No abstract

Therefore, this study employs Large Eddy Simulation to investigate the impinging heat transfer of the pulsed chevron jet on a semi-cylindrical concave plate at f=20Hz and H/d=4. The instantaneous temperature of the target plate is highly associated with the behavior of the pulsed jet. The temperature sharply decreases once it is covered by the cooling wall jet, and then sharps increases only when the jet injection is off. The pulsation plays a significant role in the formation and evolvement of the coherence structure. At the time of t=0.1 φ, the pulsed jet has covered the stagnation region. The stripe-shaped coherence structure is vertical to the ring-shaped secondary vortex. The secondary vortex becomes broken and unsteady as moving downstream. When the jet is off, the wall jet moves downstream because of inertia. There is no remnant cooling wall jet covering the target plate. There is no recirculation zone along the curvilinear direction during the duty cycle, while the recirculation zone is formed only when the jet injection is off. The hot wall jet along the curvilinear direction is entrained through large-scale recirculation and then returns to the target plate. The influencing area of the recirculation zone of the pulsation becomes larger and more closed to the jet mainstream compared with the steady jet. The existence of pulsation enlarges the spreading width of the jet core compared with a steady jet. The proportion of velocity and pressure in primary frequency dominates the pulsed jet, and the proportion in higher order can be neglected.