Fundamental Research on Flow and Heat Transfer Characteristrics of Turbulent Duct Flow with Injection

对圆管内均匀喷射流过管壁的热流AIF流动进行了数值分析。结果表明，该分析方法可用于预测自保流区的壁面摩擦系数和压力梯度。对雷诺数为6000的完全发展的湍流流动进行了实验研究，得到了在两种注入速率下，均匀的流体通过底部多孔壁进入矩形亚克力管道的实验结果。利用激光多普勒测速仪测量了流场的流向和横向速度分布。得出以下结论：(1)在多孔壁附近，-UV的绝对值在喷射点附近急剧减小，流动趋于局部层流。这是由于湍流的产生和再分配机制的改变所致。(2)靠近上壁面，流动也趋于层流。这一趋势是由水流加速和湍流再分布机制的改变引起的。对上述信号进行了象限处理。研究发现，随着喷射率的增加，多孔壁面附近相干流体运动中喷出引起的雷诺剪应力减小。为定量预测喷嘴起始点附近的再分层和测量自保流区内的湍流量，近期将进行数值分析。

Numerical analysis was carried out for thurbulent aif flow in a circular tube with uniform injection through the tube wall surface. The analysis was found to be useful for predicting the skin-friction coefficient and the pressure gradient in the self-preserving flow region. The present analysis predicted also qualitatively well the local reduction of turbulence intensity in a region just downstream of the starting point of the injection.An experimental study was made on a fully developed turbulent flow of air at a Reynolds number of 6000, entering a rectangular acrylic duct with uniform fluid injection through the bottom porous wall at two injection rates. Measurements were made of the streamwise and transverse velocity distributions by means of a Laser Doppler Velocimeter. The following conclusions were drawn: (1) Close to the porous wall, the absolute value of -UV^^^ decreases rather sharply around the starting point of injection, and the flow tends to be locally laminar. This is caused by the change of mechanisms both the turbulence production and the redistribution of turbulence. (2)Close to the upper wall, the flow also tends to be laminar. The tendency is caused by the flow acceleration and by the change of the redistribution mechanism of turbulence.The signals obtained above were also processed by using a quadrant method. It was found that the Reynolds shear stress caused by the ejection in the coherent fluid motion near the porous wall decreases with an increase of the injection rate.Some features of the turbulent duct flow with injection were clarified by the present research. The numerical analysis for predicting quantitatively the relaminarization near the starting point of injection and measurement of turbulence quantities in the self-preserving flow ragion will be proceeded in the near future.