Tail shapes lead to different propulsive mechanisms in the body/caudal fin undulation of fish

2020 ◽  
pp. 095440622096768
Author(s):  
Jialei Song ◽  
Yong Zhong ◽  
Ruxu Du ◽  
Ling Yin ◽  
Yang Ding
Keyword(s):  
Numerical Simulation ◽  
Aspect Ratio ◽  
High Efficiency ◽  
The Body ◽  
Caudal Fin ◽  
Fish Model ◽  
Swimming Efficiency ◽  
Simulation Results ◽  
Propulsive Mechanism ◽  
High Depth

In this paper, we investigate the hydrodynamics of swimmers with three caudal fins: a round one corresponding to snakehead fish ( Channidae), an indented one corresponding to saithe ( Pollachius virens), and a lunate one corresponding to tuna ( Thunnus thynnus). A direct numerical simulation (DNS) approach with a self-propelled fish model was adopted. The simulation results show that the caudal fin transitions from a pushing/suction combined propulsive mechanism to a suction-dominated propulsive mechanism with increasing aspect ratio ( AR). Interestingly, different from a previous finding that suction-based propulsion leads to high efficiency in animal swimming, this study shows that the utilization of suction-based propulsion by a high- AR caudal fin reduces swimming efficiency. Therefore, the suction-based propulsive mechanism does not necessarily lead to high efficiency, while other factors might play a role. Further analysis shows that the large lateral momentum transferred to the flow due to the high depth of the high- AR caudal fin leads to the lowest efficiency despite the most significant suction.

A New Method to Concentrate Electromagnetic Field Within ROI Using a High Dielectric Material in 3T Body MRI

2013 ◽  
Author(s):  
Bu S. Park ◽  
Sunder S. Rajan ◽  
Leonardo M. Angelone
Keyword(s):  
Numerical Simulation ◽  
Electromagnetic Field ◽  
Human Body ◽  
Region Of Interest ◽  
Dielectric Materials ◽  
The Body ◽  
Human Body Model ◽  
Body Model ◽  
Simulation Results ◽  
High Dielectric

We present numerical simulation results showing that high dielectric materials (HDMs) when placed between the human body model and the body coil significantly alter the electromagnetic field inside the body. The numerical simulation results show that the electromagnetic field (E, B, and SAR) within a region of interest (ROI) is concentrated (increased). In addition, the average electromagnetic fields decreased significantly outside the region of interest. The calculation results using a human body model and HDM of Barium Strontium Titanate (BST) show that the mean local SAR was decreased by about 56% (i.e., 18.7 vs. 8.2 W/kg) within the body model.

Topology Optimization of the Caudal Fin of the Three-Dimensional Self-Propelled Swimming Fish

2014 ◽  
Vol 6 (06) ◽  
pp. 732-763 ◽  
Author(s):  
Zhiqiang Xin ◽  
Chuijie Wu
Keyword(s):  
Topology Optimization ◽  
Swimming Speed ◽  
Moving Boundary ◽  
Swimming Performance ◽  
Three Dimensional ◽  
The Body ◽  
Caudal Fin ◽  
Swimming Efficiency ◽  
Vorticity Flux ◽  
3D Topology

AbstractBased on the boundary vorticity-flux theory, topology optimization of the caudal fin of the three-dimensional self-propelled swimming fish is investigated by combining unsteady computational fluid dynamics with moving boundary and topology optimization algorithms in this study. The objective functional of topology optimization is the function of swimming efficiency, swimming speed and motion direction control. The optimal caudal fin, whose topology is different from that of the natural fish caudal fin, make the 3D bionic fish achieve higher swimming efficiency, faster swimming speed and better maneuverability. The boundary vorticity-flux on the body surface of the 3D fish before and after optimization reveals the mechanism of high performance swimming of the topology optimization bionic fish. The comparative analysis between the swimming performance of the 3D topology optimization bionic fish and the 3D lunate tail bionic fish is also carried out, and the wake structures of two types of bionic fish show the physical nature that the swimming performance of the 3D topology optimization bionic fish is significantly better than the 3D lunate tail bionic fish.

Numerical Simulation of Heat and Flow of Liquid Through Minichannels

2006 ◽  
Author(s):  
Heming Yun ◽  
Lin Cheng ◽  
Liqiu Wang ◽  
Shusheng Zhang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Region ◽  
Resistance Coefficient ◽  
Equivalent Diameter ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Simulation Results

In this paper the heat transfer and flow in minichannels was investigated by using CFD methods. The numerical simulation results show that the equivalent diameter has little influence on resistance coefficient in the laminar region. In the turbulent flow region, the resistance coefficient decreases with the increasing of the equivalent diameter. In all computation region, the friction factors increases with increasing of the aspect ratio, and the friction factors decreases obviously with increasing of Reynolds number. The numerical simulation results show that the equivalent diameter has little influence on heat transfer Nusselt number in laminar flow region. In turbulent region, the Nusselt numbers are larger than those in macro channels. The Nusselt numbers increase with decreasing of equivalent diameter and the aspect ratio for a given Reynolds number.

scholarly journals Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0250837
Author(s):  
Keisuke Doi ◽  
Tsutomu Takagi ◽  
Yasushi Mitsunaga ◽  
Shinsuke Torisawa
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Flow Speed ◽  
The Body ◽  
Fluid Force ◽  
Fish Model ◽  
Swimming Motion ◽  
Computational Fluid Dynamics Analysis ◽  
Swimming Efficiency

Fish form schools because of many possible reasons. However, the hydrodynamic mechanism whereby the energy efficiency of fish schools is improved still remains unclear. There are limited examples of fish models based on actual swimming movements using simulation, and the movements in existing models are simple. Therefore, in this study, we analyzed the swimming behavior of Biwa salmon (Oncorhynchus sp., a salmonid fish) using image analyses and formulated its swimming motion. Moreover, computational fluid dynamics analysis was carried out using the formulated swimming motion to determine the fluid force acting on the fish body model with real fish swimming motion. The swimming efficiency of the fish model under parallel swimming was obtained from the calculated surrounding fluid force and compared for different neighboring distances. The flow field around the fish model was also examined. The swimming efficiency of two fish models swimming parallelly was improved by approximately 10% when they were separated by a distance of 0.4L, where L is the total length of the model. In addition, the flow field behind the fish body was examined under both inphase and antiphase conditions and at inter-individual distances of 0.8L and 1.2L. The apparent flow speed in the distance range of 0.5–2.0L from the midpoint of the snouts of the two individuals was lower than the swimming speed. The pressure distribution on the fish model showed an elevated pressure at the caudal fin. Interestingly, we obtained an isopleth map similar to that of a caudal peduncle. To avoid a negative thrust, the aft part of the body must be thin, as shown in the isopleth map obtained in this study.

An Observer for Rigid Body Motion With Almost Global Finite-Time Convergence

2014 ◽  
Author(s):  
Amit K. Sanyal ◽  
Maziar Izadi ◽  
Jan Bohn
Keyword(s):  
Numerical Simulation ◽  
Rigid Body ◽  
Finite Time ◽  
The Body ◽  
Measurement Noise ◽  
Body Motion ◽  
Nonlinear Observer ◽  
Control Force ◽  
Finite Time Convergence ◽  
Simulation Results

An observer that obtains estimates of the translational and rotational motion states for a rigid body under the influence of known forces and moments is presented. This nonlinear observer exhibits almost global convergence of state estimates in finite time, based on state measurements of the rigid body’s pose and velocities. It assumes a known dynamics model with known resultant force and resultant torque acting on the body, which may include feedback control force and control torque. The observer design based on this model uses the exponential coordinates to describe rigid body pose estimation errors on SE(3), which provides an almost global description of the pose estimate error. Finite-time convergence of state estimates and the observer are shown using a Lyapunov analysis on the nonlinear state space of motion. Numerical simulation results confirm these analytically obtained convergence properties for the case that there is no measurement noise and no uncertainty (noise) in the dynamics. The robustness of this observer to measurement noise in body velocities and additive noise in the force and torque components is also shown through numerical simulation results.

A High-Loaded Supersonic Axial Compressor Aerodynamic Design Principle

2012 ◽  
Author(s):  
Yingjiao Hu ◽  
Songtao Wang
Keyword(s):  
Numerical Simulation ◽  
Design Principle ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Axial Compressor ◽  
Axial Flow ◽  
Internal Flow ◽  
Aerodynamic Design ◽  
Simulation Results

Reviewed the historical development of the supersonic axial flow compressor, and gave an outlook for its future developments and research orientations. According to the internal flow characteristics of the conventional supersonic axial flow compressors, put forward a high load of supersonic axial compressor aerodynamic design principle. A preliminary design verification of the principle has been carried. The 3D viscous numerical simulation results show that, under the tip tangential speed 360m / s, has achieved a stage pressure ratio 2.3 with efficiency 86.5%. In addition, considering the rotor under impulse condition can get the maximum rotor total pressure ratio with high efficiency, a design principle has also been put forward to solve the high entrance Mach number problem of the downstream stator. But the numerical simulation results show that the multi-shock structure does not have any advantages to reduce the stator losses.

Numerical Simulation of Vibration Compacting Process on Hydrous Embankment by Discrete Element Method

2012 ◽  
Vol 594-597 ◽  
pp. 506-511
Author(s):  
Bao Tao Huang ◽  
Xin Yuan ◽  
Jie Zhou ◽  
Ding Liu
Keyword(s):  
Numerical Simulation ◽  
Discrete Element Method ◽  
Discrete Element ◽  
The Body ◽  
Coarse Grained ◽  
Material Parameters ◽  
Irregular Particle ◽  
Micro Particles ◽  
Simulation Results ◽  
Element Method

In this article, the discrete element method is used to investigate the coarse particle material close-grained space structure evolutionary process submitted to a vibrating compressive load. 2-D generation algorithm about irregular particle generation and particle contact interface generation was adopted. Irregular particles were randomly generated in the designated categories with this algorithm. The microcosmic material parameters are endowed to irregular particle and pore space. The microcosmic material parameters are also endowed to water. The irregular micro-particles close-grained process was been analyzed under vibrating compressive. The numerical simulation results demonstrate that the coarse-grained soil Irregular particles compacting effect of the simulation results with the actual theoretic situation in the basic line. The Irregular particles were whirligig and movement, location of the rearrangement as a whole to show the close-grained process. The use of discrete element method can be clearly informed that the simulation of the embankment particles in the body vibration. This research offers a new idea and continent method for compaction dense of hydrous embankment.

Numerical Simulation of Agitated Flow Field of Submersible Mixer Based on Computational Fluid Dynamics

2010 ◽  
Vol 34-35 ◽  
pp. 1545-1548
Author(s):  
Wei Xing Xu ◽  
Shou Qi Yuan
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Flow Field ◽  
Constant Velocity ◽  
Simulation Software ◽  
Volume Flow ◽  
The Body ◽  
Design Parameters ◽  
Turbulent Model ◽  
Simulation Results

The flow formulation is founded as console formulation first, and with the body-fitted coordinate system and standard turbulent model, the numerical simulation of the internal 3-D incompressible turbulent flow agitated flow field of submersible mixer is carried out by numerical simulation software Fluent. The results showed that: the mixer impeller produced vortex jet flow, the constant velocity lines advanced as ellipse, the velocity along the centerline are larger than others, and utilized volume flow to transport the liquid. And, by changing some design parameters of mixer impeller, we can compare and analyze the numerical simulation results and present some optimal methods.

scholarly journals Experimental Study of Body-Fin Interaction and Vortex Dynamics Generated by a Two Degree-Of-Freedom Fish Model

Biomimetics ◽  
2019 ◽  
Vol 4 (4) ◽  
pp. 67 ◽  
Author(s):  
Seth A. Brooks ◽  
Melissa A. Green
Keyword(s):  
Performance Metrics ◽  
The Body ◽  
Degree Of Freedom ◽  
Half Cycle ◽  
Velocity Data ◽  
Trailing Edge ◽  
Caudal Fin ◽  
Freestream Velocity ◽  
Fish Model ◽  
Two Degree Of Freedom

Oscillatory modes of swimming are used by a majority of aquatic swimmers to generate thrust. This work seeks to understand the phenomenological relationship between the body and caudal fin for fast and efficient thunniform swimming. Phase-averaged velocity data was collected and analyzed in order to understand the effects of body-fin kinematics on the wake behind a two degree-of-freedom fish model. The model is based on the yellowfin tuna (Thunnus albacares) which is known to be both fast and efficient. Velocity data was obtained along the side of the tail and caudal fin region as well as in the wake downstream of the caudal fin. Body-generated vortices were found to be small and have an insignificant effect on the caudal fin wake. The evolution of leading edge vortices formed on the caudal fin varied depending on the body-fin kinematics. The circulation produced at the trailing edge during each half-cycle was found to be relatively insensitive to the freestream velocity, but also varied with body-fin kinematics. Overall, the generation of vorticity in the wake was found to dependent on the trailing edge motion profile and velocity. Even relatively minor deviations from the commonly used model of sinusoidal motion is shown to change the strength and organization of coherent structures in the wake, which have been shown in the literature to be related to performance metrics such as thrust and efficiency.

Independent caudal fin actuation enables high energy extraction and control in two-dimensional fish-like group swimming

2018 ◽  
Vol 850 ◽  
pp. 304-335 ◽  
Author(s):  
Amy Gao ◽  
Michael S. Triantafyllou
Keyword(s):  
High Efficiency ◽  
Unscented Kalman Filter ◽  
High Energy ◽  
The Body ◽  
Destructive Interference ◽  
Main Body ◽  
Control Mechanisms ◽  
Energy Extraction ◽  
Flow Measurements ◽  
Caudal Fin

We study through numerical simulation the optimal hydrodynamic interactions and basic vorticity control mechanisms for two fish-like bodies swimming in tandem. We show that for a fish swimming in the wake of an upstream fish, using independent pitch control of its caudal fin, in addition to optimized body motion, results in reduction of the energy needed for self-propulsion by more than 50 %, providing a quasi-propulsive efficiency of 90 %, up from 60 % without independent caudal fin control. Such high efficiency is found over a narrow parametric range and is possible only when the caudal fin is allowed to pitch independently from the motion of the main body. We identify the vorticity control mechanisms employed by the body and tail to achieve this remarkable performance through thrust augmentation and destructive interference with the upstream fish-generated vortices. A high sensitivity of the propulsive performance to small variations in caudal fin parameters is found, underlying the importance of accurate flow sensing and feedback control. We further demonstrate that using lateral line-like flow measurements to drive an unscented Kalman filter, the near-field vortices can be localized within 1 % of the body length, and be used with a phase-lock controller to drive the body and tail undulation of a self-propelled fish, moving within the wake of an upstream fish, to stably reach the optimal gait and fully achieve maximum energy extraction.

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