Flow around fishlike shapes studied using multiparticle collision dynamics (original) (raw)
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Fluid dynamics of moving fish in a two-dimensional multiparticle collision dynamics model
Physical Review E, 2012
The fluid dynamics of animal locomotion, such as that of an undulating fish, are of great interest to both biologists and engineers. However, experimentally studying these fluid dynamics is difficult and time consuming. Model studies can be of great help because of their simpler and more detailed analysis. Their insights may guide empirical work. Particularly the recently introduced multiparticle collision dynamics method may be suitable for the study of moving organisms because it is computationally fast, simple to implement, and has a continuous representation of space. As regards the study of hydrodynamics of moving organisms, the method has only been applied at low Reynolds numbers (below 120) for soft, permeable bodies, and static fishlike shapes. In the present paper we use it to study the hydrodynamics of an undulating fish at Reynolds numbers 1100-1500, after confirming its performance for a moving insect wing at Reynolds number 75. We measure (1) drag, thrust, and lift forces, (2) swimming efficiency and spatial structure of the wake, and (3) distribution of forces along the fish body. We confirm the resemblance between the simulated undulating fish and empirical data. In contrast to theoretical predictions, our model shows that for steadily undulating fish, thrust is produced by the rear 2/3 of the body and that the slip ratio U/V (with U the forward swimming speed and V the rearward speed of the body wave) correlates negatively (instead of positively) with the actual Froude efficiency of swimming. Besides, we show that the common practice of modeling individuals while constraining their sideways acceleration causes them to resemble unconstrained fish with a higher tailbeat frequency.
Hydrodynamics of a fish using fluid structure interaction
Materials Today: Proceedings, 2018
Systems which involve flexible bodies interacting with surrounding fluid flow are commonplace. For example flapping flags and swimming fishes are becoming increasingly prevalent in bio-fluid engineering applications. These phenomena are challenging to model numerically on account of complex geometries and freely moving boundaries, which give rise to complicated fluid dynamics. In these systems, the flexible body acts on the surrounding fluid, forcing it to move with the moving boundary. On the other manner, the fluid exerts forces on the flexible body through pressure differences and viscous shear stresses. Collectively, the interactions between the fluid and the flexible-body can give rise to self-sustained oscillations such as the flapping of a flag. The fluid-flexible structure interaction is also an essential aspect of the tail and wing motions of swimming and flying animals. Fish is one of the oldest aquatic beings known to man. It has not only fascinated him but also has been a source of inspiration. A large number of scientists and engineers are working on developing a underwater vehicle with the efficiency of that of a fish. The current work aims at understanding the hydrodynamics involved in swimming of a fish using fluid structure interaction. The magnitude and frequencies of disturbances formed due to Von Karmen Vortex past the fish are calculated thus providing an insight into the drag effects due to these deformation on the fish.
Multi-particle collision dynamics: Flow around a circular and a square cylinder
Europhysics Letters (EPL), 2001
A particle-based model for mesoscopic fluid dynamics is used to simulate steady and unsteady flows around a circular and a square cylinder in a two-dimensional channel for a range of Reynolds number between 10 and 130. Numerical results for the recirculation length, the drag coefficient, and the Strouhal number are reported and compared with previous experimental measurements and computational fluid dynamics data. The good agreement demonstrates the potential of this method for the investigation of complex flows.
Hydrodynamics of Fishlike Swimming
Annual Review of Fluid Mechanics, 2000
Interest in novel forms of marine propulsion and maneuvering has sparked a number of studies on unsteadily operating propulsors. We review recent experimental and theoretical work identifying the principal mechanism for producing propulsive and transient forces in oscillating flexible bodies and fins in water, the formation and control of large-scale vortices. Connection with studies on live fish is made, explaining the observed outstanding fish agility. Annu. Rev. Fluid Mech. 2000.32:33-53. Downloaded from arjournals.annualreviews.org by UNIVERSITY OF MAINE -ORONO on 04/13/08. For personal use only. Annu. Rev. Fluid Mech. 2000.32:33-53. Downloaded from arjournals.annualreviews.org by UNIVERSITY OF MAINE -ORONO on 04/13/08. For personal use only. Annu. Rev. Fluid Mech. 2000.32:33-53. Downloaded from arjournals.annualreviews.org by UNIVERSITY OF MAINE -ORONO on 04/13/08. For personal use only.
The hydrodynamics of flexible-body manoeuvres in swimming fish
Physica D: Nonlinear Phenomena, 2008
Swimming in flexible bodied animals like fish is characterised by a travelling wave passing along the spinal-chord of the body. Symmetric transverse undulations of the body generate thrust and propel the fish forward. Turns are effected by generating an asymmetric transverse movement of the fish body, frequently as a C-shaped bend. Typical fish swimming speeds allow for simplifying assumptions of incompressible and inviscid flow. The objective of the current work is to use existing theoretical models developed for forward swimming, to analyse fish turns. Lighthill's classical elongated-body theory for fish swimming forms the fundamental basis for the three dimensional flow model and 'recoil' correction concept implemented here. In the methods developed here, transverse motion of a thin 'waving' plate is prescribed by a displacement signal acting along the midline, for finite time to. Lighthill's approach to calculate the rigid body motion or 'recoil' correction is implemented to ensure zero net force and moments act on the body. Accordingly, angular and transverse motion are computed and final orientation of the plate after the manoeuvre is calculated. A three-dimensional boundary value algorithm has been developed using a vortex lattice method. The essential methodology, modifications for turning and comparisons with the analytical methods in the small and large aspect ratio limits will be presented.
2009
In this review, we describe and analyze a mesoscale simulation method for fluid flow, which was introduced by Malevanets and Kapral in 1999, and is now called multi-particle collision dynamics (MPC) or stochastic rotation dynamics (SRD). The method consists of alternating streaming and collision steps in an ensemble of point particles. The multi-particle collisions are performed by grouping particles in collision cells, and mass, momentum, and energy are locally conserved. This simulation technique captures both full hydrodynamic interactions and thermal fluctuations. The first part of the review begins with a description of several widely used MPC algorithms and then discusses important features of the original SRD algorithm and frequently used variations. Two complementary approaches for deriving the hydrodynamic equations and evaluating the transport coefficients are reviewed. It is then shown how MPC algorithms can be generalized to model non-ideal fluids, and binary mixtures with a consolute point. The importance of angular-momentum conservation for systems like phase-separated liquids with different viscosities is discussed. The second part of the review describes a number of recent applications of MPC algorithms to study colloid and polymer dynamics, the behavior of vesicles and cells in hydrodynamic flows, and the dynamics of viscoelastic fluids.
On the swimming of fish like bodies near free and fixed boundaries
European Journal of Mechanics - B/Fluids, 2012
In this paper, we study the two dimensional motion of three linked rigid bodies moving through a fluid which may be infinite in extent or confined to a tank under gravity with Reynolds number ℜ in the range 10^3 < ℜ < 13×10^3. The motion of the bodies is determined by specifying the angles between them as functions of time so that the resultant motion mimics the swimming of fish. In contrast to previous simulations, the bodies are connected by an elastic skin that alters the flow around them and gives the appearance, and some of the properties, of swimming fish. We show that, as expected, the presence of the skin reduces the energy required to move the linked body system a specified distance in a specified time. We simulate the system with the particle method Smoothed Particle Hydrodynamics (SPH), using three types of particles: fluid particles, boundary force particles, and skin particles. These particles interact by means of pair forces along their line of centres. Our treatment of the rigid and elastic boundaries is related to the immersed boundary method, but differs from it in detail. We compare the motion of rigid bodies with and without skin and determine how the speed and power output depends on the presence or absence of skin, and whether the bodies are more like an eel or a mackerel. We apply our model to study swimming under gravity near a free surface or a rigid bottom boundary in a tank and determine the scaling relations for the speed and power generated. The scaling relation for speed is remarkably similar to that known for aquatic swimming. The optimum strategy for the gait we use, measured in terms of least energy per unit distance, is to swim as close as possible to the free surface without causing large wave breaking. The algorithm is simple and robust and can be applied to bodies of arbitrary shape.
On the hydrodynamics and nonlinear interaction between fish in tandem configuration
Ocean Engineering, 2018
We perform numerical simulations using immersed boundary methods for flow over fish, single and in tandem arrangements, performing traveling wave like motion. We analyze nonlinear mechanics of hydrodynamic lateral side-force and drag/thrust coefficients. We compute their Fourier spectra and find that lateral side force carries fundamental and odd harmonics while drag is composed of even harmonics when single fish swim in free-stream. For tandem arrangement, we set the phase-speed of downstream fish as 0.75 times that of upstream fish. Fourier spectra of lateral force for both upstream and downstream fish are composed of forcing frequencies of both the fish. Even harmonics of forcing frequencies along with combined modes at sum and difference of these frequencies appear in their drag-spectra. We also investigate the symmetric or antisymmetric nature of the fundamental and combined modes using the conventional symmetry principles and proper orthogonal decomposition technique. We show that the results obtained from both of these techniques agree well with each other. However, we also find some anomalies in case of fish swimming in tandem configuration.
2018
The present work is dedicated to the application of the recently developed (-SPH) scheme to the self-propulsive fishlike swimming hydrodynamics. In the numerical method, a particle shifting technique (PST) is implemented in the framework of-SPH, combining with an adaptive particle refinement (APR) which is a numerical technique adopted to refine the particle resolution in the local region and de-refine particles outside that region. This comes into being the so-called-SPH scheme which contributes to higher numerical accuracy and efficiency. In the fishlike swimming modeling, a NACA0012 profile is controlled to perform a wavy motion mimicking the fish swimming in water. Thanks to the mesh-free characteristic of SPH method, the NACA0012 profile can undergo a wavy motion with large amplitude and move forward freely, avoiding the problem of mesh distortion. A parallel staggered algorithm is adopted to perform the fluid-structure interaction between the foil and the surrounding fluid. Two different approaches are adopted for the fishlike swimming problem. In Approach 1, the foil is fixed and flaps in a free stream and in Approach 2, the wavy foil can move forward under the self-driving force. The numerical results clearly demonstrate the capability of the-SPH scheme in modeling such kind of self-propulsive fishlike swimming problems. Fishes are very smart swimmers in water. Fishes are able to make full use of the flows around their bodies, saving forces, and obtaining the optimal hydrodynamic performance [1]. So far the man-made underwater vehicle is very difficult to swim in such a high efficiency like a fish. Humans still need to learn a lot form animals. Fishlike swimming has been a classic hydrodynamic problem which attracts the attention of researchers for a long history [2-5]). Many works has been done, trying to explain the mechanism of swimming propulsion of single fish [6-8] and the reason of fish schooling [5, 9, 10]. The fishlike swimming problem also has many applications in the field of naval architecture and ocean engineering. One remarkable application is in the propulsion of marine vehicles. The swimming propulsion or bionic propulsion can have higher efficiency than the using of screw propeller and can avoid the problem of hydroacoustic noise and cavitation erosion. Recently, with the rapid development in the research of underwater vehicles, many of them are designed to have a fishlike shape, use a swimming propulsion and therefore have superior stealth property. In the early years, the study of fishlike swimming hydro-dynamics are mainly based on experimental observations [3]. Recently as the development of the computational fluid dynamics (CFD), the investigations based on the numerical models are also rapidly growing. One representative numerical method is the immersed boundary method (IBM) which uses a Lagrangian boundary to track the surface of the rigid or deformable structure with complex shapes [11]. With the hybrid of IBM and other Naiver-Stocks solvers, fishlike swimming problems have been modeled for both two dimensional (2D) [9, 10, 12] and three di
Dynamic behavior of collision of elastic spheres in viscous fluids
Powder Technology, 1999
The dynamic behavior of the collision of two elastic spheres in a stagnant viscous fluid is investigated in this study for particle Reynolds numbers ranging from 5 to 300. The interactive behavior of these particles is examined both experimentally and theoretically. Specifically, the trajectory and velocity of a moving particle in collinear and oblique collisions with a fixed particle are measured using a Ž . high speed video system and an Infinity lens. The lattice-Boltzmann LB simulation is conducted to obtain the detailed three-dimensional flow field and the forces around the particles during the course of collision. Furthermore, a mechanistic model is developed which Ž . Ž . Ž . accounts for four stages of collision processes, including: 1 immediately before the collision, 2 compression during the collision, 3 Ž . rebound during the collision, and 4 immediately after the collision. The LB simulation and experimental results lead to an empirical expression for the drag force on the particle during the close-range particle-particle interaction. This close-range interaction between two approaching particles is taken into account in the equation of motion of the particle. The pressure force and added mass force are derived, based on collisions in inviscid fluids, as a function of separation distance. Results of the LB simulation and prediction by the mechanistic model are in good agreement with the experimental results. The viscous effects on the compression and rebound processes of colliding particles with regard to the elasticity properties of the particle are examined. The studies are also conducted for simulation based on a hard sphere model, which is commonly used in accounting for the particle collision behavior in gas. The study concludes that the key to proper quantification of the particle collision characteristics in liquid is the ability to accurately predict the particle velocity upon contact. q 1999 Elsevier Science S.A. All rights reserved. 0032-5910r99r$ -see front matter q 1999 Elsevier Science S.A. All rights reserved.