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For predicting three-dimensional incompressible potential flows around a body accompanied by a wake vortex, surface singularity methods (i.e., panel methods) have been employed extensively, owing to their ease of use and low solution times. In the case of lifting/vortical flow, the Kutta condition is applied, in order to insure smooth flow at the t...
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... can be seen, for example, that the high pressure (red) on the left side of the tail (Fig. 27(a)) pushes the body forward, while the low pressure (blue) on the right side of the tail (Fig. 27(b)) pulls the body forward, resulting in the thrust force. The added masses were calculated by accelerating the ambient fluid in the xyz-directions while the shark was at rest, and by accelerating the shark in those directions in a fluid at rest; it was assumed Table 4. It can be seen that the -Difference‖ value is the same (17.06 ...
Citations
... Experimental studies often employ methods such as particle image velocimetry using live or robotic fish [25][26][27][28][29][30]. Numerical simulations have been conducted employing various techniques, including panel methods with potential flow assumptions for laminar or inertial regimes [25,31,32], the immersed boundary method [15,[33][34][35][36][37], as well as the combined level set/immersed boundary method developed by Cui et al. [22] and Tekkethil et al. [26]. Other studies have employed unsteady Reynolds-average Navier-Stokes equations to address three-dimensional viscous flow [38], in which they employed various turbulence models to address turbulence closure problems. ...
Research into how fish and other aquatic organisms propel themselves offers valuable natural references for enhancing technology related to underwater devices like vehicles, propellers, and biomimetic robotics. Additionally, such research provides insights into fish evolution and ecological dynamics. This work carried out a numerical investigation of the most relevant dimensionless parameters in a fish swimming environment (Reynolds Re, Strouhal St, and Slip numbers) to provide valuable knowledge in terms of biomechanics behavior. Thus, a three-dimensional numerical study of the fish-like lambari, a BCF swimmer with carangiform kinematics, was conducted using the URANS approach with the k-ω-SST transition turbulence closure model in the OpenFOAM software. In this study, we initially reported the equilibrium Strouhal number, which is represented by St∗, and its dependence on the Reynolds number, denoted as Re. This was performed following a power–law relationship of St∝Re(−α). We also conducted a comprehensive analysis of the hydrodynamic forces and the effect of body undulation in fish on the production of swimming drag and thrust. Additionally, we computed propulsive and quasi-propulsive efficiencies, as well as examined the influence of the Reynolds number and Slip number on fish performance. Finally, we performed a vortex dynamics analysis, in which different wake configurations were revealed under variations of the dimensionless parameters St, Re, and Slip. Furthermore, we explored the relationship between the generation of a leading-edge vortex via the caudal fin and the peak thrust production within the motion cycle.
... On the other hand, numerical simulations are running under different approaches. For example, in the laminar or inertial regime, we find investigations based on panel methods with potential flow assumptions [8,5,9] and the immersed boundary method [10,11,12]. Besides, Cui et al. [13] and Tekkethil et al. [6] developed a problem solution employing the Level Set/Immersed Boundary method. ...
Traditionally, the literature about fish swimming focuses on investigating the fish trailing wake. However, recently, Borazjani and Daghooghi [1] reported that studying the leadingedge vortex generated during fish swimming is a crucial issue in biomechanics analysis, in the same direction that similar works about the flight of insects and birds. Thus, we investigate the leading-edge vortex induced by a fish-like lambari (Astyanax bimaculatus) swimming in a three-dimensional viscous flow and the force productions at different Reynolds and Strouhal number. Numerical simulations are carried out employing the URANS approach with turbulence closure model transition k-?-SST and a deformable mesh condition to the fish swimming. It is observed that the leading-edge vortex attached to the caudal fin increases the propulsive force at equilibrium configurations (thrust and drag balanced). Besides, at lower Reynolds numbers, it is noted that the vortex, once detached, travels more slowly in the wake, locating closer to the caudal fin due to the delay of fluid convection.
... While this method appears in itself way more straightforward than the previous formulation, it does require the knowledge of the velocity potential on the mesh. In order to obtain this potential, rather than attempting to derive the potential contributions of each velocity component, we use a simple spacial integration formulated by Ogami [86]. Ogami's formulation allows for the computation of velocity potential based solely on the value of the complete velocity on the mesh, as will be shown in Section 2.4. ...
... While it might be possible to retrace the velocity potential induced by vorticity carrying particles, this subject is much less common in the literature and would require further theoretical developments and possibly significant additions to the simulation code. A second and far simpler possibility for the computation of the velocity potential is given in the recent work of Ogami [86]. By "integrating" the complete velocity on the obstacle mesh, he is able to obtain an approximation of its potential at the cost of a matrix resolution. ...
... Ogami [86] proposes a method of calculating the potential ϕ of the complete velocity u on the body surface, independently from the specifics of the velocity computation. The potential is calculated after determining the distribution of surface velocity vectors induced by the surface singularities, the fluid particles, and any other relevant contribution. ...
In the current context of diversification of renewable energies, tidal turbines are set to occupy an important niche, and numerical simulation is a crucial tool for their investigation. The in-house simulation code DOROTHY developed in collaboration between IFREMER and LOMC uses the Vortex Particle Method offering a good compromise between physical realism and and computational time. Some additional developments are required in order to make of this software a fully rounded numerical tool able to mimic advanced realistic configurations. Firstly, an important overhaul of its computation of loads has been undertaken, including a new framework to represent the previously simplified and now fully-rendered turbine blades. This endeavour includes the mathematical justification, investigation, and preliminary validation of additional integral methods accounting for the turbine body. Secondly, the importance of the impact of ambient turbulence on the wake interaction and power output within a turbine farm cannot be ignored. This element is introduced using a Synthetic Eddy Method uniquely adapted to the present Lagrangian framework. All aspects of this method as well as a promising alternative are closely examined, culminating in the demonstration of its capabilities for the simulation of the flow and prediction of detrimental interaction effects throughout a projected four turbine pilot farm configuration.
... Several aquatic specimens, such as dolphins, are fully adapted to maximize propulsion and minimize drag [1]. Since a long time ago, substantial research using different experimental techniques, simulations, and modelling procedures have been conducted on the thrust of aquatic specimens [2][3][4][5][6][7]. In comparison with the body of evidence on aquatic animals thrust, the knowledge on human thrust in water is very limited. ...
... A study conducted on the thrust of aquatic animals suggested that the mean thrust by dolphins is approximately 80N [3]. In another study, conducted in still water, the thrust generated by great white sharks was modelled by computational fluid dynamics to be 295N [7]. Unsurprisingly, the magnitude of human thrust was far lower as compared to aquatic animals. ...
Herein, we analyse by experimental techniques the human kicking thrust and measure the effect of a warm-up routine that includes post-activation potentiation (PAP) sets on front-crawl flutter kick thrust, kinematics, and performance. Sixteen male competitive swimmers with 22.13 ± 3.84 years of age were randomly assigned in a crossover manner to undergo a standard warm-up (non-PAP; control condition) and a warm-up that included PAP sets (PAP; experimental condition) consisting in 2 × 5 repetitions of unloaded countermovement jump. Participants performed a 25 m all-out trial in front-crawl with only flutter kicks eight min after each warm-up. Kinetics (i.e., peak thrust, mean thrust, and thrust-time integral) and kinematics (i.e., speed, speed fluctuation and kicking frequency) were experimentally collected by an in-house customized system composed of differential pressure sensors, speedo-meter, and underwater camera. Peak thrust (P = 0.02, d = 0.66) and mean thrust (P = 0.10, d = 0.40) were increased by 15% in PAP compared to non-PAP. Large and significant differences were noted in speed (P = 0.01, d = 0.54) and speed fluctuation (P = 0.02, d = 0.58), which improved by 10% in PAP compared with non-PAP. In conclusion, a warm-up that includes PAP sets improves kicking thrust, kinematics and performance.
