Numerical simulation of the cavitation micro–jet velocity and erosion on a plane–convex hydrofoil with semicylindrical obstacle

AbstractThe high-speed liquid-jet velocity achieved using an injector strongly depends on the piston motion, physical property of the liquid, and container shape of the injector. Herein, we investigate the liquid ejection mechanism and a technique for estimating the ejection velocity of a high-speed liquid jet using a pyro jet injector (PJI). We apply a two-dimensional numerical simulation with an axisymmetric approximation using the commercial software ANSYS/FLUENT. To gather the input data applied during the numerical simulation, the piston motion is captured with a high-speed CMOS camera, and the velocity of the piston is measured using motion tracking software. To reproduce the piston motion during the numerical simulation, the boundary-fitted coordinates and a moving boundary method are employed. In addition, we propose a fluid dynamic model (FDM) for estimating the high-speed liquid-jet ejection velocity based on the piston velocity. Using the FDM, we consider the liquid density variation but neglect the effects of the liquid viscosity on the liquid ejection. Our results indicate that the liquid-jet ejection velocity estimated by the FDM corresponds to that predicted by ANSYS/FLUENT for several different ignition-powder weights. This clearly shows that a high-speed liquid-jet ejection velocity can be estimated using the presented FDM when considering the variation in liquid density but neglecting the liquid viscosity. In addition, some characteristics of the presented PJI are observed, namely, (1) a very rapid piston displacement within 0.1 ms after a powder explosion, (2) piston vibration only when a large amount of powder is used, and (3) a pulse jet flow with a temporal pulse width of 0.1 ms.

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Numerical Simulation on Micromixer Based on Syntehtic Jet

ASME 5th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2007-30110 ◽

2007 ◽

Author(s):

M. H. Liu ◽

X. F. Zhang ◽

X. D. Cai ◽

Y. L. Chen

Keyword(s):

Numerical Simulation ◽

Numerical Simulations ◽

Rectangular Channel ◽

Synthetic Jet ◽

Mixing Efficiency ◽

Mixing Index ◽

Inlet Velocity ◽

Velocity Magnitude ◽

Jet Velocity

This paper studied a concept of micromixer with a synthetic jet placed at the bottom of a rectangular channel. Due to periodic ejections from and suctions into the channel, the fluids are mixed effectively. To study the effects of the inlet velocity, the jet intensity and frequency, and the jet location on the mixing efficiency, 3-D numerical simulations of the micromixer have been carried out. It has been found that when the jet intensity and the frequency are fixed, the mixing efficiency increases when Re<50, and decreases when Re>50 with the best mixing efficiency achieved at Re=50. When the ratio of the jet velocity magnitude to the inlet velocity is taken as 10 and the jet frequency is 100Hz, the mixing index reaches the highest value. It has also been found that to get better mixing efficiency, the orifice of the synthetic jet should be asymmetrically located away from the channel’s centerline.

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Influence of Jet Hole Configuration on Drag Reduction of Bionic Jet Surface

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.461.725 ◽

2013 ◽

Vol 461 ◽

pp. 725-730 ◽

Cited By ~ 3

Author(s):

Yun Qing Gu ◽

Jing Ru ◽

Zhao Gang ◽

Zhao Yuan Li ◽

Wen Bo Liu ◽

...

Keyword(s):

Numerical Simulation ◽

Flow Field ◽

Drag Reduction ◽

Reduction Rate ◽

Experimental Tests ◽

Isosceles Triangle ◽

Hole Configuration ◽

Field Velocity ◽

Jet Velocity ◽

Reduction Characteristics

According to the jet hole configuration mode of bionic jet surface and its influence on the drag reduction, as the basic form of jet hole configuration is the isosceles triangle elements, so this was used to establish the computational model of jet hole configuration. In this case, the height and base of the triangles were considered as variable. The SST k-ω turbulence model was used to simulate and research the drag reduction characteristics of bionic jet surface in different configuration modes of jet holes at the main flow field velocity value of 20m/s and the jet velocity value of 0.4~2.0m/s. Also the influence of different configurations of height and base on drag reduction characteristics of bionic jet surface was studied, which got the optimum size of jet hole configuration. Results show that in triangle configuration elements, the drag reduction characteristics of bionic jet surface can be influenced by the jet hole of different configurations of height and base; the drag reduction of bionic jet surface reaches the peak of 32.74% at 8mm height, 11mm base, and the jet velocity value of 2.0m/s. At the same flow field velocity, the drag reduction rate results achieved by experimental tests and by numerical simulation were changing consistently and were found same, which verifies correctness of numerical simulation results.

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Numerical study on edge tone with compressible direct numerical simulation: Sound intensity and jet motion

International Journal of Aeroacoustics ◽

10.1177/1475472x211003296 ◽

2021 ◽

pp. 1475472X2110032

Author(s):

Sho Iwagami ◽

Ryoya Tabata ◽

Taizo Kobayashi ◽

Yuji Hattori ◽

Kin’ya Takahashi

Keyword(s):

Numerical Simulation ◽

Direct Numerical Simulation ◽

Transition Region ◽

Power Law ◽

Numerical Study ◽

Sound Intensity ◽

Mode Transition ◽

The Third ◽

Velocity Variance ◽

Jet Velocity

A two-dimensional model of the edge tone is studied by a highly accurate and reliable method of direct numerical simulation of the compressible Navier-Stokes equations, and used to verify key features observed in previous experimental and numerical studies, and to discover new features related to the jet motion and the edge tone generation mechanism. The first and second modes of the edge tone that are numerically reproduced agree well with Brown’s equation. In the mode transition region, dynamical mode transition is observed at a fixed jet velocity. For both first and second modes, the pressure distributions are antisymmetric with respect to the edge plate, and the sound intensity is proportional to the fifth power of the jet velocity. These results are consistent with the edge tone being radiated from a dipole-like source. Spatial profiles of the velocity and the velocity variance of the oscillating jet are also investigated for each mode over a range of the jet velocity including the mode transition regime. The amplitude of the velocity oscillation becomes constant with increasing jet velocity, while a measure of the amplitude of the velocity variance profile, which is introduced to characterize the strength of the jet fluctuation and named the ’fluctuation strength’, is proportional to the third power of the jet velocity. Some properties of the fluctuation strength correspond to properties of the sound intensity, including the first mode having larger amplitude than the second mode, and the way of deviating from the power law at smaller values of jet velocity and in the mode transition region. It is proposed that the third-power law exhibited by behavior of the fluctuation strength could be related to the increase of the skewness observed in the velocity profile with increase of jet velocity, and a model calculation is used to support this proposal.

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The Numerical Simulation and Research and Application of Energy-Saving Effect of Hot Air Curtain Jet Velocity of the Dining Room

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.919-921.1744 ◽

2014 ◽

Vol 919-921 ◽

pp. 1744-1747

Author(s):

Kun Ru Ma ◽

Xin Wang

Keyword(s):

Numerical Simulation ◽

Energy Saving ◽

Physical Model ◽

Outdoor Air ◽

Air Curtain ◽

Hot Air ◽

Jet Velocity ◽

Dining Room ◽

Set Up ◽

Saving Effect

There are often people and goods in and out of the dinning room door, so the door is often open. Heating and air conditioning construction to save energy and to prevent the outdoor air form influencing on indoor environment, set up the air curtain at the entrance of the dinning room to stop outdoor air, the frequently-used air curtain is beam type of air curtain.The project in view of the dinning room of the new campus of hebei university of science and technology, sets up air curtain physical model of the ground floor dining room door at the first area, and carry on reasonable simplification, make sure the numerical simulation calculation area and the sealing condition of air curtain. Then set up physical model for wind pressure, multiply of hot pressure and the local hot pressure at the dinning room door of the air curtain air flow in CFD method. Through the numerical simulation for different jet velocity of the hot air curtain, analysis the temperature field, velocity field, heat loss,heat load parameter, etc. and demonstrate the energy saving effect, and provide reference basis for the selection of air curtain.

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Direct numerical simulation of round turbulent jets in crossflow

Journal of Fluid Mechanics ◽

10.1017/s0022112006004034 ◽

2007 ◽

Vol 574 ◽

pp. 59-84 ◽

Cited By ~ 112

Author(s):

SUMAN MUPPIDI ◽

KRISHNAN MAHESH

Keyword(s):

Numerical Simulation ◽

Kinetic Energy ◽

Direct Numerical Simulation ◽

Near Field ◽

Leading Edge ◽

Turbulent Jets ◽

Energy Budgets ◽

Mean Velocity ◽

Field Peak ◽

Jet Velocity

Direct numerical simulation is used to study a round turbulent jet in a laminar crossflow. The ratio of bulk jet velocity to free-stream crossflow velocity is 5.7 and the Reynolds number based on the bulk jet velocity and the jet exit diameter is 5000. The mean velocity and turbulent intensities from the simulations are compared to data from the experiments by Su & Mungal (2004) and good agreement is observed. Additional quantities, not available from experiments, are presented. Turbulent kinetic energy budgets are computed for this flow. Examination of the budgets shows that the near field is far from a state of turbulent equilibrium – especially along the jet edges. Also – in the near field – peak kinetic energy production is observed close to the leading edge, while peak dissipation is observed toward the trailing edge of the jet. The results are used to comment upon the difficulty involved in predicting this flow using RANS computations. There exist regions in this flow where the pressure transport term, neglected by some models and poorly modelled by others, is significant. And past the jet exit, the flow is not close to established canonical flows on which most models appear to be based.

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Numerical Simulation of the Air-Assisted Boom Spraying and Droplets Transporting Process

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.516-517.769 ◽

2012 ◽

Vol 516-517 ◽

pp. 769-772 ◽

Cited By ~ 1

Author(s):

Juan Juan Zhang ◽

Jun Feng Wang ◽

Wen Long Mao ◽

Feng Gu ◽

Yuan Ping Huo

Keyword(s):

Numerical Simulation ◽

Two Phase Flow ◽

Flow Fields ◽

Phase Flow ◽

Crop Canopy ◽

Two Phase ◽

Air Jet ◽

Drift Potential ◽

Jet Velocity

The conflict between increasing the deposition on target and reducing off-target losses in conventional pesticide spraying is an issue. It has been confirmed that air-assisted spraying can effectively reduce the drift compared to the conventional spraying. The work presented here reports on the numerical simulation of an air-assisted boom spraying and droplets transporting process. The purpose of this study is to understand the gas and droplet two-phase flow fields and analyze the spraying distribution and droplets transporting under the different given operations of air assistance. The air-assisted spraying drift potential decreases with air-jet velocity. As the air-jet velocity is higher than 25m/s, the accretion of droplets on the upper surface of crop canopy focus on narrow areas. Air -assistance can reduce the drift of small droplets (50-200μm) effectively. In all cases, the angle between the air-jet and the nozzle is 0° or10°.

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