The Investigation of the Hydrodynamics of an Artificial Reef - Aquaculture and the Environment: A Shared Destiny - page 91

4.2.4 The effect of reef height on the back vortex flow field
The length of the back vortex flow is almost equal to the distance of the water flow
reattachment point from the original point, which is a significant characteristic quantity for
back vortex flow. Consequently, L rp and S e are used to measure the scale of the back vortex
flow field. The unit artificial reef effect relative to the length and area of the back vortex flow
field is represented by L eA and S eA .
In Fig. 12, the length from the water current reattachment point to the artificial reef and
the area of back vortex flow increase continually with increasing reef height. L rp with h
(in x axis) presents an exponential growth relationship, and the relevant relational
equation is y=1.09e x/5.46 +0.20. A good correlation coefficient of 0.9976 is acquired. The
quadratic polynomial fitted equation for the area of the back vortex flow (y) and reef
height (x) is expressed by y=0.21x 2 -1.11x+3.03, and the homologous correlation
coefficient is 0.9973.
Fig. 12. L rp and S e with different heights of artificial reefs
As shown in Fig. 13, the variation curves of L eA and S eA with reef height are similar to some
degree. The values of L eA and S eA are the minimum at the reef height of 6.0 cm; after that
point, there is a relatively fast increase, and a steady value is maintained until 9.0. There are
three large values appearing at the heights of 4.0, 7.5 and 10.0, which can be used for the
artificial reef designers as a reference.
Fig. 13. L eA and S eA with different heights of artificial reefs
4.2.5 Brief conclusion
Considering the economical problems and the stability of artificial reef in a certain depth of
water, the height of artificial reef cannot be raised excessively. According to the results