Cavitation Bubble in Compressible Fluid Near the Rigid Wall Subjected to the Acoustic Wave with Arbitrary Incidence Angle in Three-Dimensional

2014 ◽  
Vol 31 (3) ◽  
pp. 307-318 ◽  
Author(s):  
X. Ye ◽  
X.-L. Yao ◽  
L.-Q. Sun ◽  
B. Wang
Keyword(s):  
Acoustic Wave ◽  
Cavitation Bubble ◽  
High Speed ◽  
Incidence Angle ◽  
Oscillation Amplitude ◽  
Three Dimensional ◽  
Sound Field ◽  
Rigid Wall ◽  
Boundary Integral ◽  
Three Dimensional Model

AbstractA balanced cavitation bubble is released near the rigid wall in the sound field generated by the incidence plane wave and its reflecting wave. With the modified boundary integral equation, the dynamics of bubble is solved considering the compressibility of fluid in this paper. Also the Bernoulli equation as the boundary condition for cavitation bubble in sound field is deduced using Euler equation. Since the arbitrary incidence angle of acoustic wave, the three-dimensional model is utilized. The bubble will expand or contract at first according to the initial phase of acting acoustic pressure on bubble surface. And during the contraction phase, the liquid jet with high speed will be generated pointing to rigid wall but be deflected to the incidence direction of acoustic wave. The oblique degree of jet will be affected by the incidence angle and initial distance between bubble center and rigid wall. The oscillation amplitude of bubble will be affected by the incidence amplitude and incidence frequency, but be limited by the rigid wall. Since the compressibility of fluid, the perturbation will propagate to the far-field. Thus the oscillation amplitude of bubble will be reduced.

CFD Simulation of Particle Transport and Dispersion in Indoor Environment by Human Walking

2012 ◽  
Author(s):  
Iman Goldasteh ◽  
Goodarz Ahmadi ◽  
Andrea Ferro
Keyword(s):  
Particulate Matter ◽  
High Speed ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Study Data ◽  
Turbulent Dispersion ◽  
Experimental Chamber ◽  
Indoor Environments ◽  
Three Dimensional Model ◽  
Particle Resuspension

Particle resuspension is an important source of particulate matter in indoor environments that significantly affects the indoor air quality and could potentially have adverse effect on human health. Earlier efforts to investigate indoor particle resuspension hypothesized that high speed airflow generated at the floor level during the gate cycle is the main cause of particle resuspension. The resuspended particles are then assumed to be dispersed by the airflow in the room, which is impacted by both the ventilation and the occupant movement, leading to increased PM concentration. In this study, a three dimensional model of a room was developed using FLUENT™ CFD package. A RANS approach with the RNG k-ε turbulence model was used for simulating the airflow field in the room for different ventilation conditions. The trajectories of resuspended particulate matter were computed with a Lagrangian method by solving the equations of particle motion. The effect of turbulent dispersion was included with the use of the eddy lifetime model. The resuspension of particles due to gait cycle was estimated and included in the computational model. The dispersion and transport of particles resuspended from flooring as well as particle re-deposition on flooring and walls were simulated. Particle concentrations in the room generated by the resuspension process were evaluated and the results were compared with experimental chamber study data as well as simplified model predictions, and good agreement was found.

Analysis and Research of High Speed Milling of Thin-Walled Bracket Part Based on UG NX

2010 ◽  
Vol 129-131 ◽  
pp. 256-260
Author(s):  
Yi Shu Hao ◽  
Chuang Hai ◽  
Xin Xing Zhu
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Structural Features ◽  
Milling Process ◽  
Analysis Method ◽  
Three Dimensional Model ◽  
Machining Processes ◽  
Element Analysis ◽  
High Speed Milling ◽  
Tool Paths

Treating high speed milling theory as the guidance, this paper researched high speed milling process of bracket part based on UG NX. Combined with the structural features of bracket part, three dimensional model is built by UG NX CAD and machining processes are worked out after analysis. UG CAM module was applied to fabricate tool paths. At last, finite element analysis method is introduced to study the processing deformation by UG NX NASTRAN module, based on which measures to restrain processing deformations is advanced and processing sequences are optimized.

Investigation of Dynamic Photoelasticity Based on a Three-Dimensional Model

2011 ◽  
Vol 83 ◽  
pp. 261-266
Author(s):  
Bin Li ◽  
Guo Biao Yang ◽  
Fan Ni ◽  
Qi Rong Zhu
Keyword(s):  
Boundary Conditions ◽  
High Speed ◽  
Three Dimensional ◽  
Green Laser ◽  
Structure Design ◽  
Dynamic Photoelasticity ◽  
Three Dimensional Model ◽  
Design And Optimization ◽  
True Value ◽  
Dimensional Models

Dynamic photoelasticity has been widely utilized to investigate the phenomena generated by impact loading. The dynamic parameters of structures, such as propagation of stress wave and stress concentration, are obtained through this method, which provide guidelines for structure design and optimization. In the previous studies, two-dimensional models are wildly used by researchers. In these models, the inaccuracy of the boundary conditions leads to error amplification during the conversion of the tested results into real ones. In this study of dynamic photoelasticity, three-dimensional models are used. An improved digital dynamic photoelastic system is also adopted to calculate elastic wave propagation in the medium, where the diode-pumped solid-state green laser and high-speed CCD are used as light source luminaries and recording system respectively. Based on these models, where the boundary conditions approach to true value, the resulting data are higher in resolution than is possible with other experimental techniques. This method has been adopted and tested successfully by generating better results with less amplification of errors.

Fragmentation of acoustically levitating droplets by laser-induced cavitation bubbles

2016 ◽  
Vol 805 ◽  
pp. 551-576 ◽  
Author(s):  
Silvestre Roberto Gonzalez Avila ◽  
Claus-Dieter Ohl
Keyword(s):  
Shock Wave ◽  
Experimental Study ◽  
Surface Tension ◽  
Cavitation Bubble ◽  
High Speed ◽  
Size Range ◽  
Sound Field ◽  
Negative Pressures ◽  
Impulsive Pressure ◽  
Small Bubbles

We report on an experimental study on the dynamics and fragmentation of water droplets levitated in a sound field exposed to a single laser-induced cavitation bubble. The nucleation of the cavitation bubble leads to a shock wave travelling inside the droplet and reflected from pressure release surfaces. Experiments and simulations study the location of the high negative pressures inside the droplet which result into secondary cavitation. Later, three distinct fragmentation scenarios are observed: rapid atomization, sheet formation and coarse fragmentation. Rapid atomization occurs when the expanding bubble, still at high pressure, ruptures the liquid film separating the bubble from the surrounding air and a shock wave is launched into the surrounding air. Sheet formation occurs due to the momentum transfer of the expanding bubble; for sufficiently small bubbles, the sheet retracts because of surface tension, while larger bubbles may cause the fragmentation of the sheet. Coarse fragmentation is observed after the first collapse of the bubble, where high-speed jets emanate from the surface of the droplet. They are the result of surface instability of the droplet combined with the impulsive pressure generated during collapse. A parameter plot for droplets in the size range between 0.17 and 1.5 mm and laser energies between 0.2 and 4.0 mJ allows the separation of these three regimes.

Numerical Study of the Pusher-Type Billet Reheating Furnace

2005 ◽  
Author(s):  
Linjiang Zou ◽  
Chaoxiang Li ◽  
Yinmei Yuan ◽  
Wei Guo ◽  
Fan Yang ◽  
...  
Keyword(s):  
Software Package ◽  
High Speed ◽  
Gas Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cfd Model ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Iron And Steel ◽  
Reheating Furnace

In the present work, a commercial CFD software package, FLUENT, was used to develop a three-dimensional model of pusher-type billet reheating furnace for the second high speed wire rod plant of XiangTan Iron and steel Co. Ltd. The purpose of the study was to gain a better understanding of the gas flow and velocity and pressure distribution in the furnace. The results show that the numerical results are in agreement with the practice and the characteristics of the furnace configuration. The CFD model can be used to improve the performance and structure by analyzing and studying the behavior of the reheating furnace.

Influence Characteristics of Tool Vibration and Wear on Machined Surface Topography in High-Speed Milling

2014 ◽  
Vol 800-801 ◽  
pp. 585-589
Author(s):  
Bin Jiang ◽  
Guang Lei Cao ◽  
Ming Hui Zhang ◽  
Shou Zheng Sun ◽  
Xuan Chi Liu
Keyword(s):  
Tool Wear ◽  
Surface Topography ◽  
High Speed ◽  
Three Dimensional ◽  
Cutting Parameters ◽  
Three Dimensional Model ◽  
Machined Surface ◽  
Tool Vibration ◽  
Key Factor ◽  
Vibration Measuring

Existing research on machined surface topography, only consider its response to vibration or wear certain factors, both vibration and wear impact on machined surface topography exist ambiguity and uncertainty, it cannot solve the design conflicts of machined surface topography. For this, this paper analyzes blade installation error, tool wear, vibration and deformation to reveal effects of tip space trajectory, build a three-dimensional model of machined surface topography in simulation, extract its characteristic parameters, by simulation of different amplitudes and wear, found that axis amplitude is a key factor affecting surface residual height, flank wear affects contour distribution distance significantly, by specimen milling experiments, use vibration measuring instrument and ultra-depth microscopy to obtain vibration, wear characteristics and machined surface topography parameters under different cutting parameters, then use the gray system theory to get correlation analysis of the test data, results showed that the influence of tool wear on machined surface topography is prominent than tool vibration.

The Influence of Internal Friction on the Stability of High Speed Rotors With Anisotropic Supports

1969 ◽  
Vol 91 (4) ◽  
pp. 1105-1113 ◽  
Author(s):  
E. J. Gunter ◽  
P. R. Trumpler
Keyword(s):  
Internal Friction ◽  
High Speed ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Analog Computer ◽  
Three Dimensional Model ◽  
Stiffness Properties ◽  
Stiffness Characteristics ◽  
The Stability ◽  
Internal Rotor

This paper evaluates the stability of the single mass rotor with internal friction on damped, anisotropic supports. The paper shows under what conditions the rotor stability may be improved by an undamped support with anisotropic stiffness properties. A three dimensional model is presented to show the influence of rotor and support stiffness characteristics on stability. Curves are also presented on how support damping may also improve or even reduce rotor stability. An analog computer solution of the governing equations of motion is presented showing the shaft transient motion for various speed ranges, and also plots of the rotor steady state motion are given for various speeds up to and including the stability threshold. The analysis is used to explain many of the experimental observations of B. L. Newkirk concerning stability due to internal rotor friction.

Based on Pro/E High Speed Milling of Thin-Walled Stents of Research

2011 ◽  
Vol 295-297 ◽  
pp. 2487-2491
Author(s):  
Jian Qiang Wang
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Structural Features ◽  
Milling Process ◽  
Analysis Method ◽  
Three Dimensional Model ◽  
Machining Processes ◽  
Element Analysis ◽  
High Speed Milling ◽  
Tool Paths

Treating high speed milling theory as the guidance, this paper researched high speed milling process of bracket part based on Pro/E. Combined with the structural features of bracket part, three dimensional model is built by Pro/E and machining processes are worked out after analysis. Pro/E module was applied to fabricate tool paths. At last, finite element analysis method is introduced to study the processing deformation by Pro/E module, based on which measures to restrain processing deformations is advanced and processing sequences are optimized.

Quasi-three-dimensional simulation of crescent-shaped waves

2020 ◽  
Author(s):  
Alexander Dosaev ◽  
Yuliya Troitskaya
Keyword(s):  
Water Waves ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Rogue Waves ◽  
Boundary Integral ◽  
Main Direction ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Wave Interactions

<p>Many features of nonlinear water wave dynamics can be explained within the assumption that the motion of fluid is strictly potential. At the same time, numerically solving exact equations of motion for a three-dimensional potential flow with a free surface (by means of, for example, boundary integral method) is still often considered too computationally expensive, and further simplifications are made, usually implying limitations on wave steepness. A quasi-three-dimensional model, put forward by V. P. Ruban [1], represents another approach at reducing computational cost. It is, in its essence, a two-dimensional model, formulated using conformal mapping of the flow domain, augmented by three-dimensional corrections. The model assumes narrow directional distribution of the wave field and is exact for two-dimensional waves. It was successfully applied by its author to study a nonlinear stage of of Benjamin-Feir instability and rogue waves formation.</p><p>The main aim of the present work is to explore the behaviour of the quasi-three-dimensional model outside the formal limits of its applicability. From the practical point of view, it is important that the model operates robustly even in the presence of waves propagating at large angles to the main direction (although we do not attempt to accurately describe their dynamics). We investigate linear stability of Stokes waves to three-dimensional perturbations and suggest a modification to the original model to eliminate a spurious zone of instability in the vicinity of the perpendicular direction on the perturbation wavenumber plane. We show that the quasi-three-dimensional model yields a qualitatively correct description of the instability zone generated by resonant 5-wave interactions. The values of the increment are reasonably close to those obtained from the exact equations of motion [2], despite the fact that the corresponding modes of instability consist of harmonics that are relatively far from the main direction. Resonant 5-wave interactions are known to manifest themselves in the formation of the so-called “horse-shoe” or “crescent-shaped” wave patterns, and the quasi-three-dimensional model exhibits a plausible dynamics leading to formation of crescent-shaped waves.</p><p>This research was supported by RFBR (grant No. 20-05-00322).</p><p>[1] Ruban, V. P. (2010). Conformal variables in the numerical simulations of long-crested rogue waves. <em>The European Physical Journal Special Topics</em>, <em>185</em>(1), 17-33.</p><p>[2] McLean, J. W. (1982). Instabilities of finite-amplitude water waves. <em>Journal of Fluid Mechanics</em>, <em>114</em>, 315-330.</p>

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