We propose a simple model for turbulent contribution to the frictional drag in a wall-bounded turbulent flow based on the characteristic parameters of turbulent bursting events, it is verified on water and drag-reduci...We propose a simple model for turbulent contribution to the frictional drag in a wall-bounded turbulent flow based on the characteristic parameters of turbulent bursting events, it is verified on water and drag-reducing surfactant solution flows investigated by particle image velocimetry in experiments. It is obtained that the turbulent contribution to the skin friction factor is linearly proportional to the product of the spatial frequency and strength of turbulent bursts originated from the wall.展开更多
We report the detailed information of a purely elastic instability and its mixing enhancement effect in a viscoelastic fluid flow driven by a constant pressure gradient along a curvilinear channel obtained for the fir...We report the detailed information of a purely elastic instability and its mixing enhancement effect in a viscoelastic fluid flow driven by a constant pressure gradient along a curvilinear channel obtained for the first time from the three-dimensional direct numerical simulations(DNSs)of this kind of flow geometry.Three-dimensional unstable flow structures similar to those visualized in experiments are realized through the DNSs.The inception of elastic instability,conformation of microstructures,statistical and dynamic information of velocity field and the mixing enhancement effect caused by elastic instability are then discussed.展开更多
文摘We propose a simple model for turbulent contribution to the frictional drag in a wall-bounded turbulent flow based on the characteristic parameters of turbulent bursting events, it is verified on water and drag-reducing surfactant solution flows investigated by particle image velocimetry in experiments. It is obtained that the turbulent contribution to the skin friction factor is linearly proportional to the product of the spatial frequency and strength of turbulent bursts originated from the wall.
基金Supported by National Natural Science Foundation of China under Grant No 51076036the Foundation for Innovative Research Groups of the National Natural Science Foundation of China under Grant No 51121004+1 种基金the Fundamental Research Funds for the Central Universities under Grant No HIT.BRET1.2010008the Japan Society for the Promotion of Science(JSPS)Research Fellowship.
文摘We report the detailed information of a purely elastic instability and its mixing enhancement effect in a viscoelastic fluid flow driven by a constant pressure gradient along a curvilinear channel obtained for the first time from the three-dimensional direct numerical simulations(DNSs)of this kind of flow geometry.Three-dimensional unstable flow structures similar to those visualized in experiments are realized through the DNSs.The inception of elastic instability,conformation of microstructures,statistical and dynamic information of velocity field and the mixing enhancement effect caused by elastic instability are then discussed.
