scholarly journals Two typical merging events of oceanic mesoscale anticyclonic eddies

Ocean Science ◽  
2019 ◽  
Vol 15 (6) ◽  
pp. 1545-1559 ◽  
Author(s):  
Zi-Fei Wang ◽  
Liang Sun ◽  
Qiu-Yang Li ◽  
Hao Cheng
Keyword(s):  
Potential Energy ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Center Of Mass ◽  
Gravitational Potential Energy ◽  
Initial State ◽  
Final State ◽  
Inverse Energy Cascade ◽  
Eddy Potential Energy ◽  
Anticyclonic Eddies

Abstract. The long-term theoretical “energy paradox” of whether the final state of two merging anticyclones contains more energy than the initial state is studied by considering two typical merging events of ocean mesoscale eddies. The results demonstrate that the total mass (volume), total circulation (area integration of vorticity), and total angular momentum (AM) are conserved if the orbital AM relative to the center of mass is taken into account as the eddies rotate around the center of mass before merging. For subsurface merging, the mass trapped by the Taylor–Proudman effect above the subsurface eddies should also be included. Both conservation laws of circulation and orbital AM have been overlooked in previous theoretical studies. As a result of fusion during merging, the total eddy kinetic energy decreases slightly. In contrast, the total eddy potential energy (EPE) increases after merging. The increase in EPE is mostly supported by the loss of gravitational potential energy (PE) via eddy sinking below the original level prior to merging. This implies that the merging of eddies requires background gravitational PE to be converted to EPE. In contrast, the vorticity and enstrophy consequently decrease after merging. Thus, the eddy merging effect behaves as a “large-scale energy pump” in an inverse energy cascade. It is noted that eddy conservation and conversion laws depend on the laws of physical dynamics, even if additional degrees of freedom can be provided in a mathematical model.

scholarly journals Two typical merging events of oceanic mesoscale anticyclonic eddies

2019 ◽  
Author(s):  
Zi-Fei Wang ◽  
Liang Sun ◽  
Qiu-Yang Li ◽  
Hao Cheng
Keyword(s):  
Potential Energy ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Center Of Mass ◽  
Gravitational Potential Energy ◽  
Initial State ◽  
Final State ◽  
Inverse Energy Cascade ◽  
Eddy Potential Energy ◽  
Anticyclonic Eddies

Abstract. The long-term theoretical energy paradox of whether the final state of two merging anticyclones contains more energy than the initial state is studied by observing two typical merging events of ocean mesoscale eddies. It is found that the total mass (volume), total circulation (area integration of vorticity) and total angular momentum (AM) are conserved if the orbital AM relative to the center of mass is taken into account as the eddies rotate around the center of mass before merging. For subsurface merging, the mass trapped by the Taylor–Proudman effect above the subsurface eddies should also be included. Both circulation conservation laws and orbital AM have been overlooked in previous theoretical studies. The total eddy kinetic energy slightly decreases after merging due to fusion. On the contrary, the total eddy potential energy (EPE) significantly increases after the merging. The increase of the EPE is mostly supported by the loss of gravitational potential energy (PE) via eddy sinking below the original level. This implies that the merging of eddies requires the background gravitational PE to convert to the EPE. In contrast, the vorticity and enstrophy consequently decrease after merging. Thus, the eddy merging effect behaves as a large-scale energy pump in an inverse energy cascade. It is noted that eddy conservation and conversion laws depend on laws of physical dynamics, even if additional degrees of freedom can be provided in a mathematical model.

scholarly journals Walking in simulated reduced gravity: mechanical energy fluctuations and exchange

1999 ◽  
Vol 86 (1) ◽  
pp. 383-390 ◽  
Author(s):  
Timothy M. Griffin ◽  
Neil A. Tolani ◽  
Rodger Kram
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Inverted Pendulum ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Gravitational Potential Energy ◽  
Reduced Gravity

Walking humans conserve mechanical and, presumably, metabolic energy with an inverted pendulum-like exchange of gravitational potential energy and horizontal kinetic energy. Walking in simulated reduced gravity involves a relatively high metabolic cost, suggesting that the inverted-pendulum mechanism is disrupted because of a mismatch of potential and kinetic energy. We tested this hypothesis by measuring the fluctuations and exchange of mechanical energy of the center of mass at different combinations of velocity and simulated reduced gravity. Subjects walked with smaller fluctuations in horizontal velocity in lower gravity, such that the ratio of horizontal kinetic to gravitational potential energy fluctuations remained constant over a fourfold change in gravity. The amount of exchange, or percent recovery, at 1.00 m/s was not significantly different at 1.00, 0.75, and 0.50 G (average 64.4%), although it decreased to 48% at 0.25 G. As a result, the amount of work performed on the center of mass does not explain the relatively high metabolic cost of walking in simulated reduced gravity.

scholarly journals The Possibility of Zero Limb-Work Gaits in Sprawled and Parasagittal Quadrupeds: Insights from Linkages of the Industrial Revolution

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
J R Usherwood
Keyword(s):  
Potential Energy ◽  
Industrial Revolution ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Phase Fluctuation ◽  
Vertical Axis ◽  
The Body ◽  
Mechanical Work ◽  
Gravitational Potential Energy ◽  
Pull Out

Synopsis Animal legs are diverse, complex, and perform many roles. One defining requirement of legs is to facilitate terrestrial travel with some degree of economy. This could, theoretically, be achieved without loss of mechanical energy if the body could take a continuous horizontal path supported by vertical forces only—effectively a wheel-like translation, and a condition closely approximated by walking tortoises. If this is a potential strategy for zero mechanical work cost among quadrupeds, how might the structure, posture, and diversity of both sprawled and parasagittal legs be interpreted? In order to approach this question, various linkages described during the industrial revolution are considered. Watt’s linkage provides an analogue for sprawled vertebrates that uses diagonal limb support and shows how vertical-axis joints could enable approximately straight-line horizontal translation while demanding minimal mechanical power. An additional vertical-axis joint per leg results in the wall-mounted pull-out monitor arm and would enable translation with zero mechanical work due to weight support, without tipping or toppling. This is consistent with force profiles observed in tortoises. The Peaucellier linkage demonstrates that parasagittal limbs with lateral-axis joints could also achieve the zero-work strategy. Suitably tuned four-bar linkages indicate this is feasibly approximated for flexed, biologically realistic limbs. Where “walking” gaits typically show out of phase fluctuation in center of mass kinetic and gravitational potential energy, and running, hopping or trotting gaits are characterized by in-phase energy fluctuations, the zero limb-work strategy approximated by tortoises would show zero fluctuations in kinetic or potential energy. This highlights that some gaits, perhaps particularly those of animals with sprawled or crouched limbs, do not fit current kinetic gait definitions; an additional gait paradigm, the “zero limb-work strategy” is proposed.

Mechanics of locomotion in lizards.

1997 ◽  
Vol 200 (16) ◽  
pp. 2177-2188 ◽  
Author(s):  
C T Farley ◽  
T C Ko
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Inverted Pendulum ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Gravitational Potential Energy ◽  
Lateral Bending ◽  
Walking Gait ◽  
Bending Force

Lizards bend their trunks laterally with each step of locomotion and, as a result, their locomotion appears to be fundamentally different from mammalian locomotion. The goal of the present study was to determine whether lizards use the same two basic gaits as other legged animals or whether they use a mechanically unique gait due to lateral trunk bending. Force platform and kinematic measurements revealed that two species of lizards, Coleonyx variegatus and Eumeces skiltonianus, used two basic gaits similar to mammalian walking and trotting gaits. In both gaits, the kinetic energy fluctuations due to lateral movements of the center of mass were less than 5% of the total external mechanical energy fluctuations. In the walking gait, both species vaulted over their stance limbs like inverted pendulums. The fluctuations in kinetic energy and gravitational potential energy of the center of mass were approximately 180 degrees out of phase. The lizards conserved as much as 51% of the external mechanical energy required for locomotion by the inverted pendulum mechanism. Both species also used a bouncing gait, similar to mammalian trotting, in which the fluctuations in kinetic energy and gravitational potential energy of the center of mass were nearly exactly in phase. The mass-specific external mechanical work required to travel 1 m (1.5 J kg-1) was similar to that for other legged animals. Thus, in spite of marked lateral bending of the trunk, the mechanics of lizard locomotion is similar to the mechanics of locomotion in other legged animals.

scholarly journals The phase shift between potential and kinetic energy in human walking

2020 ◽  
Vol 223 (21) ◽  
pp. jeb232645
Author(s):  
Giovanni A. Cavagna ◽  
Mario A. Legramandi
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Sagittal Plane ◽  
Center Of Mass ◽  
Phase Relationship ◽  
Gravitational Potential Energy ◽  
External Work ◽  
Unit Distance ◽  
Factors Affecting

ABSTRACTIt is known that mechanical work to sustain walking is reduced, owing to a transfer of gravitational potential energy into kinetic energy, as in a pendulum. The factors affecting this transfer are unclear. In particular, the phase relationship between potential and kinetic energy curves of the center of mass is not known. In this study, we measured this relationship. The normalized time intervals α, between the maximum kinetic energy in the sagittal plane (Ek) and the minimum gravitational potential energy (Ep), and β, between the minimum Ek and the maximum Ep, were measured during walking at various speeds (0.5–2.5 m s−1). In our group of subjects, α=β at 1.6 m s−1, indicating that, at this speed, the time difference between Ep and Ek extremes is the same at the top and the bottom of the trajectory of the center of mass. It turns out that, at the same speed, the work done to lift the center of mass equals the work to accelerate it forwards, the Ep–Ek energy transfer approaches a maximum and the mass-specific external work per unit distance approaches a minimum.

Elevator Energy Storage Systems

2019 ◽  
pp. 97-106
Author(s):  
Thomas Fong
Keyword(s):  
Energy Storage ◽  
Potential Energy ◽  
Power Systems ◽  
Gravitational Potential ◽  
Large Scale ◽  
Social Impact ◽  
Storage Systems ◽  
Gravitational Potential Energy ◽  
Energy Storage Systems ◽  
Power Storage

Elevator energy storage systems provide reliable energy storage using the gravitational potential energy of elevators. The chapter provides evidence that harnessing the gravity of existing infrastructure is economically, environmentally, and socially more responsible than its competitors (large scale hydraulic and lithium battery storage). EESS proposes a heterodox approach to individuals' relationships with power systems. By the use of existing capital to provide power storage, the capitalist cycle, which constructs new capital for the sake of monetary growth, is disrupted. The next generation of energy storage will look to re-constrain its parameters of acceptability on the grounds of environmental and social impact rather than efficiency and megawatt output.

Halting scale and energy equilibration in two-dimensional quasigeostrophic turbulence

2013 ◽  
Vol 721 ◽  
Author(s):  
R. K. Scott ◽  
D. G. Dritschel
Keyword(s):  
Energy Spectrum ◽  
Potential Energy ◽  
Large Scale ◽  
Scaling Law ◽  
Dissipative System ◽  
Two Dimensional ◽  
Simple Representation ◽  
Inverse Energy Cascade ◽  
Numerical Integrations ◽  
Deformation Length

AbstractThe halting scale of the inverse energy cascade and the partition between kinetic and potential energy are considered for the case of forced quasigeostrophic turbulence in the regime of intermediate Rossby deformation length, for which the deformation length is comparable to the energy-containing scales of the flow. Phenomenological estimates for the halting scale and equilibrated energy of the forced–dissipative system with a simple representation of large-scale thermal damping are tested against numerical integrations and are found to poorly describe the numerically obtained dependence on damping coefficient; a modified scaling law is proposed that more accurately describes the dependence. The scale-selective nature of the damping leads to a large-scale spectral bottleneck that steepens the energy spectrum, consistent with previous studies of hypodiffusive dissipation. It is found that, across the parameter range considered, the blocking is largely insensitive to the ratio of deformation radius to the energy-containing scales.

Static Balancing of Spatial Six-Degree-of-Freedom Parallel Mechanisms With Revolute Actuators

1998 ◽  
Author(s):  
Jiegao Wang ◽  
Clément M. Gosselin
Keyword(s):  
Potential Energy ◽  
Center Of Mass ◽  
Total Potential Energy ◽  
Degree Of Freedom ◽  
Gravitational Potential Energy ◽  
Parallel Mechanisms ◽  
Static Balancing ◽  
Total Potential ◽  
Global Center ◽  
Six Degree Of Freedom

Abstract The static balancing of spatial six-degree-of-freedom parallel mechanisms or manipulators with revolute actuators is studied in this paper. Two static balancing methods, namely, using counterweights and using springs, are used. The first method leads to mechanisms with a stationary global center of mass while the second approach leads to mechanisms whose total potential energy (including the elastic potential energy stored in the springs as well as the gravitational potential energy) is constant. The position vector of the global center of mass and the total potential energy of the manipulator are first expressed as functions of the position and orientation of the platform. Then, conditions for static balancing are derived from the resulting expressions. Finally, examples are given in order to illustrate the design methodologies.

scholarly journals Design of a Five-Degrees of Freedom Statically Balanced Mechanism with Multi-Directional Functionality

Robotics ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 11
Author(s):  
Terence Essomba
Keyword(s):  
Potential Energy ◽  
Degrees Of Freedom ◽  
Surgical Instruments ◽  
Gravitational Potential Energy ◽  
Cad Model ◽  
Linear Motion ◽  
Mechanical Parameters ◽  
End Effector ◽  
Elastic Potential Energy ◽  
Selection Of

A statically balanced mechanism is designed as a potential solution for the positioning of surgical instruments. Its kinematics with five degrees of freedom that decouples linear and angular motions is proposed for that objective. The linear motion of its end effector is provided by a classical parallelogram linkage. To enhance its adaptability, a mechanical system allows re-orienting the position mechanism in three different working modes (horizontal, upward and downward) while preserving its static balance. Based on the mechanical concept, a uniformized static balancing condition that considers all working modes is given. The orientation of the end effector is provided by a spherical decoupled mechanism. It generates a remote center of motion which is highly representative of kinematics in surgery requirements. Based on the mechanism kinematics, the evolution of its gravitational potential energy is studied. Two different mechanical concepts are then proposed to generate a compensating elastic potential energy. A CAD model of the entire mechanism has allowed the estimation of all mechanical parameters for the selection of the appropriate tension springs and for carrying out validation simulations. A prototype of the statically balanced mechanism is fabricated and successfully tested.

Driving Torsion Scans with Wavefront Propagation

2020 ◽  
Author(s):  
Yudong Qiu ◽  
Daniel Smith ◽  
Chaya Stern ◽  
mudong feng ◽  
Lee-Ping Wang
Keyword(s):  
Potential Energy ◽  
Force Field ◽  
Degrees Of Freedom ◽  
Computational Cost ◽  
Initial Guess ◽  
Field Development ◽  
Force Field Development ◽  
Wavefront Propagation ◽  
Open Source Software Package

<div>The parameterization of torsional / dihedral angle potential energy terms is a crucial part of developing molecular mechanics force fields.</div><div>Quantum mechanical (QM) methods are often used to provide samples of the potential energy surface (PES) for fitting the empirical parameters in these force field terms.</div><div>To ensure that the sampled molecular configurations are thermodynamically feasible, constrained QM geometry optimizations are typically carried out, which relax the orthogonal degrees of freedom while fixing the target torsion angle(s) on a grid of values.</div><div>However, the quality of results and computational cost are affected by various factors on a non-trivial PES, such as dependence on the chosen scan direction and the lack of efficient approaches to integrate results started from multiple initial guesses.</div><div>In this paper we propose a systematic and versatile workflow called \textit{TorsionDrive} to generate energy-minimized structures on a grid of torsion constraints by means of a recursive wavefront propagation algorithm, which resolves the deficiencies of conventional scanning approaches and generates higher quality QM data for force field development.</div><div>The capabilities of our method are presented for multi-dimensional scans and multiple initial guess structures, and an integration with the MolSSI QCArchive distributed computing ecosystem is described.</div><div>The method is implemented in an open-source software package that is compatible with many QM software packages and energy minimization codes.</div>

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