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为了研究过渡流下后向台阶的流动与瞬态传热特性,建立了二维不可压缩后向台阶流动的数值传热模型,采用非定常数值方式模拟了后向台阶的内部流场,比较了台阶下游底面瞬时努塞尔数Nu和时均努塞尔数Nu_m的分布,分析了台阶下游通道内温度分布规律。结果表明:过渡流下台阶底面Nu数沿着流动方向出现多个峰值,Nu数始终围绕Nu_m数发生波动。Re数为700时,主回流区未出现二次回流,Nu数在主回流区下游才发生波动;Re数为1200时,主回流区出现二次回流,Nu数在主回流区就发生了波动。台阶下游通道内温度沿法向呈阶梯式变化,Re数越大,近底面处的温度变化梯度也越大。
In order to study the characteristics of flow and transient heat transfer after the transition flow, the numerical model of two-dimensional incompressible backward flow is established, and the unsteady numerical simulation is used to simulate the flow field of the backward flow. The instantaneous Nusselt Nu number and the Nusselt number Nu_m at the bottom of the downstream are analyzed and the temperature distribution in the downstream channel is analyzed. The results show that there are several peaks along the flow direction of Nu number in the bottom of transitional step, and the Nu number always fluctuates around Nu_m number. When the Re number is 700, no secondary backflow occurs in the main recirculation zone and Nu number fluctuates downstream of the main recirculation zone. When the Re number is 1200, the secondary recirculation occurs in the main recirculation zone and the Nu number fluctuates in the main recirculation zone . The temperature in the downstream channel of the step changes in a stepwise manner along the normal direction. The larger the Re number is, the greater the gradient of the temperature change near the bottom surface is.