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In this paper, a dimensionless numerical study of the flow-field and heat transfer characteristics of an incompressible turbulent slot jet impinging obliquely over a moving surface of finite thickness is presented. Simulations were performed using $k-ϵ$ eddy viscosity turbulence model. The temperature field was solved simultaneously in the solid and the fluid domain. For a fixed impingement distance and a fixed Reynolds number, the impingement angle ($\varphi$) and plate velocity ($U_p$) were varied in the range of 30–75^∘ and 0–0.3, respectively. In the results, the length of the potential core depends on the jet inclination, which increases with increase in jet angle. The jet angle and plate velocity have more influence on the uphill side compared to the downhill side. The location of stagnation displaces toward the uphill side as the inclination angle decreases, and the drifting of stagnation point is noted with the variation in plate velocity. The average skin-friction coefficient increases with increase in $\varphi$ and $U_p$, and the influence of $U_p$ on the skin-friction coefficient is reduced as $\varphi$ increases. The maximum Nusselt number ($N{u}_{max}$) increases with increase in $\varphi$, and the drifting of $N{u}_{max}$ is observed with increase in plate velocity. It is found that the average Nusselt number increases quickly with increase in plate velocity for lower angles of impingement. The distribution of local heat flux follows the same trend as the local Nusselt number.

This paper presents an implementation of an improved smoothed particle hydrodynamics (SPH) method for simulating violent water impinging jet flow problems. The presented SPH method involves three major modifications on the traditional SPH method, (1) The kernel gradient correction (KGC) and density correction are used to improve the computational accuracy and obtain smoothed pressure field, (2) a coupled dynamic solid boundary treatment (SBT) is used to remove the numerical oscillation near the solid boundary and ensure no penetration condition, (3) a free surface condition, which is obtained from the summation of kernel function and volume, is used to describe the water jet accurately. Different cases about violent impinging jet flows are simulated. The influences of impact velocity and angles are investigated. It is demonstrated that the presented SPH method has very good performance with accurate impinging jet patterns and pressure field distribution. It is also found that the pressure time histories of observation points are greatly influenced by the rarefaction wave from surrounding air. Closer distance from free surface can lead to quicker decay of the pressure time history.

According to recent trends in the field of miniature electronics, the need for compact cooling solutions compatible with very thin profiles and small footprint areas is inevitable. Impinging synthetic jets are recognized as a promising technique for cooling miniature surfaces like laptops, tablets, smart phones and slim TV systems. Effect of jet to cooled surface spacing is crucial in cooling performance as well as predicting Nusselt number for such spacing. An experimental study has been performed to investigate the cooling performance of two different synthetic jets actuated with piezoelectric actuators cooling over a vertical surface. Results showed that a major degradation of heat transfer when jets are close to the surface is occurred. Slot synthetic jets showed a better performance in terms of coefficient of performance (COP) than semi-confined circular jets for small jet to surface spacing. Later, a correlation is proposed for predicting Nu number for a semi-confined circular synthetic jet accounting the effects of Re number ($500\le \mathrm{\text{Re}}{}_j\le 1150$), jet-to-surface spacing ($H∕D=2$ and $H∕D=4$) and the stroke length ($1.75\le L{}_0∕D\le 4.75$ and $L{}_0∕H<2.5$). It is found that correlation can provide predictions with an $R{}^2$ value of over 98%.