Entrainment rate predictions of axis-symmetric non-swirling free jets for engineering applications: Hydrogen, helium, propane and carbon dioxide jets entraining air

As an extension to our previous work “ Entrainment Rate Predictions of Axis-Symmetric Non-Swirling Jets using Free-Jet-Theory, Reynolds-Averaged Navier-Stokes Modelling and Large-Eddy-Simulations Resolved up to Kolmogorov Scale ”, it is necessary to determine whether the drawn conclusions remain applicable to low and high-density fluids. In this paper Helium, Hydrogen, Carbon-Dioxide and Propane jets entraining air are computed using RANS based Computational Fluid Dynamics with five turbulence models. The focus is on the entrainment in the far-field region e.g. x/d 0 ≥ 60. It has been observed that Realizable k-є model predicts the entrainment with an error margin not larger than 2 % also for the variable density jets outperforming by far the other turbulence models. The well-known Ricou&Spalding correlation provides the entrainment figures within 4 % error margin. We recommend both tools for engineering applications where speed and simplicity matter. The helium jet was also computed using Large Eddy Simulations with the filter size of the order of Kolmogorov scale throughout the jet flow-field; the entrainment was predicted within 0.2 % margin from the measure data for the helium jet. Such an excellent accuracy was however achieved at the expense of prohibitively large computational resources. • This publication is an extension of our previous work to gases different from air. • Realizable k-є model has outperformed the other turbulence models by far. • The LES has provided excellent predictions - just as Realizable k-є model - for the low Reynolds number jet.