Comparative study of the vorticity field in turbulent flows: Theory, experiments and computations. Final report

Abstract

We have carried out a comprehensive study of unexcited and excited elliptic jets, addressing the effects of initial conditions, aspect ratio, excitation frequency, and excitation amplitude. We have studied the dynamics of the preferred mode structure and interactions of coherent structure in the near field of elliptic jets. The dynamics of elliptic jets are quite different from the extensively studied plane and circular jets -- owing mainly to the fact that the azimuthal curvature variation of a vortical structure causes a nonuniform self-induction and hence complex three-dimensional deformation. Such deformation, combined with properly selected excitation, can substantially alter entrainment and other turbulence phenomenon, thus suggesting a preference for the elliptic shape in many jet applications. In the following, we mention a few key results.