Dissipation Model Research Articles

Hydrodynamic modelling of dynamical tide dissipation in Jupiter’s interior as revealed by Juno

Context. The Juno spacecraft has acquired exceptionally precise data on Jupiter’s gravity field, offering invaluable insights into Jupiter’s tidal response, interior structure, and dynamics, establishing crucial constraints. Aims. We aim to develop a new model for calculating Jupiter’s tidal response based on its latest interior model, while also examining the significance of different dissipation processes for the evolution of its system. We studied the dissipation of dynamical tides in Jupiter by thermal, viscous, and molecular diffusivities acting on gravito-inertial waves in stably stratified zones and inertial waves in convection ones. Methods. We solved the linearised equations for the equilibrium tide. Next, we computed the dynamical tides using linear hydrodynamical simulations based on a spectral method. The Coriolis force is fully taken into account, but the centrifugal effect is neglected. We studied the dynamical tides occurring in Jupiter using internal structure models that respect Juno’s constraints. We specifically looked at the dominant quadrupolar tidal components, and our focus is on the frequency range that corresponds to the tidal frequencies associated with Jupiter’s Galilean satellites. Results. By incorporating the different dissipation mechanisms, we calculated the total dissipation and determined the imaginary part of the tidal Love number. We find a significant frequency dependence in dissipation spectra, indicating a strong relationship between dissipation and forcing frequency. Furthermore, our analysis reveals that, in the chosen parameter regime in which kinematic viscosity and thermal and molecular diffusivities are equal, the dominant mechanism contributing to dissipation is viscosity, exceeding both thermal and chemical dissipation in magnitude. We find that the presence of stably stratified zones plays an important role in explaining the high dissipation observed in Jupiter.

Gravity Investigation to Characterize Enceladus's Ocean and Interior

A key objective for the future exploration of the icy moon Enceladus is the characterization of the habitable conditions in its internal ocean. Radio science instrumentation on board a spacecraft in a low-altitude orbit about Enceladus would enable gravity measurements that are fundamental to providing constraints on its internal structure. We present here the concept of operations and expected results of the gravity investigation for a New Frontiers–class mission. Numerical simulations are carried out to determine the gravity field in spherical harmonics to degree and order 30 and the Love number k 2 and its phase. By combining Enceladus’s shape measured by Cassini and the geophysical constraints obtained through the processing of the simulated radio science data, a Bayesian inference network is used for the interior model inversion. Our results indicate that the gravity investigation would enable tight constraints on core radius and density, ocean depth and density, and ice shell rigidity. By assuming a high core rigidity and a preliminary modeling of dissipation in the ice shell, our interior model inversion also yields information on the ice shell viscosity. Further data on the hydrosphere properties might be gathered through optical navigation data by accurately measuring Enceladus’s orientation model.

A Unified Model for Multiepoch Neutrino Events and Broadband Spectral Energy Distribution of TXS 0506+056

The blazar TXS 0506+056 has been proposed as a high-energy neutrino emitter. However, it has been shown that the standard one-zone model cannot produce sufficiently high neutrino flux due to constraints from the X-ray data, implying more complex properties of the radiation zones in the blazar than that described by the standard one-zone model. In this work, we investigate multiepoch high-energy muon-neutrino events associated with the blazar TXS 0506+056 that occurred in 2014–2015, 2017–2018, 2021–2022, and 2022–2023, respectively. We applied the so-called “stochastic dissipation model” to account for the neutrino-blazar associations detected in the four epochs simultaneously. This model describes a scenario in which the emission of the blazar arises from the superimposition of two components: a persistent component related to the quasi-stable state of the blazar and a transient component responsible for the sudden enhancement of the blazar’s flux, either in electromagnetic radiation or in neutrino emission. The latter component could form at a random distance along the jet by a strong energy dissipation event. Under such an assumption, the multiepoch broadband spectral energy distribution can be well explained, and the expected number of high-energy neutrino events is statistically realistic. The expected number of neutrino events in half year is around 8.2, 0.07, 0.73, and 0.41, corresponding to the epoch in 2014–2015, 2017–2018, 2021–2022, and 2022–2023, respectively. Hence, our model self-consistently explains the episodic neutrino emission from TXS 0506+056.

Geometric Phase of a Transmon in a Dissipative Quantum Circuit.

Superconducting circuits reveal themselves as promising physical devices with multiple uses. Within those uses, the fundamental concept of the geometric phase accumulated by the state of a system shows up recurrently, as, for example, in the construction of geometric gates. Given this framework, we study the geometric phases acquired by a paradigmatic setup: a transmon coupled to a superconductor resonating cavity. We do so both for the case in which the evolution is unitary and when it is subjected to dissipative effects. These models offer a comprehensive quantum description of an anharmonic system interacting with a single mode of the electromagnetic field within a perfect or dissipative cavity, respectively. In the dissipative model, the non-unitary effects arise from dephasing, relaxation, and decay of the transmon coupled to its environment. Our approach enables a comparison of the geometric phases obtained in these models, leading to a thorough understanding of the corrections introduced by the presence of the environment.

Evaluation of orderliness of underground workplace system based on occupational ergonomics: A case study in Guangzhou and Chengdu metro depots.

An underground workplace (UGW) is a complex system with multiple subsystems that interact with each other. However, the research on UGW from a systemic perspective has not received due attention. This study constructs an evaluation approach to the orderliness of UGW and systematically evaluates the UGW with Guangzhou and Chengdu metro depots as case studies. First, the evaluation index system is established based on occupational ergonomics. Second, the system entropy model is constructed based on information entropy. Third, a dissipative structure judgment model is built based on the Brusselator. Fourth, the orderliness evaluation model is constructed based on information entropy and synergetics. The UGW of the metro depot has not yet reached the dissipative structure and is in a medium-order state. But the system is in the trend of orderly development. The entropy increase caused by the physical environment and health status is the main obstacle for the system to move toward order. The equipment configuration is an essential source of system negative entropy. The coordination between equipment configuration, health status, and physical environment is low, and that of work effectiveness, equipment aging and failure, and organizational environment is high. Equipment configuration cannot fully cope with the harsh physical environment and meet the needs of underground workers. Safety security equipment has more room for improvement. Humanized support facilities can introduce more negative entropy to the system. Organizational intervention can reduce the negative impact of adverse factors on the system.

Multivariable analysis of vortex generator-aided heat transfer enhancement for 18650 battery thermal management system

Currently, electric vehicles and hybrid cars have emerged as global solutions to replace internal combustion engine vehicles, with lithium-ion batteries being the most widely chosen option due to their low discharge rates and high energy density. Air-cooling systems, recognized for their cost-effectiveness and stability, are extensively employed in the thermal management systems of automotive batteries. However, conventional air-cooling models exhibit drawbacks in uniformly cooling battery packs. In this study, a numerical investigation is conducted to explore the enhanced cooling heat transfer facilitated by a vortex generator in the air-cooled battery thermal management system. The heat generation and transfer of a battery pack are analyzed using the experimentally validated 2C discharge heat dissipation model for batteries. The assessment focuses on the impact of a vortex generator on the heat transfer performance of a series-connected battery pack. The results indicate that fluid mixing, boundary layer modification, and flow instability are the primary factors contributing to enhanced heat transfer. Through the utilization of orthogonal experimental design and fuzzy grey relational analysis, the influence of three parameters (vortex generator position, angle of attack, and fin height) on thermal performance was systematically analyzed. The analysis reveals that the vortex generator position exerts the most significant impact on the heat transfer index, followed by height, with the angle having the least effect. Nusselt number and entropy generation were chosen as optimization indicators for a comparative analysis of enhancing heat transfer with and without optimized vortex generator assistance. The research results demonstrate that the optimal scenario occurs when entropy generation is minimized, resulting in a 56.4 % reduction in temperature difference (2.66 K) and a 12.1 % decrease in the maximum temperature (2.75 K). This study provides valuable guidance for further optimizing battery thermal management.

Low-velocity impact experiments of porous ice balls simulating Saturn's ring particles: Porosity dependence of restitution coefficients and the mechanism of inelastic collision

We investigated the porosity dependence of the restitution coefficient (ε) of porous ice balls with porosities of 49.6%, 53.8%, and 60.8% colliding with granite, ice and porous ice plates at a low impact velocity (vi = 0.93–96.9 cm s−1) and temperature of −13.8 °C. The relationship between the impact velocity and the restitution coefficient was divided into two regions by the critical velocity vc: In the quasi-elastic region (vi≤vc), the restitution coefficient had a constant value of εqe regardless of the impact velocity and could be explained by using Dilley's viscous dissipation model. In the inelastic region (vi≥vc), the restitution coefficient decreased with the impact velocity and could be explained by using the improved Andrews' plastic deformation model. We then determined the porosity dependence of the εqe and vc empirically for collisions between the porous ice ball and the porous ice plate from our results. Then we extrapolated the porosity dependence of the restitution coefficient by substituting the calculated εqe and vc for the porosity of 10 to 70%. The restitution coefficient was found to decrease with increasing porosity of the porous ice, and to be strongly dependent on the porosity of the porous ice. Considering the energy budget in the steady-state dense ring system which is controlled by the restitution coefficient of the ring particles, the velocity dispersion of the ring particles was estimated to be ∼10−2 mm s−1 to cm s−1 for the ring particles with the porosity from 45% to 70% and < 10–90 cm s−1 for those with the porosity <45%.

Mechanism evaluations of conventional and suspended HVOF thermal spraying based on EDC and EDM combustion models

Suspended high-velocity oxygen fuel (SHVOF) thermal spraying technology can spray solid particles with nano or sub-micron scale, and effectively prepare high quality coatings by wrapping solid particles into suspension with solvent. The HVOF and SHVOF processes are numerically simulated in this study. The gas phase and discrete phase were simulated by the bidirectional coupling Euler-Lagrange method. The state equation of ideal gas and realizable k-ε turbulence model were used to simulate gas phase flow. The effect of eddy dissipation model (EDM) and eddy dissipation concept (EDC) model on turbulent combustion reaction was discussed. Due to that EDM model simplifies the Arrhenius rate of different reactions, there are errors in the prediction of spraying combustion process. To solve the problem, the chemical kinetic mechanism of multi-component combustion reaction for the propylene, ethanol and oxygen was introduced in EDC model for the first time in this study. This method has not yet been used in the modeling of thermal spraying. The suspended droplets are a mixture of ethanol and WC-12Co powder. Results show that the atomization and evaporation of suspension significantly disturb the flow field and reduce the internal pressure and temperature of spray gun. Compared with the EDM model, the EDC model can well predict the peak temperature in the combustion chamber, the prediction of particle temperature and velocity is higher, and the temperature and velocity decay are slower during flight. Compared with the median particle size d50 in actual, two combustion models can effectively predict the median particle size after drying, which is the premise of accurately predicting the flight characteristics of particles.

Large eddy simulations fire modeling of JIS A 1310 façade calibration test with respect to sidewall

AbstractThe full‐scale façade standard test is widely employed as a comprehensive method to assess the façade fire spread. Within this approach, the calibration test without combustible façade decouples the intricate interaction between gas‐phase combustion and material pyrolysis, which simplifies diagnostics and provides an ideal scenario for model validation. This paper presents large eddy simulations (LES) accompanied by comparisons of calibration tests in accordance with JIS A 1310. The calibration tests were conducted to obtain the flame morphologies, gas‐phase temperature, and heat flux of over‐ventilated façade fires, and the LES modeling is complemented by the modified eddy dissipation model for combustion, the one‐equation model for the sub‐grid scale turbulence, and the discrete ordinate method with the gray mean absorption‐emission approach for thermal radiation. The accuracy of LES data is discussed by comparing with measurements, and the mesh resolution is optimized as 2.5 cm for achieving mesh independency with good qualitative agreement. Furthermore, simulations are conducted to investigate the impact of sidewall distances on façade flame spread. The results highlight that the enhancement of sidewall in façade flame spread occurs under external heat release rate, and the 0.2 m sidewall distance for the designated JIS test is identified as a critical threshold increasing façade thermal load.

Design Aspects of the Emittance Diagnostic for the Scorpius Accelerator

A multi-pulse linear induction accelerator, Scorpius, will be constructed at the NNSS U1A facility for use in radiographic experiments. One of the many diagnostics, the injector emittance diagnostic, will provide information on the quality of the beam emanating from the injector and therefore the quality of the beam in the accelerator. A slit-harp design was chosen for the emittance diagnostic. We have modeled the performance of the diagnostic for various simulated Scorpius beams, using several computational tools depending on the physics of the effects under investigation. Additional modeling of electron stopping power, energy deposition, heat dissipation, and x-ray attenuation drove material choices for the collimator jaws and harp wires. The signal chain is designed around constraints of signal extraction, biasing to suppress crosstalk between harp wires via secondary electron emission, and multi-pulse record capability. The ensemble of materials, electrical, and mechanical aspects of the design to reconstruct the emittance from the injector of the accelerator are described.

Minimal numerical ingredients describe chemical microswimmers' 3-D motion.

The underlying mechanisms and physics of catalytic Janus microswimmers is highly complex, requiring details of the associated phoretic fields and the physiochemical properties of catalyst, particle, boundaries, and the fuel used. Therefore, developing a minimal (and more general) model capable of capturing the overall dynamics of these autonomous particles is highly desirable. In the presented work, we demonstrate that a coarse-grained dissipative particle-hydrodynamics model is capable of describing the behaviour of various chemical microswimmer systems. Specifically, we show how a competing balance between hydrodynamic interactions experienced by a squirmer in the presence of a substrate, gravity, and mass and shape asymmetries can reproduce a range of dynamics seen in different experimental systems. We hope that our general model will inspire further synthetic work where various modes of swimmer motion can be encoded via shape and mass during fabrication, helping to realise the still outstanding goal of microswimmers capable of complex 3-D behaviour.

Modeling the thermo-mechanical response and phase changes in metallic additive manufacturing (MAM) processes using a dissipative phase-field model

Additive manufacturing (AM) has emerged as a highly promising manufacturing technique, offering unprecedented possibilities for creating complex geometries and functional structures. However, harnessing the full potential of AM requires the development of a robust computational framework capable of capturing the intricate multi-scale and multi-physics nature of the process. The constitutive and structural responses encountered in AM are particularly challenging to reproduce due to the complex behavior of the material involved. This research aims to address these challenges by presenting a comprehensive computational approach that incorporates a material model capable of accurately representing the behavior of different phases occurring during AM. To achieve this, the finite element method, using the Lagrangian framework in the implicit time scheme, is employed through the widely adopted ABAQUS software. Computational implementation is facilitated using the FORTRAN programming language. By employing weakly coupled thermal and mechanical constitutive equations, the framework enables the analysis of thermal stresses, strains, and displacements during realistic solidification processes, which inherently involve highly nonlinear constitutive relations. Through a series of numerical examples, the capabilities of the proposed model are demonstrated across various computational scales, particularly during the rapid melting and solidification phases. These simulations reveal the formation of residual stresses, which can lead to part distortion and have detrimental effects on the mechanical properties of the manufactured components. This research contributes to the advancement of additive manufacturing by providing a reliable computational tool that integrates the complex interplay between thermal and mechanical phenomena. The developed framework enhances our understanding of the AM process, offering valuable insights into the factors influencing the structural integrity and performance of additively manufactured parts.

Effect of fretting wear on TC4 alloy prepared by laser shock peening at high temperature

The fretting wear properties of a nanocrystalline layer with laser shock peening (LSP) on the surface of Ti–6Al–4V (TC4) alloy were investigated to improve the fretting friction performance at 25 °C and 500 °C. The fretting operation characteristics and material damage mechanism of the LSP–TC4 alloy were investigated through a friction dissipation model and two kinds of operation fretting models. The contact morphology and three-body behaviour on the surface were also revealed. The wear resistance performances of the strengthened surfaces exceeded those of unreinforced surfaces at 25 °C and 500 °C but the LSP-treated alloy was more stable at 25 °C. As revealed in the operation fretting models, the fretting running region of the LSP layer consisted of a mixed slip regime and gross slip regime. The material response area was composed of slight and abrasive wear areas at 500 °C. The improved fretting fatigue resistance of TC4 alloy was attributed to the refined internal organisation and high-density dislocation organisation of LSP, which inhibits the initiation and propagation of fatigue cracks.

Simulation of temperature field and optimization of heat dissipation structure for lithium-ion power battery pack based on multi-objective function optimization

In order to improve the thermal power dissipation of batteries and reduce the maximum temperature difference of batteries, the air conditioning system using battery type was optimized. Using multi-objective optimization method based on orthogonal experiment and multiple rotations, the local optimum values of multi-objective were obtained: the left end height A of entrance area and the height B of air outlet were 9 mm and 28 mm, respectively, with a tolerance value C of 0.4 mm for battery spacing. The simulation results of this optimization model show that the maximum temperature difference of the battery volume is 306.627 K (33.477?C) and 3.815 K (3.815?C), respectively. Compared with the initial model, they are reduced by 9.55% and 25.89%, respectively. Compared with the single factor analysis optimization model, they are reduced by 0.36% and 20.27%, respectively, indicating that the multi-objective optimization results are better. This multi-objective programming solves the problem of different parameters of air conditioning heat dissipation model to some extent, and can provide reference for the optimization design of other models.

A dissipation model for concrete based on an enhanced Timoshenko beam

&lt;p&gt;A novel Timoshenko beam model enriched to account for dissipation in cement-based materials was presented in this paper. The model introduced a new variable representing the relative sliding inside microcracks within the material. In the paper, the microcrack density was not supposed to increase, assuming a small deformation regime that implied no damage growth. The model utilized an expanded version of the principle of virtual work whose contributions came from external forces, internal elastic forces, and dissipation due to the microcrack's microstructure. The elastic energy included terms related to microcrack sliding and micro-macro interactions, accounting for nonlinearity in the material behavior. Numerical simulations, conducted using the finite element method, evaluated the mechanical properties of cement-based materials under three-point flexural tests and compression tests. These tests enabled the assessment of the material dissipative behavior under cyclic loading. Results showed dissipated energy cycles and mechanical responses influenced by the microcrack mechanics. Additionally, a parametric study, varying the friction force amplitude, revealed its impact on dissipated energy. The study highlighted a non-monotonic relationship between friction force amplitude and dissipated energy, with an optimal value maximizing dissipation. Overall, the model provided insights into the mechanics of cement-based materials, particularly regarding dissipation, which was essential for understanding their behavior in structural applications.&lt;/p&gt;

Numerical modeling of the working process in an oxygen-methane combustion chamber operating on gaseous fuel

A method for three-dimensional numerical modeling of the working process in the oxygen-methane combustion chamber of a heat engine operating on gaseous fuel is presented. The advantages and disadvantages of the method based on the gross reaction equation written for the stoichiometric ratio are considered. The vortex dissipation model is used as a combustion model, and the ideal gas model is used for the working body. A justification is given for the effects in the combustion chamber obtained as a result of modeling. The results of three-dimensional numerical modeling and thermodynamic calculations are compared. Recommendations are given for improving the design of the combustion chamber and increasing its effectiveness. Keywords heat engine, combustion chamber, vortex dissipation model, combustion, numerical modeling, thermodynamic calculation, gross reaction

Brownian motion of soft particles near a fluctuating lipid bilayer.

The dynamics of a soft particle suspended in a viscous fluid can be changed by the presence of an elastic boundary. Understanding the mechanisms and dynamics of soft-soft surface interactions can provide valuable insights into many important research fields, including biomedical engineering, soft robotics development, and materials science. This work investigates the anomalous transport properties of a soft nanoparticle near a visco-elastic interface, where the particle consists of a polymer assembly in the form of a micelle and the interface is represented by a lipid bilayer membrane. Mesoscopic simulations using a dissipative particle dynamics model are performed to examine the impact of micelle's proximity to the membrane on its Brownian motion. Two different sizes are considered, which correspond to ≈10-20nm in physical units. The wavelengths typically seen by the largest micelle fall within the range of wavenumbers where the Helfrich model captures fairly well the bilayer mechanical properties. Several independent simulations allowed us to compute the micelle trajectories during an observation time smaller than the diffusive time scale (whose order of magnitude is similar to the membrane relaxation time of the largest wavelengths), this time scale being hardly accessible by experiments. From the probability density function of the micelle normal position with respect to the membrane, it is observed that the position remains close to the starting position during ≈0.05τd (where τd corresponds to the diffusion time), which allowed us to compare the negative excess of mean-square displacement (MSD) to existing theories. In that time range, the MSD exhibits different behaviors along parallel and perpendicular directions. When the micelle is sufficiently close to the bilayer (its initial distance from the bilayer equals approximately twice its gyration radius), the micelle motion becomes quickly subdiffusive in the normal direction. Moreover, the temporal evolution of the micelle MSD excess in the perpendicular direction follows that of a nanoparticle near an elastic membrane. However, in the parallel direction, the MSD excess is rather similar to that of a nanoparticle near a liquid interface.

Optimization of plate-fin heat exchanger performance for heat dissipation of thermoelectric cooler

A plate-fin heat sink is usually used for the hot side of thermoelectric coolers. The plate-fin heat sink should be optimized to improve its heat dissipation capability and eventually elevate the thermoelectric cooler performance. In this paper, a heat dissipation model of the thermoelectric cooler hot side with a plate-fin sink is established, to explore the performances of the plate-fin sink with two types of fins (rectangular and V-type), two convective conditions (lateral and vertical) and three arrangements (single-row, double-row aligned, and double-row staggered). The results show that under vertical jet conditions, double-row aligned rectangular fins have the best heat dissipation capability for the thermoelectric cooler hot side. In order to optimize the fin geometry and maximize its overall performance, a multi-objective optimization of the fins was performed using a machine learning approach based on artificial neural networks (ANN) and non-dominated sorting genetic algorithm (NSGA-ІІ). The corresponding Pareto front is obtained and the technique for order preference by similarity to ideal solution (TOPSIS) method is applied to take the point. Compared with the base case at the same mass flow rate, the fins designed by this method resulted in a 23.3 % reduction in the mean temperature of the hot side.

Power Dissipation and Wear Modeling in Wheel–Rail Contact

This paper is concerned with the modeling of power dissipation due to friction and its relation with wear estimation in wheel–rail contact. Wear is a complex multi-scale and multi-physical phenomenon appearing in rolling contact. Wear is generated by high contact stress and the work of friction forces. This phenomenon leads to the appearing of the worn material in the form of wear debris between contacting surfaces. In contact models, wear is usually described in terms of the wear depth function. This function modifies the gap between the contacting bodies as well as the shape of the surfaces of the wheel and rail in contact. In this paper, besides the wear depth function, the dissipated energy, rather than the contact stress, is taken into account to evaluate the wear impact on rail or wheel surfaces. The dissipated energy allows us to more precisely evaluate the wear debris amount as well as the depth of wear and its distribution along the contact interface. A two-dimensional rolling contact problem with frictional heat flow is considered. The elasto-plastic deformation of the rail is considered. This contact problem is governed by a coupled system of mechanical and thermal equations in terms of generalized stresses, displacement and temperature. The finite element method is used to discretize this problem. A discretized system of equations with nonpenetration and friction conditions is transformed and formulated as a nonlinear complementarity problem. The generalized Newton method is applied to numerically solve this mechanical subproblem. The Cholesky method is used to find the solution of the heat-conductive problem. The dissipated power is evaluated based on the resultant force and slip at a reference point. Numerical results including the distribution of slip velocity, power factor and wear rate are provided and discussed.

A simplified consistent nonlinear mild-slope equation model for random waves propagation and dissipation

The model for ocean surface wave propagation can be formulated either in the form of deterministic models or stochastic models. The stochastic models appear to be particularly attractive in the global domain due to their computational efficiency. However, in the nearshore region, the phase becomes highly correlated, and the phase information therefore becomes critical. Therefore, a simplified consistent nonlinear mild-slope equation model has been developed in order to take advantage of the deterministic model for handling phase information, as well as the stochastic model for numerical simplicity. We demonstrate the advanced performance of the present model for random waves by comparing it with laboratory data and previous models.