Turbulent mixing of coaxial jets between hydrogen and air

Hydrogen-air mixing in coaxial jets was investigated using a one-equation model to simulate the velocity scale of turbulence. Combining the density fluctuation with other fluctuating components to define the eddy exchange coefficients, a set of empirical constants was derived for the closure of the partial differential equations that govern the mixing process of heterogeneous fluids. Comparing the numerical results with available experimental data, good agreements were obtained for distributions in velocity, shear stress, enthalpy, and species concentration along both axial and radial directions. The density fluctuation in hydrogen-air mixing, which is very difficult to measure, can be treated by the same method for compressible flows in a homogeneous fluid, provided that the kinetic energy of turbulence is considered simultaneously with all other governing equations.