scholarly journals Gravitational Potential Energy Balance for the Thermal Circulation in a Model Ocean

2006 ◽  
Vol 36 (7) ◽  
pp. 1420-1429 ◽  
Author(s):  
Rui Xin Huang ◽  
Xingze Jin
Keyword(s):  
Energy Balance ◽  
Equation Of State ◽  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Mechanical Energy ◽  
Vertical Mixing ◽  
Gravitational Potential Energy ◽  
Thermal Circulation ◽  
Model Ocean

Abstract The gravitational potential energy balance of the thermal circulation in a simple rectangular model basin is diagnosed from numerical experiments based on a mass-conserving oceanic general circulation model. The vertical mixing coefficient is assumed to be a given constant. The model ocean is heated/cooled from the upper surface or bottom, and the equation of state is linear or nonlinear. Although the circulation patterns obtained from these cases look rather similar, the energetics of the circulation may be very different. For cases of differential heating from the bottom with a nonlinear equation of state, the circulation is driven by mechanical energy generated by heating from the bottom. On the other hand, circulation for three other cases is driven by external mechanical energy, which is implicitly provided by tidal dissipation and wind stress. The major balance of gravitational energy in this model ocean is between the source of energy due to vertical mixing and the conversion from kinetic energy at low latitudes and the sink of energy due to convection adjustment and conversion to kinetic energy at high latitudes.

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.

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.

Tracker-assisted modelling: simultaneous validation of the conservation law of energy and the work-energy theorem

2021 ◽  
Vol 57 (1) ◽  
pp. 015012
Author(s):  
Unofre B Pili ◽  
Renante R Violanda
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Conservation Law ◽  
Gravitational Potential Energy ◽  
Time Data ◽  
Home Based ◽  
Basic Physics ◽  
Free Falling ◽  
Work Done

Abstract The video of a free-falling object was analysed in Tracker in order to extract the position and time data. On the basis of these data, the velocity, gravitational potential energy, kinetic energy, and the work done by gravity were obtained. These led to a rather simultaneous validation of the conservation law of energy and the work–energy theorem. The superimposed plots of the kinetic energy, gravitational potential energy, and the total energy as respective functions of time and position demonstrate energy conservation quite well. The same results were observed from the plots of the potential energy against the kinetic energy. On the other hand, the work–energy theorem has emerged from the plot of the total work-done against the change in kinetic energy. Because of the accessibility of the setup, the current work is seen as suitable for a home-based activity, during these times of the pandemic in particular in which online learning has remained to be the format in some countries. With the guidance of a teacher, online or face-to-face, students in their junior or senior high school—as well as for those who are enrolled in basic physics in college—will be able to benefit from this work.

scholarly journals Feedback of outflows in the Taurus Molecular Cloud

2012 ◽  
Vol 8 (S292) ◽  
pp. 47-47
Author(s):  
Huixian Li ◽  
Di Li ◽  
Rendong Nan
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Molecular Cloud ◽  
Feedback Effect ◽  
Total Kinetic Energy ◽  
Gravitational Potential Energy ◽  
Taurus Molecular Cloud

AbstractWe collected 27 outflows from the literature and found 8 new ones in the FCRAO CO maps of the Taurus molecular cloud. The total kinetic energy of the 35 outflows is found to be about 3% of the gravitational potential energy from the whole cloud. The feedback effect due to the outflows is minor in Taurus.

A Friction-Bearing Calorimeter Experiment Yielding Joule's Constant

1996 ◽  
Vol 24 (4) ◽  
pp. 235-242 ◽  
Author(s):  
R. S. Mullisen
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Laboratory Experiment ◽  
Heat Loss ◽  
Gravitational Potential ◽  
Data Reduction ◽  
Gravitational Potential Energy ◽  
Experimental Procedure ◽  
Friction Bearing ◽  
Elastic Potential Energy

A simple, friction-bearing calorimeter that yields Joule's constant is described in this paper. The apparatus is easily constructed at minimal expense and may be used as a laboratory experiment. Although the design is very simple, the experimental procedure and data reduction analysis account for gravitational potential energy, elastic potential energy, translational and rotational kinetic energy, and heat loss. The result is a Joule's constant value accurate within 3%.

scholarly journals Energy Conversion, Mixing Energy, and Neutral Surfaces with a Nonlinear Equation of State

2011 ◽  
Vol 41 (1) ◽  
pp. 28-41 ◽  
Author(s):  
Jonas Nycander
Keyword(s):  
Equation Of State ◽  
Nonlinear Equation ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Stationary Flow ◽  
Gravitational Potential Energy ◽  
Surrounding Water ◽  
Mixing Energy ◽  
Nonlinear Character ◽  
Water Parcel

Abstract A local neutral plane is defined so that a water parcel that is displaced adiabatically a small distance along the plane continues to have the same density as the surrounding water. Since such a displacement does not change the density field or the gravitational potential energy, it is generally assumed that it does not produce a restoring buoyancy force. However, it is here shown that because of the nonlinear character of the equation of state (in particular the thermobaric effect) such a neutral displacement is accompanied by a conversion between internal energy E and gravitational potential energy U, and an equal conversion between U and kinetic energy K. While there is thus no net change of U, K does change. This implies that a force is in fact required for the displacement. It is further shown that displacements that are orthogonal to a vector P do not induce conversion between U and K, and therefore do not require a force. Analogously to neutral surfaces, which are defined to be approximately orthogonal to the dianeutral vector N, one may define “P surfaces” to be approximately orthogonal to P. These P surfaces are intermediate between neutral surfaces and surfaces of constant σ0 (potential density reference to the surface). If the equation of state is linear, there exists a well-known expression for the mixing energy in terms of the diapycnal flow. This expression is here generalized for a general nonlinear equation of state. The generalized expression involves the velocity component along P. Since P is not orthogonal to neutral surfaces, this means that stationary flow along neutral surfaces in general requires mixing energy.

scholarly journals Thermodynamics/Dynamics Coupling in Weakly Compressible Turbulent Stratified Fluids

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Rémi Tailleux
Keyword(s):  
Equation Of State ◽  
Nonlinear Equation ◽  
Potential Energy ◽  
Mechanical Energy ◽  
Fluid Flows ◽  
Boussinesq Approximation ◽  
Gravitational Potential Energy ◽  
Transient Flows ◽  
Diffusive Effects ◽  
Boussinesq Fluid

In traditional and geophysical fluid dynamics, it is common to describe stratified turbulent fluid flows with low Mach number and small relative density variations by means of the incompressible Boussinesq approximation. Although such an approximation is often interpreted as decoupling the thermodynamics from the dynamics, this paper reviews recent results and derive new ones that show that the reality is actually more subtle and complex when diabatic effects and a nonlinear equation of state are retained. Such an analysis reveals indeed: (1) that the compressible work of expansion/contraction remains of comparable importance as the mechanical energy conversions in contrast to what is usually assumed; (2) in a Boussinesq fluid, compressible effects occur in the guise of changes in gravitational potential energy due to density changes. This makes it possible to construct a fully consistent description of the thermodynamics of incompressible fluids for an arbitrary nonlinear equation of state; (3) rigorous methods based on using the available potential energy and potential enthalpy budgets can be used to quantify the work of expansion/contraction in steady and transient flows, which reveals that is predominantly controlled by molecular diffusive effects, and act as a significant sink of kinetic energy.

A Design Scheme of the Automatic Obstacle-Avoidance Car

2013 ◽  
Vol 779-780 ◽  
pp. 1094-1097
Author(s):  
Guo Chang Qiao ◽  
Deng Bin Qiao
Keyword(s):  
Energy Consumption ◽  
Potential Energy ◽  
Obstacle Avoidance ◽  
Gravitational Potential ◽  
Simple Structure ◽  
Mechanical Energy ◽  
Constant Speed ◽  
Gravitational Potential Energy ◽  
Design Scheme ◽  
Implementation Method

This design is an implementation method based on the "automatic obstacle avoidance car", which gravitational potential energy can be converted into mechanical energy and driving as the motivation .This car can automatically avoid obstacles on the track settings in advance. The greatest feature of the car is during its operation, accelerating first then maintaining a constant speed, so that less energy consumption are required. Besides that, the walking track is closing to the sinusoidal curve. The convenient manufacture has a simple structure as well as high transmit efficiency.

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.

scholarly journals The Mechanical Energy Input to the Ocean Induced by Tropical Cyclones

2008 ◽  
Vol 38 (6) ◽  
pp. 1253-1266 ◽  
Author(s):  
Ling Ling Liu ◽  
Wei Wang ◽  
Rui Xin Huang
Keyword(s):  
Potential Energy ◽  
Tropical Cyclones ◽  
Wind Stress ◽  
Gravitational Potential ◽  
General Circulation ◽  
Energy Input ◽  
Mechanical Energy ◽  
Gravitational Potential Energy ◽  
Diapycnal Mixing ◽  
The Past

Abstract Wind stress and tidal dissipation are the most important sources of mechanical energy for maintaining the oceanic general circulation. The contribution of mechanical energy due to tropical cyclones can be a vitally important factor in regulating the oceanic general circulation and its variability. However, previous estimates of wind stress energy input were based on low-resolution wind stress data in which strong nonlinear events, such as tropical cyclones, were smoothed out. Using a hurricane–ocean coupled model constructed from an axisymmetric hurricane model and a three-layer ocean model, the rate of energy input to the world’s oceans induced by tropical cyclones over the period from 1984 to 2003 was estimated. The energy input is estimated as follows: 1.62 TW to the surface waves and 0.10 TW to the surface currents (including 0.03 TW to the near-inertial motions). The rate of gravitational potential energy increase due to tropical cyclones is 0.05 TW. Both the energy input from tropical cyclones and the increase of gravitational potential energy of the ocean show strong interannual and decadal variability with an increasing rate of 16% over the past 20 years. The annual mean diapycnal upwelling induced by tropical cyclones over the past 20 years is estimated as 39 Sv (Sv ≡ 106 m3 s−1). Owing to tropical cyclones, diapycnal mixing in the upper ocean (below the mixed layer) is greatly enhanced. Within the regimes of strong activity of tropical cyclones, the increase of diapycnal diffusivity is on the order of (1 − 6) × 10−4 m2 s−1. The tropical cyclone–related energy input and diapycnal mixing may play an important role in climate variability, ecology, fishery, and environments.

Sign in / Sign up

Export Citation Format

Share Document