Numerical Simulation Of Flow Field Effects On Artificial Reefs

Based on Fluent software,a numerical model of the flow field effects of artificial reefs under the action of both wave and current dynamics was established and verified respectively to prove the correctness and validity of the numerical model.Firstly,the velocity distribution pattern around the artificial reef and the relative area of upwelling area and slow flow area were used as two parameters to describe and evaluate the flow field effect of the reef,and the flow field effect of three different structural types of artificial reefs,namely,cubic type,hexagonal type and frame type,were compared and analyzed.The results show that the relative area of the upwelling area of the hexagonal reef is larger under the same water flow conditions(the difference of the slow flow area is not significant),and it is easier to construct a soft flow field suitable for fish survival.Secondly,the effects of flow direction and velocity,Re number,relative submergence depth and reef relative width on the flow field effect of hexagonal artificial reef were discussed under the current conditions.The research results show that the relative height and area of the upwelling and slow flow areas show a decreasing trend as the angle of water flow increases,so the reefs should be placed against the flow in the practical application of engineering;The relative area of upwelling varies in the range of 1.9 to 2.0 as the current velocity increases,and the area of the slow flow region is about 3 to 4 times the area projected by the incoming flow toward the reef;When Re is 1.5～30E6,the relative length and relative area of the slow flow area are gradually decreasing,so the reefs should be placed in the sea area with smaller Re in the practical application of engineering;With the increase of relative inundation depth,the scope of upwelling area is gradually reduced and the decreasing trend of slow flow area is significant.Among them,the relative submergence depth is 0.2,the relative length and relative area of the slow flow area is the largest,so the relative submergence depth of the reef is set to about 0.2 in the practical application of engineering;When the relative width of the reef is 1～5,the best width to height ratio to obtain the relative area of upwelling and slow flow area is 2～4and 2 respectively,therefore,the width of the hexagonal artificial reef should be taken as 2times of the height in the practical application of engineering.Finally,the effects of wave height and period on the flow field effects of hexagonal artificial reefs were discussed under wave conditions.When the period is fixed at 9s and the wave height varies in the range of 2m to 5m,the effect range of vertical velocity is about 1.5 to1.6 times of the reef height,and the effect range of horizontal velocity is about 1.1 to 1.5 times of the reef length.When the wave height is fixed at 3.5m and the period varies from 5s to 11 s,the influence range of vertical velocity is about 1.1 to 1.7 times of the reef height,and the influence range of horizontal velocity is about 1.0 to 1.7 times of the reef length.