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Insights into the local heat transfer of a submerged impinging jet: Influence of local flow acceleration and vortex-wall interaction

机译:深入了解水下撞击射流的局部传热:局部流加速度和涡流-壁相互作用的影响

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摘要

The present study of low Reynolds number submerged impinging jets, re-examines the cause of peaks in the radial distribution of the Nusselt number by way of a direct numerical simulation. Two peaks, commonly named the inner and the outer, were particularly studied. The laminar flow behavior within a Reynolds number range of 392 ≤ Re ≤ 1804 as well as different velocity inlet profiles (parabolic, 7th power, uniform) were examined under axisymmetric conditions. The inner peak was found to be associated to the radial distribution of the radial flow acceleration, which is strongly influenced by the velocity profile of the incoming jet. Based on an energy balance, a critical inflow velocity near the wall for the presence of the inner peak was derived analytically. The uniform velocity profile generates strong radial acceleration, which leads to the required inflow and the occurrence of the inner peak. The outer peak was found to be related to the appearance of large scale vortices and their interaction with the heated wall. However, in order to generate such large scale vortices a fluctuating inlet velocity was required. Both peaks, existing under laminar flow conditions, were found not to be related to turbulence, as is widely assumed in literature.
机译:低雷诺数浸没式射流的当前研究,通过直接数值模拟的方法重新检查了努塞尔数径向分布峰值的原因。专门研究了两个通常称为内部和外部的峰。在轴对称条件下检查了392≤Re≤1804的雷诺数范围内的层流行为以及不同的速度入口曲线(抛物线,7次方,均匀)。发现内峰与径向流加速度的径向分布有关,径向流加速度受到径向流的强烈影响。基于能量平衡,通过分析得出存在内峰的壁附近的临界流入速度。均匀的速度分布会产生很强的径向加速度,从而导致所需的流入和内部峰的出现。发现外峰与大规模旋涡的出现及其与加热壁的相互作用有关。然而,为了产生如此大的涡旋,需要波动的入口速度。正如文献中广泛假设的那样,发现在层流条件下存在的两个峰均与湍流无关。

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