后向台阶尾部流场高分辨层析PIV数据集中的流动结构辨识
The flow behind a backward facing step of 6 mm in height has been investigated by means of highresolutiontomographic PIV. The shedding of vortices was stabilized by acoustic excitation, enabling phaselockedmeasurements of the flow field in a volume of 70x95x7 mm3. The gathered vector volumes with avector spacing of approx. 0.25 mm in each direction were investigated by the method of conditionalaveraging. Basic flow structures, related to Q2 and Q4-events were extracted and their development in timewas characterized, using methods of joint probability density functions of the fluctuations and of theinvariants of the velocity gradient tensor.