Showing papers on "Dissipation published in 2018"
TL;DR: In this article, the authors provide a critical summary of recent work on turbulent flows from a unified point of view and present a classification of all known transfer mechanisms, including direct and inverse energy cascades.
315 citations
TL;DR: It is found that the bulk viscosity takes values close to its resonant maximum in a typical merger, motivating a more careful assessment of the role of bulk viscous dissipation in the gravitational-wave signal from merging neutron stars.
Abstract: Inferring the properties of dense matter is one of the most exciting prospects from the measurement of gravitational waves from neutron star mergers. However, it requires reliable numerical simulations that incorporate viscous dissipation and energy transport as these can play a significant role in the survival time of the post-merger object. We calculate time scales for typical forms of dissipation and find that thermal transport and shear viscosity will not be important unless neutrino trapping occurs, which requires temperatures above 10 MeV and gradients over length scales of 0.1 km or less. On the other hand, if direct-Urca processes remain suppressed, leaving modified-Urca processes to establish flavor equilibrium, then bulk viscous dissipation could provide significant damping to density oscillations right after merger. When comparing with data from state-of-the-art merger simulations, we find that the bulk viscosity takes values close to its resonant maximum in a typical merger, motivating a more careful assessment of the role of bulk viscous dissipation in the gravitational-wave signal from merging neutron stars.
146 citations
TL;DR: In this paper, the authors considered flow characteristics of Williamson fluid between two rotating disks and calculated the total entropy generation rate through the implementation of second law of thermodynamics, where the lower and upper disks have different stretching rates and angular velocities.
135 citations
TL;DR: In this paper, Tangent hyperbolic nanomaterial model is used to describe the important slip mechanism, namely Brownian and thermophoresis diffusions, and an optimization of entropy generation is performed through thermodynamics second law.
132 citations
TL;DR: In this article, the energy dissipation generated by tangential damping of the bolted joints under different bolt preloads was modeled analytically based on fractal contact theory, which took the imperfect interface into account.
Abstract: Monitoring of bolt looseness is essential for ensuring the safety and reliability of equipment and structures with bolted connections. It is well known that tangential damping has an important influence on energy dissipation during wave propagation across the bolted joints, which require different levels of preload. In this paper, the energy dissipation generated by tangential damping of the bolted joints under different bolt preloads was modeled analytically based on fractal contact theory, which took the imperfect interface into account. A saturation value exists with the increase of the bolt preload, and the center frequency of emitted signal is demonstrated to affect the received energy significantly. Compared with previous similar studies based on experimental techniques and numerical method, the investigation presented in this paper explains the phenomenon from the inherent mechanism, and achieves the accurate quantitative monitoring of bolt looseness directly, rather than an indirect failure index. Finally, the validity of the proposed method in this paper was demonstrated with an experimental study of a bolted joint with different preload levels.
130 citations
TL;DR: In this paper, the pull-in characteristics of a microplate-based microelectromechanical system (MEMS) are investigated via a multi-degree freedom energy-based technique where the in-plane and out-of-plane motions are retained in the modelling and simulations.
120 citations
TL;DR: In this paper, an energy absorption lattice, comprised of multiple tetra-beam-plate unit cells with negative stiffness, was designed, fabricated by selective laser sintering method, and analyzed both numerically and experimentally.
117 citations
TL;DR: In this article, the authors quantify the irreversibility of a noninteracting active particle in two dimensions by treating both conjugated and time-reversed dynamics, and identify a hidden rate of entropy production required to maintain persistence and prevent the rapidly relaxing momenta from thermalizing, even in the limit of very large friction.
Abstract: Collections of self-propelled particles that move persistently by continuously consuming free energy are a paradigmatic example of active matter. In these systems, unlike Brownian "hot colloids," the breakdown of detailed balance yields a continuous production of entropy at steady state, even for an ideal active gas. We quantify the irreversibility for a noninteracting active particle in two dimensions by treating both conjugated and time-reversed dynamics. By starting with underdamped dynamics, we identify a hidden rate of entropy production required to maintain persistence and prevent the rapidly relaxing momenta from thermalizing, even in the limit of very large friction. Additionally, comparing two popular models of self-propulsion with identical dissipation on average, we find that the fluctuations and large deviations in work done are markedly different, providing thermodynamic insight into the varying extents to which macroscopically similar active matter systems may depart from equilibrium.
116 citations
TL;DR: In this article, flux differencing, quadrature-based projections, and SBP-like operators are used to construct discretely entropy conservative schemes for DG methods under more arbitrary choices of volume and surface quadratures rules.
106 citations
TL;DR: In this article, the authors investigated the transport equations for velocity variances using data from DNS of incompressible channel flows at up to 5200, and showed that the energy is transferred from the streamwise elongated modes to modes with a range of orientations through nonlinear interactions.
Abstract: The transport equations for velocity variances are investigated using data from DNS of incompressible channel flows at $Re_\tau$ up to 5200. Each term in the transport equation has been spectrally decomposed to expose the contribution of turbulence at different length scales to the processes governing the flow of energy in the wall-normal direction, in scale and among components.
The outer-layer turbulence is dominated by very large-scale streamwise elongated modes. Away from the wall, production occurs primarily in these large-scale streamwise-elongated modes in the streamwise velocity, but dissipation occurs nearly isotropically in both velocity components and scale. For this to happen, the energy is transferred from the streamwise elongated modes to modes with a range of orientations through non-linear interactions, and then transferred to other velocity components. This allows energy to be transferred more-or-less isotropically from these large scales to the small scales at which dissipation occurs. The VLSMs also transfer energy to the wall-region resulting in a modulation of the autonomous near-wall dynamics.
The near-wall energy flows are consistent with the well-known autonomous near-wall dynamics. Through the overlap region between outer and inner layer turbulence, there is a self-similar structure to the energy flows. The VLSM production occurs at spanwise scales that grow with $y$. There is transport of energy away from the wall over a range of scales that grows with $y$. And, there is transfer of energy to small dissipative scales which grow like $y^{1/4}$. Finally, the small-scale near-wall processes characterised by wavelengths less than 1000 wall units are largely Reynolds number independent, while the larger-scale outer layer process are strongly Reynolds number dependent. The interaction between them appears to be relatively simple.
104 citations
TL;DR: In this paper, the authors formulate a linear elastic second gradient isotropic two-dimensional continuum model accounting for irreversible damage, defined as the condition in which the damage parameter reaches 1, at least in one point of the domain.
Abstract: In this paper, we formulate a linear elastic second gradient isotropic two-dimensional continuum model accounting for irreversible damage. The failure is defined as the condition in which the damage parameter reaches 1, at least in one point of the domain. The quasi-static approximation is done, i.e., the kinetic energy is assumed to be negligible. In order to deal with dissipation, a damage dissipation term is considered in the deformation energy functional. The key goal of this paper is to apply a non-standard variational procedure to exploit the damage irreversibility argument. As a result, we derive not only the equilibrium equations but, notably, also the Karush–Kuhn–Tucker conditions. Finally, numerical simulations for exemplary problems are discussed as some constitutive parameters are varying, with the inclusion of a mesh-independence evidence. Element-free Galerkin method and moving least square shape functions have been employed.
TL;DR: In this article, a computational investigation has been accomplished on nonlinear radiative flow between two impermeable stretchable rotating disks, where Von Karman similarity transformations are utilized to develop coupled nonlinear ordinary differential systems and then tackled by semi computational/analytical technique namely homotopy technique.
TL;DR: In this paper, the experimental tests and the numerical simulations of two types of joints are shown and discussed with the aim of developing pre-qualified configurations, which are designed to be easily removable from both the lower beam flange and the column face by means of bolted connections.
TL;DR: Nonequilibrium energetics of single molecule translational motor kinesin was investigated by measuring heat dissipation from the violation of the fluctuation-response relation of a probe attached to the motor using optical tweezers, concluding that internal dissipation is dominant.
Abstract: Nonequilibrium energetics of single molecule translational motor kinesin was investigated by measuring heat dissipation from the violation of the fluctuation-response relation of a probe attached to the motor using optical tweezers. The sum of the dissipation and work did not amount to the input free energy change, indicating large hidden dissipation exists. Possible sources of the hidden dissipation were explored by analyzing the Langevin dynamics of the probe, which incorporates the two-state Markov stepper as a kinesin model. We conclude that internal dissipation is dominant.
TL;DR: Electronic nanothermometry is realized by measuring local current fluctuations, or shot noise, associated with ultrafast hot-electron kinetic processes (~21 terahertz) using a scanning and contact-free tungsten tip as a local noise probe and directly visualize hot-Electron distributions before their thermal equilibration with the host gallium arsenide/aluminium gallium arsenic arsenide crystal lattice.
Abstract: In modern microelectronic devices, hot electrons accelerate, scatter, and dissipate energy in nanoscale dimensions. Despite recent progress in nanothermometry, direct real-space mapping of hot-electron energy dissipation is challenging because existing techniques are restricted to probing the lattice rather than the electrons. We realize electronic nanothermometry by measuring local current fluctuations, or shot noise, associated with ultrafast hot-electron kinetic processes (~21 terahertz). Exploiting a scanning and contact-free tungsten tip as a local noise probe, we directly visualize hot-electron distributions before their thermal equilibration with the host gallium arsenide/aluminium gallium arsenide crystal lattice. With nanoconstriction devices, we reveal unexpected nonlocal energy dissipation at room temperature, which is reminiscent of ballistic transport of low-temperature quantum conductors.
TL;DR: The emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases is studied, finding that vortex-induced phase slippage is the dominant microscopic source of Dissipation across the Bose-Einstein condensate-Bardeen-Cooper-Schrieffer crossover.
Abstract: We study the emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases. We find that vortex-induced phase slippage is the dominant microscopic source of dissipation across the Bose-Einstein condensate--Bardeen-Cooper-Schrieffer crossover. We explore different dynamical regimes by tuning the bias chemical potential between the two superfluid reservoirs. For small excitations, we observe dissipation and phase coherence to coexist, with a resistive current followed by well-defined Josephson oscillations. We link the junction transport properties to the phase-slippage mechanism, finding that vortex nucleation is primarily responsible for the observed trends of conductance and critical current. For large excitations, we observe the irreversible loss of coherence between the two superfluids, and transport cannot be described only within an uncorrelated phase-slip picture. Our findings open new directions for investigating the interplay between dissipative and superfluid transport in strongly correlated Fermi systems, and general concepts in out-of-equilibrium quantum systems.
TL;DR: In this article, an analysis of entropy generation and heat transfer in the boundary layer flow over a thin needle moving in a parallel stream is performed in the presence of viscous dissipation and non-linear Rosseland thermal radiation.
TL;DR: In this paper, a hierarchical manifold microchannel heat sink array is fabricated and experimentally characterized for uniform heat flux dissipation over a footprint area of 5'mm'×'5'mm.
TL;DR: In this article, a self-centering variable damping energy dissipation (SC-VDED) brace is proposed to reduce the activation force and sudden change in stiffness after activation of selfcentering EED braces.
TL;DR: In this paper, the authors show that the nonequilibrium work relation remains valid in this situation, and test this assertion experimentally using a system engineered from an optically trapped ion.
Abstract: Although nonequilibrium work and fluctuation relations have been studied in detail within classical statistical physics, extending these results to open quantum systems has proven to be conceptually difficult. For systems that undergo decoherence but not dissipation, we argue that it is natural to define quantum work exactly as for isolated quantum systems, using the two-point measurement protocol. Complementing previous theoretical analysis using quantum channels, we show that the nonequilibrium work relation remains valid in this situation, and we test this assertion experimentally using a system engineered from an optically trapped ion. Our experimental results reveal the work relation's validity over a variety of driving speeds, decoherence rates, and effective temperatures and represent the first confirmation of the work relation for non-unitary dynamics.
18 Jun 2018
TL;DR: In this article, a study combining spectral filtering and numerical simulations at enhanced spatial and/or temporal resolution is used to clarify the proper scaling of dissipation and enstrophy in forced incompressible isotropic turbulence.
Abstract: A study combining spectral filtering and numerical simulations at enhanced spatial and/or temporal resolution is used to clarify the proper scaling of dissipation and enstrophy in forced incompressible isotropic turbulence.
TL;DR: It is shown that the sliding friction of a graphene/graphene system can decrease with increasing normal load and collapse to nearly zero at a critical point, enriching the fundamental understanding about superlubricity and isostructural phase transitions and offering a novel means of achieving nearly frictionless sliding interfaces.
Abstract: From daily intuitions to sophisticated atomic-scale experiments, friction is usually found to increase with normal load. Using first-principle calculations, here we show that the sliding friction of a graphene/graphene system can decrease with increasing normal load and collapse to nearly zero at a critical point. The unusual collapse of friction is attributed to an abnormal transition of the sliding potential energy surface from corrugated, to substantially flattened, and eventually to counter-corrugated states. The energy dissipation during the mutual sliding is thus suppressed sufficiently under the critical pressure. The friction collapse behavior is reproducible for other sliding systems, such as Xe/Cu, Pd/graphite, and MoS2/MoS2, suggesting its universality. The proposed mechanism for diminishing energy corrugation under critical normal load, added to the traditional structural lubricity, enriches our fundamental understanding about superlubricity and isostructural phase transitions and offers a novel means of achieving nearly frictionless sliding interfaces.
TL;DR: Log-normality suggests that a few high-dissipation locations dominate the integrated energy and enstrophy budgets, which should be taken into account when making inferences from simplified models and inferring global energy budgets from sparse observations.
Abstract: Data from turbulent numerical simulations of the global ocean demonstrate that the dissipation of kinetic energy obeys a nearly log-normal distribution even at large horizontal scales O(10 km). As the horizontal scales of resolved turbulence are larger than the ocean is deep, the Kolmogorov-Yaglom theory for intermittency in 3D homogeneous, isotropic turbulence cannot apply; instead, the down-scale potential enstrophy cascade of quasigeostrophic turbulence should. Yet, energy dissipation obeys approximate log-normality-robustly across depths, seasons, regions, and subgrid schemes. The distribution parameters, skewness and kurtosis, show small systematic departures from log-normality with depth and subgrid friction schemes. Log-normality suggests that a few high-dissipation locations dominate the integrated energy and enstrophy budgets, which should be taken into account when making inferences from simplified models and inferring global energy budgets from sparse observations.
TL;DR: Gong et al. as mentioned in this paper showed that the absorbed energy of a rock at a crack point has a linear relation with the confining pressure, and the energy dissipation is linearly related to the lateral deformation.
Abstract: Similar to investigations of failure mechanisms using the stress–strain relationship of rock materials, the energy analysis method, as a branch of the rock failure research methods, has already been applied to the field of rock mechanics and engineering applications because of its advantages in compensating for the deficiencies of classical elastoplastic mechanics theory (Thomas and Filippov 1999; Hua and You 2001; Wasantha et al. 2014). In addition, theoretical and experimental studies have confirmed that energy plays a highly crucial role in the process of deformation and destruction of rock materials (Bernabé and Revil 1995; Sujatha and Kishen 2003; Xie et al. 2004, 2005, 2009, 2011; Ju et al. 2010; Peng et al. 2015; Zhang and Gao 2015; Deng et al. 2016). The rock deformation and failure process can essentially be considered a process of energy storage, dissipation, and release (Xu et al. 2013). Hence, it is of great significance to further explore the range of rock energy-based research systems, and a macro–meso–micro system based on energy analysis has been suggested (Xie et al. 2004, 2005, 2011). Over the last few decades, numerous relevant attempts have been made by scholars, and considerable findings have been achieved. For the energy characteristics of rocks under uniaxial compression, Li et al. (2014) showed that the absorbed strain energy, damage strain energy, and elastic strain energy all increase with the strain rate. With the aid of uniaxial cyclic loading and unloading compressive tests, Meng et al. (2016) researched the characteristics of energy accumulation, evolution, and dissipation of sandstone and found that with increasing axial loading stress, the stored energy varied rapidly, followed by the elastic energy, and then the dissipated energy. In addition, a series of rock failure criteria or energy-based indexes and stability evaluation methods were also presented from the perspective of energy (Bhattacharya et al. 1998; Li 2001; Cornetti et al. 2006; Ferro 2006; Wu et al. 2006; Liu 2009; Zhou et al. 2009; Ai et al. 2016; Liu et al. 2016; Munoz et al. 2016a, b, 2017). Among the research studies regarding the energy mechanism of rocks under triaxial compression, You and Hua (2002) and Chen et al. (2013) suggested that the absorbed energy of a rock at a crack point has a linear relation with the confining pressure, and the energy dissipation is linearly related to the lateral deformation. The initial confining pressure significantly affects the energy accumulation, dissipation and release (Huang and Li 2014), i.e., a higher pressure increases the energy input intensity, improves the energy accumulation efficiency, and inhibits the energy release degree of rock (Zhang et al. 2017). Analogously, to characterize the crack propagation of sandstone under triaxial stress conditions, energy dissipation and release laws were proposed by Yang et al. (2016), who reported that as confining pressure increases, the elastic strain energy increases, and the dissipated energy density linearly decreases. These efforts have greatly enriched rock mechanics and promoted their development. The aforementioned research studies show that the previous works mostly focused on tests that were under conditions of uniaxial or triaxial compressions; the energy evolution characteristics of rocks under tension conditions have not been adequately studied, as exceedingly limited data can be found in the previous investigations. In general, rock * Feng-qiang Gong fengqiangg@126.com
TL;DR: It is demonstrated that the implementation of a two-phonon Jaynes-Cummings Hamiltonian under coherent driving of the qubit yields a dissipative phase transition with similarities to the one predicted in the model of the degenerate parametric oscillator.
Abstract: We present a method to implement two-phonon interactions between mechanical resonators and spin qubits in hybrid setups, and show that these systems can be applied for the generation of nonclassical mechanical states even in the presence of dissipation. In particular, we demonstrate that the implementation of a two-phonon Jaynes-Cummings Hamiltonian under coherent driving of the qubit yields a dissipative phase transition with similarities to the one predicted in the model of the degenerate parametric oscillator: beyond a certain threshold in the driving amplitude, the driven-dissipative system sustains a mixed steady state consisting of a ``jumping cat,'' i.e., a cat state undergoing random jumps between two phases. We consider realistic setups and show that, in samples within reach of current technology, the system features nonclassical transient states, characterized by a negative Wigner function, that persist during timescales of fractions of a second.
TL;DR: This work establishes that the discrete energy is conserved in the undamped regime, and that it dissipates in the damped scenario, and proposes an explicit finite-difference discretization of the authors' fractional model based on the use of fractional centered differences.
TL;DR: In this article, a model for fatigue life prediction is proposed on the basis of energy dissipation of fatigued rock salt, and a simple model for evolution of the accumulative dissipated energy is established.
Abstract: The fatigue test for rock salt is conducted under different stress amplitudes, loading frequencies, confining pressures and loading rates, from which the evaluation rule of the dissipated energy is revealed and analysed. The evolution of energy dissipation under fatigue loading is divided into three stages: the initial stage, the second stage and the acceleration stage. In the second stage, the energy dissipation per cycle remains stable and shows an exponential relation with the stress amplitude; the failure dissipated energy only depends on the mechanical behaviour of the rock salt and confining pressure, but it is immune to the loading conditions. The energy dissipation of fatigued rock salt is discussed, and a novel model for fatigue life prediction is proposed on the basis of energy dissipation. A simple model for evolution of the accumulative dissipated energy is established. Its prediction results are compared with the test results, and the proposed model is validated.
TL;DR: In this paper, a theoretical framework for the level repulsion between two degenerate modes due to coupling is proposed and demonstrated experimentally through engineered dissipation in a multimode superconducting microwave optomechanical circuit.
Abstract: Level repulsion---the opening of a gap between two degenerate modes due to coupling---is ubiquitous anywhere from solid-state theory to quantum chemistry. In contrast, if one mode has negative energy, the mode frequencies attract instead. They converge and develop imaginary components, leading to an instability; an exceptional point marks the transition. This only occurs if the dissipation rates of the two modes are comparable. Here we expose a theoretical framework for the general phenomenon and realize it experimentally through engineered dissipation in a multimode superconducting microwave optomechanical circuit. Level attraction is observed for a mechanical oscillator and a superconducting microwave cavity, while an auxiliary cavity is used for sideband cooling. Two exceptional points are demonstrated that could be exploited for their topological properties.
TL;DR: The present research work explores the effects of suction/injection and viscous dissipation on entropy generation in the boundary layer flow of a hybrid nanofluid over a nonlinear radially stretching porous disk and concludes that entropy generation inside the boundary layers of a hybrids is high compared to a convectional nan ofluid.
Abstract: The present research work explores the effects of suction/injection and viscous dissipation on entropy generation in the boundary layer flow of a hybrid nanofluid (Cu–Al2O3–H2O) over a nonlinear radially stretching porous disk. The energy dissipation function is added in the energy equation in order to incorporate the effects of viscous dissipation. The Tiwari and Das model is used in this work. The flow, heat transfer, and entropy generation analysis have been performed using a modified form of the Maxwell Garnett (MG) and Brinkman nanofluid model for effective thermal conductivity and dynamic viscosity, respectively. Suitable transformations are utilized to obtain a set of self-similar ordinary differential equations. Numerical solutions are obtained using shooting and bvp4c Matlab solver. The comparison of solutions shows excellent agreement. To examine the effects of principal flow parameters like suction/injection, the Eckert number, and solid volume fraction, different graphs are plotted and discussed. It is concluded that entropy generation inside the boundary layer of a hybrid nanofluid is high compared to a convectional nanofluid.