Calculation Of Temperature Field Research Articles

On the Sensitivity of Large-Eddy Simulations of the Atmospheric Boundary Layer Coupled with Realistic Large-Scale Dynamics

Abstract We present a new ensemble of 36 numerical experiments aimed at comprehensively gauging the sensitivity of nested large-eddy simulations (LES) driven by large-scale dynamics. Specifically, we explore 36 multiscale configurations of the Weather Research and Forecasting (WRF) Model to simulate the boundary layer flow over the complex topography at the Perdigão field site, with five nested domains discretized at horizontal resolutions ranging from 11.25 km to 30 m. Each ensemble member has a unique combination of the following input factors: (i) large-scale initial and boundary conditions, (ii) subgrid turbulence modeling in the gray zone of turbulence, (iii) subgrid-scale (SGS) models in LES, and (iv) topography and land-cover datasets. We probe their relative importance for LES calculations of velocity, temperature, and moisture fields. Variance decomposition analysis unravels large sensitivities to topography and land-use datasets and very weak sensitivity to the LES SGS model. Discrepancies within ensemble members can be as large as 2.5 m s−1 for the time-averaged near-surface wind speed on the ridge and as large as 10 m s−1 without time averaging. At specific time points, a large fraction of this sensitivity can be explained by the different turbulence models in the gray zone domains. We implement a horizontal momentum and moisture budget routine in WRF to further elucidate the mechanisms behind the observed sensitivity, paving the way for an increased understanding of the tangible effects of the gray zone of turbulence problem. Significance Statement Several science and engineering applications, including wind turbine siting and operations, weather prediction, and downscaling of climate projections, call for high-resolution numerical simulations of the lowest part of the atmosphere. Recent studies have highlighted that such high-resolution simulations, coupled with large-scale models, are challenging and require several important assumptions. With a new set of numerical experiments, we evaluate and compare the significance of different assumptions and outstanding challenges in multiscale modeling (i.e., coupling large-scale models and high-resolution atmospheric simulations). The ultimate goal of this analysis is to put each individual assumption into the wider perspective of a realistic problem and quantify its relative importance compared to other important modeling choices.

MODELLING AND SIMULATION OF NONLINEAR DYNAMIC FLOW FIELD AND TEMPERATURE FIELD OF DEPYROGENATION TUNNEL

Nonlinear dynamics plays a crucial role particularly in equipment validation of preparation production, validation results of which will significantly influence the results and period of drug registration in drug production processes. In this research, the flow field and temperature field simulation, calculation and analysis are creatively carried out in terms of depyrogenation tunnel, a very popular preparation drying-sterilization equipment in pharmaceutical processes with strong dynamic characteristics. After construction of 3D model of this equipment using Catia and mesh generation applying ANSYS, the computational fluid dynamic (CFD) method and verification of irrelevance method are carried out regarding 6.05 million of meshes to identify the flow velocity model and heat transfer model inside the equipment, to further provide methodology for pharmaceutical process validation and to further optimize the design of control methods. After calculation and simulation, the low-velocity vortices of different sizes inside the hood and the drying chamber are identified, which could cause vials to fall down; meanwhile, vials that are farther away from the outlet receives less heat exchange effect, which would shrink the effective sterilization area, indicating an inadequate validation methodology in pharmaceutical processes.

Temperature field calculation of rail flash welding

The forging stage of rail flash welding has a decisive influence on joint strength, and the study of the temperature distribution in the process has an important role in further improving joint strength. In this paper, three calculation methods for the temperature field are given. First, the finite element model of the temperature field before forging rail flash welding is established by using the transient heat module of Ansys software and verified by infrared temperature measurement. Second, the temperature distribution of different parts of the rail before flash welding is obtained by using infrared thermal imaging equipment. Third, Matlab software is used to calculate the temperature of the non-measured part. Finally, the temperature distribution function along the rail axis is fitted through the temperature measurement data. The temperature distribution before the top forging of the rail flash welding can be used to analyze the joint and heat-affected zone organization and properties effectively and to guide the parameter setting and industrial production.

Research on the Adaptability of Packers for Integrated String Fracturing Operations in Low Porosity and Low Permeability Reservoirs

To study the failure of conventional packers in the fracturing and stimulation of low-porosity and low-permeability reservoirs and reduce the failure accidents of packers in the fracturing process, a suitable integrated string packers was selected in the process of fracturing and stimulation in an oilfield in the Middle East as a case study. Three different well types have been established. The wellbore temperature distribution and the axial force of the string can be calculated under the conditions of various wellhead pressures and different displacement, and it is found that the temperature at the bottom of the well can reach 130 °C, and the maximum axial force at the wellhead is 500 kN. At the same time, the applicability of retrievable tubing testing squeeze (RTTS) and hydraulic-set retrievable (RH) packer in different working conditions was evaluated, and it was found that only RTTS packers can meet the needs of the oil field. According to the calculated temperature field and axial force distribution, the stress on different components of the packer under different working conditions is established during the fracturing-stimulation operation. In the worst working conditions, the maximum stress of the packer occurs at the lower part of the central pipe, reaching 303.83 MPa, which is in a safe state. The contact stress on rubber rings can reach 30 MPa, indicating that the sealing performance can meet the requirements of on-site use. The temperature and axial force data calculated by the model provide a theoretical basis for safe well control. Through model evaluation, it was found that the RTTS packer can be suitable for the fracturing and stimulation needs of the oilfield. The research methods and achievements in the article provide theoretical guidance for evaluating the applicability of packers in the fracturing and stimulation process of low porosity and low permeability reservoirs.

Continuous GHz femtosecond laser interacting with aluminum film: Simulation and experiment

GHz femtosecond laser has attracted more research interest due to the so-called high-efficiency cold ablation effect. In this study, behavior of continuous GHz (cGHz), i.e., GHz repetition frequency femtosecond laser with no burst mode, interacting with aluminum (Al) film has been investigated numerically and experimentally. For this purpose, an axisymmetric two-temperature model was used, accounting for the thermodynamical evolution of Al film. Laser irradiating Al film experiments were also carried out simultaneously. The calculated temperature field evolution was in good agreement with the observed experimental results. Effects of laser fluence and scanning speed on morphology, area, height, and volume of the residual Al film were then sequentially studied. Interestingly to see, for this cGHz femtosecond laser source, melting and re-solidification lead to the material removal under low laser fluence, say, ≤0.0337 J/cm2 in this study. For the whole Al film, with laser fluence increasing, the outmost lattice evaporation and beneath lattice melting occur together, both responsible for material removal and morphology variation. Finally, a potentially beneficial GHz femtosecond laser mode for high-quality microfabrication is proposed.

Analysis of the Cooling Modes of the Lining of a Ferroalloy-Casting Ladle

Analysis of the Cooling Modes of the Lining of a Ferroalloy-Casting Ladle

IMPROVEMENT OF THE METHODOLOGY FOR OPTIMIZING THE PARAMETERS OF COMPLEX SYSTEMS UNDER THE INFLUENCE OF THERMAL LOAD SOURCES

The article investigates some aspects of solving the problem of constructing mathematical models for optimizing the parameters of local laser action on multilayer microbiological systems. The constraints on the desired laser parameters and on the temperature field in the material subject to laser fission are set. Verification of compliance with the restrictions on not exceeding the maximum value of the temperature field requires multiple calculations of the corresponding temperature field in the microbiological material. Control over the temperature field limits ensures the viability of its parts during the biotechnological process of laser fission. To construct adequate optimization mathematical models, the author substantiates the adequacy of the computational mathematical models describing the state of a microbiological system under the action of laser radiation sources. A multi-point boundary value problem with a system of inhomogeneous differential heat conduction equations for a multilayer microbiological medium is investigated and the correctness of this problem is substantiated for minor perturbations of the right-hand side of the differential equation. The results obtained in the article guarantee the adequacy of applied optimization mathematical models for finding rational values of technical parameters of laser emitters. In order to improve the accuracy of optimization of the technical parameters of laser emitters, the article presents a mathematical modeling of the preparatory stage of embryo defrosting. The presented mathematical models and methods of their implementation are necessary to improve the quality of embryo defrosting. Improvement of the methodology for solving applied biotechnological problems will certainly lead to the complication of mathematical models, but it will increase the accuracy of calculation and optimization of technical parameters of the biotechnological process of laser embryo division.

APPLICATION OF GRADIENT DEFORMATION CRITERION FOR ANALYSIS OF THERMOMECHANICAL DESTRUCTION OF REFRACTORIES IN A TEMPERATURE FIELD

An approach to the analysis of refractories thermomechanical destruction in service under the influence ofrapid temperature change, called as thermal shocks, is proposed. The proposed approach, based on sequential calculations of the temperature field in the refractory lining and the fields of elastic thermal deformations of the material, performed by the finite element method. The obtained results processed using the deformation gradient criterion of brittle fracture introduced by the authors.The introduced criterion allows identify zones of onset of crack formation, determine the moment of the onset of destruction and predict the direction of crack growth, using of the dynamic calculation of temperature fields in the lining and the calculation of the corresponding static fields of elastic deformations of materials. In addition, the temperature dependence of the elastic properties of refractory materials taken into account, a feature of which is a change in the nature of destruction from brittle to plastic at operating temperatures close to the phase transition temperature of the refractory material or any of its components.Various options for installing products in linings and the corresponding fields of elastic deformations that arise during a sharp rise in temperature in the unit considered. Sharp one-sided heating of one of the lining surfaces is the most dangerous stage of operation of high-temperature equipment from the point of view of thermomechanical stresses.An assessment of the average speed of crack propagation and the possibility of stopping it during the growth process subsequently carried out by analyzing the energy state of the vicinity of the crack tip by comparing the energy of elastic deformation of the material region with the surface energy of the growing defect. The practical application of the approach and validation of the research results considered using the example of a typical failure of the working lining of a steel-pouring ladle.

Numerical calculation and analysis of temperature field in ultrasonic welding of polypropylene dialyzer

Ultrasonic plastic welding is widely used in the bonding process of medical device accessories. In this paper, a thermo-force indirect coupling finite element analysis model was established in the ultrasonic plastic welding process between the blood cap and the shell of polypropylene (PP) dialyzer. The temperature field distribution between the blood cap and the shell was simulated and analyzed by using finite element analysis software, and the influence of welding process parameters on the temperature field was studied. The results show that: by changing the ultrasonic amplitude parameters, welding time parameters, initial pressure, etc., the longer the ultrasonic welding time, the temperature of the welding area will increase. In order to ensure the quality of the dialyzer, it should be controlled within 0.8-1 seconds. The increase of ultrasonic amplitude will make the welding temperature continue to rise, and in order to avoid poor welding, the amplitude should not exceed 120 ?m. The initial pressure has little effect on the temperature field.

Modeling heat and mass transfer in grain drying processes under the influence of electromagnetic field

Drying of grain materials by traditional convective methods typically involves significant energy consumption, primarily due to unproductive losses of thermal energy with the exhausted drying agent. Optimizing this process entails reducing the volume of drying agent used and compensating for reduced thermal energy through non-contact heat transfer methods such as microwave (MW) or infrared (IR) irradiation. However, mathematical modeling of these processes requires refinement as they differ from traditional convective heat drying processes. Grain drying is a complex thermophysical process, with heat and moisture transfer occurring within the capillary-porous material in a mutually dependent manner. To better understand these processes, it is necessary to establish mathematical models that account for the influence of the electromagnetic field. This article aims to theoretically investigate the drying process of plant raw materials under the influence of MW and IR electromagnetic fields based on analytical mathematical models. The conducted research indicates the potential of using electromagnetic fields to intensify the drying of plant raw materials, particularly through MW and IR irradiation, which allows for targeted heating of the moist zones of the material. The obtained analytical dependencies enable the calculation of temperature and moisture content fields in materials and determine the degree of influence of electromagnetic field parameters on heating and drying processes. These dependencies also help to more accurately identify heat and mass transfer model coefficients based on experiments. Such an analytical-empirical approach can be utilized to calculate rational processing regimes for grain raw materials under the influence of electromagnetic fields.

Thermal conductivity prediction of aerogel considering heat treatment effect and the application to a TPS of long endurance HFVs

Purpose For a thermal protection system (TPS) of long endurance hypersonic flight vehicle (HFV), its thermal insulation property not only determines by the manufactured morphology but also changes along time. A thermal conductivity prediction model for aerogel considering heat treatment effect is carried out and applied to solve the heat conduction problem of a TPS. The aim of this study is to provide theoretical and numerical references for further development of aerogels applying to TPSs. Design/methodology/approach A thermal conductivity prediction model for aerogel is established considering treatment effect. The heat conduction problem of a TPS is derived and solved by combining the differential quadrature method and the Runge–Kutta method. The prediction results of aerogel thermal conductivities are verified by comparing with those in literature, while the calculated temperature field of TPS is verified by comparing with that by ABAQUS. Findings Numerical results show that when applying the current prediction model, the calculated high temperature area in the aerogel layer is narrowed due to the decrease of the thermal conductivity during heat treatment process. Originality/value This study will be beneficial to carry out the precise design of TPS for long endurance HFVs.

Research on the nonuniform contact characteristics and thermal behavior of friction pairs involving the radial conical buckling deformation in hydro-viscous drive

An equivalent model and a finite element method was established and used for simulating the change of contact state and pressure distribution of friction pairs under the axial pressure to obtain the radial nonuniform contact characteristics and temperature field of conical friction pairs during the soft-start condition. A two-dimensional temperature field calculation model was established based on the results of contact characteristics and convective heat transfer conditions, and the transient temperature field of friction pairs during soft-start was calculated by the finite difference method. Finally, the effects of the soft-start time, deformation degree, and thickness of the steel disk were studied. The results show that the temperature and contact pressure distribution of conical deformation friction pairs exhibit local high-temperature and high-pressure areas during the soft-start process. In the early stage of soft-start, the conical friction element locally contacts in its radial central area. The contact area spreads from the center to both sides as the soft start time increases, and two contact pressure peak areas are formed near the inner and outer diameters with the increase in axial pressure. The degree of axial deformation of conical steel disk has a significant impact on contact pressure. The larger the axial deformation, the pressure distribution would be more uneven. The distribution of temperature field is significantly affected by the contact pressure. It spreads from the middle to both sides, forming high-temperature regions in the pressure peak areas. Meanwhile, the temperature on the outer side of the friction element is higher than that of the inner side due to the influence of convective heat transfer. The duration of soft start also has a significant impact on the maximum temperature and maximum temperature difference. The results could provide a theoretical basis for exploring the correlation between the thermal buckling deformation and torque instability.

Analysis on Effects of Material Parameters on Thermoelastic Instability of Separate Plate in Wet Clutch

Abstract The working characteristics of wet clutches have an important impact on the safety performance of vehicles. In order to obtain the thermoelastic instability characteristics of wet clutch separate plate, a finite element modeling method is proposed. The temperature field calculation model of separate plate and its thermo-hydro-mechanical coupling relationship are constructed. The distribution law of high-temperature hot spots on the surface of separate plate is obtained and the thermoelastic instability mechanism is revealed. Effectiveness of the simulation model is verified by road test, and surface topography of separate plate is observed by scanning electron microscope. A thermoelastic instability calculation model considering different material parameters is established. The temperature field distribution law is reviewed under different elastic moduli, specific heat capacities, thermal conductivities, and thermal expansion coefficients. Results show that increasing the specific heat capacity and thermal conductivity of the separate plate, decreasing the elastic modulus and thermal expansion coefficient can improve the stability of the system. The thermal conductivity and thermal expansion coefficient have important effects on the thermoelastic instability. The specific heat capacity has a certain effect, and the elastic modulus’ effect is the least. The research results of this paper can provide theoretical support for optimizing the structure of wet clutch and improving the stability of the system.

Laser-induced localized and maskless electrodeposition of micro-copper structure on silicon surface: Simulation and experimental study

The simulation and experimental study of laser-induced localized and maskless electrodeposition of micro-copper (Cu) structures on p-type silicon (Si) surface is investigated. Firstly, calculations of the internal temperature field and free electron density distribution within Si under nanosecond laser irradiation were carried out, to demonstrate the selective enhancing effect of laser irradiation on electrical conductivity via the thermal and photoconductive manner. Secondly, experimental tests of the laser-induced electrodeposition of micro-wires, regional coatings and complicated patterns on Si surface without mask were performed successively, to illustrate the effectiveness of the proposed method. The experimental results indicate that laser pulse width and scanning space significantly affect the quality of the deposited layer. Specifically, dense and flat micro wires can be achieved when the laser pulse width is 100 ns, which is associated with a width of about 71.7 μm and thickness of around 10.9 μm. In addition, the laser scanning space should be well optimized to balance the uniformity of the regional coating and the stray deposition near the edge. Finally, the reduction of Cu2+ and deposition of Cu atom at Si surface were discussed, as well as the development of transitional layer, to supply an in-depth analysis of the electrodeposition mechanism.

Research on Temperature Field of Controllable Bonded Prestressed Structure Based on Electrothermal Method.

Controllable bonded prestress represents an innovative advancement stemming from retard-bonded prestress systems, distinguished by its intrinsic controllability in bonding. The controllable bonded binder can be artificially heated and cured rapidly through DC heating after the completion of prestressed tension, allowing for enhanced control over the process. FLUENT simulates controllable bonded prestressed structure's temperature field, yielding a 1.73% max error validated against measured data. Based on the theory of heat transfer, the maximum error of the calculated temperature field of the controllable bonded test beam under DC heating using the Stehfest numerical algorithm is 1.28%, which exhibits a strong alignment with both simulated and measured results. The parameter analysis identifies current, binder thickness, and steel-strand diameter as key temperature distribution influencers. The relationship between the current and heating time follows a quadratic inverse pattern. Increasing the heating current can significantly reduce the duration of heating. Under identical heating conditions, the temperature of the controllable binder is directly proportional to its thickness. A higher thickness results in a higher temperature. Additionally, larger diameters of steel-stranded wire lead to a lower heating efficiency.

A fast natural convection algorithm based on dividing fluid development stages

We develop a numerical method for fast computation of natural convection, which proposes a new dimensionless number (Fs) to characterize the degree of influence of convection on the temperature field in the flow field and determines the moment of pause for the updating of the flow field by designing judgmental conditions to delineate the stage of development of the flow field, where the loosely coupled computation is turned on to improve the efficiency of the transient temperature field computation. The accuracy of the algorithm is verified using an experimental case of a standard model of natural convection, and the robustness of the algorithm is verified by specifying different monitoring boundaries and setting different numbers of monitoring steps, and the algorithm is applied to a model of natural convection in the equipment in the cabin of the vehicle. The results show that the computational speed is increased by 8.8, 6.4, and 3.5 times after turning on the loosely coupled computation in the first, second, and third development phases, respectively, and the average errors of the monitored point temperatures are 0.7%, 0.1%, and 0.028%, respectively. By monitoring the change in Fs during the loosely coupled computation, the error of the first development stage under the variable boundary is reduced by 95.1%, and the computation speed is 2.2 times faster than that of the second development stage.

Calculation of Temperature Fields in a Lithium Ceramic Pebble Bed during Reactor Irradiation in a Vacuum.

Two-phase lithium ceramic Li2TiO3-Li4SiO4 is considered as a tritium multiplier for use in the solid blanket of fusion reactors. To date, the most accurate understanding of the processes of tritium and helium production and release occurring in the breeder blanket materials under neutron irradiation can only be obtained from experiments in fission research reactors. At that, irradiations in vacuum give the possibility to register even very fast gas release processes (bursts) from the ceramics' voids and pores, although it reduces the thermal conductivity of the pebble bed. The purpose of this work was to simulate the heating of mono-sized pebble bed (1 mm in diameter) of two-phase lithium ceramic 25 mol%Li2TiO3+75 mol%Li4SiO4 in an ampoule device during neutron irradiation at the WWR-K research reactor under vacuum conditions, and to determine experimental parameters in order to prevent heating of the lithium ceramics up to the Li4SiO4-Li2SiO3 phase transition temperatures (>900 °C). For the first time, it was obtained that the effective thermal conductivity of a 1 mm mono-sized pebble bed of 25 mol%Li2TiO3+75 mol%Li4SiO4 significantly decreases (four times) when it is irradiated with neutrons in a vacuum (at a helium pressure of approximately 10 Pa), compared to a similar calculation at 100 kPa of helium (when the He sweep is used). It was concluded that it is difficult to evaluate the maximal temperature of the ceramics in the capsule by measuring the temperature of its outer metal wall (according to thermocouple readings) without using the results of thermophysical calculations for each type of ceramic, taking into account its quantity, specific heat release and pebble size(s). To control the temperature of the ceramics during an irradiation experiment in a vacuum, an in-capsule thermocouple should be used, placed in the center of the pebble bed. Measuring the temperature of the pebble bed based on the capsule wall temperature can lead to overheating of the ceramics and phase changes.

The numerical investigation of cladding layer forming process in laser additive manufacturing with wire feeding

Laser additive manufacturing with wire feeding is extensively applied in the numerous fields such as rail transit, aerospace and biomedical since the high efficiency and flexibility. The formed cladding layer has great influence on determining the quality of manufactured products during the additive manufacturing process. Therefore, a three-dimensional numerical model is developed in this paper to analyze the molten metal behaviors and the cladding layer formation process in the laser additive manufacturing with wire feeding by 316L stainless steel wire. The calculated temperature field and flow field of the molten pool are analyzed and discussed in detail. It is found that the molten metal is transported into molten pool periodically in the droplet shape along the 316L stainless steel wire and then solidified gradually as the cladding layer with the corrugated surface. The simulated results are kept consistent with experimental results from the literatures. The proposed model is of great importance for obtaining the desired cladding layer and is efficient for improving the laser additive manufacturing quality.

A finite layer analysis method proposed for energy pile modeling under coupled thermo-mechanical loads

This study proposes a new hybrid analytical and numerical approach to analyze energy piles by coupling thermal and mechanical loads. Conceived through the finite unit method, the Finite Layer Analysis Method (FLM) boasts promising results when applied to energy piles in soil, which is typically layered or multilayer mediums. This methodology effectively reduces a complex, three-dimensional geotechnical problem to two dimensions, yielding marked improvements in computational efficiency. The FLM for energy pile consists of temperature field calculation and thermo-mechanical coupling calculation, for which the theory and derivation are carefully introduced and elaborated. To validate the accuracy and robustness of the newly proposed FLM method, both the temperature field calculation and the thermo-mechanical coupling calculation are verified meticulously with the finite-length heat source analysis theory, together with the Finite Element results. The validations are also performed against a variety of field trial data including those from London and Lausanne tests.

An Efficient and High-Precision Electromagnetic–Thermal Bidirectional Coupling Reduced-Order Solution Model for Permanent Magnet Synchronous Motors

The traditional electromagnetic–thermal bidirectional coupling model (EMTBCM) of permanent magnet synchronous motors (PMSMs) requires a long time to solve, and the temperature-induced torque change is not accounted for in the finite element (FE) numerical calculation of the EM field. This paper presents a precise and efficient EMTBC reduced-order solution model. The specific methods are as follows: First, a torque control technology based on the current injection method is proposed for determining the effect of temperature on the properties of EM materials and EM torque in an EM field, and the accuracy of the FE numerical calculation model is improved. Second, we use the improved EM field finite element numerical calculation model (FEMNCM) to analyze the correlation between the EM loss, the temperature, and the load, and we replace the FEMNCM with the EM field reduction model using the least-squares method. Then, we analyze the law of the PMSM’s internal temperature distribution. We choose the GA-BP algorithm with as few samples as possible and a high accuracy and stability to build the regression prediction model of the temperature field. We use this regression prediction model to replace the complex temperature field calculation. After analyzing the EMTBCM solution strategy, the original complex EMTBC numerical calculation model is substituted with iterations of the magnetic field reduction model and the temperature field regression prediction model. The FE numerical calculation is then used to validate the reduced-order model. The proposed model is validated through numerical simulations. The numerical results indicate that the proposed reduced-order EMTBC model in this paper is accurate and computationally efficient.