Vortex Structure and Heat Transfer in the Stagnation Region of a Two-Dimensional Impinging Jet (Simultaneous Measurements of Velocity and Temperature Fields by DPIV and LIF)

Velocity and temperature in the stagnation region of a two dimensional impinging jet were simultaneously measured by digital particle image velocimetry (DPIV) and Laser-induced fluorescence (LIF). Instantaneous thermal flow fields and spatial correlation of the vorticity and the turbulent heat flux show that a streamwise vortex pair in the stagnation region sweeps cold fluid toward the wall and ejects high-temperature fluid toward the outer region. The weighted PDF of the turbulent heat flux indicates that the contribution of the ejection to the net heat flux is dominant. The streamwise vortex pair is transported from the free-jet region and the vorticity is amplified by the mean strain in the vicinity of the wall.