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首页> 外文会议>American Society of Mechanical Engineers(ASME) Summer Heat Transfer Conference(HT2005); 20050717-22; San Francisco,CA(UA) >FLOW BIFURCATIONS AND HEAT TRANSFER ENHANCEMENT IN ASYMMETRIC GROOVED CHANNELS
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FLOW BIFURCATIONS AND HEAT TRANSFER ENHANCEMENT IN ASYMMETRIC GROOVED CHANNELS

机译：不对称槽形通道中的分流和传热增强

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摘要

Numerical investigations of the flow bifurcations, transition scenario and heat transfer enhancement in asymmetric grooved channels are performed by direct numerical simulations of the mass, momentum and energy equations. The governing equations are solved for laminar and time-dependent transitional flow regimes by the spectral element method in a periodic computational domain with appropriated boundary conditions. Numerical results show a flow transition scenario with two Hopf bifurcations B_1 and B_2, occurring in critical Reynolds numbers Re_(c1) y Re_(c2), respectively. Fundamental frequencies ω_1 and ω_2 and super harmonic combinations of both develop as the Reynolds number increases from a laminar to higher transitional flow regime. Numerical calculations demonstrate that the time-average mean Nusselt number (the non-dimensional heat transfer rate), increases significantly as the flow passes from a laminar to a periodic-and then to a quasi-periodic flow regime. This increase is accompanied by a reasonable increase in both the friction factor and the pumping power. The obtained behavior is comparable to other geometries and configurations as well as to previously reported numerical results for the studied geometry. This numerical investigation shows a transition scenario at the onset of turbulence, similar to the Ruelle-Takens-Newhouse scenario, which has not been found or reported by other researchers using this geometry. The numerical simulation results also show the existence of a bifurcation scenario that develops a path-dependent flow and heat transport behavior. In the vicinity of the first Hopf flow bifurcation (and consequently, the critical Reynolds number Re_(c1)) the resulting stable time periodic flow depends on both the initial flow conditions and the way in which the incremental process to higher flow regimes is carried out.
机译：通过质量，动量和能量方程的直接数值模拟，对非对称沟槽通道中的流动分叉，过渡情况和传热增强进行了数值研究。在适当的边界条件下，通过周期性计算域中的谱元方法，针对层流和时间相关的过渡流态求解了控制方程。数值结果表明，在临界雷诺数Re_（c1）y Re_（c2）中分别出现具有两个Hopf分叉B_1和B_2的流动过渡情形。随着雷诺数从层流向更高的过渡流态增加，基本频率ω_1和ω_2以及超谐波组合都会发展。数值计算表明，随着流从层流流向周期性流向准周期性流态，时间平均Nusselt数（无量纲传热速率）显着增加。这种增加伴随着摩擦系数和泵送功率的合理增加。所获得的行为可与其他几何形状和配置以及先前报告的研究几何数据的数值进行比较。此数值研究显示了湍流开始时的过渡情形，类似于Ruelle-Takens-Newhouse情形，其他研究人员尚未发现或报告过使用这种几何形状的情形。数值模拟结果还显示了存在分叉情况的情况，该分叉情况发展了与路径有关的流动和传热行为。在第一霍普夫分流附近（因此，临界雷诺数Re_（c1）），所产生的稳定的时间周期流量取决于初始流量条件和进行向更高流量状态的增量过程的方式。

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