Eddy-Viscosity and Stress-Transport Turbulence Models in Application to a Plane Synthetic Jet

A two-dimensional unsteady plane jet is computed using four turbulence models. The strain field generated by the ‘synthetic’ (reciprocating) jet under consideration contains regions of strong normal and shear straining, while vortex pairs formed by the issuing jet are highly rotational. Turbulence closures at the eddy-viscosity level (standard k???ε and two-timescale models) and two stress-transport closures (the ‘basic’ model and a two-component-limit scheme) are examined against experimental data. It is found that the extreme nature of the strain environment presents a severe challenge to the models tested; in particular, fundamental weaknesses in the constitutive equation of linear eddy viscosity models are highlighted. An additional term in the dissipation rate equation of the two-timescale model is found to hinder the formation of clearly defined starting vortex pairs which play a critical role in determining the near-field pattern of synthetic jet development. The stress-transport models are able to reproduce measured turbulence quantities with a greater degree of accuracy, and the two-component-limit formulation shows an improvement over the basic model.