CFD Simulation of Effect of Vortex Ring for Squid Jet Propulsion and Expeiments on a Bionic Jet Propulsor
International Journal of u- and e- Service, Science and Technology
Using jet propulsion, squid can swim at high speed or at low speed with good maneuverability, which makes them quiet valuable to be studied for biomimetic purposes. Vortex rings usually occur in the highly-unsteady jet flow in squid, and they play quite important roles in the jet propulsion of squid. This paper tries to investigate the squid jet structure by computational fluid dynamics (CFD) analysis. A simplified squid body model was established. The mantle motion during jet locomotion was
... t locomotion was explicitly included into the simulations by using a deforming mesh. By solving the 2D-axisymmetric, incompressible, laminar, unsteady Navier-Stokes equations, different vortex evolution behaviors were observed depending on different mantle contraction velocities and nozzle diameters. An important parameter, the formation number of the vortex rings, L/D, which decide the propulsive efficiency of jet propulsion directly, was also discussed in this paper. The numerical results show that adult squid propel themselves by long jet flows with a large formation number, L/D. The results also prove that smaller squid have larger relative funnel diameter. Interaction of vortex rings was simulated in two jet process, which might interpret squid increase their contraction frequencies with elevated swimming speed. To validate the force generated in the simulation, a bionc squid mantel jet propulsor is investigated and tested. 212 Copyright ⓒ 2016 SERSC movement during escape jet behavior and focused on the relationship between ontogenetic changes in the kinematics of the mantle and the thrust generated during the escape jet. They measured the peak thrust and the kinematics of the mantle of squid ranged in size from 5 to 40 mm tethered to a force transducer [2-3]. Houshuo Jiang and Mak A. Grosenbaugh set up a numerical model to simulate squid jet propulsion. Object numerical simulation of a symmetrical body having a round shaft opening, with internal piston, the piston movement of water discharged through the use of a deformable mesh simulated movement of the piston. According to the ratio of different backgrounds and piston velocity (U/Up)and the ratio of the speed of the piston stroke and the opening diameter(Lm/D), observe the evolution of the vortex behavior. The basic principle is that the interaction between the jet and the starting vortex layer between the layers  . Usually squid would die as soon as they are captured from the ocean, even if they were live, they may not be able to swim as well as in the vast ocean, so direct observation of squid in oceans need complicated experimental equipments such as underwater vehicle and underwater camera which will result in high expense and long period. Consequently, it is difficult to do experiments on live squid. As the development of computer technology, computational fluid dynamics (CFD) analysis has been applied to understanding the mechanism of swimming fish successfully. This method not only can save money and time, but also can obtain comprehensive experimental data. In the present study, a CFD simulation of 2D-axisymmetric simplified squid jet model has been developed to investigate the well-developed jet flow in swimming squid. The mantle motion during escape-jet locomotion was explicitly included into the simulations by using a deforming mesh. A parametric analysis of variables which affect vortex evolution behavior is presented, associated with flow visualization.