scholarly journals Numerical Investigation of Unsteady Cavitation Flow around E779A Propeller in a Nonuniform Wake with an Insight on How Cavitation Influences Vortex

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Chengzao Han ◽  
Yun Long ◽  
Xiaorui Bai ◽  
Bin Ji
Keyword(s):  
Relative Vorticity ◽  
Cavitation Flow ◽  
Cavitation Model ◽  
Propeller Wake ◽  
Model Combining ◽  
Baroclinic Torque ◽  
Sst Turbulence Model ◽  
Vorticity Generation ◽  
Cavity Evolution ◽  
Vorticity Transport

In the current study, the turbulent cavitation flow around a marine propeller in a nonuniform wake is simulated with the shear stress transport (k−ω SST) turbulence model combining Zwart–Gerber–Belamri (ZGB) cavitation model. The predicted cavity evolution shows a fairly well agreement with the available experimental results. Important mechanisms of propeller cavitation flow, including side-entrant jet and cavitation-vortex interaction, are analyzed in this paper. Vorticity is found to be mainly located in cavitation regions and the propeller wake during propeller rotating. The unsteady behavior of cavitation and side-entrant jet can both promote local vorticity generation and flow unsteadiness. In addition, it is indicated with the relative vorticity transport equation that the stretching term plays a major role in vorticity transportation, while baroclinic torque and Coriolis force term mainly influence the vorticity distribution along the liquid-vapor interface.

Numerical Simulation and Vorticity Analysis of Cavitating Flow Around a Marine Propeller Behind the Hull

2019 ◽  
Author(s):  
Yun Long ◽  
Chengzao Han ◽  
Bin Ji ◽  
Xinping Long ◽  
Zhirong Zhang
Keyword(s):  
Experimental Data ◽  
Pressure Fluctuations ◽  
Relative Vorticity ◽  
Cavitating Flow ◽  
Numerical Results ◽  
Tip Vortex ◽  
Marine Propeller ◽  
Thrust Coefficient ◽  
Sheet Cavitation ◽  
Vorticity Transport

Abstract In this paper, the unsteady cavitating turbulent flow around a marine propeller behind the hull is simulated by the k-ω SST turbulence model coupled with the Zwart cavitation model. Three systematic refined structured meshes around the hull and propeller have been generated to study the predicted cavitation patterns and pressure fluctuations. Numerical results indicate that the predicted transient cavitating flow behind the hull wake, including sheet cavitation and tip vortex cavitation, shows quasi-periodic feature and agrees fairly well with the available experimental data. The deviations of pressure fluctuations between experimental data and numerical results are much small. With mesh refining, the cavitation region and the magnitudes of the calculated pressure fluctuations increase, while the differences between two adjacent sets of grids become smaller. In addition, the uncertainty of the thrust coefficient obtained by Factor of Safety method is significantly small. Further, the interaction between the cavitation and the vortex by the relative vorticity transport equation is illustrated. Results show that the magnitude of stretching term is obviously larger than the other three terms, and the dilatation term and the baroclinic term both have an important influence on the generation of vortices.

scholarly journals Experimental and numerical investigation of geometric effect on cavitation flow through orifice

2021 ◽  
Vol 22 ◽  
pp. 31
Author(s):  
Mohammad Reza Davoudi ◽  
Miralam Mahdi
Keyword(s):  
Numerical Solutions ◽  
Great Influence ◽  
Finite Volume Methods ◽  
Diameter Ratio ◽  
Cavitation Flow ◽  
Cavitation Model ◽  
Geometric Effect ◽  
Single Hole ◽  
Cavitation Phenomenon ◽  
Flow Through

Due to the set of factors and conditions, the stream pressure through the orifice decreases, which can lead to the occurrence of the cavitation phenomenon. The most important factor in this regard is the geometry of orifice. In the first part of this study, the flow through two types of single-hole orifice and a multi-hole orifice were experimentally studied. The results showed that the single hole orifice with a two-sided sloped edge caused less pressure drop, which in order to control the cavitation phenomenon is more efficient compared to the single-hole and multi-hole orifices with one-sided sloped edges and the same equal diameter ratio. Additionally, all experiments were simulated in the second part of this research using finite volume methods. Considering the complexity of the problem, several numerical solutions were investigated to approach the experimental results. Finally, it was determined that the type of gridding, turbulence method, and cavitation model have a great influence on the accuracy of the obtained numerical results.

Numerical Study of Cavitating Turbulent Flow Around Propellers: Relationship of Cavity Volume Evolution and Pressure Fluctuation

2011 ◽  
Author(s):  
Bin Ji ◽  
Xianwu Luo ◽  
Xiaoxing Peng ◽  
Yulin Wu ◽  
Hongyuan Xu
Keyword(s):  
Turbulent Flows ◽  
Pressure Fluctuation ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Pressure Oscillation ◽  
Skew Angle ◽  
Cavitation Model ◽  
Marine Propellers ◽  
Sst Turbulence Model ◽  
Relationship Of

The cavitating turbulent flows around two marine propellers, where one is a conventional propeller (CP) and the other is a highly skewed propeller (HSP), operating in non-uniform wake have been simulated by applying a mass transfer cavitation model based on Rayleigh-Plesset equation and k-omega SST turbulence model. From comparison of the numerical results with the experiment, it is noted that the unsteady cavitation patterns as well as the pressure oscillation amplitudes of the dominant components of marine propellers in non-uniform wake are reasonably predicted by present numerical methods. The results indicate that the effect of skew angle is very important on the cavitation characteristics as well as pressure fluctuations, and the amplitude of pressure fluctuation for HSP is reduced by 50–70% compared with that for CP. Therefore, the HSP propeller may help to avoid noise and vibration rather than the CP propeller. Further, the relation between hull pressures and changing cavitation patterns is verified based on CFD results, as the blades sweep through the high wake region. It is demonstrated that volumetric acceleration is the main reason for the pressure fluctuation, which agrees with the experiment by Duttweller and Brennen (2002).

Cavitation Model Verification and Validation for Water and Liquid Nitrogen in an Inducer

2017 ◽  
Author(s):  
Yuqiao Zhang ◽  
Xuesong Li ◽  
Yuhong Li
Keyword(s):  
Liquid Nitrogen ◽  
Saturation Pressure ◽  
Model Verification ◽  
Vapor Bubbles ◽  
Cavitation Flow ◽  
Cavitation Model ◽  
Model Verification And Validation ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Thermodynamic Effects

Cavitation is the formation of vapor bubbles within a liquid where flow dynamics cause the local static pressure to drop below the saturation pressure. Compared to the water, cavitation in cryogens is more complex due to the thermodynamic effects of cryogens. Existing Computational fluid dynamics (CFD) methods for water may not simulate the cryogens accurately. This paper presents the steady CFD results of cavitation in water and liquid nitrogen flow through a rotating inducer with four different cavitation models, and the experimental results are displayed to compare with the CFD results to verify the cavitation models’ applicability in water and the liquid nitrogen. The four cavitation models could simulate the cavitation flow in water, and the simulation result presents a consistent trend, which is stable in the high σ regime and drop down suddenly due to the blockage in blade passages caused by vapor as the cavitation number decreases. The “Zwart-Gerber-Belamri model” and the “Schnerr & Sauer model” have better performance on simulating the cavitation flow in water compared with the other two models, and the simulation results are close to the experimental one. The full cavitation model is applicable for cavitation prediction in liquid nitrogen, and the results of other three models are not satisfactory in liquid nitrogen.

scholarly journals The investigation of natural super-cavitation flow behind three-dimensional cavitators: Full cavitation model

2017 ◽  
Vol 45 ◽  
pp. 165-178 ◽  
Author(s):  
Ebrahim Kadivar ◽  
Erfan Kadivar ◽  
Khodayar Javadi ◽  
Seyyed Morteza Javadpour
Keyword(s):  
Three Dimensional ◽  
Cavitation Flow ◽  
Cavitation Model

Numerical Simulation of Liquid Nitrogen around Hydrofoil Cryogenic Cavitation

2012 ◽  
Vol 152-154 ◽  
pp. 1760-1765
Author(s):  
Xiang Fu Ma ◽  
Ying Jie Wei ◽  
Cong Wang ◽  
Wei Cao ◽  
Wen Hu Huang
Keyword(s):  
Numerical Simulation ◽  
Liquid Nitrogen ◽  
Surface Pressure ◽  
Fluid Pressure ◽  
Flow Characteristics ◽  
Pressure Profile ◽  
Cryogenic Liquid ◽  
Numerical Results ◽  
Cavitation Flow ◽  
Cavitation Model

Cavitation typically occurs when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. The aim of this paper is a numerical investigation of the cryogenic cavitation flow characteristics, considering variable thermodynamic properties of liquid nitrogen and numerical simulation liquid nitrogen around hydrofoil cryogenic cavitation flow characteristics. Based on homogeneous flow model and Zwart cavitation model, calculates hydrofoil isothermal and cryogenic cavitation in liquid nitrogen steadily, updates the evaporation and condensation coefficients of Zwart cavitation model, gives the hydrofoil surface pressure profile, temperature depression and distribution of cavitation intensity, contrasts the isothermal and cryogenic cavitation flow characteristics. Numerical results show that thermodynamics effect in cryogenic liquid cavitation significantly. Meanwhile, the hydrofoil surface pressure and temperature numerical results with experimental data and more Hord compared to verify the validity of the numerical simulation.

Cavitation-Vortex-Pressure Fluctuation Interaction in a Centrifugal Pump Using Bubble Rotation Modified Cavitation Model Under Partial Load

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Weihua Sun ◽  
Lei Tan
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Volume Fraction ◽  
Great Influence ◽  
Rotation Period ◽  
Rotation Frequency ◽  
Relative Vorticity ◽  
Calculation Model ◽  
Cavitation Model ◽  
Partial Load

Abstract Cavitation is a complicated phenomenon in the centrifugal pump. In this work, the improved unsteady calculation model based on bubble-rotation-based Zwart–Gerber–Belamri (BRZGB) cavitation model is used to investigate the cavitation-vortex-pressure fluctuation interaction in a centrifugal pump under partial load with experimental validation. Spatial–temporal evolution of cavitation can be classified into three stages: developing stage, shedding stage, and collapsing stage. The cavitation evolution period is found as 1/4T (T is impeller rotation period), corresponding to the frequency 4fi (fi is impeller rotation frequency). On the analysis of the relative vorticity transport equation, it is revealed that the cavity is stretched by the relative vortex stretching term (RVS) and developed by the relative vortex dilation term (RVD), and they have great influence on the cavity shedding. The peak value of pressure fluctuation intensity occurs near the vapor–liquid interface at cavity rear, and shifts downstream with the cavitation development. The hysteresis between the vapor volume fraction, vorticity, and pressure fluctuation is observed, and the variation of vapor volume fraction is the source of cavitation-vortex-pressure interaction.

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