Turbulent Kinetic Energy in Bolt Fishway

Swimming kinematics of rainbow trout behind cylinder arrays: the effect of vortex street periodicity and turbulence kinetic energy

Fish in the wild often contend with complex flows that are produced by natural and artificial structures. Research into fish interactions with turbulence often investigates metrics such as turbulence kinetic energy (TKE) or fish positional location, with less attention paid to the specific interactions between vortex organization and body swimming kinematics. Here we compare the swimming kinematics of rainbow trout ( Oncorhynchus mykiss ) holding station in flows produced by two different 3 x 5 cylinder arrays. We systematically utilized computational fluid dynamics to generate one array that produced a Kármán vortex street with high vortex periodicity and TKE (KVS array), and another that produced low periodicity and TKE, similar to a parallel vortex street (PVS array). The only difference in swimming kinematics between cylinder arrays was an increased tail beat amplitude in the KVS array. In both cylinder arrays, the tail beat frequency decreased and snout amplitude increased compared with the freestream. The center of mass amplitude was greater in the PVS array than in only the freestream, however, suggesting some buffeting of the body by the fluid. Notably, we did not observe Kármán gaiting in the KVS array as in previous studies. We hypothesize that this is because (1) vorticity was dissipated in the region where fish held station in this study and (2) cylinder arrays produced vortices that were in-line rather than staggered. These results are the first to quantify the kinematics and behavior of fishes swimming in the wake of multiple cylinder arrays, which has important implications for biomechanics, fluid dynamics, and fisheries management.

SUMMARY STATEMENT

The swimming kinematics of rainbow trout are largely preserved across two, 3 x 5 cylinder array treatments that differed in vortex periodicity and turbulence kinetic energy.

Turbulent Kinetic Energy Distribution around Experimental Permeable Spur Dike

The spur dike is widely used in the waterway renovation project in the upper reaches of the Yangtze River as a remediation structure, but its water destruction is very common, and the influence of the permeable characteristics of the riprap spur dike on its stability has been neglected in many studies. Through the method of combining a generalized flume test and theoretical analysis, the influence of the submerged degree of the permeable spur dike, the porosity of the spur dike body, and the size of the void on its nearby turbulent kinetic energy is studied. The results show that the turbulent kinetic energy in the front of the spur dike increases with the increase of the submerged degree, decreases with the increase of the porosity, and first increases and then decreases with the increase of the pore size. At the axis of the dike, the turbulent kinetic energy increases with the increase of the submerged degree, decreases first and then increases with the increase of the porosity, and increases with the increase of the pore size. In the rear area of the dike, the turbulent kinetic energy decreases with the increase of the submerged degree, firstly decreases and then increases with the increase of the porosity, and first increases and then decreases with the increase of the pore size. The research results are of great significance to further understanding the water dike age of a permeable spur dike, and can provide scientific guidance for the design and restoration of spur dikes.