On self-preserving, variable-density, turbulent free jets (Q1106051)

Appropriately defined Gaussian error-functions are shown to represent closed-form solutions of self-preserving, axisymmetric, variable density, free turbulent jets. The turbulent diffusivities of momentum, mass or heat associated with such solutions are found to vary both in the streamwise and radial directions, and are different from each other. An entrainment function for the jet can also be derived from the present analysis. The entrainment coefficient is found to be uniquely related to the turbulent Reynolds number, \(Re_ t\), of the jet, which is one of the two parameters in the closed-form solutions. Inverse centreline values of velocity, density, mass fraction and temperature are found to be linearly proportional to the streamwise coordinate as are the spread of velocity and scalar. If the two parameters are determined from jet spread data, the resulting closed-form solutions are in good agreement with measurements.