Two-dimensional Flow Field Effect And Physical Stability Of Combined Artificial Reefs With PIV

Artificial reefs are man-made structure in the ocean, which is to improve the Marine ecological environment, to create a good habitat environment of Marine biological, and provide the place for fish breeding, growing, feeding and avoid the enemy, to protect, proliferate and enhance the catches. The study of the artificial reef flow field characteristics is the basis of the study, due to artificial reefs flow field-effect can cause biological changes in the environment, resulting in significant ecological effects, the size and strength of upwelling and back eddy flows are the two most important factors. The physical stability of the artificial reef put in the ocean is the emphasis of study at present, people should take full account of the stability of the actual seas which put artificial reefs, ensuring reefs can maximize their ecological benefits, and the stability of the reef has an important influence on ecological stability of the reef. At present, the physical stability analyze of artificial reef is to analyze anti-slip and anti-roll coefficient in the role of wave forces and current forces of the reef, to judge and stable performance of the reef.In this paper, we analyzed field-effect of the monomer and combination reef of the combination reef model(HTSK-CN-3) at different flow velocity and layout spaces by two-dimensional velocimetry analysis PIV, and get the best kind of place, layout spaces, as well as the high degree of reef and water depth ratio. And we analyzed and calculated the wave and current resistance of the combination reef(HTSK-CN-3) and pyramid reef(HTR-25 S type, TR-10 type), researched the force, anti-drift and anti-roll coefficient by combining the method of theoretical analysis and model test. We obtained stability of reefs in different conditions, and validated the results combined with on-site observations in eight different wave conditions and six different flow velocity conditions. The results show that: first, the rise velocity, height, area and back eddy area of single reef in combined reef model(HTSK-CN-3) were increasing with flow velocity, the largest speed of upwelling flow is 0.23 time as much as the incoming flow. Second, the scale and intensity of vertical combination reefs was best in pitch 1.0D, the model synergies was stronger and the area of vortices between the reef is larger than area of vortices behind the second post-reef, were less than single reef. Third, speed and wave height and wave period of the combined reef model was increasing with both force of wave and the flow, anti-drift safety factor S1 and S2 gradually decreases as the flow velocity,wave height and wave period, in eight condition safety factors of the anti-drift wave S1 was greater than 8.8, the anti-rollover safety factor S2 was greater than 10.6; come in six different anti-drift velocity S1 safety factor greater than 5.54, the anti-rollover safety factor was greater than 6.66. Fourth, to calculate the anti-drift safety factor S1 and S2 is 1.02 and 4.256 respectively, can remain stable in the waters, the stability of the model and the observed reefs are basically the same. Fifth, the wave force and drag force of TR-10 type of artificial reef are along with inflow velocity, wave height and wave period increasing. Both of the resistance to drift safety coefficient S1 and the rolling resistance safety coefficient S2 are gradually decreasing with increasing of inflow velocity and wave period. The resistance to drift safety coefficient S1 are always over than 1.027, the rolling resistance safety coefficient S2 are always over than 2.18 in 6 different inflow velocity. The resistance to drift safety coefficient S1 are always more than 1 under 7 different wave climate, but while under the wave climate H18T16, the anti-sliding coefficient is 0.987, the rolling resistance safety coefficient S2 are always over than 2.095 in 8 different wave climate. Based on the above analysis shows that the anti-slip, anti-roll performance of these three reefs is good, its function remains solid after putting on long-term, the best laid combination reef vertical spacing 1.0D.This article is willing to provide theoretical basis for reef-type optimization design, choosing of settling land, planning for the area of artificial reef region and reaching of their ecological effect; also supporting some scientific reference foundations for the constructing and development of artificial reef by comprehensively analyzing the fluid field effect and physical stability of 3 kinds of reef models.