Showing papers on "Dissipation published in 1996"
TL;DR: In this article, the authors proposed a scaling for the rate of dissipation based on wind and wave parameters, and concluded that the dissipation rate under breaking waves depends on depth, to varying degrees, in three stages.
Abstract: The dissipation of kinetic energy at the surface of natural water bodies has important consequences for many Physical and biochemical processes including wave dynamics, gas transfer, mixing of nutrients and pollutants, and photosynthetic efficiency of plankton. Measurements of dissipation close to the surface obtained in a large lake under conditions of strong wind forcing are presented that show a layer of enhanced dissipation exceeding wall layer values by one or two orders of magnitude. The authors propose a scaling for the rate of dissipation based on wind and wave parameters, and conclude that the dissipation rate under breaking waves depends on depth, to varying degrees, in three stages. Very near the surface, within one significant height, the dissipation rate is high (an order of magnitude greater than that predicted by wall layer theory) and roughly constant. Below this is an intermediate region where the dissipation decays as z−2. The thickness of this layer (relative to the significant...
603 citations
TL;DR: In this article, a new third-generation ocean wind wave model is presented, which is based on previously developed input and nonlinear interaction source terms and a new dissipation source term.
Abstract: A new third-generation ocean wind wave model is presented. This model is based on previously developed input and nonlinear interaction source terms and a new dissipation source term. It is argued that the dissipation source term has to be modeled using two explicit constituents. A low-frequency dissipation term analogous to wave energy loss due to oceanic turbulence is therefore augmented with a diagnostic high-frequency dissipation term. The dissipation is tuned for the model to represent idealized fetch-limited growth behavior. The new model results in excellent growth behavior from extremely short fetches up to full development. For intermediate to long fetches results are similar to those of WAM, but for extremely short fetches the present model presents a significant improvement (although the poor behavior of WAM appears to be related to correctable numerical constraints). The new model furthermore gives smoother results and appears less sensitive to numerical errors. Finally, limitations of...
516 citations
TL;DR: In this article, the authors investigate how an initially homogeneous magnetic field responds to random large-scale shearing motions on two boundaries, by numerically solving the dissipative MHD equations, with resolutions ranging from 24 3 to 136 3.
Abstract: To contribute to the understanding of heating and dynamic activity in boundary-driven, low-beta plasmas such as the solar corona, we investigate how an initially homogeneous magnetic field responds to random large-scale shearing motions on two boundaries, by numerically solving the dissipative MHD equations, with resolutions ranging from 24 3 to 136 3 . We find that even a single application of large-scale shear, in the form of orthogonal sinusoidal shear on two boundaries, leads to the formation of tangential discontinuities (current sheets). The formation time scales logarithmically with the resistivity and is of the order of a few times the inverse shearing rate for any reasonable resistivity, even though no mathematical discontinuity would form in a finite time in the limit of vanishing resistivity. The reason for the formation of the current sheets is the interlocking of two magnetic flux systems. Reconnection in the current sheets is necessary for the field lines to straighten out. The formation of current sheets causes a transition to a very dynamic plasma state, where reconnection drives supersonic and super-Alfvenic jet flows and where these, in turn, cause the formation of smaller-scale current sheets. A statistically steady state level for the average Poynting flux and the average Joule dissipation is reached after a few correlation times, but both boundary work and Joule dissipation are highly fluctuating in time and space and are only weakly correlated. Strong and bursty Joule dissipation events are favored when the volume has a large length/diameter ratio and is systematically driven for periods longer than the Alfven crossing time. The understanding of the reason for the current sheet formation allows a simple scaling law to be constructed for the average boundary work. Numerical experiments over a range of parameter values, covering over 3 orders of magnitude in average dissipation, obey the scaling law to within a factor of 2. The heating rate depends on the boundary velocity amplitude and correlation time, the Alfven speed, and the initial magnetic field strength but appears to be independent of the resistivity because of the formation of a hierarchy of current sheets. Estimates of the photospheric boundary work on the solar coronal magnetic field using the scaling law are consistent with estimates of the required coronal heating rates. We therefore conclude that the work supplied to the solar corona as a consequence of the motion of the magnetic foot points in the solar photosphere and the emergence of new flux is a significant contributor to coronal heating and flaring and that it quite plausibly is the dominant one.
385 citations
TL;DR: In this paper, an analysis of the evolution of turbulence characteristics in wind-turbine wakes has been carried out based on experimental results and on numerical results obtained with a CFD code, complemented with some theoretical considerations.
262 citations
TL;DR: In this paper, the authors studied the perturbation of a Lie-Poisson (or equivalently an Euler-Poincare) system by a special dissipation term that has Brockett's double bracket form and showed that a formally unstable equilibrium of the unperturbed system becomes a spectrally and hence nonlinearly unstable equilibrium after the dissipation is added.
Abstract: This paper studies the perturbation of a Lie-Poisson (or, equivalently an Euler-Poincare) system by a special dissipation term that has Brockett's double bracket form. We show that a formally unstable equilibrium of the unperturbed system becomes a spectrally and hence nonlinearly unstable equilibrium after the perturbation is added. We also investigate the geometry of this dissipation mechanism and its relation to Rayleigh dissipation functions. This work complements our earlier work (Bloch, Krishnaprasad, Marsden and Ratiu [1991, 1994]) in which we studied the corresponding problem for systems with symmetry with the dissipation added to the internal variables; here it is added directly to the group or Lie algebra variables. The mechanisms discussed here include a number of interesting examples of physical interest such as the Landau-Lifschitz equations for ferromagnetism, certain models for dissipative rigid body dynamics and geophysical fluids, and certain relative equilibria in plasma physics and stellar dynamics.
248 citations
TL;DR: In this paper, an experimental investigation of the inhomogeneous, three-dimensional flow around a surface mounted cube in a channel is presented, where LDA measurements of single point velocity correlations are used to determine the production, convection and transport of the turbulence kinetic energy, k, in the obstacle wake.
Abstract: Results of an experimental investigation of the inhomogeneous, three‐dimensional flow around a surface mounted cube in a channel are presented. LDA measurements of single‐point velocity correlations are used to determine the production, convection and transport of the turbulence kinetic energy, k, in the obstacle wake. The turbulence dissipation rate is obtained as a closing term to the balance of the k‐transport equation. The results provide some insight to the evolution of the turbulence dissipation rate from the near field recirculation zone to the asymptotic wake. Also presented is a comparison between measured and modeled transport terms.
237 citations
TL;DR: In this article, a predictor-corrector explicit time integration algorithm is presented for solving structural dynamics problems, which is based on the implicit generalized-α method developed by the authors.
233 citations
TL;DR: In this paper, the authors reported new measurements of turbulent kinetic energy dissipation made in the North Atlantic Ocean from a SWATH ship during the recent Surface Waves Dynamics Experiments (SWADE).
Abstract: Recent experiments measuring turbulence dissipation rates in the upper ocean can be divided into two types: those supporting an analogy between the upper ocean and lower atmosphere, with dissipation rates following wall layer behavior, and those finding oceanic dissipation rates to be much higher than wall layer predictions. In an attempt to reconcile these two diverse acts of observations, Terray et al. proposed a wave-dependent scaling of the dissipation rate based on the significant wave height and the rate of energy input from the wind to the waves. Their parameterization was derived from observations of strongly forced, fetch-limited waves, although they conjectured that it would apply in typical oceanic conditions as well. This paper reports new measurements of turbulent kinetic energy dissipation made in the North Atlantic Ocean from a SWATH ship during the recent Surface Waves Dynamics Experiments (SWADE).These data support the scaling of Terray et al., verifying its validity when applied...
193 citations
TL;DR: In this article, numerical simulations of a two-dimensional section of a coronal loop subject to random magnetic forcing are presented, and the results show the highly intermittent spatial distribution of current concentrations generated by the coupling between internal dynamics and external forcing.
Abstract: Numerical simulations of a two-dimensional section of a coronal loop subject to random magnetic forcing are presented. The forcing models the link between photospheric motions and energy injection in the corona. The results show the highly intermittent spatial distribution of current concentrations generated by the coupling between internal dynamics and external forcing. The total power dissipation is a rapidly varying function of time, with sizable jumps even at low Reynolds numbers, and is caused by the superposition of magnetic dissipation in a number of localized current sheets. Both spatial and temporal intermittency increase with the Reynolds number, suggesting that the turbulent nature of the corona can physically motivate statistical theories of solar activity.
183 citations
TL;DR: In this article, the role of wave breaking and the energy transfer among spectral components due to triad interactions is considered, and the spectral dissipation due to wave breaking is formulated in a spectral form, both for energy-density models and complex-amplitude models.
Abstract: The nonlinear transformation of wave spectra in shallow water is considered, in particular, the role of wave breaking and the energy transfer among spectral components due to triad interactions Energy dissipation due to wave breaking is formulated in a spectral form, both for energy-density models and complex-amplitude models The spectral breaking function distributes the total rate of random-wave energy dissipation in proportion to the local spectral level, based on experimental results obtained for single-peaked spectra that breaking does not appear to alter the spectral shape significantly The spectral breaking term is incorporated in a set of coupled evolution equations for complex Fourier amplitudes, based on ideal-fluid Boussinesq equations for wave motion The model is used to predict the surface elevations from given complex Fourier amplitudes obtained from measured time records in laboratory experiments at the upwave boundary The model is also used, together with the assumption of random, independent initial phases, to calculate the evolution of the energy spectrum of random waves The results show encouraging agreement with observed surface elevations as well as spectra
182 citations
10 Jun 1996
TL;DR: In this paper, a theory is presented for calculating the fluctuations in a laminar boundary layer when the free stream is turbulent and the kinetic energy equation for these fluctuations is derived and a new mechanism for their production.
Abstract: A theory is presented for calculating the fluctuations in a laminar boundary layer when the free stream is turbulent. The kinetic energy equation for these fluctuations is derived and a new mechanism is revealed for their production. A methodology is presented for solving the equation using standard boundary layer computer codes. Solutions of the equation show that the fluctuations grow at first almost linearly with distance and then more slowly as viscous dissipation becomes important. Comparisons of calculated growth rates and kinetic energy profiles with data show good agreement.In addition, a hypothesis is advanced for the effective forcing frequency and free-stream turbulence level which produce these fluctuations. Finally, a method to calculate the onset of transition is examined and the results compared to data.Copyright © 1996 by ASME
TL;DR: In this article, an inviscid estimate for the viscous dissipation rate of turbulent kinetic energy and a mixing length estimation for the turbulent heat flux were derived from measurements of the energy-containing scales of turbulence in the ocean thermocline.
Abstract: From measurements of the energy-containing scales of turbulence in the ocean thermocline, two new formulations are examined: (1) an inviscid estimate for the viscous dissipation rate of turbulent kinetic energy and (2) a mixing length estimate for the turbulent heat flux. These formulations are tested using coincident measurements of the relevant properties of both energy-containing and dissipation scales of stratified turbulence in the ocean's main thermocline obtained from a vertical microstructure profiler. It is found that energy-containing scale estimates of both dissipation rate and heat flux compare favorably with dissipation scale estimates. Since the energy-containing scales are many times greater than the dissipation scales, the measurement constraints on these new estimates are considerably less strict than for dissipation scale estimates of the same quantities. These observations also suggest that the timescale for viscous decay of turbulent motions is greater than that for diffusive smoothing of scalar fluctuations. It is argued that this is consistent with current estimates of mixing efficiencies.
TL;DR: In this article, a simple vortex model, involving a dense packing of discus-shaped structures connected by vortex lines that alternate between horizontal and vertical orientation, is shown to be consistent with both the observed velocity and vorticity fields, and the evolution of measured length scales in orthogonal planes.
TL;DR: In this paper, Luo et al. investigated the instability of the steady solution and details of the resulting oscillations when it is unstable, by studying the time-dependent problem and developed a simulation of the coupled flow membrane problem, using the Spine method to treat the moving boundary and a secondorder time integration scheme with variable time increments.
Abstract: The collapse of a compressed elastic tube conveying a flow occurs in several physiological applications and has become a problem of considerable interest. Laboratory experiments on a finite length of collapsible tube reveal a rich variety of self-excited oscillations, indicating that the system is a complex, nonlinear dynamical system. Following our previous study on steady flow in a two-dimensional model of the collapsible tube problem (Luo & Pedley 1995), we here investigate the instability of the steady solution, and details of the resulting oscillations when it is unstable, by studying the time-dependent problem. For this purpose, we have developed a time-dependent simulation of the coupled flow – membrane problem, using the Spine method to treat the moving boundary and a second-order time integration scheme with variable time increments.It is found that the steady solutions become unstable as tension falls below a certain value, say Tu, which decreases as the Reynolds number increases. As a consequence, steady flow gives way to self-excited oscillations, which become increasingly complicated as tension is decreased from Tu. A sequence of bifurcations going through regular oscillations to irregular oscillations is found, showing some interesting dynamic features similar to those observed in experiments. In addition, vorticity waves are found downstream of the elastic section, with associated recirculating eddies which sometimes split into two. These are similar to the vorticity waves found previously for flow past prescribed, time-dependent indentations. It is speculated that the mechanism of the oscillation is crucially dependent on the details of energy dissipation and flow separation at the indentation.As tension is reduced even further, the membrane is sucked underneath the downstream rigid wall and, although this causes the numerical scheme to break down, it in fact agrees with another experimental observation for flow in thin tubes.
TL;DR: In this article, the velocity field, subgrid-scale (SGS) stresses and SGS dissipation are calculated using the velocity fields obtained from the DNS of plane channel flow.
Abstract: Conditional averages of the velocity field, subgrid‐scale (SGS) stresses and SGS dissipation are calculated using the velocity fields obtained from the DNS of plane channel flow. The detection criteria isolate the coherent turbulent structures that contribute most strongly to the energy transfer between the large, resolved scales and the subgrid, unresolved, ones. Separate averages are computed for forward and backward scatter. The interscale energy transfer is found to be strongly correlated with the presence of the turbulent structures typical of wall‐bounded flows: quasi‐streamwise and hairpin vortices, sweeps and ejections. In the buffer layer, strong SGS dissipation is observed near lifted shear layers; the forward scatter is associated with ejections, the backscatter with sweeps. Both backward and forward scatter occur in close proximity to longitudinal vortices that form a very shallow angle to the wall. Further away from the solid boundary, in the logarithmic region and beyond, both forward and backward energy transfer are associated prevalently with ejections. Eddy viscosity models do not predict the three‐dimensional structure of these events adequately, while scale‐similar models reproduce the correlation between the large‐scale coherent structures and the SGS events more accurately.
TL;DR: It is shown that anharmonic coupling of phonons in the adsorbed monolayer can account for the rate of energy dissipation seen in these experiments.
Abstract: Molecular-dynamics simulations and analytical calculations are used to investigate the mechanism of energy dissipation in monolayer films sliding across a substrate. An explanation is given for the viscous friction found experimentally in both fluid and incommensurate solid adsorbates, and for the observation that solids slide more easily than fluids. We show that anharmonic coupling of phonons in the adsorbed monolayer can account for the rate of energy dissipation seen in these experiments. @S0163-1829~96!04935-1#
TL;DR: In this article, the authors used a compressible Hall MHD code with a constant magnetic field and a polytropic equation of state Artificial dissipation in the form of a bi-Laplacian operator is used to suppress numerical instabilities, allowing a clear separation of the dissipative scales from the ion cyclotron scales.
Abstract: Solar wind frequency spectra show a distinct steepening of the ƒ−5/3 power law inertial range spectrum at frequencies above the Doppler-shifted ion cyclotron frequency This is commonly attributed to dissipation due to wave-particle interactions We consider the extent to which this steepening can be described, using a magnetohydrodynamic formulation that includes the Hall term An important characteristic of Hall MHD is that although the ion cyclotron resonance is included, there is no wave-particle dissipation of energy In this study we use a compressible Hall MHD code with a constant magnetic field and a polytropic equation of state Artificial dissipation in the form of a bi-Laplacian operator is used to suppress numerical instabilities, allowing for a clear separation of the dissipative scales from the ion cyclotron scales A distinct steepening appears in the simulation power spectra near the cyclotron resonance for certain types of initial conditions This steepening is associated with the appearance of right circularly polarized fluctuations at frequencies above the ion cyclotron resonance Similar steepenings and polarization enhancements are observed in solar wind magnetic field data
TL;DR: In this paper, the authors derived hydrodynamic equations for systems not in local thermodynamic equilibrium, that is, where the local stationary measures are non-Gibbsian and do not satisfy detailed balance with respect to the microscopic dynamics.
Abstract: We derive hydrodynamic equations for systems not in local thermodynamic equilibrium, that is, where the local stationary measures are “non-Gibbsian” and do not satisfy detailed balance with respect to the microscopic dynamics. As a main example we consider thedriven diffusive systems (DDS), such as electrical conductors in an applied field with diffusion of charge carriers. In such systems, the hydrodynamic description is provided by a nonlinear drift-diffusion equation, which we derive by a microscopic method ofnonequilibrium distributions. The formal derivation yields a Green-Kubo formula for the bulk diffusion matrix and microscopic prescriptions for the drift velocity and “nonequilibrium entropy” as functions of charge density. Properties of the hydrodynamic equations are established, including an “H-theorem” on increase of the thermodynamic potential, or “entropy”, describing approach to the homogeneous steady state. The results are shown to be consistent with the derivation of the linearized hydrodynamics for DDS by the Kadanoff-Martin correlation-function method and with rigorous results for particular models. We discuss also the internal noise in such systems, which we show to be governed by a generalizedfluctuation-dissipation relation (FDR), whose validity is not restricted to thermal equilibrium or to time-reversible systems. In the case of DDS, the FDR yields a version of a relation proposed some time ago by Price between the covariance matrix of electrical current noise and the bulk diffusion matrix of charge density. Our derivation of the hydrodynamic laws is in a form—the so-called “Onsager force-flux form” which allows us to exploit the FDR to construct the Langevin description of the fluctuations. In particular, we show that the probability of large fluctuations in the hydrodynamic histories is governed by a version of the Onsager “principle of least dissipation,” which estimates the probability of fluctuations in terms of the Ohmic dissipation required to produce them and provides a variational characterization of the most probable behavior as that associated to least (excess) dissipation. Finally, we consider the relation of longrange spatial correlations in the steady state of the DDS and the validity of ordinary hydrodynamic laws. We also discuss briefly the application of the general methods of this paper to other cases, such as reaction-diffusion systems or magnetohydrodynamics of plasmas.
TL;DR: In this article, the authors presented qualitative investigations on the energy behavior of structures into which hysteretic dampers are incorporated, where the second stiffness relative to the initial stiffness is α, and they found that with the increase of α the total input energy tends to increase but the increase is confined to a narrow range of natural periods.
Abstract: This paper presents qualitative investigations on the energy behaviour of structures into which hysteretic dampers are incorporated. Emphasis was given to the ratio of the structural stiffness after the yielding of hysteretic dampers to the initial elastic stiffness, with a premise that this ratio, termed α in this study, tends to be large for structures with hysteretic dampers. Structures concerned were represented by discrete spring-mass systems having bilinear restoring force behaviour, in which the second stiffness relative to the initial stiffness is α. It was found that with the increase of α the total input energy tends to increase, but the increase is confined to a narrow range of natural periods. Both the total input energy and hysteretic energy were found to become less sensitive to the yield strength with the increase of α. A simple formula was also proposed to estimate the maximum deformation given the knowledge of the hysteretic energy. Analysis of MDOF systems revealed that, even when α is large, the total input energy and hysteretic energy for MDOF systems are approximately the same as those of the equivalent SDOF system, and the hysteretic energy can be distributed uniformly over the stories if α is large.
TL;DR: In this paper, the role of plastic-frictional energy dissipation in the fracture process zone plays in the work-of-fracture method for measuring the fracture energy of concrete or other quasibrittle materials is analyzed.
Abstract: The role that plastic-frictional energy dissipation in the fracture process zone plays in the work of-fracture method for measuring the fracture energy of concrete or other quasibrittle materials is analyzed, and a possible improvement of this method is proposed. It is shown that by measuring the unloading compliance at a sufficient number of states on the post-peak descending load-deflection curve, it is possible to calculate the pure fracture energy, representing the energy dissipated by the fracture process alone. However, this value of fracture energy is pertinent only if the material model (constitutive law and fracture law) used in structural analysis takes into account separately the fracture-damage deformations and the plastic-frictional deformations. Otherwise, one must use the conventional fracture energy, which includes plastic-frictional energy dissipation. Either type of fracture energy should properly be determined by extrapolation to infinite specimen size. Further, it is shown that the unloading compliancies to be used in the calculation of the pure fracture energy can be corrected to approximately eliminate the time-dependent effects (material viscoelasticity) and reverse plasticity. Finally, it is proposed to improve the work-of-fracture method by averaging the work done by fracture over only a central portion of the ligament. However, experiments are needed to check whether the specimen size required for this improved method would not be impracticably large.
Journal Article•
TL;DR: In this article, the authors investigated the characteristics of the turbulence energy dissipation and the overall energy distribution in the impeller region of a stirred tank using laser Doppler anemometry (LDA).
Abstract: Turbulence energy dissipation is important in the study of turbulent mixing phenomena in stirred tanks. This paper investigates the characteristics of the turbulence energy dissipation and the overall energy distribution in the impeller region of a stirred tank. One radial flow impeller (Rushton turbine (RT)) and two axial flow impellers (the pitched blade turbine (PBT) and a fluidfoil turbine (A310)) were used. The mean and root-mean-square velocity (RMS) profiles close to the three impellers were measured in a cylindrical baffled tank using laser Doppler anemometry (LDA). The average turbulence energy dissipation, e i was calculated using a macroscopic energy balance equation over several control volumes. The local turbulence energy dissipation e was estimated using e=Av 3 /L with A=1 and L=D/10. Integration of the local dissipation over a control volume consistently gave results within 6% of the macroscopic energy balance. The bulk of the energy is dissipated in the small volume occupied by the impeller and the impeller discharge stream for all three impellers: in order of increasing percentages 38.1% (A310), 43.5% (RT) and 70.5% (PBT). The dominant characteristics of energy distribution are different for each impeller. The A310 was most efficient at generating convective flow. The RT generated the most turbulence, and the PBT derived a much larger portion of its energy from the return flow.
TL;DR: In this paper, the uniqueness of solution of a natural initial, mixed boundary value problem is proved in the context of the linear theory of thermoelasticity without energy dissipation for homogeneous and isotropic materials.
Abstract: In the context of the linear theory of thermoelasticity without energy dissipation for homogeneous and isotropic materials, the uniqueness of solution of a natural initial, mixed boundary value problem is proved. The proof depends on an equation of energy balance formulated entirely in terms of temperature and velocity fields.
TL;DR: In this paper, the linear theory of thermoelasticity without energy dissipation for homogeneous and isotropic materials is employed to study one-dimensional waves in a half-space.
Abstract: The linear theory of thermoelasticity without energy dissipation for homogeneous and isotropic materials is employed to study one-dimensional waves in a half-space The waves are supposed to be due to sudden inputs of temperature and stress/strain on the boundary The Laplace transform method is employed to solve the problem Exact solutions, in closed form, for the displacement, temperature, strain, and stress fields are obtained The characteristic features of the underlying theory are analyzed in light of these solutions and their counterparts in earlier works
TL;DR: In this paper, a simple numerical scheme based on analytical solutions to the dissipative MHD equations in the quasi-singular resonance layer was proposed to compute global discrete eigenmodes with characteristic frequencies lying within the range of the continuous spectrum.
Abstract: Quasi-modes, which are important for understanding the MHD wave behavior of solar and astro-physical magnetic plasmas, are computed as eigenmodes of the linear dissipative MHD equations. This eigenmode computation is carried out with a simple numerical scheme, which is based on analytical solutions to the dissipative MHD equations in the quasi-singular resonance layer. Nonuniformity in magnetic field and plasma density gives rise to a continuous spectrum of resonant frequencies. Global discrete eigenmodes with characteristic frequencies lying within the range of the continuous spectrum may couple to localized resonant Alfven waves. In ideal MHD, these modes are not eigenmodes of the Hermitian ideal MHD operator, but are found as a temporal dominant, global, exponentially decaying response to an initial perturbation. In dissipative MHD, they are really eigenmodes with damping becoming independent of the dissipation mechanism in the limit of vanishing dissipation. An analytical solution of these global modes is found in the dissipative layer around the resonant Alfvenic position. Using the analytical solution to cross the quasi-singular resonance layer, the required numerical effort of the eigenvalue scheme is limited to the integration of the ideal MHD equations in regions away from any singularity. The presented scheme allows for a straightforward parametric study. The method is checked with known ideal quasi-mode frequencies found for a one-dimensional box model for the Earthis magnetosphere (Zhu & Kivelson). The agreement is excellent. The dependence of the oscillation frequency on the wavenumbers for a one-dimensional slab model for coronal loops found by Ofman, Davila, & Steinolfson is also easily recovered.
TL;DR: In this paper, an initial boundary value problem in terms of stress and entropy-flux is formulated and the uniqueness of its solution established in the context of the linear theory of thermoelasticity without energy dissipation.
Abstract: In the context of the linear theory of thermoelasticity without energy dissipation for homogeneous and isotropic materials, an initial boundary value problem in terms of stress and entropy-flux is formulated and the uniqueness of its solution established.
TL;DR: It is demonstrated that a system of two linearly coupled GL equations with gain and dissipation in one subsystem and pure Dissipation in another produces absolutely stable solitons and their bound states.
Abstract: As is known, a solitary pulse in the complex cubic Ginzburg-Landau (GL) equation is unstable. We demonstrate that a system of two linearly coupled GL equations with gain and dissipation in one subsystem and pure dissipation in another produces absolutely stable solitons and their bound states. The problem is solved in a fully analytical form by means of the perturbation theory. The soliton coexists with a stable trivial state; there is also an unstable soliton with a smaller amplitude, which is a separatrix between the two stable states. This model has a direct application in nonlinear fiber optics, describing an erbium-doped laser based on a dual-core fiber.
TL;DR: In this article, a variational principle that includes kinetics is proposed to minimize the free energy rate and a dissipation potential involving the domain wall mobility. But the approach is limited to the case of one or two degrees of freedom.
TL;DR: In this article, a model based on energy conversion and dissipation has been proposed to characterize the damping behavior of the piezo-materials, and an equivalent electrical circuit model is put forward to determine the required load resistance, and a mechanical spring-dashpot model is used to describe the dampness capacity of the PAs.
TL;DR: In this paper, the authors presented the general proof for a new design principle, the principle of equipartition of forces, for coupled transports of heat, mass, and charge using irreversible thermodynamics combined with Cauchy−Lagrange optimization procedures.
Abstract: This paper presents the general proof for a new design principle: the principle of equipartition of forces. The principle has been derived for coupled transports of heat, mass, and charge using irreversible thermodynamics combined with Cauchy−Lagrange optimization procedures. The principle says that the best trade-off between energy dissipation and transfer area is achieved when the thermodynamic driving forces are uniformly distributed over the transfer area. A new strategy for the design of energy optimal transfer processes follows. Practical problems in applications of the principle are discussed.
TL;DR: In this article, a wave energy transformation model, which includes wave breaking within the surf zone described by surface rollers, is developed for randomly varying waves over arbitrary bathymetry.