Study On Local Characteristics Of The Flow Through A Circular Array Of Non-submerged Cylinders

Aquatic plants is an important part of natural river ecological system.Vegetation communities which provide hydrophilic animals with food and habitat make the water possess the vitality of aquatic ecological environment,thus it preserve the biodiversity of the aquatic environment.However,although aquatic plants can improve the water environment,maintain the biodiversity and the riverbed stability,simultaneously it increase the flow resistance and energy consumption,lower the river velocity,improves the rivers level,reduces the flood discharge capacity of the channel and finally increase the risk of flooding.The open-channel flow within vegetation which make two unrelated subject fluid mechanics and ecology closely linked together became a focal point of environmental fluid mechanics,therefore the study of this problem has very important engineering significance.Rigid cylinders are chosen as the numerical model after reviewing and summarizing the theoretical development system and recent research progress about this research subject.A 3D numerical simulation for the flow through a circular array of non-submerged rigid cylinders is performed using hydrodynamic numerical model with free surface coupled with SST(shear strain transport)k-?turbulent model.The model is first verified and validated by means of the comparison analysis with experimental data.The characteristic of circumferential flow field is analyzed to study the steady shear layer length in the wake region,shear layer infiltration length inside the patch,the distribution of the Reynolds stress and turbulence kinetic energy and the spatial distribution of the bed shear stress induced by flows with different cylinder Reynolds numbers and different solid volume fraction.The main work in this paper is given as follows:(1)This paper based on he transverse longitudinal time average velocity distribution analysis the steady shear layer length in the wake region,shear layer infiltration length inside the patch and the width of the shear layer along the flow direction with different cylinder Reynolds numbers and different solid volume fraction.It determine the trend along with the Re_d and?.(2)This paper study the cylinders how to affect the bed sediment based on the analysis of dimensionless bed stress.(3)Instantaneous vorticity field and velocity contours within the patch and the wake region are given to analyzed the instantaneous flow field structure.This paper according to the time fluctuating velocity study the distribution of Reynolds stress at different cross section within the patch and the wake region.