Experimental Study Of Coherent Structure In A Solid-liquid Turbulent Boundary Layer

Solid-liquid turbulent flows are common in industrial and engineering processes.Study the interactions between particles and turbulence and turbulence modulation are extremely significant,which can play an guidance function on practical engineering application for heat and/or mass transfer in chemical process.Coherent structure in the turbulent boundary layer of particle-laden flows was experimentally investigated using Particle Image Velocimetry(PIV).Study the change of mean velocity profile and turbulent intensity in the horizontal turbulent boundary layer of water and with polythene,which was used as dispersed phase.According to the relationship of the logarithmic law mean velocity profile and friction velocity,fluid viscosity coefficient etc.inner scale physics quantities,the turbulent fricition drag and friction coefficient are measured with the method of mean velocity profile,by nonlinear iterating to fit the skin friction coefficient_*u.Providing experimental foundations for acquainting the mechanism of effect of particle on turbulence.Based on the concept of multi-scale spatial locally averaged structure function,conditional sampling and phase average methods were employed to extract and analysis the spatial topologies of streamwise and normal fluctuating velocities,spanwise vorticity,Reynolds shear stress for the ejection and sweep events.The result show that the buffer layer of turbulent boundary layer has thinning tendency and logarithmic layer down-shift,the turbulence intensity and reynolds stress were also enhanced due to the existence of particle.The amplitude of longitudinal and vertical fluctuating velocity components,as well as spanwise vorticity and Reynolds shear stress were manipulated obviously both for ejection and sweeping events,all parameters were increased.It is implying that the the turbulence intensity of two burst events near-wall region increase,momentum and energy transport strengthen.