低速轴对称层流射流流动形态和失稳机制的实验研究

本文应用染色液和悬浮粒子显示方法,进一步实验研究轴对称层流射流的流动形态及其失稳机制。首次成功地在从一定口径的喷嘴流出的低速轴对称层流射流中观察到环形回流流动。给出了射流随速度演化及实验容器边界对其流动形态影响的显示照片,发现实际射流的轴对称波动及失稳过程正好对应射流在容器底部产生的环形旋涡的生长和破碎过程。本文认为由于实验空间有限尺度对流动的限制改变了原来射流的流动形态和流场空间的拓扑性质,射流与实际边界的相互作用对实际射流的失稳和转捩有重要的影响。

EXPERIMENTAL STUDY OF LAMINAR FLOW AND INSTABILITY MECHANISM OF ROUND JET WITH LOW SPEED

The laminar flow and instability mechanism of a round jet are investigated by visualization methods of dye and particle tracers. The toroidal backflow in a low speed round jet issuing from a nozzle was observed successfully for the first time. The flow visualization photographs demonstrated both the evolution of jet flow and effect on it of bottom boundary of the test vessel. It was found that the axisymmetric disturbance occurring in the real jet and its instability process are corresponding just right to the growing and breakdown of the circle vortex due to the interaction of jet and vessel boundary. Since the finite dimension of test space will finally change the original jet flow and its topology, it can be held that the interaction of jet and vessel boundary has important influence on the instability and transitios process of the round jet. The experiment also shows that the upstream disturbance and buoyancy effects of dye liquid can deform the toroidal backflow of low speed round jet, which is why the phenomena was not observed in previous experiments.