas model. It is found that when the ideal gas model is employed, the deviation of inlet boundary condition defined by p_{in} T_{in}, ρ_{in}, and win from the real ones (taking the data from the SRK real gas model as reference) due to the real gas effect is much smaller than the deviation of the stagnation quantity ρs. As to the Abel-Noble gas model, though its ρs plot performs well and is quite accurate compared with the referenced SRK real gas model, its deviation of the inlet boundary conditions p_{in} T_{in}, ρ_{in}, and win due to the real gas effect is much larger than its deviation of the stagnation quantity ρs. The Abel-Noble gas model is not so ideal to be employed in the hydrogen jet simulation when the nozzle inlet boundary conditions p_{in} T_{in}, ρ_{in}, and win. are utilized. By these discussion it is made clear that how much the deviation is when for a hydrogen jet calculation the ideal gas or Abel-Noble gas model is utilized to determine the nozzle inlet boundary conditions p_{in} T_{in}, ρ_{in}, and win.
high pressure, hydrogen jet, inlet boundary condition, nozzle inlet, real gas effect