Locomotion of a Submerged Cosserat Beam

2009 ◽  
Author(s):  
Sigrid Leyendecker ◽  
Eva Kanso
Keyword(s):  
Incompressible Fluid ◽  
Potential Flow ◽  
Deformable Body ◽  
Mass Effect ◽  
Added Mass ◽  
The Body ◽  
Ambient Fluid ◽  
Torsional Loading ◽  
Neutrally Buoyant ◽  
Shape Deformations

We study the dynamics and locomotion of a neutrally-buoyant deformable body that can undergo finite shape deformations and is immersed in a perfect and incompressible fluid. We model the body as a constrained Cosserat beam, more precisely, a Kirchhoff beam, and we derive the equations governing its motion in potential flow where the ambient fluid is accounted for using the added mass effect. We show that the submerged beam can undergo net locomotion due to applied torsional loading on its centerline.

Swimming due to transverse shape deformations

2009 ◽  
Vol 631 ◽  
pp. 127-148 ◽  
Author(s):  
EVA KANSO
Keyword(s):  
Potential Flow ◽  
Deformable Body ◽  
Three Dimensional ◽  
Point Vortices ◽  
Vortex Wake ◽  
Balance Laws ◽  
Reactive Force ◽  
Slender Bodies ◽  
Shape Changes ◽  
Shape Deformations

Balance laws are derived for the swimming of a deformable body due to prescribed shape changes and the effect of the wake vorticity. The underlying balances of momenta, though classical in nature, provide a unifying framework for the swimming of three-dimensional and planar bodies and they hold even in the presence of viscosity. The derived equations are consistent with Lighthill's reactive force theory for the swimming of slender bodies and, when neglecting vorticity, reduce to the model developed in Kanso et al. (J. Nonlinear Sci., vol. 15, 2005, p. 255) for swimming in potential flow. The locomotion of a deformable body is examined through two sets of examples: the first set studies the effect of cyclic shape deformations, both flapping and undulatory, on the locomotion in potential flow while the second examines the effect of the wake vorticity on the net locomotion. In the latter, the vortex wake is modelled using pairs of point vortices shed periodically from the tail of the deformable body.

scholarly journals Fluid Added-Mass Effect on Flexural Vibration of Hemispherical Shell Structure

2020 ◽  
Vol 25 (1) ◽  
pp. 104-111
Author(s):  
Shahrokh Sepehrirahnama ◽  
Felix Bob Wijaya ◽  
Darren Oon ◽  
Eng Teo Ong ◽  
Heow Pueh Lee ◽  
...  
Keyword(s):  
Shell Structure ◽  
Potential Flow ◽  
Natural Frequencies ◽  
Flexural Vibration ◽  
Mass Effect ◽  
Added Mass ◽  
Fluid Viscosity ◽  
Hemispherical Shell ◽  
Wide Range ◽  
Fluid Added Mass

In this hydroelasticity study, the fluid added-mass effect on a hemispherical shell structure under flexural vibration is investigated. The vibration response of the hemisphere is solved by using a commercial finite element software (ABAQUS) coupled with an in-house boundary element code that models the fluid as potential flow. The fluid-structure interaction is solved as a fully-coupled system by modal superposition to reduce the number of degrees of freedom. The need for an iterative scheme to pass displacement/force information between the two solvers is avoided by direct coupling between the fluid and structure equations. The numerical results on the downward shift in natural frequencies due to added-mass effect compare well with vibration measurements conducted on a stainless-steel bowl with interior and exterior fluid. For water and soap-water solution used in the experiments, the fluid viscosity (varying over a wide range) did not have any significant effect on the wet natural frequencies. This is due to the small viscous boundary layer (milimetre scale) compared to the nominal size of the bowl in centimetres. For such cases, the fluid-added mass only depends on the density of the fluid and the use of potential flow in the numerical model is applicable.

scholarly journals Higgs mechanism and the added-mass effect

2015 ◽  
Vol 471 (2176) ◽  
pp. 20140803 ◽  
Author(s):  
Govind S. Krishnaswami ◽  
Sachin S. Phatak
Keyword(s):  
Mass Matrix ◽  
Vector Boson ◽  
Mass Effect ◽  
Added Mass ◽  
Higgs Mechanism ◽  
The Body ◽  
Boson Mass ◽  
Composite Body ◽  
Weak Force ◽  
Physical Analogy

In the Higgs mechanism, mediators of the weak force acquire masses by interacting with the Higgs condensate, leading to a vector boson mass matrix. On the other hand, a rigid body accelerated through an inviscid, incompressible and irrotational fluid feels an opposing force linearly related to its acceleration, via an added-mass tensor. We uncover a striking physical analogy between the two effects and propose a dictionary relating them. The correspondence turns the gauge Lie algebra into the space of directions in which the body can move, encodes the pattern of gauge symmetry breaking in the shape of an associated body and relates symmetries of the body to those of the scalar vacuum manifold. The new viewpoint is illustrated with numerous examples, and raises interesting questions, notably on the fluid analogues of the broken symmetry and Higgs particle, and the field-theoretic analogue of the added mass of a composite body.

Forces, moments, and added masses for Rankine bodies

1956 ◽  
Vol 1 (3) ◽  
pp. 319-336 ◽  
Author(s):  
L. Landweber ◽  
C. S. Yih
Keyword(s):  
Unsteady Flow ◽  
Incompressible Fluid ◽  
Rotational Motion ◽  
Added Mass ◽  
Dynamical Theory ◽  
The Body ◽  
Added Masses

The dynamical theory of the motion of a body through an inviscid and incompressible fluid has yielded three relations: a first, due to Kirchhoff, which expresses the force and moment acting on the body in terms of added masses; a second, initiated by Taylor, which expresses added masses in terms of singularities within the bòdy; and a third, initiated by Lagally, which expresses the forces and moments in terms of these singularities. The present investigation is concerned with generalizations of the Taylor and Lagally theorems to include unsteady flow and arbitrary translational and rotational motion of the body, to present new and simple derivations of these theorems, and to compare the Kirchhoff and Lagally methods for obtaining forces and moments. In contrast with previous generalizations, the Taylor theorem is derived when other boundaries are present; for the added-mass coefficients due to rotation alone, for which no relations were known, it is shown that these relations do not exist in general, although approximate ones are found for elongated bodies. The derivation of the Lagally theorem leads to new terms, compact expressions for the force and moment, and the complete expressions of the forces and moments in terms of singularities for elongated bodies.

Stability of a Submerged Deformable Body

2009 ◽  
Author(s):  
Fangxu Jing ◽  
Eva Kanso
Keyword(s):  
Vortex Shedding ◽  
Deformable Body ◽  
Mass Effect ◽  
Added Mass ◽  
Bending Stiffness ◽  
Body Dimensions ◽  
Fish Model ◽  
The Stability ◽  
Parameter Values ◽  
Stable Passive

We study the stability of passive motion of a fish model. The (articulated body) fish model accounts for the finite dimensions of the fish, its bending stiffness (via the torsional springs at the joints), the unsteadiness of the flow (via the added mass effect) but it does not take into consideration vortex shedding from the trailing edge of the fish. The stability analysis shows that there is a range of parameter values (bending stiffness versus body dimensions) that support stable passive swimming in the direction of the body’s length.

scholarly journals Effects of body elasticity on stability of underwater locomotion

2011 ◽  
Vol 690 ◽  
pp. 461-473 ◽  
Author(s):  
F. Jing ◽  
E. Kanso
Keyword(s):  
Deformable Body ◽  
The Body ◽  
Passive Stability ◽  
External Perturbations ◽  
Straight Line ◽  
Fish Morphology ◽  
Active Stabilization ◽  
The Stability ◽  
Neutrally Buoyant ◽  
Passive Stabilization

AbstractWe examine the stability of the ‘coast’ motion of fish, that is to say, the motion of a neutrally buoyant fish at constant speed in a straight line. The forces and moments acting on the fish body are thus perfectly balanced. The fish motion is said to be unstable if a perturbation in the conditions surrounding the fish results in forces and moments that tend to increase the perturbation, and it is stable if these emerging forces tend to reduce the perturbation and return the fish to its original state. Stability may be achieved actively or passively. Active stabilization requires neurological control that activates musculo-skeletal components to compensate for the external perturbations acting against stability. Passive stabilization on the other hand requires no energy input by the fish and is dependent upon the fish morphology, i.e. geometry and elastic properties. In this paper, we use a deformable body consisting of an articulated body equipped with torsional springs at its hinge joints and submerged in an unbounded perfect fluid as a simple model to study passive stability as a function of the body geometry and spring stiffness. We show that for given body dimensions, the spring elasticity, when properly chosen, leads to passive stabilization of the (otherwise unstable) coast motion.

scholarly journals On the added mass in a viscous incompressible fluid

2019 ◽  
Vol 488 (5) ◽  
pp. 493-497 ◽  
Author(s):  
G. Ya. Dynnikova
Keyword(s):  
Incompressible Fluid ◽  
Constant Velocity ◽  
Viscous Incompressible Fluid ◽  
Added Mass ◽  
The Body ◽  
Potential Flows ◽  
Acceleration Vector ◽  
Added Masses ◽  
History Of ◽  
Instantaneous Distribution

It is proved that at the same instantaneous distribution of the flow velocity of a viscous incompressible fluid, the forces acting on a body moving with acceleration differ from forces acting on the body moving with constant velocity by a vector, which is equal to the added masses tensor multiplied by the acceleration vector. The tensor of the added masses coincides with the tensor calculated for potential flows with the same geometry of the body and surrounding surfaces, and does not depend either on viscosity or on the distribution of vorticity in the flow space. While the force corresponding to the motion with constant velocity depends on the history of movement.

On The Motion of Dispersed Balls in a Potential Flow: A Kinetic Description of the Added Mass Effect

1999 ◽  
Vol 60 (1) ◽  
pp. 61-83 ◽  
Author(s):  
Henar Herrero ◽  
Brigitte Lucquin-Desreux ◽  
Benoı⁁t Perthame
Keyword(s):  
Potential Flow ◽  
Mass Effect ◽  
Added Mass ◽  
Kinetic Description

scholarly journals An Application of Hankel Transforms in Axially Symmetric Potential Flow

1956 ◽  
Vol 9 (3) ◽  
pp. 128-131
Author(s):  
A. G. Mackie
Keyword(s):  
New York ◽  
Incompressible Fluid ◽  
Circular Hole ◽  
Potential Flow ◽  
Fourier Transforms ◽  
The Other ◽  
Axially Symmetric ◽  
Symmetric Potential ◽  
Physical Interest ◽  
Hankel Transforms

In his book on Hydrodynamics, Lamb obtained a solution for the potential flow of an incompressible fluid through a circular hole in a plane wall. More recently Sneddon (Fourier Transforms, New York, 1951) obtained Lamb's solution by an elegant application of Hankel transforms.Since the streamlines in this solution are symmetric about the wall, it is not of particular physical interest. In this note, Sneddon's method is used to give a solution in which the fluid is infinite in extent on one side of the aperture but issues as a jet of finite diameter on the other side.

Survey on the Indirect Methods of Potential Flow Used for the Optimization of Airships Profile

2014 ◽  
Vol 554 ◽  
pp. 717-723
Author(s):  
Reza Abbasabadi Hassanzadeh ◽  
Shahab Shariatmadari ◽  
Ali Chegeni ◽  
Seyed Alireza Ghazanfari ◽  
Mahdi Nakisa
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flow Field ◽  
Drag Coefficient ◽  
Body Surface ◽  
Potential Flow ◽  
The Body ◽  
Indirect Methods ◽  
Singularity Method ◽  
Singularity Distribution

The present study aims to investigate the optimized profile of the body through minimizing the Drag coefficient in certain Reynolds regime. For this purpose, effective aerodynamic computations are required to find the Drag coefficient. Then, the computations should be coupled thorough an optimization process to obtain the optimized profile. The aerodynamic computations include calculating the surrounding potential flow field of an object, calculating the laminar and turbulent boundary layer close to the object, and calculating the Drag coefficient of the object’s body surface. To optimize the profile, indirect methods are used to calculate the potential flow since the object profile is initially amorphous. In addition to the indirect methods, the present study has also used axial singularity method which is more precise and efficient compared to other methods. In this method, the body profile is not optimized directly. Instead, a sink-and-source singularity distribution is used on the axis to model the body profile and calculate the relevant viscose flow field.

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