scholarly journals Thermal Accelerometer Simulation by the R‑Functions Method

2020 ◽  
Vol 10 (23) ◽  
pp. 8373
Author(s):  
Mikhail Basarab ◽  
Alain Giani ◽  
Philippe Combette
Keyword(s):  
Mathematical Simulation ◽  
Performance Optimization ◽  
Transfer Problem ◽  
Thermal Characteristics ◽  
Temperature Response ◽  
Novel Approach ◽  
Diffusion Convection ◽  
Analytical Approaches ◽  
Benchmark Solutions ◽  
R Functions

As well as many modern devices, thermal accelerometers (TAs) need a sophisticated mathematical simulation to find the ways for their performance optimization. In the paper, a novel approach for solving computational fluid dynamics (CFD) problems in the TA’s cavity is proposed (MQ-RFM), which is based on the combined use of Rvachev’s R-functions method (RFM) and the Galerkin technique with multiquadric (MQ) radial basis functions (RBFs). The semi-analytical RFM takes an intermediate position between traditional analytical approaches and numerical methods, such as the finite-element method (FEM), belonging to the family of the so-called meshless techniques which became popular in the last decades in solving various CFD problems in complex-shaped cavities. Mathematical simulation of TA by using the MQ-RFM was carried out with the purpose to simulate the temperature response of the device and to study and improve its performance. The results of numerical experiments were compared with well-known analytical and numerical benchmark solutions for the circular annulus geometry and it demonstrated the effectiveness of the MQ-RFM for solving the convective heat-transfer problem in the TA’s cavity. The use of solution structures allows one to take a relatively small number of expansion terms to achieve an appropriate accuracy of the approximate solution satisfying at the same time the given boundary conditions exactly. The application of the MQ-RFM gives the possibility to obtain semi-analytical solutions to the diffusion-convection problems and to identify the main thermal characteristics of the TA, that allows one to improve the device performance.

Analysis of the Temperature Profile of Ceramic Composite Materials Exposed to Combined Conduction–Radiation Between Concentric Cylinders

1998 ◽  
Vol 120 (2) ◽  
pp. 271-275 ◽  
Author(s):  
A. Tremante ◽  
F. Malpica
Keyword(s):  
Ceramic Composite ◽  
Numerical Study ◽  
Thermal Characteristics ◽  
Ceramic Matrix Composites ◽  
Gray Model ◽  
Matrix Composites ◽  
Semitransparent Materials ◽  
Concentric Cylinders ◽  
Benchmark Solutions ◽  
Potential Use

A numerical study is made of the thermal characteristics of semitransparent materials exposed to simultaneous conduction and radiation between concentric cylinders. For extremely high-temperature applications, where radiative transfer plays an important role, ceramic-matrix composites, considered as semitransparent materials, are being explored for potential use in turbine and compressor components, spacecraft structures, engine control systems and nuclear reactors. Through the use of a gray model and the two-flux method, specialized equations are developed that generate a system of nonlinear ordinary differential equations. To facilitate the solution of this system, an iterative strategy is adopted. In order to demonstrate the versatility and accuracy of the proposed methodology, the results of several numerical experiments are presented and compared with benchmark solutions.

Tuning the dispersion of reactive solute by steady and oscillatory electroosmotic–Poiseuille flows in polyelectrolyte-grafted micro/nanotubes

2019 ◽  
Vol 880 ◽  
pp. 73-112
Author(s):  
Milad Reshadi ◽  
Mohammad Hassan Saidi
Keyword(s):  
Hydrodynamic Dispersion ◽  
Asymptotic State ◽  
Late Time ◽  
Band Broadening ◽  
Zeta Potentials ◽  
Tracer Particles ◽  
Ion Partitioning ◽  
Analytical Approaches ◽  
Benchmark Solutions ◽  
Poiseuille Flows

This paper extends the analysis of solute dispersion in electrohydrodynamic flows to the case of band broadening in polyelectrolyte-grafted (soft) capillaries by accounting for the effects of ion partitioning, irreversible catalytic reaction and pulsatile flow actuation. In the Debye–Hückel limit, we present the benchmark solutions of electric potential and velocity distribution pertinent to steady and oscillatory mixed electroosmotic–pressure-driven flows in soft capillaries. Afterwards, the mathematical models of band broadening based on the Taylor–Aris theory and generalized dispersion method are presented to investigate the late-time asymptotic state and all-time evolution of hydrodynamic dispersion, respectively. Also, to determine the heterogeneous dispersion behaviour of solute through all spatiotemporal stages and to relax the constraint of small zeta potentials, a full-scale numerical simulation of time-dependent solute transport in soft capillaries is presented by employing the second-order-accurate finite difference method. Then, by inspecting the dispersion of passive tracer particles in Poiseuille flows, we examine the accuracy of two analytical approaches against the simulation results of a custom-built numerical algorithm. Our findings from hydrodynamic dispersion in Poiseuille flows reveal that, compared to rigid capillaries, more time is required to approach the longitudinal normality and transverse uniformity of injected solute in soft capillaries. For the case of dispersion in mixed electrohydrodynamic flows, it is found that the characteristics of the soft interface, including the thickness, permittivity, fixed charge density and friction coefficient of the polymer coating layer, play a significant role in determining the Taylor diffusion coefficient, advection speed and dispersion rate of solutes in soft capillaries.

Parametric and Topological Control in Shape Optimization

2006 ◽  
Author(s):  
Jiaqin Chen ◽  
Vadim Shapiro ◽  
Krishnan Suresh ◽  
Igor Tsukanov
Keyword(s):  
Shape Optimization ◽  
Optimization Techniques ◽  
Free Form ◽  
Large Space ◽  
Design And Optimization ◽  
B Splines ◽  
Novel Approach ◽  
Higher Dimensional ◽  
Special Cases ◽  
R Functions

We propose a novel approach to shape optimization that combines and retains the advantages of the earlier optimization techniques. The shapes in the design space are represented implicitly as level sets of a higher-dimensional function that is constructed using B-splines (to allow free-form deformations), and parameterized primitives combined with R-functions (to support desired parametric changes). Our approach to shape design and optimization offers great flexibility because it provides explicit parametric control of geometry and topology within a large space of freeform shapes. The resulting method is also general in that it subsumes most other types of shape optimization as special cases. We describe an implementation of the proposed technique with attractive numerical properties. The effectiveness of the method is demonstrated by several numerical examples.

Numerical and Experimental Investigation on Thermal Characteristics of Deformable Thin Film Mirrors Package and Its Performance Optimization

2008 ◽  
Author(s):  
Jae Choon Kim ◽  
Jin Taek Chung ◽  
Jae Hong Min ◽  
Dong Jin Lee ◽  
Ji-Hyuk Yu ◽  
...  
Keyword(s):  
Thin Film ◽  
Control System ◽  
Ambient Temperature ◽  
Temperature Change ◽  
Performance Optimization ◽  
Thermal Characteristics ◽  
Critical Factor ◽  
Temperature Control System ◽  
Optical Modulators ◽  
Temperature Feedback

This paper presents the thermal characteristics of a microelectro-mechanical deformable thin film mirrors package for the optical modulators used in mobile equipment such as cellphones, lab tops and PDA. One critical factor which affects the performance of the package is the ambient temperature change. To reduce the effect of the ambient temperature change, the temperature control system by a micro heater and a temperature feedback circuit was developed. The thermal characteristics histories were numerically modeled, the results of which were validated by the experimental data. The magnitude of the fluctuation was reduced within 1°C under the controlled system. In addition, required time to reach the steady state temperature was reduced by using the proposed control system.

scholarly journals A novel approach to generate non-isotropic surfaces for numerical quantification of thermal contact conductance

2021 ◽  
Vol 2116 (1) ◽  
pp. 012024
Author(s):  
Thorsten Helmig ◽  
Tim Göttlich ◽  
Reinhold Kneer
Keyword(s):  
Heat Transfer ◽  
Thermal Contact ◽  
Surface Structures ◽  
Thermal Contact Conductance ◽  
Machining Parameters ◽  
Transfer Coefficients ◽  
Contact Heat ◽  
Contact Heat Transfer ◽  
Novel Approach ◽  
Analytical Approaches

Abstract The quantification of heat flow between machine tool components is of major importance for a precise thermal prediction of the entire system. A common coupling condition between individual components is the contact heat transfer coefficient connecting the temperature field with the corresponding heat transfer at the investigated interface. However, the majority of numerical and analytical approaches assume isotropic contact surface profiles and neglect distinct surface structures caused by the manufacturing process. This assumption causes inaccuracies in the modeling as isotropic surfaces lead to an overprediction in heat transfer. Hence, this paper presents a novel approach to generate surface structures for numerical calculations considering the used machining parameters. Predicted contact heat transfer coefficients of the old as well as the new generation approach are presented and compared to experimental results offering the basis for future comprehensive investigations considering multiple parameters and materials.

Temperature

1997 ◽  
Author(s):  
Douglas V. Hoyt ◽  
Kenneth H. Shatten
Keyword(s):  
Solar Activity ◽  
Solar Irradiance ◽  
Temperature Response ◽  
Personal Communication ◽  
Balance Model ◽  
Solar Cycles ◽  
Tropical Ocean ◽  
Temperature Changes ◽  
Boundary Crossings ◽  
Novel Approach

How the bulk of the sun’s energy variations, which arise from the solar-irradiance changes, contribute to terrestrial changes will be the subject of this and the next few chapters. Although it’s a simplification, the hypothesis that only the largest solar activity–related energy contributors to the Earth’s atmosphere need to be considered allows us to ignore such far-flung ideas as the influence of sector boundary crossings, cosmic rays, and other less energetic phenomena. If the Foukal and Lean model of solar irradiance is a close approximation of known solar behavior on the 11-year time scale, what are the climatic consequences of these variations? We can ignore all the other proposed solar cycles ranging from 6 to 7 days to hundreds or thousands of years. Although some of these other proposed solar cycles may be real, we will not indulge in cyclomania here. North and his colleagues in 1983 developed a theoretical energy-balance model with a geographical distribution of land and ocean. Testing the model to see how well it reproduced the observed annual cycle of temperatures revealed satisfactory agreement, so North et al. subjected their model to other cyclic solar forcings. Figure 5.1 shows a 10-year cycle imposed on the Earth. Climatologists were not too surprised by the conclusions, as the solar-irradiance and temperature changes are nearly in phase because Earth’s time constant (about 3–5 years) is less than the imposed cycle time. The response over the land is greater than that over the oceans because the land holds less heat than water does and responds more strongly. The amplitude of the temperature variations is very small, no larger than about 0.11 °C. The maximum response is also centered near Arabia. Not everyone agrees that Earth’s temperature response to solar cycle changes will follow the scenario shown in Figure 5.1. In the last chapter, we described a novel approach suggesting the possibility of a larger response to solar activity than North’s and similar models provide. Kim in 1994 argues that tropical ocean waters, about 30° north or south of the equator, are the center of response to solar variations, (personal communication).

Analysis of Combined Conductive-Radiative Heat Transfer in a Two-Dimensional Rectangular Enclosure With a Gray Medium

1988 ◽  
Vol 110 (2) ◽  
pp. 468-474 ◽  
Author(s):  
W. W. Yuen ◽  
E. E. Takara
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Diffusion Approximation ◽  
Radiative Heat ◽  
Transfer Problem ◽  
Numerical Procedure ◽  
Numerical Data ◽  
Two Dimensional ◽  
One Dimensional ◽  
Benchmark Solutions

Combined conductive–radiative heat transfer in a two-dimensional enclosure is considered. The numerical procedure is based on a combination of two previous techniques that have been demonstrated to be successful for a two-dimensional pure radiation problem and a one-dimensional combined conductive–radiative heat transfer problem, respectively. Both temperature profile and heat transfer distributions are generated efficiently and accurately. Numerical data are presented to serve as benchmark solutions for two-dimensional combined conductive–radiative heat transfer. The accuracy of two commonly used approximation procedures for multidimensional combined conductive–radiative heat transfer is assessed. The additive solution, which is effective in generating approximation to one-dimensional combined conductive–radiative heat transfer, appears to be an acceptable empirical approach in estimating heat transfer in the present two-dimensional problem. The diffusion approximation, on the other hand, is shown to be generally inaccurate. For all optical thicknesses and conduction-radiation parameters considered (including the optically thick limit), the diffusion approximation is shown to yield significant errors in both the temperature and heat flux predictions.

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