Kinematics and Hydrodynamics of Invertebrate Undulatory Swimming

2018 ◽  
Author(s):  
Jianghong Tian ◽  
Pan Han ◽  
Xiaolong Deng ◽  
Royce E. Lindengren ◽  
Geng Liu ◽  
...  
Keyword(s):  
Vertical Plane ◽  
Amplitude Distribution ◽  
Hydrodynamic Performance ◽  
Immersed Boundary ◽  
Flow Solver ◽  
Pressure Distributions ◽  
Swimming Motion ◽  
Thrust Generation ◽  
Swimming Mode ◽  
Undulatory Swimming

Dorsoventral undulation is adopted by aquatic mammals for propulsion. However, it is not too common to find invertebrate aquatic animals that undulate their bodies in the vertical plane, which results from antiphasic contractions of dorsal and ventral muscles. To explore the mechanisms of the soft-bodied propulsion, in this work, an annelid swimmer employing up and down undulatory swimming mode is chosen, and the related kinematics and hydrodynamics are studied using a combined experimental and computational approach. A fully calibrated photogrammetry system with three highspeed cameras from different views is used to record the forward swimming motion of this invertebrate swimmer, namely leech. The vertically undulating kinematics are then reconstructed from those videos. With the detailed reconstruction, the undulating wavelength and amplitude distribution the swimmer exhibits during propulsion are quantified. Kinematics analysis results show that the invertebrate swimmer swims in a vertical anguilliform mode and the wavelength is about 0.7BL (body length) when it swims at a velocity of 1.5BL/s. An in-house immersed-boundary-method based flow solver is used to conduct the numerical simulations, with which the hydrodynamic performance and wake structures are investigated. The thrust generation and power consumption of the undulating body are described quantitatively. Furthermore, along the undulating body, the pressure distributions are studied.

Computational Analysis of 3D Fin-Fin Interaction in Fish’s Steady Swimming

2016 ◽  
Author(s):  
Pan Han ◽  
Geng Liu ◽  
Yan Ren ◽  
Haibo Dong
Keyword(s):  
Immersed Boundary Method ◽  
Computational Analysis ◽  
Three Dimensional ◽  
Hydrodynamic Performance ◽  
Immersed Boundary ◽  
Caudal Fin ◽  
Wake Patterns ◽  
Undulatory Swimming ◽  
Swimming Kinematics ◽  
Full Body

Three-dimensional numerical simulations are used to investigate the hydrodynamic performance and the wake patterns of a sunfish in steady swimming. Immersed boundary method for deformable attaching bodies (IBM-DAB) are used to handle complex moving boundaries of one solid body (fish body) attached with several membranes (fins). The effects of the vortices shed from both the dorsal and anal fins on the hydrodynamic performance of the caudal fin are analyzed by prescribing an undulatory swimming kinematics to a full body sunfish model. Results show that both the dorsal fin vortices and the anal fin vortices can increase the thrust and efficiency of the caudal fin comparing to caudal fin only case. This is because the dorsal/anal fin not only can feed vorticity into the caudal fin wake via vortex shedding, but also can modulate the flow in the downstream in a way of forming a jet with stronger backward component.

Effects of Tail Geometries on the Performance and Wake Pattern in Flapping Propulsion

2016 ◽  
Author(s):  
Geng Liu ◽  
Haibo Dong
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Computational Study ◽  
Hydrodynamic Performance ◽  
Immersed Boundary ◽  
Caudal Fin ◽  
Flow Solver ◽  
Wide Range ◽  
Wake Patterns ◽  
Caudal Fin Shape

Swimming fishes exhibit remarkable diversities of the caudal fin geometries. In this work, a computational study is conducted to investigate the effects of the caudal fin shape on the hydrodynamic performance and wake patterns in flapping propulsion. We construct the propulsor models in different shapes by digitizing the real caudal fins of fish across a wide range of species spanning homocercal tails with low aspect ratio (square shape used by bluegill sunfish, rainbow trout, etc.) or high aspect ratio (lunate shape adopted by tuna, swordfish, etc.), and even heterocercal caudal fin adopted by sharks. Those fin models perform the same flapping motion in a uniform flow to mimic fish’s forward swimming. We then simulate the flow around the flapping fins by an in-house immersed-boundary-method based flow solver. According to the analysis of the hydrodynamic performance, we have found that the lunate shape model (high aspect-ratio) always generates a larger thrust compared to other models. The comparison of the propulsive efficiency shows that the large aspect ratio fins (tuna and shark) have a higher efficiency when the Strouhal number (St) is in the range of steady swimming (0.2<St<0.4), while the lower aspect ratio caudal fins (catfish, trout, etc.) are more efficient when St>0.4, in which the fish is accelerating or maneuvering. Finally, the 3D wake patterns of those propulsors are analyzed in detail.

Thrust efficiency of harmonically oscillating flexible flat plates

2011 ◽  
Vol 674 ◽  
pp. 43-66 ◽  
Author(s):  
PAULO J. S. A. FERREIRA de SOUSA ◽  
JAMES J. ALLEN
Keyword(s):  
Immersed Boundary Method ◽  
Leading Edge ◽  
Immersed Boundary ◽  
Flat Plates ◽  
Flexible Membrane ◽  
Fluid Structure ◽  
Flow Solver ◽  
Thrust Generation ◽  
Flow Field Characteristics ◽  
Structural Mass

We consider the efficiency of thrust-producing inextensible membranes with variable bending rigidities. The present study is a numerical investigation of the thrust generation and flow-field characteristics of a two-dimensional flapping flexible membrane, fixed at its leading edge. To study the time-dependent response of the membranes, a fluid/structure solver that couples a compact finite-difference immersed boundary method flow solver with a thin-membrane structural solver was developed. Using a body-fitted grid, external forcing to the structure is calculated from the boundary fluid dynamics. A systematic series of runs of the fluid/structure solver was performed in order to obtain a clear picture of the thrust-producing characteristics of membranes with bending rigidities ranging between EI = 5 × 10−6 and EI = 2 × 10−5 and structural mass coefficients between ρsh = 0.01 and ρsh = 0.04, for a Reynolds number of Re = 851.

scholarly journals A Mixed-Fidelity Numerical Study for Fan–Distortion Interaction

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Yunfei Ma ◽  
Jiahuan Cui ◽  
Nagabhushana Rao Vadlamani ◽  
Paul Tucker
Keyword(s):  
Immersed Boundary Method ◽  
Numerical Study ◽  
Immersed Boundary ◽  
Fan Performance ◽  
Inlet Distortion ◽  
Eddy Simulation ◽  
Pressure Distributions ◽  
Large Eddy ◽  
Dynamics Method ◽  
Good Agreement

Inlet distortion often occurs under off-design conditions when a flow separates within an intake and this unsteady phenomenon can seriously impact fan performance. Fan–distortion interaction is a highly unsteady aerodynamic process into which high-fidelity simulations can provide detailed insights. However, due to limitations on the computational resource, the use of an eddy resolving method for a fully resolved fan calculation is currently infeasible within industry. To solve this problem, a mixed-fidelity computational fluid dynamics method is proposed. This method uses the large Eddy simulation (LES) approach to resolve the turbulence associated with separation and the immersed boundary method (IBM) with smeared geometry (IBMSG) to model the fan. The method is validated by providing comparisons against the experiment on the Darmstadt Rotor, which shows a good agreement in terms of total pressure distributions. A detailed investigation is then conducted for a subsonic rotor with an annular beam-generating inlet distortion. A number of studies are performed in order to investigate the fan's influence on the distortions. A comparison to the case without a fan shows that the fan has a significant effect in reducing distortions. Three fan locations are examined which reveal that the fan nearer to the inlet tends to have a higher pressure recovery. Three beams with different heights are also tested to generate various degrees of distortion. The results indicate that the fan can suppress the distortions and that the recovery effect is proportional to the degree of inlet distortion.

High Reynolds Number Airfoil Simulations Using the Immersed Boundary Method

2012 ◽  
Author(s):  
James P. Johnson ◽  
Gianluca Iaccarino ◽  
Kuo-Huey Chen ◽  
Bahram Khalighi
Keyword(s):  
Immersed Boundary Method ◽  
High Reynolds Number ◽  
Aerodynamic Force ◽  
Reynolds Numbers ◽  
Computational Approach ◽  
Immersed Boundary ◽  
Pressure Distributions ◽  
Boundary Method ◽  
High Reynolds ◽  
Naca 0012

The Immersed-Boundary Method is coupled to an incompressible-flow RANS solver, based on a two-equation turbulence model, to perform unsteady numerical simulations of airflow past the NACA-0012 airfoil for several angles of attack and Reynolds numbers of 5.0×105 and 1.8×106. Qualitative characterizations of the flow in the vicinity of the airfoil are obtained to show the need for locally refined grids to capture the thin boundary layers close to the airfoil leading edges. Quantitative analysis of aerodynamic force coefficients and wall pressure distributions are also reported and compared to experimental results and those from body-fitted grid simulations using the same solver to assess the accuracy and limitations of this approach. The Immersed-Boundary simulations compared well to the experimental and body-fitted results up to the occurrence of separation. After that point, neither computational approach provided satisfactory solutions.

Leading edge strengthening and the propulsion performance of flexible ray fins

2012 ◽  
Vol 693 ◽  
pp. 402-432 ◽  
Author(s):  
Kourosh Shoele ◽  
Qiang Zhu
Keyword(s):  
Phase Difference ◽  
Structural Characteristics ◽  
Leading Edge ◽  
Immersed Boundary ◽  
Propulsion Performance ◽  
Thrust Generation ◽  
Generation Capacity ◽  
Effective Angle ◽  
Edge Separation ◽  
Thrust Production

AbstractA numerical model of a ray-reinforced fin is developed to investigate the relation between its structural characteristics and its force generation capacity during flapping motion. In this two-dimensional rendition, the underlying rays are modelled as springs, and the membrane is modelled as a flexible but inextensible plate. The fin kinematics is characterized by its oscillation frequency and the phase difference between different rays (which generates a pitching motion). An immersed boundary method (IBM) is applied to solve the fluid–structure interaction problem. The focus of the current paper is on the effects of ray flexibility, especially the detailed distribution of ray stiffness, upon the capacity of thrust generation. The correlation between thrust generation and features of the surrounding flow (especially the leading edge separation) is also examined. Comparisons are made between a fin with rigid rays, a fin with identical flexible rays, and a fin with flexible rays and strengthened leading edge. It is shown that with flexible rays, the thrust production can be significantly increased, especially in cases when the phase difference between different rays is not optimized. By strengthening the leading edge, a higher propulsion efficiency is observed. This is mostly attributed to the reduction of the effective angle of attack at the leading edge, accompanied by mitigation of leading edge separation and dramatic changes in characteristics of the wake. In addition, the flexibility of the rays causes reorientation of the fluid force so that it tilts more towards the swimming direction and the thrust is thus increased.

scholarly journals Red muscle function in stiff-bodied swimmers: there and almost back again

2011 ◽  
Vol 366 (1570) ◽  
pp. 1507-1515 ◽  
Author(s):  
Douglas A. Syme ◽  
Robert E. Shadwick
Keyword(s):  
Body Size ◽  
Muscle Function ◽  
Tail Region ◽  
Red Muscle ◽  
Lateral Undulation ◽  
Thresher Shark ◽  
Swimming Mode ◽  
The Common ◽  
Undulatory Swimming

Fishes with internalized and endothermic red muscles (i.e. tunas and lamnid sharks) are known for a stiff-bodied form of undulatory swimming, based on unique muscle–tendon architecture that limits lateral undulation to the tail region even though the red muscle is shifted anteriorly. A strong convergence between lamnid sharks and tunas in these features suggests that thunniform swimming might be evolutionarily tied to this specialization of red muscle, but recent observations on the common thresher shark ( Alopias vulpinus ) do not support this view. Here, we review the fundamental features of the locomotor systems in lamnids and tunas, and present data on in vivo muscle function and swimming mechanics in thresher sharks. These results suggest that the presence of endothermic and internalized red muscles alone in a fish does not predict or constrain the swimming mode to be thunniform and, indeed, that the benefits of this type of muscle may vary greatly as a consequence of body size.

Flow Field Analysis Around the Ship Fin Stabilizer Including Free Surface

2009 ◽  
Author(s):  
Fatemah Hoseini Dadmarzi ◽  
Hassan Ghassemi ◽  
Parviz Ghadimi ◽  
Babak Ommani
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Numerical Data ◽  
Numerical Results ◽  
Field Analysis ◽  
Hydrodynamic Performance ◽  
Pressure Distributions ◽  
Flow Field Analysis ◽  
Ship Roll ◽  
Fin Stabilizer

Fin stabilizers are very important device for controlling the ship roll motion against the external moments due to wave. This paper presents numerical results for flow field simulation and the hydrodynamic performance of fin stabilizer attached to a ship hull with free surface effects. Combination of CFD and RANS method has been used for this study. The fin is non-rectangular NACA0015 profile section with a finite aspect ratio. The numerical results include pressure distributions and flow field around the fin which are used to calculate lift coefficients and free surface elevation as the main interest. Some results are compared with available experimental and numerical data in literature and they show good agreement.

scholarly journals A Mixed-Fidelity Numerical Study for Fan-Distortion Interaction

2018 ◽  
Author(s):  
Yunfei Ma ◽  
Jiahuan Cui ◽  
Nagabhushana Rao Vadlamani ◽  
Paul G. Tucker
Keyword(s):  
Numerical Study ◽  
Immersed Boundary ◽  
High Fidelity Simulation ◽  
Resource Limitations ◽  
Inlet Distortion ◽  
Eddy Simulation ◽  
Pressure Distributions ◽  
Large Eddy ◽  
Cfd Method ◽  
Good Agreement

Inlet distortion often occurs at off-design points when flow separates within an intake. This unsteady phenomenon could seriously impact fan performance. Fan-distortion interaction is a highly unsteady aerodynamic phenomenon. High-fidelity simulation can provide a detailed insight into these interactions. However, due to computational resource limitations, the use of eddy resolving methods for a fully resolved fan calculation is currently infeasible for industry. To solve this problem, a mixed-fidelity CFD method is proposed. This method uses the Large Eddy Simulation (LES) to resolve the turbulence associated with separation, and the Immersed Boundary Method with Smeared Geometry (IBMSG) for the fan. The method is validated by an experiment of Darmstadt Rotor, which shows a good agreement in terms of total pressure distributions. A detailed investigation is then conducted on a subsonic rotor with an annular beam generating inlet distortion. A range of studies are performed to investigate fan influence on distortions. Compared to the case without fan, it shows that a fan has a significant effect in reducing distortions. Three fan locations are examined. The fan nearer to the inlet tends to have a higher pressure recovery. Three beams with different heights are also tested to generate various degrees of distortions. The results indicate that the fan can suppress the distortions and its recovery effect is proportional to the degree of inlet distortion.

scholarly journals Modal Analysis of a Discrete System in the Form of a Rocket Launcher Installed on a Motor Vehicle

2016 ◽  
Vol 7 (3) ◽  
pp. 47-58
Author(s):  
Zbigniew DZIOPA ◽  
Maciej NYCKOWSKI
Keyword(s):  
Modal Analysis ◽  
Degrees Of Freedom ◽  
Motor Vehicle ◽  
Vertical Plane ◽  
Amplitude Distribution ◽  
Analytical Form ◽  
Distribution Coefficients ◽  
Characteristic Values ◽  
Definition Of ◽  
Second Order Equations

A discrete model of an unguided rocket missile launcher installed on a motor vehicle was developed on the basis of a real assembly. The model is simplified to a vertical plane; it has four degrees of freedom and is adapted for a modal analysis. A mathematical model was derived using the variational method on the basis of the assumed physical model. Analytical dependencies in the form of adjoint second order equations taking ordinary derivatives describe the dynamics of the considered system. The equations describing the autonomous motion of the system provided a definition of the generalized eigenvalue problem and the age equation forming the basis of the characteristic values. An analytical form of particular integrals was assumed for equations describing proper vibrations and the amplitude distribution coefficients were calculated. Four forms of proper vibrations of the considered system were obtained on the basis of the determined eigenvectors.

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