A Comparative Study Between Two-Dimensional and Three-Dimensional Simulation Results of Melting Inside a Container

2020 ◽  
Author(s):  
Nan Hu ◽  
Li-Wu Fan
Keyword(s):  
Velocity Profile ◽  
Heating Temperature ◽  
Three Dimensional ◽  
Detailed Comparison ◽  
Melting Rate ◽  
Two Dimensional ◽  
End Effects ◽  
Wall Superheat ◽  
Simulation Results ◽  
Dimensional Simulation

Abstract Bother two-dimensional (2D) and three-dimensional (3D) simulations on two example melting problems, i.e., melting in a differentially-heated rectangular cavity and constrained melting in a horizontal cylindrical capsule, were carried out to investigate the rationality of 2D simplification. The effects of thermophysical properties of the phase change material, size of the container along the direction perpendicular to the 2D cross-section, as well as wall superheat were taken into consideration for a systematic and detailed comparison. It was shown that a small length of the container perpendicular to 2D plane will result in a confine space to limit the development of velocity distribution (i.e., parabolic velocity profile) due to the end effects, leading to to an almost identical melting rate to that obtained by the 2D simplified case. A larger size indicates stronger thermal convection (bulk uniform velocity profile) and faster melting rate. When fixing a large size of the container perpendicular to the 2D plane, decreasing the heating temperature and increasing the viscosity of liquid PCM (e.g., by adding nanoparticles) reduce the discrepancy between 2D and 3D simulation results.

Direct simulation of evolution and control of three-dimensional instabilities in attachment-line boundary layers

1995 ◽  
Vol 291 ◽  
pp. 369-392 ◽  
Author(s):  
Ronald D. Joslin
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Plate Boundary ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Computationally Efficient ◽  
Simulation Results ◽  
Dimensional Simulation ◽  
Attachment Line

The spatial evolution of three-dimensional disturbances in an attachment-line boundary layer is computed by direct numerical simulation of the unsteady, incompressible Navier–Stokes equations. Disturbances are introduced into the boundary layer by harmonic sources that involve unsteady suction and blowing through the wall. Various harmonic-source generators are implemented on or near the attachment line, and the disturbance evolutions are compared. Previous two-dimensional simulation results and nonparallel theory are compared with the present results. The three-dimensional simulation results for disturbances with quasi-two-dimensional features indicate growth rates of only a few percent larger than pure two-dimensional results; however, the results are close enough to enable the use of the more computationally efficient, two-dimensional approach. However, true three-dimensional disturbances are more likely in practice and are more stable than two-dimensional disturbances. Disturbances generated off (but near) the attachment line spread both away from and toward the attachment line as they evolve. The evolution pattern is comparable to wave packets in flat-plate boundary-layer flows. Suction stabilizes the quasi-two-dimensional attachment-line instabilities, and blowing destabilizes these instabilities; these results qualitatively agree with the theory. Furthermore, suction stabilizes the disturbances that develop off the attachment line. Clearly, disturbances that are generated near the attachment line can supply energy to attachment-line instabilities, but suction can be used to stabilize these instabilities.

Impact of Cavity on Sunroof Buffeting: A Two Dimensional CFD Study

2004 ◽  
Author(s):  
Chang-Fa An ◽  
Seyed Mehdi Alaie ◽  
Michael S. Scislowicz
Keyword(s):  
Fluid Dynamics ◽  
Wind Tunnel ◽  
Three Dimensional ◽  
Leading Edge ◽  
Two Dimensional ◽  
Deep Insight ◽  
Simulation Results ◽  
Dimensional Simulation ◽  
The Impact ◽  
Insight Into

Driven by fluid dynamics principles, the concept for buffeting reduction, a cavity installed at the leading edge of the sunroof opening, is analyzed. The cavity provides a room to hold the vortex, shed from upstream, and prevents the vortex from escaping and from directly intruding into the cabin. The concept has been verified by means of a two dimensional simulation for a production SUV using the CFD software — FLUENT. The simulation results show that the impact of the cavity is crucial to reduce buffeting. It is shown that the buffeting level may be reduced by 3 dB by adding a cavity to the sunroof configuration. Therefore, the cavity could be considered as a means of buffeting reduction, in addition to the three currently-known concepts: wind deflector, sunroof glass comfort position and cabin venting. Thorough understanding of the buffeting mechanism helps explain why and how the cavity works to reduce buffeting. Investigation of the buffeting-related physics provides a deep insight into the flow nature and, therefore, a useful hint to geometry modification for buffeting reduction. The buffeting level may be further reduced by about 4 dB or more by cutting the corners of the sunroof opening into smooth ramps, guided by ideas coming from careful examining the physics of flow. More work including three dimensional simulation and wind tunnel experiment should follow in order to develop more confidence in the functionality of the cavity to hopefully promote this idea to the level that it can be utilized in a feasible way to address sunroof buffeting.

Design of finite-time guidance law based on observer and head-pursuit theory

2021 ◽  
pp. 095441002098456
Author(s):  
Chenqi Zhu
Keyword(s):  
Finite Time ◽  
Three Dimensional ◽  
Hypersonic Vehicle ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Reaching Law ◽  
Guidance Law ◽  
Fast Power ◽  
Simulation Results ◽  
Guidance Laws

In order to improve the guiding accuracy in intercepting the hypersonic vehicle, this article presents a finite-time guidance law based on the observer and head-pursuit theory. First, based on a two-dimensional model between the interceptor and target, this study applies the fast power reaching law to head-pursuit guidance law so that it can alleviate the chattering phenomenon and ensure the convergence speed. Second, target maneuvers are considered as system disturbances, and the head-pursuit guidance law based on an observer is proposed. Furthermore, this method is extended to a three-dimensional case. Finally, comparative simulation results further verify the superiority of the guidance laws designed in this article.

scholarly journals Analysis of spatial thermal field in a magnetic bearing

Open Physics ◽  
2018 ◽  
Vol 16 (1) ◽  
pp. 52-56
Author(s):  
Dawid Wajnert ◽  
Bronisław Tomczuk
Keyword(s):  
Temperature Field ◽  
Mathematical Models ◽  
Computer Simulations ◽  
Thermal Field ◽  
Three Dimensional ◽  
Magnetic Bearing ◽  
Field Analysis ◽  
Two Dimensional ◽  
Temperature Distributions ◽  
Dimensional Simulation

AbstractThis paper presents two mathematical models for temperature field analysis in a new hybrid magnetic bearing. Temperature distributions have been calculated using a three dimensional simulation and a two dimensional one. A physical model for temperature testing in the magnetic bearing has been developed. Some results obtained from computer simulations were compared with measurements.

A THREE-DIMENSIONAL SIMULATION OF BRITTLE SOLID FRACTURE

1996 ◽  
Vol 07 (05) ◽  
pp. 717-729 ◽  
Author(s):  
ALEXANDER V. POTAPOV ◽  
CHARLES S. CAMPBELL
Keyword(s):  
Three Dimensional ◽  
Three Dimensions ◽  
Size Distributions ◽  
Two Dimensional ◽  
Brittle Solid ◽  
Space Filling ◽  
Comparison With Experiment ◽  
Linear Dimensions ◽  
Dimensional Simulation ◽  
Simulated Material

This paper describes an extension into three dimensions of an existing two-dimensional technique for simulating brittle solid fracture. The fracture occurs on a simulated solid created by "gluing" together space-filling polyhedral elements with compliant interelement joints. Such a material can be shown to have well-defined elastic properties. However, the "glue" can only support a specified tensile stress and breaks when that stress is exceeded. In this manner, a crack can propagate across the simulated material. A comparison with experiment shows that the simulation can accurately reproduce the size distributions for all fragments with linear dimensions greater than three element sizes.

Stability of a compressible two-dimensional vortex under a three-dimensional perturbation

1984 ◽  
Vol 392 (1803) ◽  
pp. 279-299 ◽  
Keyword(s):  
Mach Number ◽  
Velocity Profile ◽  
Incompressible Flow ◽  
Compressible Fluid ◽  
Three Dimensional ◽  
Critical Value ◽  
Two Dimensional ◽  
Rankine Vortex ◽  
The Core ◽  
Critical Boundary

Kelvin showed that a two-dimensional vortex under a two-dimensional disturbance in incompressible flow responds at a discrete set of eigenvalues, which were found by Broadbent & Moore ( Phil. Trans. R. Soc. Lond. A 290, 353-371 (1979) to become unstable in a compressible fluid. It is now shown that three-dimensional perturbations are also unstable provided the wavelength is greater than some critical value that depends on the Mach number of the vortex. A critical boundary dividing stable from unstable modes is defined. Most of the results relate to a Rankine vortex, as in the previous work mentioned above, but some results are also given for a vortex with a different velocity profile within the core; qualitatively the same kind of behaviour is found.

Simulation of electromagnetic signal of profile observations from a drifting surface

2020 ◽  
Author(s):  
Polina S. Osipova ◽  
◽  
Arkadiy V. Zlobinskiy ◽  
Vladimir V. Potapov ◽  
◽  
...  
Keyword(s):  
Electric Dipole ◽  
Born Approximation ◽  
Three Dimensional ◽  
Arctic Region ◽  
The Arctic ◽  
Electromagnetic Signal ◽  
Simulation Results ◽  
Dimensional Simulation ◽  
The Arctic Region

As part of the RSF project, the use of a drifting surface on which geophysical installations will be placed is proposed to study the environment in the Arctic region. The proposed method of electrical exploration is sounding with a circular electric dipole as a source. Studying the applicability of the technique requires three–dimensional simulation of the received signal. The paper shows some simulation results using the previously proposed algorithm based on the Born approximation.

scholarly journals Influence of Electric Field Coupling Model on the Simulated Performances of a GaN Based Planar Nanodevice

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
K. Y. Xu ◽  
Z. N. Wang ◽  
Y. N. Wang ◽  
J. W. Xiong ◽  
G. Wang
Keyword(s):  
Electric Field ◽  
3D Model ◽  
Second Harmonic ◽  
Strong Electric Field ◽  
Three Dimensional ◽  
Harmonic Oscillation ◽  
Two Dimensional ◽  
Dc Bias ◽  
Simulation Results ◽  
2D Model

The performances of a two-dimensional electron gas (2DEG) based planar nanodevice are studied by a two-dimensional-three-dimensional (2D-3D) combined model and an entirely 2D model. In both models, 2DEGs are depicted by 2D ensemble Monte Carlo (EMC) method. However electric field distributions in the devices are obtained by self-consistently solving 2D and 3D Poisson equations for the 2D model and the 2D-3D model, respectively. Simulation results obtained by both models are almost the same at low bias while showing distinguished differences at high bias. The 2D model predicts larger output current and slightly higher threshold voltage of Gunn oscillations. Although the fundamental frequencies of current oscillations obtained by both models are similar, the deviation of wave shape from sinusoidal waveform obtained by the 2D model is more serious than that obtained by 2D-3D model. Moreover, results obtained by the 2D model are more sensitive both to the bias conditions and to the change of device parameters. Interestingly, a look-like second harmonic oscillation has been observed at DC bias. We contribute the origin of divergences in simulation results to the different coupling path of electric field in the two models. And the second-harmonic oscillations at DC bias should be the result of the appearance of concomitant oscillations beside the channel excited by strong electric-field effects.

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