Bubble Tracking Simulation of Cavitating Flow in an Atomization Nozzle

2002 ◽  
Author(s):  
Akira Sou ◽  
Shinichi Nitta ◽  
Tsuyoshi Nakajima
Keyword(s):  
Numerical Simulation ◽  
Pressure Distribution ◽  
Cavitation Bubble ◽  
Injection Pressure ◽  
Cavitating Flow ◽  
Experimental Result ◽  
Axisymmetric Nozzle ◽  
Cloud Cavitation ◽  
Vena Contracta ◽  
Bubble Clouds

Numerical simulation of transient cavitating flow in a axisymmetric nozzle was conducted in order to investigate the detailed motion of cavitation bubble clouds which may be dominant to atomization of a liquid jet. Two-way coupled bubble tracking technique was assigned in the present study to predict the unsteady cloud cavitation phenomena. Large Eddy Simulation (LES) was used to predict turbulent flow. Calculated pressure distribution and injection pressure were compared with measured ones. Then, calculated motion of cavitation bubble clouds was carefully investigated to understand the cavitation phenomena in a nozzle. As a result, the following conclusions were obtained: (1) Calculated result of pressure distribution along the wall, the relation between injection pressure vs. flow rate, and bubble distribution agreed with existing experimental result. (2) Cavitation bubble clouds were periodically shed from the tail of vena contracta, which usually formed by the coalescence of a few small bubble clouds. (3) Collapse of cavitation bubbles due to the re-entrant jet was observed in the numerical simulation.

scholarly journals THE NUMERICAL SIMULATION OF UNSTEADY CAVITATION EVOLUTION INDUCED BY PRESSURE WAVE

2014 ◽  
Vol 34 ◽  
pp. 1460374
Author(s):  
B.C. KHOO ◽  
J.G. ZHENG
Keyword(s):  
Numerical Simulation ◽  
Cavitation Bubble ◽  
Pressure Wave ◽  
External Perturbation ◽  
Compressible Liquid ◽  
Cavitating Flow ◽  
Bubble Collapse ◽  
Material Erosion ◽  
Noise Vibration ◽  
Compressibility Effects

The present study is focused on the numerical simulation of pressure wave propagation through the cavitating compressible liquid flow, its interaction with cavitation bubble and the resulting unsteady cavitation evolution. The compressibility effects of liquid water are taken into account and the cavitating flow is governed by one-fluid cavitation model which is based on the compressible Euler equations with the assumption that the cavitation is the homogeneous mixture of liquid and vapour which are locally under both kinetic and thermodynamic equilibrium. Several aspects of the method employed to solve the governing equations are outlined. The unsteady features of cavitating flow due to the external perturbation, such as the cavitation deformation and collapse and consequent pressure increase are resolved numerically and discussed in detail. It is observed that the cavitation bubble collapse is accompanied by the huge pressure surge of order of 100 bar, which is thought to be responsible for the material erosion, noise, vibration and loss of efficiency of operating underwater devices.

Numerical and Experimental Investigations of Cavitating Flow in a Vertical Multi-Hole Injector Nozzle

2010 ◽  
Author(s):  
Zhixia He ◽  
Jing Bai ◽  
Qian Wang ◽  
Qingmu Mu ◽  
Yunlong Huang
Keyword(s):  
Numerical Simulation ◽  
Numerical Models ◽  
Three Dimensional ◽  
Injection Pressure ◽  
Cavitating Flow ◽  
Critical Conditions ◽  
Experimental Investigations ◽  
Nozzle Flow ◽  
Cavitation Inception ◽  
Injector Nozzle

The presence of cavitation and turbulence in a diesel injector nozzle has significant effect on the subsequent spray characteristics. However, the mechanism of the cavitating flow and its effect on the subsequent spray is unclear because of the complexities of the nozzle flow, such as the cavitation phenomena and turbulence. A flow visualization experiment system with a transparent scaled-up vertical multi-hole injector nozzle tip was setup for getting the experimental data to make a comparison to validate the calculated results from the three dimensional numerical simulation of cavitating flow in the nozzle with mixture multi-phase cavitating flow model and good qualitative agreement was seen between the two sets of data. The critical conditions for cavitation inception were derived as well as the relationship between the discharge coefficient and non-dimensional cavitation parameter. After wards, the testified numerical models were used to analyze the effects of injection pressure, back pressure, cavitation parameter, Reynolds number, injector needle lift and needle eccentricity on the cavitating flow inside the nozzle. Combined with visual experimental results, numerical simulation results can clearly reveal the three-dimensional nature of the nozzle flow and the location and shape of the cavitation induced vapor distribution, which can help understand the nozzle flow better and eventually put forward the optimization ideas of diesel injectors.

Visual experiment and numerical simulation of cavitation instability in a high-speed inducer

2019 ◽  
Vol 234 (4) ◽  
pp. 470-480 ◽  
Author(s):  
Baoling Cui ◽  
Jie Chen
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Volume Fraction ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Design Flow ◽  
Local Pressure ◽  
Cloud Cavitation ◽  
Sheet Cavitation ◽  
Cavitation Instability

Cavitation instabilities in a high-speed inducer at a design flow rate were investigated for different cavitation numbers in numerical simulations and visual experiments. On the basis of a shear stress transport k–ω turbulence model and Zwart–Gerber–Belamri cavitation model, the transient cavitating flow in a high-speed centrifugal pump with an inducer is numerically simulated using ANSYS-CFX 15.0 software. Visual experiments were carried out to capture the evolution of cavitating flow in the inducer by using a high-speed camera. The performance and cavitation characteristic curves from numerical simulation agree with those from experiment. With a decreasing cavitation number, the cavitation development in the high-speed inducer goes through incipient cavitation, developing cavitation, critical cavitation, and deteriorated cavitation and presents vortex cavitation, sheet cavitation, cloud cavitation, backflow cavitation, and a cavitation surge. The region having a high vapor volume fraction basically coincides with the region of low local pressure at the same cavitation number. The position of largish blade loading on the inducer changes with the development of cavitation. A cavitation surge as one type of cavitation instability appears in the inducer at lower cavitation numbers. The drop or rise of the head coefficient is affected by an increasing or decreasing cavitation area in the cycle of a cavitation surge.

Numerical simulation of a vectored axisymmetric nozzle

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

Numerical Simulation of Cavitating Flow in a Francis Turbine

2008 ◽  
Author(s):  
Lingjiu Zhou ◽  
Zhengwei Wang ◽  
Yongyao Luo ◽  
Guangjie Peng
Keyword(s):  
Numerical Simulation ◽  
Transport Equation ◽  
Flow Rate ◽  
Suction Side ◽  
Cavitating Flow ◽  
Francis Turbine ◽  
Efficiency Change ◽  
Experiment Data ◽  
Calculation Results ◽  
Vapor Fraction

The 3-D unsteady Reynolds averaged Navier-tokes equations based on the pseudo-homogeneous flow theory and a vapor fraction transport-equation that accounts for non-condensable gas are solved to simulate cavitating flow in a Francis turbine. The calculation results agreed with experiment data reasonably. With the decrease of the Thoma number, the cavity first appears near the centre of the hub. At this stage the flow rate and the efficiency change little. Then the cavity near the centre of the hub grows thick and the cavities also appear on the blade suction side near outlet. With further reduce of the Thoma number the cavitation extends to the whole flow path, which causes flow rate and efficiency decrease rapidly.

scholarly journals Numerical Study of Pressure Attenuation Effect on Tunnel Structures Subjected to Blast Loads

2021 ◽  
Vol 11 (12) ◽  
pp. 5646
Author(s):  
Cheng-Wei Hung ◽  
Ying-Kuan Tsai ◽  
Tai-An Chen ◽  
Hsin-Hung Lai ◽  
Pin-Wen Wu
Keyword(s):  
Numerical Simulation ◽  
Orifice Plate ◽  
Experimental Result ◽  
Scale Model ◽  
Pressure Reduction ◽  
Expansion Chamber ◽  
Pressure Relief ◽  
Attenuation Effect ◽  
The One ◽  
Better Than

This study used experimental and numerical simulation methods to discuss the attenuation mechanism of a blast inside a tunnel for different forms of a tunnel pressure reduction module under the condition of a tunnel near-field explosion. In terms of the experiment, a small-scale model was used for the explosion experiments of a tunnel pressure reduction module (expansion chamber, one-pressure relief orifice plate, double-pressure relief orifice plate). In the numerical simulation, the pressure transfer effect was evaluated using the ALE fluid–solid coupling and mapping technique. The findings showed that the pressure attenuation model changed the tunnel section to diffuse, reduce, or detour the pressure transfer, indicating the blast attenuation effect. In terms of the effect of blast attenuation, the double-pressure relief orifice plate was better than the one-pressure relief orifice plate, and the single-pressure relief orifice plate was better than the expansion chamber. The expansion chamber attenuated the blast by 30%, the one-pressure relief orifice plate attenuated the blast by 51%, and the double-pressure relief orifice plate attenuated the blast by 82%. The blast attenuation trend of the numerical simulation result generally matched that of the experimental result. The results of this study can provide a reference for future protective designs and reinforce the U.S. Force regulations.

Numerical Simulation Study on High-Temperature Ventilated Cavitating Flow Considering the Compressibility of Gases

2012 ◽  
Vol 569 ◽  
pp. 395-399
Author(s):  
Jing Zhao ◽  
Guo Yu Wang ◽  
Yan Zhao ◽  
Yue Ju Liu
Keyword(s):  
Numerical Simulation ◽  
State Equation ◽  
Field Structure ◽  
Cavitating Flow ◽  
Simulation Approach ◽  
Gas Velocity ◽  
Simulation Data ◽  
Ventilated Cavity ◽  
Supercavitating Flow ◽  
Fluctuation Range

A numerical simulation approach of ventilated cavity considering the compressibility of gases is established in this paper, introducing the gas state equation into the calculation of ventilated supercavitating flow. Based on the comparison of computing results and experimental data, we analyzes the differences between ventilated cavitating flow fields with and without considered the compressibility of gases. The effect of ventilation on the ventilated supercavitating flow field structure is discussed considering the compressibility of gases. The results show that the simulation data of cavity form and resistance, which takes the compressibility of gases into account, accord well with the experimental ones. With the raising of ventilation temperature, the gas fraction in the front cavity and the gas velocity in the cavity increase, and the cavity becomes flat. The resistance becomes lower at high ventilation temperature, but its fluctuation range becomes larger than that at low temperature.

Numerical Simulation Study of Metal Transfer in MIG Welding with Magnetic Control

2014 ◽  
Vol 532 ◽  
pp. 545-548 ◽  
Author(s):  
Chao Yang ◽  
Shu Yuan Jiang ◽  
Hai Bo Bi
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Mathematical Model ◽  
Simulation Study ◽  
Electromagnetic Theory ◽  
Metal Transfer ◽  
Experimental Result ◽  
Magnetic Control ◽  
Mig Welding ◽  
Model Based

This paper simulate the mode of metal transfer in MIG magnetic control welding by using CFD software FLUENT, establishing mathematical model based on fluid dynamics and electromagnetic theory, and simulate the form, grow and drop process of metal transfer with and without magnetic. Meanwhile, do experiments to confirm the simulate result, and it is well consistent with the experimental result.

Behavior of Bubble in Small Water Tank Used for Food Processing Using Underwater Shock Wave

2011 ◽  
Vol 673 ◽  
pp. 225-230 ◽  
Author(s):  
Hideki Hamashima ◽  
Manabu Shibuta ◽  
Shigeru Itoh
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Food Processing ◽  
High Speed ◽  
Underwater Explosion ◽  
Video Camera ◽  
Experimental Result ◽  
Water Tank ◽  
Underwater Shock Wave ◽  
Small Water

The food processing technology using a shock wave can prevent deterioration of the food by heat because it can process food in a short time. Generally, since the shock wave used for food processing is generated by underwater explosion, the load of a shock wave to the food becomes very complicated. Therefore, in order to process safely, it is important to clarify the behaviors of the shock wave and the bubble pulse generated by underwater explosion. In this research, in order to investigate the behavior of the shock wave in the water tank used for food processing, the optical observation experiment and the numerical simulation were performed. In the experiment, the shock wave generated by underwater explosion was observed with the high-speed video camera. The numerical simulation about the behavior of bubble pulse was performed using analysis software LS-DYNA. Comparing and examining were performed about the experimental result and the numerical simulation result. The result of the numerical simulation about the behavior of the shock wave generated by underwater explosion and the shock wave generated by the bubble pulse and the bubble pulse was well in agreement with the experimental result.

scholarly journals Numerical Simulation and Experimental Study of Capacitive Imaging Technique as a Non-Destructive Testing Method

2021 ◽  
Author(s):  
Farima Abdollahi Mamoudan ◽  
Sebastien Savard ◽  
Tobin Filleter ◽  
Clemente Ibarra-Castanedo ◽  
Xavier Maldague
Keyword(s):  
Numerical Simulation ◽  
Surface Defects ◽  
Capacitive Sensor ◽  
Experimental Result ◽  
Destructive Testing ◽  
Fe Modelling ◽  
Inspection Method ◽  
Physical Experiments ◽  
Imaging Performance ◽  
Non Destructive

It was recently demonstrated that a co-planar capacitive sensor could be applied to the evaluation of materials without the disadvantages associated with the other techniques. This technique effectively detects changes in the dielectric properties of the materials due to, for instance, imperfections or variations in the internal structure, by moving a set of simple electrodes on the surface of the specimen. An AC voltage is applied to one or more electrodes and signals are detected by others. This is a promising inspection method for imaging the interior structure of the numerous materials, without the necessity to be in contact with the surface of the sample. In this paper, Finite Element (FE) modelling was employed to simulate the electric field distribution from a co-planar capacitive sensor and the way it interacts with a non-conducting sample. Physical experiments with a prototype capacitive sensor were also performed on a Plexiglas sample with sub-surface defects, to assess the imaging performance of the sensor. A good qualitative agreement was observed between the numerical simulation and experimental result.

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