RANS simulations of the U and V grooves effect in the subcritical flow over four rotated circular cylinders

This paper presents a CFD study about the effect of the V and U grooves in the flow over four cylinders in diamond shape configuration at subcritical flow conditions（Re= 41 000）. The k- ε Realizable turbulence model was implemented to fully structured hexahedral grids with near-wall refinements. Results showed that the numerical model was able to reproduce the impinging flow pattern and the repulsive forces present in the lateral cylinders of the smooth cylinder array. As a consequence of the flow alignment induced by the grooves, a jet-flow is formed between the lateral cylinders, which could cause an important vortex induced vibration effect especially in the rear cylinder. The magnitudes of the shear stresses at the valleys and peaks for the V grooved cylinders were lower than those of the U grooved cylinders, but the separation points were delayed due the U grooves presence. It is discussed the presence of a blowing effect caused by counter-rotating eddies located near the grooves peaks that cause a decrease of the shear stresses in the valleys, and promote them at the peaks.

Different initial density turbidite sediments with coarse grain injection and their corresponding flow pattern: Additional insights from numerical simulation in a study case of South China Sea

The work presents the sedimentology and depositional results of the turbidity flow from Miocene to Pliocene along the North Slope of South China Sea(SCS).The integration of the core-log-seismic data has enabled us to clarify turbidity flow with different density and characterize their corresponding seismic geomorphic sedimentation.Based on the differences between the initial density and the later,we classified the turbidity flow into two types,namely:low-and high-density flow with coarse grain injection.According to the hydrodynamic numerical simulation results,we constructed different subcritical turbidity flow models with various density and rebuilt the depositional pattern along the slope.As to the numerical simulation model,we introduced the erosion rate into the classical full Reynolds-averaged N-S(RANS)equation,which is suitable to the deep-sea slope area.Through comparison of the above simulation models,the results show that the high-density turbidites with coarse-grained injection are mostly developed with lower vertical erosion rates and higher lateral abrasion rates.They are characterized with multi-branched and lobe-shaped sedimentary volumes,while low-density turbidites with coarse-grained injection are characterized with higher vertical erosion rates and lower lateral abrasion rates.And this kind of turbidites can generate single-branched and banding deposits.In addition,the fluctuating sea levels and the varying topographies are important to influence the subcritical turbidity flow models in the deep-water slope.