水流中实验流体力学和计算流体力学的研究检测方案(粒子图像测速)

A complementary experimental and computational study of plunging breaking waves is presented that are generated in a two dimensional open channel flume using a bottom bump and impulsive accelerated flow. The time evolution of the transient wave and its flow properties are measured using experimental fluid dynamics (EFD): upstream and downstream velocity and flow rates using pitot probes; air-water interface elevation measurements and two dimensional particle image velocimetry in the wave breaking region. The computational fluid dynamics (CFD) methods are: Cartesian grid; embedded- boundary; hybrid HSM/GF/particle level set and VOF methods, and LES. CFD wave profiles at various time steps identifies the overall wave breaking process and major events: max wave height, first plunge, oblique splash-up, vertical jet, air entrainment, two repeats of these processes, dissipation and wave swept downstream which is qualitatively validated by EFD results. Both EFD and CFD results showed two subsequent plunging and splash-up events after the first plunge. After the wave breaks, the flow trends in mean velocity and vorticity observed in EFD are very similar to CFD which has more detailed resolutions of plunging, splashing, vertical jet and bubble entrainment. Current studies also revealed the occurrence of chaotic multiple splash-up events after the third plunging that produce span-wise vorticity and turbulence. Generation of a clockwise rotating bump vortex and an anticlockwise rotating span-wise wave breaking vortex that is created from the entrapped air after the breaking which transports turbulence from the trough towards the bulk fluid, were identified as the two important events. Mean values of turbulent kinetic energy (TKE) below the broken wave showed that the TKE levels increase by almost 90% after the first plunge and another 40% after the second plunge, after which as the wave is swept downstream by the accelerating mean flow the TKE dissipates.