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首页> 外文会议>2002 ASME International Mechanical Engineering Congress and Exposition , Nov 17-22, 2002, New Orleans, Louisiana >Control of Convective Heat Transfer in a Confined Laminar Impinging Jet by Low Amplitude Forcing
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Control of Convective Heat Transfer in a Confined Laminar Impinging Jet by Low Amplitude Forcing

机译：低振幅强迫控制密闭层流射流中的对流传热

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A numerical finite-difference model, derived using a control-volume approach, was used to compute the flow and heat transfer characteristics in a two-dimensional confined laminar air jet impinging on an isothermal surface. Several cases were considered with Re=650, 750, and nozzle to plate spacing, H/W=5. The behavior of the jet and the attendant heat transfer from the target wall were investigated when the jet was forced by fluidic excitation at the nozzle exit. At Re between 585 and 610, the unforced jet exhibits a transition to an unsteady regime leading to asymmetric vortex shedding and jet flapping. Investigation of the velocity spectra indicate three distinct dominant modes; the lowest frequency is associated with the jet flapping while the highest frequency is associated with the asymmetric vortex formation which causes buckling of the jet column. As a result of the two combined modes, the peak heat transfer is enhanced and the lateral cooling extent is broadened. The jet was subjected to forcing by introduction of numerical excitation at each side of the jet that modeled fluidic excitation. The jet was forced on both opposing sides at its exit, both with in-phase and out-of-phase modes. Under some conditions, out of phase forcing at Re=650 at the highest frequency leads to stabilization of the normally separated flow on one side only. This unusual asymmetric flow field is unsteady but repeatable, and results in an enhancement of the heat transfer. At Reynolds number of 750, forcing with an out of phase mode at the highest frequency leads to a complete stabilization of the jet. The forcing suppresses the high-amplitude low frequency flapping mode leaving only a high frequency vortex formation mode. The suppression of the jet flapping leads to a decrease in the peak heat transfer, but because separation is suppressed, the average wall heat transfer is enhanced.
机译：使用控制体积方法导出的数值有限差分模型用于计算撞击在等温面上的二维约束层流空气射流的流动和传热特性。考虑了几种情况，Re = 650、750，喷嘴到板的间距为H / W = 5。当射流在喷嘴出口受到流体激励时，射流的行为和随之而来的从目标壁的传热被研究。在585至610之间的Re处，无力射流向不稳定状态过渡，导致涡旋脱落和射流拍打不对称。速度谱的研究表明了三种不同的主导模式。最低频率与射流拍打有关，而最高频率与不对称涡流形成有关，这会引起射流柱弯曲。两种组合模式的结果是，峰值传热得到了增强，横向冷却范围得到了扩大。通过在模拟流体激发的射流的每一侧引入数值激励，使射流受到强迫。射流以同相和异相模式被迫在其出口的两侧相对。在某些情况下，在最高频率Re = 650时，异相强制将导致仅一侧正常分离流动的稳定。这种异常的不对称流场不稳定，但可重复，从而提高了热传递。在雷诺数为750时，以最高频率强制采用异相模式会导致射流完全稳定。强迫抑制了高振幅低频拍动模式，仅留下了高频涡旋形成模式。射流拍打的抑制导致峰值传热的降低，但是由于抑制了分离，所以平均壁传热得到了增强。

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