scholarly journals Thermodynamics of the Bladderwort Feeding Strike—Suction Power from Elastic Energy Storage

2019 ◽  
Vol 59 (6) ◽  
pp. 1597-1608 ◽  
Author(s):  
Otto Berg ◽  
Krizma Singh ◽  
Maxwell R Hall ◽  
M Janneke Schwaner ◽  
Ulrike K Müller
Keyword(s):  
Reynolds Number ◽  
Stokes Flow ◽  
Elastic Energy ◽  
Size Range ◽  
Larval Fish ◽  
Viscous Friction ◽  
Carnivorous Plant ◽  
Adult Fish ◽  
Stored Energy ◽  
Suction Traps

Abstract The carnivorous plant bladderwort exemplifies the use of accumulated elastic energy to power motion: respiration-driven pumps slowly load the walls of its suction traps with elastic energy (∼1 h). During a feeding strike, this energy is released suddenly to accelerate water (∼1 ms). However, due to the traps’ small size and concomitant low Reynolds number, a significant fraction of the stored energy may be dissipated as viscous friction. Such losses and the mechanical reversibility of Stokes flow are thought to degrade the feeding success of other suction feeders in this size range, such as larval fish. In contrast, triggered bladderwort traps are generally successful. By mapping the energy budget of a bladderwort feeding strike, we illustrate how this smallest of suction feeders can perform like an adult fish.

Evolution of unstable system.

2015 ◽  
Vol 9 (3) ◽  
pp. 2487-2502 ◽  
Author(s):  
Igor V. Lebed
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Stokes Flow ◽  
Stable Solution ◽  
The State ◽  
Unstable System ◽  
Unstable Flow ◽  
Unstable Solutions ◽  
Vortex Shedding Modes ◽  
Hydrodynamics Equations

Scenario of appearance and development of instability in problem of a flow around a solid sphere at rest is discussed. The scenario was created by solutions to the multimoment hydrodynamics equations, which were applied to investigate the unstable phenomena. These solutions allow interpreting Stokes flow, periodic pulsations of the recirculating zone in the wake behind the sphere, the phenomenon of vortex shedding observed experimentally. In accordance with the scenario, system loses its stability when entropy outflow through surface confining the system cannot be compensated by entropy produced within the system. The system does not find a new stable position after losing its stability, that is, the system remains further unstable. As Reynolds number grows, one unstable flow regime is replaced by another. The replacement is governed tendency of the system to discover fastest path to depart from the state of statistical equilibrium. This striving, however, does not lead the system to disintegration. Periodically, reverse solutions to the multimoment hydrodynamics equations change the nature of evolution and guide the unstable system in a highly unlikely direction. In case of unstable system, unlikely path meets the direction of approaching the state of statistical equilibrium. Such behavior of the system contradicts the scenario created by solutions to the classic hydrodynamics equations. Unstable solutions to the classic hydrodynamics equations are not fairly prolonged along time to interpret experiment. Stable solutions satisfactorily reproduce all observed stable medium states. As Reynolds number grows one stable solution is replaced by another. They are, however, incapable of reproducing any of unstable regimes recorded experimentally. In particular, stable solutions to the classic hydrodynamics equations cannot put anything in correspondence to any of observed vortex shedding modes. In accordance with our interpretation, the reason for this isthe classic hydrodynamics equations themselves.

Adult and larval fish assemblages vary among small tributary mouths of Green Bay, Lake Michigan

2021 ◽  
Author(s):  
Amelia T McReynolds ◽  
Megan L. Hoff ◽  
Angelena A. Sikora ◽  
Cynthia I. Nau ◽  
Michael J. Pietraszek ◽  
...  
Keyword(s):  
Fish Assemblage ◽  
Lake Michigan ◽  
Fish Assemblages ◽  
Water Movement ◽  
Larval Fish ◽  
Spatial Dynamics ◽  
Spatial And Temporal Variation ◽  
Adult Fish ◽  
Green Bay ◽  
Small Tributary

Small tributaries of the Great Lakes serve as important habitat during critical life stages of many fish species, though temporal and spatial dynamics of the assemblage that uses these systems are seldom investigated. This study quantifies larval and adult fish assemblages captured by fyke net and light traps among small tributary mouths of Green Bay, Lake Michigan. Ten tributaries harbored a total of forty-five species representing seventeen families, with the most abundant including spottail shiner (Notropis hudsonius (Clinton 1824)) in adult assemblages and white sucker (Catostomus commersonii (Lacepède 1803)) in larval assemblages. Larval fish assemblage structures differed over five biweekly sampling events in May and June. Adult fish assemblage structures varied among tributaries but not among spring, summer, and fall samples. Larval and adult species assemblages at these rivermouths are likely influenced by hydrology, habitat structure, and species-specific ecology. Water movement may transport larvae into rivermouths, as larval assemblages were dominated by species that spawn in coastal habitats. Adult species richness varied with longitude, with the greatest diversity in tributaries on the west shore. This investigation of fish assemblages highlights the spatial and temporal variation that occurs in these systems and their role in shaping fish populations in Green Bay.

scholarly journals Universality in statistics of Stokes flow over a no-slip wall with random roughness

2019 ◽  
Vol 862 ◽  
pp. 1084-1104
Author(s):  
Vladimir Parfenyev ◽  
Sergey Belan ◽  
Vladimir Lebedev
Keyword(s):  
Reynolds Number ◽  
Stokes Flow ◽  
Low Reynolds Number ◽  
Rapid Development ◽  
Fluid Velocity ◽  
Flow Properties ◽  
Random Roughness ◽  
Low Reynolds Number Flows ◽  
And Control ◽  
Reynolds Number Flows

Stochastic roughness is a widespread feature of natural surfaces and is an inherent byproduct of most fabrication techniques. In view of the rapid development of microfluidics, the important question is how this inevitable problem affects the low-Reynolds-number flows that are common for micro-devices. Moreover, one could potentially turn the flaw into a virtue and control the flow properties by means of specially ‘tuned’ random roughness. In this paper we investigate theoretically the statistics of fluctuations in fluid velocity produced by the waviness irregularities at the surface of a no-slip wall. Particular emphasis is laid on the issue of the universality of our findings.

A magneto-hydrodynamic Stokes flow

1961 ◽  
Vol 260 (1300) ◽  
pp. 79-90 ◽  
Keyword(s):  
Reynolds Number ◽  
Stokes Flow ◽  
Hartmann Number ◽  
Magnetic Reynolds Number ◽  
Conducting Fluid ◽  
Slow Flow ◽  
Magnetic Pole ◽  
Total Drag ◽  
Conducting Sphere ◽  
Stokes Drag

This paper considers the slow flow of a viscous, conducting fluid past a non-conducting sphere at whose centre is a magnetic pole. The magnetic Reynolds number is assumed to be small, and the modifications to the classical Stokes flow and the free magnetic pole field are obtained for an arbitrary Hartmann number. The total drag D on the sphere has been calculated, and the ratio D / D s determined as a function of the Hartmann number M , where D s is the Stokes drag. In particular ( D — D s )/ D s = 37/210 M 2 + O ( M 4 ) for small M and ( D — D s )/ Ds ~ 0·7205 M - 1 as M → ∞.

Particle Arrestance Modeling Within Fibrous Porous Media

1999 ◽  
Vol 121 (1) ◽  
pp. 155-162 ◽  
Author(s):  
James Giuliani ◽  
Kambiz Vafai
Keyword(s):  
Reynolds Number ◽  
Numerical Model ◽  
Stokes Flow ◽  
Stokes Equations ◽  
Angular Position ◽  
Past Research ◽  
Particle Growth ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Fibrous Medium

In the present study, particle growth on individual fibers within a fibrous medium is examined as flow conditions transition beyond the Stokes flow regime. Employing a numerical model that solves the viscous, incompressible Navier-Stokes equations, the Stokes flow approximation used in past research to describe the velocity field through the fibrous medium is eliminated. Fibers are modeled in a staggered array to eliminate assumptions regarding the effects of neighboring fibers. Results from the numerical model are compared to the limiting theoretical results obtained for individual cylinders and arrays of cylinders. Particle growth is presented as a function of time, angular position around the fiber, and flow Reynolds number. From the range of conditions examined, particles agglomerate into taller and narrower dendrites as Reynolds number is increased, which increases the probability that they will break off as larger agglomerations and, subsequently, substantially reduce the hydraulic conductivity of the porous medium.

On the global stability of two-dimensional, incompressible, elastic bars in uniaxial extension

2009 ◽  
Vol 466 (2116) ◽  
pp. 1167-1176 ◽  
Author(s):  
Jeyabal Sivaloganathan ◽  
Scott J. Spector
Keyword(s):  
Elastic Energy ◽  
Energy Function ◽  
Shear Bands ◽  
Uniaxial Extension ◽  
Two Dimensional ◽  
Stored Energy ◽  
Absolute Minimizer ◽  
Local Bifurcations ◽  
Maximum Value ◽  
Incompressible Hyperelastic Material

When a rectangular bar is subjected to uniaxial tension, the bar usually deforms (approximately) homogeneously and isoaxially until a critical load is reached. A bifurcation, such as the formation of shear bands or a neck, may then be observed. One approach is to model such an experiment as the in-plane extension of a two-dimensional, homogeneous, isotropic, incompressible, hyperelastic material in which the length of the bar is prescribed, the ends of the bar are assumed to be free of shear and the sides are left completely free. It is shown that standard constitutive hypotheses on the stored-energy function imply that no such bifurcation is possible in this model due to the fact that the homogeneous isoaxial deformation is the unique absolute minimizer of the elastic energy. Thus, in order for a bifurcation to occur either the material must cease to be elastic or the stored-energy function must violate the standard hypotheses. The fact that no local bifurcations can occur under the assumptions used herein was known previously, since these assumptions prohibit the load on the bar from reaching a maximum value. However, the fact that the homogeneous deformation is the absolute minimizer of the energy appears to be a new result.

Application of the Cosserat Spectrum Theory to Stokes Flow

1999 ◽  
Vol 66 (3) ◽  
pp. 811-814
Author(s):  
W. Liu ◽  
A. Plotkin
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Laplace Equation ◽  
Analytical Solutions ◽  
Stokes Flow ◽  
Low Reynolds Number ◽  
Flow Problems ◽  
Cosserat Spectrum ◽  
Linear Shear ◽  
Flow Past A Sphere

This paper presents an application of the Cosserat spectrum theory in elasticity to the solution of low Reynolds number (Stokes flow) problems. The velocity field is divided into two components: a solution to the vector Laplace equation and a solution associated with the discrete Cosserat eigenvectors. Analytical solutions are presented for the Stokes flow past a sphere with uniform, extensional, and linear shear freestream profiles.

Flow due to a point source of momentum in a viscous fluid contained in a sphere

1967 ◽  
Vol 63 (1) ◽  
pp. 249-256
Author(s):  
K. B. Ranger
Keyword(s):  
Reynolds Number ◽  
Viscous Fluid ◽  
Stokes Flow ◽  
Fluid Motion ◽  
Perturbation Expansion ◽  
General Term ◽  
Axially Symmetric ◽  
Order Of Magnitude ◽  
Self Consistency ◽  
Viscous Fluid Motion

AbstractIt is argued that the zero Reynolds limit of the steady incompressible axially symmetric viscous fluid motion interior to a sphere due to a Landau source at the centre is a Stokes flow. The first three terms of the perturbation expansion are determined and the order of magnitude of the general term not derivable from the Landau source is established. Comparison of the convection terms with the diffusion terms for each order of the Reynolds number demonstrates self consistency at each stage of the expansion.

Stokes flow between two intersecting circular arcs

1965 ◽  
Vol 61 (1) ◽  
pp. 271-274 ◽  
Author(s):  
K. B Ranger
Keyword(s):  
Reynolds Number ◽  
Stokes Flow ◽  
Stokes Equations ◽  
Flow Region ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Reynolds Number Flow ◽  
Circular Arcs ◽  
Converging Flow ◽  
Point Of Intersection

This paper considers a family of viscous flows closely related to the exact Jeffery-Hamel solution ((l), (2)) of the two-dimensional Navier-Stokes equations, for diverging or converging flow in a channel. It is known that if the walls of the channel intersect at an angle less than π then there is a unique solution of the Navier-Stokes equations in which the streamlines are straight lines issuing from the point of intersection of the walls and the flow is everywhere diverging or everywhere converging. The flow parameters depend on the total fluid mass M emitted at the point of intersection and the angle 2α between the walls. By taking the Reynolds number R = M/ν, where v is the kinematic viscosity, the stream function can be expanded in a power series in R in which the leading term is a Stokes flow. Alternatively the solution can be developed by perturbing the Stokes flow and is one of very few examples known in which a Stokes flow can be regarded as a uniformly valid first approximation everywhere in an infinite fluid region. The class of flows to be considered is a generalization of the Jeffery–Hamel flow by taking the flow region to be finite and bounded by two circular arcs which intersect at an angle less than π At one point of intersection fluid is forced into the region and an equal amount is absorbed out at the other point. It is found to the first order that the flow at the two points of intersection corresponds to the zero Reynolds number limit for diverging and converging flow, respectively. Now since the flow at these points can be developed by perturbing the Stokes flow solution it is reasonable to assume that the zero Reynolds number flow in the entire finite region bounded by the arcs is a Stokes flow since the most likely region in which this approximation becomes invalid is locally at the points of intersection but here the validity of the approximation is ensured. A comparison of the convection terms with the viscous terms verifies that this conclusion is borne out.

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