On the turbulent energy transport related to the coherent structures in a planar jet

In this study, the turbulent energy transport related to the coherent vortex structures in the self-similarity region of a turbulent planar jet is investigated experimentally. First, two velocity components and the pressure are measured at multiple points simultaneously through the use of a “combined probe” comprising of a pressure probe and an X-type hot-wire probe. Then, proper orthogonal decomposition (POD) is applied to obtained velocity and pressure field data to extract the coherent vortex structures in the jet. A complementary technique combining POD and linear stochastic estimation is then used to reconstruct the spatiotemporal velocity and pressure field for the dominant POD modes. In the reconstructed velocity and pressure field, a coherent vortex structures which have counter-rotating vortices staggered with respect to the jet centerline are observed. This structure contained approximately 42% of the total energy. Finally, the turbulent energy transport related to the coherent vortex structure is evaluated from the reconstructed velocity and pressure field. This estimation shows that the production and pressure diffusion of the turbulent energy in the jet strongly depend on the discussed coherent vortex structures.