Radiative energy transfer in induction plasma modelling

Temporal prediction of three-dimensional spatial fields of ocean temperature, salinity and flow is important for a number of civilian and military applications. For accurate prediction of regional ocean environments, combing an accurate dynamic ocean model with optimized in-situ observations of ocean states provided by a network of marine vehicles (such as unmanned surface vehicles, autonomous underwater vehicles, and underwater gliders) is an important approach. To realize fast and accurate three-dimensional spatial prediction of regional ocean environments via ocean models and fast optimization of ocean observation strategies of marine vehicles guided by ocean models, this paper proposes a data driven dynamic model for temporal prediction of three-dimensional regional ocean environments. The proposed model is based on the deep learning method, and is developed based on the Convolutional-LSTM (long short-term memory) network. The feature of the proposed model is that the correlation of temperature, salinity and flow is considered and implemented in the neural network, with which the joint prediction of three-dimensional ocean temperature, salinity and flow fields is achieved. Data set form a numerical ocean model is used to conduct the training of the model and the results demonstrate that the proposed model could provide more accurate prediction than implementing prediction of single ocean temperature, salinity or flow field. The proposed model could be integrated with marine vehicles to form an accurate, high-resolution three-dimensional regional ocean prediction and fast-response adaptive sensing system.

We demonstrate long-wavelength operation (>700 nm) of random dye lasers (using a methylene blue dye) with the addition of rhodamine 6G and titania, enabled by radiative and non-radiative energy transfer. The pump energy is efficiently absorbed and transferred to the acceptors, to support lasing in random dye lasers in the near infrared. The optimum random laser performance with the highest emission intensity and the lowest lasing threshold was achieved for a concentration of methylene blue as the acceptor equal to 6× the concentration of rhodamine 6G (donor). Excessive levels of methylene blue increased the lasing threshold and broadened the methylene blue emission linewidth due to dye quenching from re-absorption. This is due to competition between the donor emission and energy transfer and between absorption loss and fluorescence quenching. The radiative and non-radiative energy transfer is analyzed as a function of the acceptor concentration and pump energy density, with consideration of the spectral overlap. The dependence of the radiative and non-radiative transfer efficiency on the acceptor concentration is obtained, and the energy transfer parameters, including the radiative and non-radiative energy transfer rate constants (K R and K NR), are investigated using Stern–Volmer analysis. The analysis indicates that radiative energy transfer is the dominant energy transfer mechanism in this system.

A three-dimensional mathematical model for simulation of flow, temperature, and concentration fields in a pilot-scale rotary hearth furnace (RHF) has been developed using a commercial computational fluid dynamics software, FLUENT. The layer of composite pellets under the hearth is assumed to be a porous media layer with CO source and energy sink calculated by an independent mathematical model. User-defined functions are developed and linked to FLUENT to process the reduction process of the layer of composite pellets. The standard k–e turbulence model in combination with standard wall functions is used for modeling of gas flow. Turbulence-chemistry interaction is taken into account through the eddy-dissipation model. The discrete ordinates model is used for modeling of radiative heat transfer. A comparison is made between the predictions of the present model and the data from a test of the pilot-scale RHF, and a reasonable agreement is found. Finally, flow field, temperature, and CO concentration fields in the furnace are investigated by the model.

Based on the electromagnetic vector potential representation, a two-dimensional, axisymmetric model is proposed for the calculation of the electromageetic fields in an inductively coupled, radiofrequency (r.f.) plasma. A comparative analysis made between the flow, temperature, and electromagnetic fields obtained using this model and those given by our earlier one-dimensional electromagnetic fields model show relatively little difference between the temperature fields predicted by the two models. Significant differences are observed, however, between the corresponding flow and electromagnetic fields. The new model offers an effective means of accounting for variations in the coil geometry on the flow and temperature fields in the discharge and for achieving a better representation of the electromagnetic fields under higher frequency conditions (f>10 MHz).

Temperature and velocity fields in high-temperature lead coolant flows in a circular clearance for controlled oxygen impurity content in a flow were experimentally studied at the Nizhny Novgorod State Technical University by R.E. Alekseev (NNSTU). Temperature and velocity fields were simultaneously studied in “cold” and “hot” parts of the circuit in the following operating conditions: the lead temperature is t = 400–550 °C, the thermodynamic activity of oxygen is a = 10−5–100; the Peclet number is Pe = 500–7000, the coolant flow velocity is w = 0.1–1.5 m/s, and the average heat flux is q = 50–160 kW/m2. It has been found that the oxygen impurity content and characteristics of protective oxide coatings affect temperature and velocity fields in round and circular channels. This is due to the fact that oxygen in a coolant and oxide coatings on the surfaces limiting a liquid metal flow influence characteristics of the wall boundary region. The heat transfer process that occurs when HLMC transversely flows around heat exchange pipes is investigated now at the NNSTU. The experimental facility is a combination of two high-temperature liquid-metal stands, i.e., FT-2 with the lead coolant and FT-1 with the lead-bismuth coolant combined with an experimental section. The temperature of a heat-exchange surface is measured by thermocouples of diameter 1 mm mounted in walls of heat-exchange pipes. Velocity and temperature fields in a high-temperature HLMC flow are measured by special sensors placed in the flow cross section between rows of heat-exchange pipes. Heat transfer characteristics and temperature and velocity fields in a high-temperature lead coolant flow are studied in the following operating conditions: the lead temperature is t = 450–500 °C, the thermodynamic activity of oxygen is a = 10−5–100, and the coolant flow rate through the experimental setup is Q = 3–6 m3/h, which corresponds to coolant flow velocities of V = 0.4–0.8 m/s. Integrated experimental studies of characteristics of the heat transfer that occurs when the lead coolant transversely or obliquely flows around pipes have been carried out for the first time and the dependences Nu = f(Pe) for controlled content of thermodynamically active oxygen impurity and sediments of impurities have been obtained. It is assumed that the obtained experimental data on distribution of velocity and temperature fields in a HLMC flow will permit to study heat transfer processes and to use them for developing program codes for engineering calculations of heat exchange surfaces (steam generators) with a HLMC flow around them.

Temperature field calculation is an important step in infrared image simulation. However, the existing solutions, such as heat conduction modelling and pre-generated lookup tables based on temperature calculation tools, are difficult to meet the requirements of high-performance simulation of infrared images based on three-dimensional scenes under multi-environmental conditions in terms of accuracy, timeliness, and flexibility. In recent years, machine learning-based temperature field prediction methods have been proposed, but these methods only consider the influence of meteorological parameters on the temperature value, while not considering the geometric structure and the thermophysical parameters of the object, which results in the low accuracy. In this paper, a multivariate temperature field prediction network based on heterogeneous data (MTPHNet) is proposed. The network fuses geometry structure, meteorological, and thermophysical parameters to predict temperature. First, a Point Cloud Feature Extraction Module and Environmental Data Mapping Module are used to extract geometric information, thermophysical, and meteorological features. The extracted features are fused by the Data Fusion Module for temperature field prediction. Experiment results show that MTPHNet significantly improves the prediction accuracy of the temperature field. Compared with the v-Support Vector Regression and the combined back-propagation neural network, the mean absolute error and root mean square error of MTPHNet are reduced by at least 23.4% and 27.7%, respectively, while the R-square is increased by at least 5.85%. MTPHNet also achieves good results in multi-target and complex target temperature field prediction tasks. These results validate the effectiveness of the proposed method.

Purpose – The purpose of this paper is to study the effect of feeding scheme on melt flow and temperature field during the steady-state of level-pour direct-chill (DC) casting of A390 alloy hollow billet and optimize the design of feeding scheme. Design/methodology/approach – Melt flow and temperature field are investigated by numerical simulation, which is based on a three-dimensional mathematical model and well verified by experiments. Findings – The numerical results reveal that both melt flow and temperature field are obviously affected by the feeding scheme. The homogeneity of melt flow and temperature field in hollow billet with the feeding scheme of modified four inlets are better than the other feeding schemes. Experimental results show that crack can be eliminated by increasing the number of feeding inlets. The primary Si size appears unaffected while the distribution of primary Si particles is highly affected by the change of feeding scheme. Only with the feeding scheme of modified four inlets can fine and uniformly distributed primary Si particles be achieved. Practical implications – The paper includes implications for the design of feeding scheme in level-pour DC casting of hollow billet for practical use. Originality/value – This paper develops different feeding schemes for level-pour DC casting of hollow billet and optimizes the design of feeding scheme.

Full-scale experimental and computational fluid dynamics (CFD) methods were used to investigate the velocity and temperature fields in a mechanically ventilated room. Detailed airflow fields were measured in three cases of ventilation air temperature: an isothermal case, a hot case and a cold case. The ventilation system created a round jet which developed near the ceiling. The experimental data were used to test two turbulence models: a first order k-ε turbulence model and a second order RSM turbulence model. The RSM model predicted the temperature and velocity fields better than the k-ε turbulence model. In particular, experimental global values of velocity and temperature were in good agreement with the RSM turbulence model. This model is recommended for simulation of ventilated enclosures with thermal effects.

Abstract. Loop Current rings (LCRs) are among the largest mesoscale eddies in the world ocean. They arise when bulges formed by the Loop Current in the Gulf of Mexico close off. The LCR formation process may take several weeks, and there may be several separations and reattachments before final separation occurs. It is well established that this period is characterized by a persistent saddle point in the sea surface height field, as seen in both model and satellite data. We present here a detailed study of this saddle region during the formation of Eddy Franklin in 2010, over multiple days and at several depths. Using a data-assimilating Gulf of Mexico implementation of the HYbrid Coordinate Ocean Model (HYCOM), we compare the vertical structure of the currents and temperature fields on 5 and 10 June 2010. Finite-time Lyapunov exponents (FTLE) are computed from the surface down to 200 m to estimate the location of relevant transport barriers. Several new features of the saddle region associated with LCR formation are revealed: the ridges in the FTLE fields are shown to be excellent surrogates for the manifolds delineating the material flow structures with only slight degradation at depth. The intersection of the ridges representing stable and unstable manifolds drops nearly vertically through the water column at both times; remarkably, the material boundary shapes are maintained even as they are advected. Moreover, velocity stagnation points and saddle points in the temperature field are consistently found near the intersections at all depths, and their geographic positions are also nearly constant with depth.

A conjugate heat transfer simulation of air in a rectangular cooling channel with 45-deg ribs is presented in this paper. The test channel length is 400mm and the ratio of width to height is 1. The hydraulic diameter of the channel is 40mm and the thickness of channel wall is 3mm. The rib height is 1.9mm and the distance between nearby ribs is 19mm. The flow field and the temperature field in the solid channel are obtained by using ANSYS CFX. An energy source is added in the solid domain to simulate the Low-Voltage High-Current heating method in the experiment. The GGI method is adopted for the mesh connection between the fluid domain and solid domain. The SST turbulence model and automatic wall function in ANSYS CFX are used to simulate the flow and heat transfer in near-wall region. The numerical results show great agreement with the experimental data. The temperature distribution on the channel outer wall is shown and analyzed. The Nusselt number field on the channel wall is shown and illustrated by the flow field shown by the Vortex Core Technology. There are four secondary flow vortex cores between ribs in near wall region and a strong secondary flow can be seen in main flow region. The angled ribs leads to the unbalanced temperature and Nusselt number field on the outer wall and the inner wall of the channel respectively. The distribution law of the Nusselt number on inner wall is not similar with the one of temperature on the outer wall. But the overall distribution of outer wall temperature field is more homogeneous compared with that of the inner wall Nusselt number. Some recommendations for optimization are given based on the flow field and Nusselt number distribution.

Purpose Because the local Re numbers, ratio of inertia to viscous forces, are not same at different regions of the enclosures, the present study aims to deal with the influences of using the turbulent/transition models on numerical results of the natural convection and flow field within a trapezoidal enclosure. Design/methodology/approach The three-dimensional (3D) trapezoidal enclosure with different inclined side walls of 75, 90 and 105 degrees are considered, where the side walls are heated and cooled at Ra = 1.5 × 109 for all cases. The turbulent models of the k-ε-RNG, k- ω-shear-stress transport (SST) and the newly developed transition/turbulent model of Reθ-γ-transition SST are utilized to analyze the fluid flow and heat transfer characteristics within the enclosure and compared their results with validated results. Findings Comprehensive comparisons have been carried out for all cases in terms of flow and temperature fields, as well as turbulent quantities, such as turbulent kinetic energy and turbulent viscosity ratio. Furthermore, the velocity and thermal boundary layers have been investigated, and the approximate transition regions for laminar, transitional and turbulent regimes have been determined. Finally, the heat transfer coefficient and skin friction coefficient values have been presented and compared in terms of different turbulent models and configurations. The results show that the transition/turbulence model has better prediction for the flow and heat fields than fully turbulent models, especially for local parameters for all abovementioned governing parameters. Originality value The originality of this work is to analyze the 3D turbulent/transitional natural convection with different turbulence/transition models in a trapezoidal enclosure.

Flow over a rectangular porous block placed in a fixed width channel is considered and the influence of block aspect ratio on the heat transfer rate from the block is examined. A non-porous solid block is also accommodated to compare the effect of porosity on the flow field and heat transfer characteristics. Aspect ratio and the porosity of the block are varied in the simulations. A numerical scheme employing a control volume approach is considered when predicting the flow and temperature fields. The Reynolds number is selected to yield the mix convection situation in the flow field. It is found that the aspect ratio significantly influences Nu and Gr numbers, in which case increasing the aspect ratio enhances Nu while lowering Gr. Increasing porosity improves the heat transfer rates from the porous block, provided that at high aspect ratios, this situation ceases due to blockage effect of the body in the channel.

Differential sensitivity analysis and multi-variant simulation of formation pressure and temperature in heterogeneous media

A semianalytical method based on the separation of variables is presented to solve the problem of heat transfer in multilayer skin tissues. This method is used to predict the temperature field and thermal damage of skin tissues, which are subjected to the time-varying laser heating and fluid cooling. The effect of convective heat transfer coefficient of the skin surface on temperature field and thermal damage is studied. The temperature field and thermal damage of skin tissue with different laser heating cycles are calculated. The relationship between the laser heating period and the temperature fluctuation is obtained. The effects of the peak time of laser heating on temperature and the thermal damage of skin tissues are investigated. The relationship between the peak time of laser and the temperature fluctuation of skin tissue is drawn. The results calculated in this paper can provide some guidance for hyperthermia of skin tissue. The presented semianalytical method can be applied to solve the general heat transfer problems of multilayer structures.

The current study is based on the effects of microrotational dynamics, microinertial effects, and temperature changes on electroosmotic peristalsis in a tapered microchannel. This has been addressed by an analytical study of heat transfer in the setting of electroosmotic peristaltic flow involving a micropolar fluid, specifically considering a symmetrically tapered channel. The Navier–Stokes equation, the Poisson–Boltzmann equation, the energy equation, and the micropolar fluid model are all included in the mathematical model. On the flow and temperature fields, a thorough parametric analysis is carried out, investigating the impacts of numerous variables, including the micropolar parameter, Prandtl number, Brinkman number, Grashof number, thermal conductivity ratio, and channel aspect ratio. The findings show that peristalsis and electroosmosis both contribute to higher heat transfer rates. Notably, the electroosmotic parameter and Brinkman number have a substantial impact on the distribution of temperature. The micropolar parameter and Brinkman number have a significant effect on the flow and temperature fields. Furthermore, electrokinetic phenomena are crucial in controlling the axial and spin velocities of the micropolar fluid. These findings have significant ramifications for the design and optimization of microfluidic devices in engineering and biomedical applications that employ the electroosmotic peristaltic flow of micropolar fluids.