Numerical Simulation of the Micro-Jet Velocity and Cavitation-Erosion on an Axisymmetric Nozzle

2018 ◽  
pp. 805-808
Keyword(s):  
Numerical Simulation ◽  
Cavitation Erosion ◽  
Axisymmetric Nozzle ◽  
Jet Velocity

Numerical simulation of a vectored axisymmetric nozzle

2020 ◽  
Author(s):  
Roberto Marsilio ◽  
Michele Ferlauto ◽  
M. Hadi Hamedi-Estakhrsar
Keyword(s):  
Numerical Simulation ◽  
Axisymmetric Nozzle

scholarly journals Estimation of High-Speed Liquid-Jet Velocity Using a Pyro Jet Injector

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Naohisa Takagaki ◽  
Toru Kitaguchi ◽  
Masashi Iwayama ◽  
Atsushi Shinoda ◽  
Hiroshige Kumamaru ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Liquid Jet ◽  
Liquid Density ◽  
Liquid Viscosity ◽  
Ejection Velocity ◽  
Piston Motion ◽  
Ansys Fluent ◽  
Piston Displacement ◽  
Jet Velocity

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.

Numerical Simulation on Micromixer Based on Syntehtic Jet

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.

scholarly journals Numerical Simulation of Cavitation and Aeration in Discharge Gated Tunnel of a Dam Based on the VOF Method

2011 ◽  
Vol 110-116 ◽  
pp. 2754-2761
Author(s):  
Razieh Jalalabadi ◽  
Norouz Mohammad Nouri
Keyword(s):  
Numerical Simulation ◽  
Cavitation Erosion ◽  
Vof Method ◽  
Bubbly Flows ◽  
Hydraulic Structures ◽  
Cavitating Flows ◽  
Effective Protection ◽  
Two Phase ◽  
Cavitation Inception ◽  
Numerical Studies

Cavitation, usually known as a destructive phenomenon, involves turbulent unsteady two-phase flow. Having such features, cavitating flows have been turned to a challenging topic in numerical studies and many researches are being done for better understanding of bubbly flows and proposing solutions to reduce its consequent destructive effects. Aeration may be regarded as an effective protection against cavitation erosion in many hydraulic structures, like gated tunnels. The paper concerns numerical simulation of flow in discharge gated tunnel of a dam using RNG model coupled with the volume of fluid (VOF) method and the zone which is susceptible of cavitation inception in the tunnel is predicted. Then a vent is considered in the mentioned zone for aeration and the numerical simulation is done again to study the effects of aeration. The results show that aeration is an impressively useful method to exclude cavitation in mentioned tunnels.

scholarly journals Assessment of different turbulence models in simulating axisymmetric flow in suddenly expanded nozzles

2018 ◽  
Vol 7 (3.29) ◽  
pp. 243
Author(s):  
Sher Afghan Khan ◽  
Mir Owais Ali ◽  
Miah Mohammed Riyadh ◽  
Zahid Hossen ◽  
Nafis Mahdi Arefin
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Mach Number ◽  
Numerical Simulations ◽  
Axisymmetric Flow ◽  
Turbulence Models ◽  
Experimental Results ◽  
Nozzle Flow ◽  
Axisymmetric Nozzle ◽  
Good Agreement

A numerical simulation was carried out to compare various turbulence models simulating axisymmetric nozzle flow past suddenly expanded ducts. The simulations were done for L/D = 10. The convergent-divergent nozzle has been modeled and simulated using the turbulence models: The Standard k-ε model, The Standard k-ω model and The SST k-ω model. Numerical simulations were done for Mach numbers 1.87, 2.2, and 2.58 and the nozzles were operated for NPRs in the range from 3 to 11. From the numerical analysis it is apparent that for a given Mach number and effect of NPR will result in maximum gain or loss of pressure. Numerical results are in good agreement with the experimental results.  

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

2013 ◽  
Vol 461 ◽  
pp. 725-730 ◽  
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.

scholarly journals Numerical Simulation of Hydraulic Characteristics in A Vortex Drop Shaft

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1393 ◽  
Author(s):  
Wenchuan Zhang ◽  
Junxing Wang ◽  
Chuangbing Zhou ◽  
Zongshi Dong ◽  
Zhao Zhou
Keyword(s):  
Numerical Simulation ◽  
Cavitation Erosion ◽  
Flow Characteristics ◽  
Vertical Shaft ◽  
Hydraulic Characteristics ◽  
Drop Shaft ◽  
New Type ◽  
Velocity Pressure ◽  
Inflow Conditions ◽  
Shaft Wall

A new type of vortex drop shaft without ventilation holes is proposed to resolve the problems associated with insufficient aeration, negative pressure (Unless otherwise specified, the pressure in this text is gauge pressure and time-averaged pressure) on the shaft wall and cavitation erosion. The height of the intake tunnel is adjusted to facilitate aeration and convert the water in the intake tunnel to a non-pressurized flow. The hydraulic characteristics, including the velocity (Unless otherwise specified, the velocity in this text is time-averaged velocity), pressure and aeration concentration, are investigated through model experiment and numerical simulation. The results revealed that the RNG k-ε turbulence model can effectively simulate the flow characteristics of the vortex drop shaft. By changing the inflow conditions, water flowed into the vertical shaft through the intake tunnel with a large amount of air to form a stable mixing cavity. Frictional shearing along the vertical shaft wall and the collisions of rotating water molecules caused the turbulence of the flow to increase; the aeration concentration was sufficient, and the energy dissipation effect was excellent. The cavitation number indicated that the possibility of cavitation erosion was small. The results of this study provide a reference for the analysis of similar spillways.

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

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.

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

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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