scholarly journals Numerical Study of Sheet Cavitation Breakoff Phenomenon on a Cascade Hydrofoil

2003 ◽  
Vol 125 (4) ◽  
pp. 643-651 ◽  
Author(s):  
Yuka Iga ◽  
Motohiko Nohmi ◽  
Akira Goto ◽  
Byeong Rog Shin ◽  
Toshiaki Ikohagi
Keyword(s):  
Numerical Study ◽  
Dominant Role ◽  
Homogeneous Model ◽  
Cavity Surface ◽  
Cavity Flows ◽  
Two Phase ◽  
Sheet Cavitation ◽  
Phase Medium ◽  
Flow Through ◽  
Locally Homogeneous

Two-dimensional unsteady cavity flow through a cascade of hydrofoils is numerically calculated. Particular attention is focused on instability phenomena of a sheet cavity in the transient cavitation condition, and the mechanism of the breakoff phenomenon is examined. TVD-MacCormack’s scheme employing a locally homogeneous model of compressible gas-liquid two-phase medium is applied to analyze the cavity flows. The present method permits us to treat the entire cavitating/noncavitating unsteady flowfield. By analyzing the numerical results in detail, it becomes clear that there are at least two mechanisms in the breakoff phenomenon of the sheet cavity: one is that re-entrant jets play a dominant role in such a breakoff phenomenon, and the other is that pressure waves propagating inside the cavity bring about another type of breakoff phenomenon accompanying with cavity surface waves.

Numerical Analysis of Cavitation Instabilities Arising in the Three-Blade Cascade

2004 ◽  
Vol 126 (3) ◽  
pp. 419-429 ◽  
Author(s):  
Yuka Iga ◽  
Motohiko Nohml ◽  
Akira Goto ◽  
Toshiaki Ikohagi
Keyword(s):  
Numerical Method ◽  
High Speed ◽  
Homogeneous Model ◽  
Rotating Stall ◽  
Two Phase ◽  
Wide Range ◽  
Phase Medium ◽  
Long Time ◽  
Entire Flow ◽  
Locally Homogeneous

Three types of cavitation instabilities through flat plate cascades, which are similar to “forward rotating cavitation,” “rotating-stall cavitation” and “cavitation surge” occurring in high-speed rotating fluid machinery, are represented numerically under the three-blade cyclic condition. A numerical method employing a locally homogeneous model of compressible gas-liquid two-phase medium is applied to solve the above flow fields, because this permits the entire flow field inside and outside the cavity to be treated through only one system of governing equations. In addition, the numerical method suites to analyze unsteady cavitating flow with a long time evolution. From the calculated results of the present numerical simulation with wide range of cavitation number and flow rate, we obtain a cavitation performance curve of the present three-blade cyclic cascade, analyze the aspects of unsteady cavitation, and discuss the characteristics and mechanisms of cavitation.

Numerical study on two-phase flow through fractured porous media

2011 ◽  
Vol 54 (9) ◽  
pp. 2412-2420 ◽  
Author(s):  
ZhaoQin Huang ◽  
Jun Yao ◽  
YueYing Wang ◽  
Ke Tao
Keyword(s):  
Porous Media ◽  
Two Phase Flow ◽  
Numerical Study ◽  
Fractured Porous Media ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through

Experimental Characterization of Two-Phase Flow Through Valves Applied to Liquid-Assisted Gas-Lift

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Renato P. Coutinho ◽  
Paulo J. Waltrich ◽  
Wesley C. Williams ◽  
Parviz Mehdizadeh ◽  
Stuart Scott ◽  
...  
Keyword(s):  
Water Flow ◽  
Two Phase Flow ◽  
Numerical Study ◽  
Water Flow Rate ◽  
Phase Flow ◽  
Experimental Characterization ◽  
Two Phase ◽  
Flow Through ◽  
Gas Lift

Abstract Liquid-assisted gas-lift (LAGL) is a recently developed concept to unload wells using a gas–liquid fluid mixture. The success deployment of the LAGL technology is related to the behavior of two-phase flow through gas-lift valves. For this reason, this work presents an experimental and numerical study on two-phase flow through orifice gas-lift valves used in liquid-assisted gas-lift unloading. To the knowledge of the authors, there is no investigation in the literature on experimental characterization of two-phase flow through gas-lift valves. Experimental data are presented for methane-water flow through gas-lift valves with different orifice port sizes: 12.7 and 17.5 mm. The experiments were performed for pressures ranging from 1.00 to 9.00 MPa, gas flow rates from 0 to 4.71 m3/h, and water flow rate from 0 to 0.68 m3/min. The experimental results are compared to numerical models published in the literature for two-phase flow through restrictions and to commercial multiphase flow simulators. It is observed that some models developed for two-phase flow through restrictions could successfully characterize two-phase flow thorough gas-lift valves with errors lower than 10%. However, it is first necessary to experimentally determine the discharge coefficient (CD) for each gas-lift valve. The commercial flow simulators showed a similar performance as the models available in the literature.

Experimental and numerical study on gas-solid two-phase flow through regulating valve of pulverized coal flow

2020 ◽  
Vol 155 ◽  
pp. 1-11 ◽  
Author(s):  
Meihua Chen ◽  
Haifeng Lu ◽  
Yong Jin ◽  
Xiaolei Guo ◽  
Xin Gong ◽  
...  
Keyword(s):  
Two Phase Flow ◽  
Numerical Study ◽  
Pulverized Coal ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through ◽  
Coal Flow

Pressure Surge During Cryogenic Feedline Chilldown Process

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Gagan Agrawal ◽  
S. Sunil Kumar ◽  
Deepak Kumar Agarwal
Keyword(s):  
Numerical Study ◽  
Rocket Engine ◽  
Inlet Pressure ◽  
Working Fluid ◽  
Flash Evaporation ◽  
Two Phase ◽  
Numerical Studies ◽  
Start Up ◽  
Flow Through ◽  
Pressure Surge

Cryogenic fluid entering a warm feedline absorbs heat and undergoes rapid flash evaporation leading to pressure surges, which can retard the flow inside the feedline. It may have serious repercussion in operation of the rocket engine during start up. Experimental and numerical studies are carried out to examine the effect of inlet pressure and initial feedline temperature on pressure surges. An analytical model using sinda/fluint software is developed to investigate this complex two-phase flow phenomenon including the various boiling regimes that exist during line chilling. The numerical study is carried out considering 1D flow through a cryogenic feedline of 2.47 m long and 0.01 m inner diameter with liquid nitrogen at 77.3 K as working fluid. Predictions are made for the inlet pressure in the range of 0.28–0.76 MPa and initial wall temperature of 200 K and 300 K. Subsequently, an experimental test rig is setup and the model is validated with the experimental data. The studies show that within the range of parameter considered, the magnitude of pressure surge increases exponentially with increase in inlet pressure and decreases with the prechilling of feedline.

scholarly journals CFD Modeling of Wall Steam Condensation: Two-Phase Flow Approach versus Homogeneous Flow Approach

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
S. Mimouni ◽  
N. Mechitoua ◽  
A. Foissac ◽  
M. Hassanaly ◽  
M. Ouraou
Keyword(s):  
Experimental Data ◽  
Liquid Film ◽  
Dominant Role ◽  
Droplet Diameter ◽  
Homogeneous Model ◽  
Surface Tension Force ◽  
Vapor Condensation ◽  
Cfd Modeling ◽  
Two Phase ◽  
Gravitational Forces

The present work is focused on the condensation heat transfer that plays a dominant role in many accident scenarios postulated to occur in the containment of nuclear reactors. The study compares a general multiphase approach implemented in NEPTUNE_CFD with a homogeneous model, of widespread use for engineering studies, implemented inCode_Saturne. The model implemented in NEPTUNE_CFD assumes that liquid droplets form along the wall within nucleation sites. Vapor condensation on droplets makes them grow. Once the droplet diameter reaches a critical value, gravitational forces compensate surface tension force and then droplets slide over the wall and form a liquid film. This approach allows taking into account simultaneously the mechanical drift between the droplet and the gas, the heat and mass transfer on droplets in the core of the flow and the condensation/evaporation phenomena on the walls. As concern the homogeneous approach, the motion of the liquid film due to the gravitational forces is neglected, as well as the volume occupied by the liquid. Both condensation models and compressible procedures are validated and compared to experimental data provided by the TOSQAN ISP47 experiment (IRSN Saclay). Computational results compare favorably with experimental data, particularly for the Helium and steam volume fractions.

Experimental and Numerical Study on Growth of Single Vapor Bubble in Upward Flow Through Vertical Mini-Tube

2011 ◽  
Author(s):  
Hiroshi Iwai ◽  
Motohiro Saito ◽  
Yuichi Kami ◽  
Yasuhiro Niina ◽  
Hideo Yoshida
Keyword(s):  
Numerical Study ◽  
Piecewise Linear ◽  
Numerical Procedure ◽  
Mass Conservation ◽  
Surface Force ◽  
Bubble Behavior ◽  
Two Phase ◽  
Intense Evaporation ◽  
Flow Through ◽  
Semi Empirical

A slug flow with phase change in a vertical mini-tube is numerically simulated on the basis of a scheme of continuum mechanics. To formulate two-phase flow, the volume of fluid, VOF, method is employed; the advection of the gas-liquid surface is expressed by the piecewise linear interface calculation, PLIC, scheme, while the effect of surface tension is evaluated by the continuum surface force, CSF, model. Since the treatment of liquid film between a bubble and tube wall is crucially important to properly predict both heat transfer and resulting fluid flow in a mini-tube, a semi-empirical approach based on subsidiary knowledge estimated from a preliminary experiment is newly proposed. Further, an additional numerical procedure is introduced to obtain allowable mass conservation even in the thin-film region with intense evaporation. Consequently, by introducing only one parameter, the physical meaning of which is clear, the bubble behavior is reasonably predicted, and its detailed mechanism is clarified.

SYNTHESIS OF HYDROGEN IN ACOUSTOPLASMA DISCHARGE IN A LIQUID-PHASE STREAM

2019 ◽  
pp. 42-48 ◽  
Author(s):  
N. A. Bulychev
Keyword(s):  
Liquid Phase ◽  
Organic Compounds ◽  
Electrode Materials ◽  
Solid Phase ◽  
Plasma Discharge ◽  
Raw Material ◽  
Two Phase ◽  
Reduced Pressure ◽  
External Power Source ◽  
Phase Medium

In this paper, the plasma discharge in a high-pressure fluid stream in order to produce gaseous hydrogen was studied. Methods and equipment have been developed for the excitation of a plasma discharge in a stream of liquid medium. The fluid flow under excessive pressure is directed to a hydrodynamic emitter located at the reactor inlet where a supersonic two-phase vapor-liquid flow under reduced pressure is formed in the liquid due to the pressure drop and decrease in the flow enthalpy. Electrodes are located in the reactor where an electric field is created using an external power source (the strength of the field exceeds the breakdown threshold of this two-phase medium) leading to theinitiation of a low-temperature glow quasi-stationary plasma discharge.A theoretical estimation of the parameters of this type of discharge has been carried out. It is shown that the lowtemperature plasma initiated under the flow conditions of a liquid-phase medium in the discharge gap between the electrodes can effectively decompose the hydrogen-containing molecules of organic compounds in a liquid with the formation of gaseous products where the content of hydrogen is more than 90%. In the process simulation, theoretical calculations of the voltage and discharge current were also made which are in good agreement with the experimental data. The reaction unit used in the experiments was of a volume of 50 ml and reaction capacity appeared to be about 1.5 liters of hydrogen per minute when using a mixture of oxygen-containing organic compounds as a raw material. During their decomposition in plasma, solid-phase products are also formed in insignificant amounts: carbon nanoparticles and oxide nanoparticles of discharge electrode materials.

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