Numerical study of cavitating flow over hydrofoil in the presence of air

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Włodzimierz Wróblewski ◽  
Krzysztof Bochon ◽  
Mirosław Majkut ◽  
Krzysztof Rusin ◽  
Emad Hasani Malekshah
Keyword(s):  
Numerical Study ◽  
Cavitating Flow ◽  
Cavitation Model ◽  
Two Phase ◽  
Content Type ◽  
Flow Simulations ◽  
Cavity Structure ◽  
Dynamic Forces ◽  
High Dynamic ◽  
The Impact

Purpose The presence of air in the water flow over the hydrofoil is investigated. The examined hydrofoil is ClarkY 11.7% with an angle of attack of 8 deg. The flow simulations are performed with the assumption of different models. The Singhal cavitation model and the models which resolve the non-condensable gas including 2phases and 3phases are implemented in the numerical model. The calculations are performed with the uRANS model with assumption of the constant temperature of the mixture. The two-phase flow is simulated with a mixture model. The dynamics and structures of cavities are compared with literature data and experimental results. Design/methodology/approach The cavitation regime can be observed in some working conditions of turbomachines. The phase transition, which appears on the blades, is the source of high dynamic forces, noise and also can lead to the intensive erosion of the blade surfaces. The need to control this process and to prevent or reduce the undesirable effects can be fulfilled by the application of non-condensable gases to the liquid. Findings The results show that the Singhal cavitation model predicts the cavity structure and related characteristics differently with 2phases and 3phases models at low cavitation number where the cavitating flow is highly dynamic. On the other hand, the impact of dissolved air on the cloud structure and dynamic characteristic of cavitating flow is gently observable. Originality/value The originality of this paper is the evaluation of different numerical cavitation models for the prediction of dynamic characteristics of cavitating flow in the presence of air.

Numerical Study of Cavitating Flow in Two-Phase LNG Expander

2016 ◽  
Author(s):  
Peng Song ◽  
Jinju Sun ◽  
Kaiqiang Li ◽  
Ke Wang ◽  
Changjiang Huo
Keyword(s):  
Design Optimization ◽  
Numerical Study ◽  
Temperature Drop ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Cavitation Model ◽  
Two Phase ◽  
Hydraulic Turbines ◽  
Liquefaction Process

LNG expander is developed and used as a replacement of a J-T valve in liquefaction process of natural gas to reduce significantly the energy consumption in the LNG plant. Similar to conventional hydraulic turbines, the unexpected cavitation also occurs in the LNG expander. In the present study, cavitating flow in two-phase LNG expander is investigated. With the justified Rayleigh-Plesset cavitation model, cavitating flow characteristics is investigated for the LNG expander in the entire stage environment including an annular bend, nozzle ring, and radial inflow impeller. On the basis of cavitating flow analysis, a coaxial rotating exducer is developed and fitted downstream to the impeller, so as to reduce the cavitation in impeller and subsequently prevent impeller damage. The following are demonstrated: (1) without exducer, significant cavitating flow is encountered at the impeller trailing edge and also in half streamline-wise region, and they are resulted from the viscous dissipation and flow separation; (3) with exducer, the impeller cavitation has diminished entirely but it has occurred in the successive exducer; (3) a use of exducer enhances the energy conversion capability of the rotors, but reduces the overall temperature drop and efficiency of the expander; (4) the design optimization of exducer is required to suppress the exducer cavitation, which also needs to be incorporated with the impeller design to achieve a better match between rotor/stator, so as to maximize the design optimization benefits.

scholarly journals A numerical study into the longitudinal dynamic stability of the tailless aircraft

2019 ◽  
Vol 91 (3) ◽  
pp. 428-436 ◽  
Author(s):  
Agnieszka Kwiek
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Numerical Study ◽  
Aircraft Design ◽  
Content Type ◽  
Preliminary Stage ◽  
Longitudinal Dynamic ◽  
Stability Derivatives ◽  
The Impact ◽  
Tailless Aircraft

Purpose The purpose of this research is a study into a mathematical approach of a tailless aircraft dynamic stability analysis. This research is focused on investigation of influence of elevons (elevator) on stability derivatives and consequently on the aircraft longitudinal dynamic stability. The main research question is to determine whether this impact should be taken into account on the conceptual and preliminary stage of the analysis of the longitudinal dynamic stability. Design/methodology/approach Aerodynamic coefficients and longitudinal stability derivatives were computed by Panukl (panel methods). The analysis of the dynamic stability of the tailless aircraft was made by the Matlab code and SDSA package. Findings The main result of the research is a comparison of the dynamic stability of the tailless aircraft for different approaches, with and without the impact of elevator deflection on the trim drag and stability derivatives. Research limitations/implications This paper presents research that mostly should be considered on the preliminary stage of aircraft design and dynamic stability analysis. The impact of elevons deflection on the aircraft moment of inertia has been omitted. Practical implications The results of this research will be useful for the further design of small tailless unmanned aerial vehicles (UAVs). Originality/value This research reveals that in case of the analysis of small tailless UAVs, the impact of elevons deflection on stability derivatives is bigger than the impact of a Mach number. This impact should be taken into consideration, especially for a phugoid mode.

Solid–liquid two-phase flow and erosion calculation of butterfly valves at small opening based on DEM method

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Benliang Xu ◽  
Zuchao Zhu ◽  
Zhe Lin ◽  
Dongrui Wang
Keyword(s):  
Peer Review ◽  
Two Phase Flow ◽  
Solid Particles ◽  
Phase Flow ◽  
Butterfly Valve ◽  
Two Phase ◽  
Content Type ◽  
Small Opening ◽  
Solid Liquid ◽  
The Impact

Purpose The study aims to decrease the effect of solid particles on a butterfly valve, which will cause seal failure and leakage, providing a reference for anti-wear design. Design/methodology/approach In this paper, computational fluid dynamics discrete element method (CFD-DEM) simulation was conducted to study the solid–liquid two-phase flow characteristics and erosion characteristics of a butterfly valve with a different opening. Findings Abrasion at 10% opening is affected by high-speed jets in upper and lower parts of the pipeline, where the erosion is intense. The impact of the jet on the upper part of 20% opening begins to weaken. With the top backflow vortex disappearing, the effect of lower jet is enhanced. Meanwhile, the bottom backflow vortex phenomenon is obvious, and the abrasion position moves downward. At 30% opening, the velocity is further weakened, and the circulation effect of lower flow channel is more obvious than that of the upper one. Originality/value It is the first time to use DEM to investigate the two-phase flow and erosion characteristics at a small opening of a butterfly valve, considering the effect of inter-particle collision. Therefore, this study carries on the thorough analysis and discussion. At the same opening degree, with increasing of the particle size, the abrasion of valve frontal surface increases when the size is less than 150 µm and decreases when it is greater than 150 µm. For the valve backflow surface, this boundary value becomes 200 µm. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0264/

Numerical investigation of passive cavitation control using a slot on a three-dimensional hydrofoil

2019 ◽  
Vol 30 (7) ◽  
pp. 3585-3605 ◽  
Author(s):  
Cheng Liu ◽  
Qingdong Yan ◽  
Houston G. Wood
Keyword(s):  
Three Dimensional ◽  
Cavitating Flow ◽  
Control Technique ◽  
Cavitation Model ◽  
Content Type ◽  
Eddy Simulation ◽  
Simulation Based ◽  
Large Eddy ◽  
Flow Turbulence ◽  
Cavitation Behavior

Purpose The purpose of this paper is to study the mechanism and suppression of instabilities induced by cavitating flow around a three-dimensional hydrofoil with a particular focus on cavitation control with a slot. Design/methodology/approach The transient cavitating flow around a Clark-Y hydrofoil was investigated using a transport-equation-based cavitation model and the stress-blended eddy simulation model was used to capture the flow turbulence. A homogeneous Rayleigh–Plesset cavitation model was used to model the transient cavitation process and the results were validated with test data. A slot was applied to the hydrofoil to suppress cavitation instabilities, and various slot widths and exit locations were applied to the blade and the cavitation behavior, as well as drag/lift forces, were simulated and compared to investigate the effects of slot geometries on cavitation suppression. Findings The large eddy simulation based turbulence model was able to capture the interactions between the cavitation and turbulence. Moreover, the simulation revealed that the re-entrant jet was responsible for the periodic shedding of cavities. The results indicated that a slot was able to mitigate or even suppress cavitation-induced instabilities. A jet flow was generated at the slot exit and disturbed the re-entrant jet. If the slot geometry was properly designed, the jet could block the re-entrant jet and suppress the unsteady cavitation behavior. Originality/value This study provides unique insights into the complicated transient cavitation flows around a three-dimensional hydrofoil and introduces an effective passive cavitation control technique useful to researchers and engineers in the areas of fluid dynamics and turbomachinery.

Numerical simulation of cavitation shedding flow around a hydrofoil using Partially-Averaged Navier-Stokes model

2015 ◽  
Vol 25 (4) ◽  
pp. 825-830 ◽  
Author(s):  
Desheng Zhang ◽  
Weidong Shi ◽  
Dazhi Pan ◽  
Guangjian Zhang
Keyword(s):  
Transfer Rate ◽  
Design Methodology ◽  
Mass Transfer Rate ◽  
Density Ratio ◽  
Maximum Density ◽  
Navier Stokes ◽  
Phase Flow ◽  
Cavitation Model ◽  
Two Phase ◽  
Content Type

Purpose – The purpose of this paper is to predict the unstable cavitation shedding flow around a 2D Clark-y hydrofoil. Design/methodology/approach – The paper studies Partially Averaged Navier-Stokes (PANS) model which was employed in the two-phase flow with a homogeneous cavitation model. Findings – Maximum density ratio affects the mass transfer rate between the liquid and the vapor significantly. The cavitating flow predicted by PANS model can resolve more turbulent scales by decreasing the parameter fk. Originality/value – The accuracy of numerical prediction is improved by increasing the maximum density ratio and decreasing fk.

The contribution of environmental regulation to technological innovation and quality competitiveness

2017 ◽  
Vol 11 (1) ◽  
pp. 51-71 ◽  
Author(s):  
Yuhong Cao ◽  
Jianxin You
Keyword(s):  
Economic Development ◽  
Environmental Protection ◽  
Environmental Regulation ◽  
Technological Innovation ◽  
Water Control ◽  
Two Phase ◽  
Content Type ◽  
Manufacturing Quality ◽  
The Impact ◽  
First Time

Purpose This paper aims to explore the relationship between environmental regulation, technological innovation and manufacturing quality competitiveness to provide some references for emission reduction activities and improvements in manufacturing quality competitiveness to achieve environmental protection targets and economic development as part of a win–win situation. Design/methodology/approach Based on the structure-behavior-performance paradigm and Grabowski’s research, a new empirical model was provided. The software, EViews 6.0, was used for econometric analysis. Regression analysis was adopted to explore the three indicators’ relationships. Findings First, environmental regulation can promote technological innovation effectively. Second, compared with wasted gas and wasted solids, investment in wasted water control promotes Chinese technological innovation most. Third, the impact of research and development investment, induced by environmental regulation, on manufacturing quality competitiveness is greater than that induced by non-environmental regulation. Fourth, the impact of lagged two-phase environmental regulation on manufacturing quality competitiveness is similar to that of lagged one-phase regulation. Practical implications The issue that Chinese manufacturing is facing is how to manage the trade-off between pollution control investment and improved quality competitiveness. This study enables managers to understand how to better implement environmental regulation initiatives while achieving environmental protection and quality competitiveness as part of a win–win situation. Originality/value This paper analyzes the relationships between environmental regulation, technological innovation and manufacturing quality competitiveness for the first time and provides the basic argument for integrating Chinese environmental regulation with quality competitiveness to reveal the uniqueness of the circumstances determining China’s economic development.

Natural convection in a partially heated wavy cavity filled with a nanofluid using Buongiorno’s nanofluid model

2017 ◽  
Vol 27 (4) ◽  
pp. 924-940 ◽  
Author(s):  
Ioan Pop ◽  
Mikhail Sheremet ◽  
Dalia Sabina Cimpean
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Rectangular Domain ◽  
Two Phase ◽  
Bottom Part ◽  
Content Type ◽  
Industrial Sectors ◽  
Nuclear Systems ◽  
Wavy Cavity

Purpose The main purpose of this numerical study is to provide a solution for natural convection in a partially heated, wavy cavity filled with a nanofluid using Buongiorno’s nanofluid model. Design/methodology/approach The domain of interest is a two-dimensional cavity bounded by an isothermal left wavy wall, adiabatic horizontal flat walls and right flat wall with a partial isothermal zone. To study the behaviour of the nanofluid, a two-phase Buongiorno mathematical model with the effects of the Brownian motion and thermophoresis is used. The governing dimensionless partial differential equations with corresponding boundary conditions were numerically solved by the finite difference method of the second-order accuracy using the algebraic transformation of the physical wavy cavity in a computational rectangular domain. The study has been conducted using the following values of the governing parameters: Ra = 104-106, Le = 10, Pr = 6.26, Nr = 0.1, Nb = 0.1, Nt = 0.1, A = 1, κ = 1-3, b = 0.2, hhs/L = 0.25, h1/L = 0.0-0.75 and τ = 0-0.25. Findings It is found that an increase in the undulation number leads to a weak intensification of convective flow and a reduction of Nū because of more essential cooling of the wavy troughs where the temperature gradient decreases. Variations of the heater location show a modification of the fluid flow and heat transfer. The upper position of the heater reflects the minimum heat transfer rate, while the position between the bottom part and the middle section (h1/L = 0.25) characterizes an enhancement of heat transfer. Originality/value The originality of this work is to analyse the natural convection in a partially heated wavy cavity filled by a nanofluid using Buongiorno’s nanofluid model. The results will benefit scientists and engineers to become familiar with the flow behaviour of such nanofluids, and the way to predict the properties of this flow for possibility of using nanofluids in advanced nuclear systems, in industrial sectors including transportation, power generation, chemical sectors, ventilation, air-conditioning, etc.

Simulation of Cavitating Inducer in Rocket Engine Turbopump

2005 ◽  
Author(s):  
Toshiya Kimura ◽  
Yoshiki Yoshida ◽  
Mitsuru Shimagaki
Keyword(s):  
Rocket Engine ◽  
Dynamic Change ◽  
Model Parameters ◽  
Cavitating Flows ◽  
Cavitation Model ◽  
Cfd Simulations ◽  
Two Phase ◽  
Cavity Structure ◽  
Liquid Rocket ◽  
Suction Performance

CFD simulations were applied to cavitating flows around an inducer of a liquid rocket engine turbopump. Unsteady simulations were performed for the full 3D model of an inducer using a cavitation model. The inducer has been tested with water in the cavitation tunnel at JAXA-KSPL to examine suction performance and unsteady cavitation phenomena such as rotating cavitation and cavitation surge. Experiments were conducted under various flow conditions to examine a break-down point of the suction performance and unsteady cavitation phenomena. They have suggested that the casing geometry affected the onset of unsteady cavitation phenomena. Simulations were, therefore, performed for various cavitation numbers. The steady state was firstly calculated without a cavitation model, and then the unsteady calculation was done with the bubble two-phase flow model as a cavitation model. The effect of different model parameters on cavity structure was also examined. In the calculated results, it was clearly observed that the cavity structure grew on the blade surface and accompanied with vortices. These cavities showed dynamic change of their shapes as the rotation of the inducer. The calculated head coefficient showed decrease for small cavitation numbers with similar gradient to that observed in the experiment.

Bubble flow simulations using the intersection marker (ISM) interface tracking method

2018 ◽  
Vol 28 (1) ◽  
pp. 118-137 ◽  
Author(s):  
Mark Ho ◽  
Guan Heng Yeoh ◽  
John Arthur Reizes ◽  
Victoria Timchenko
Keyword(s):  
Surface Tension ◽  
Two Phase Flow ◽  
Front Tracking ◽  
Interface Tracking ◽  
Phase Flow ◽  
Cfd Simulations ◽  
Two Phase ◽  
Content Type ◽  
Tracking Method ◽  
Flow Simulations

Purpose Interface distinct two-phase computational fluid dynamics (CFD) simulations require accurate tracking in surface curvature, surface area and volume fraction data to precisely calculate effects such as surface tension, interphase momentum and interphase heat and mass transfer exchanges. To attain a higher level of accuracy in two-phase flow CFD simulations, the intersection marker (ISM) method was developed. The ISM method has cell-by-cell remeshing capability that is volume conservative, maintains surface continuity and is suited for the tracking of interface deformation in transient two-phase flow simulations. Studies of isothermal single bubbles rising in quiescent water were carried out to test the ISM method for two-phase flow simulations. Design/methodology/approach The ISM method is a hybrid Lagrangian–Eulerian front tracking algorithm which can model an arbitrary three-dimensional surface within an array of cubic control volumes. Fortran95 was used to implement the ISM method, which resulted in approximately 25,000+ lines of written code and comments. To demonstrate the feasibility of the ISM algorithm for two-phase flow simulations, the ISM algorithm was coupled with an in-house CFD code, which was modified to simulate two-phase flows using a single fluid formulation. The constitutional equations incorporated terms of variable density and viscosity. In addition, body force source terms were included in the momentum equation to account for surface tension and buoyancy effects. Findings The performance of two-phase flow simulations was benchmarked against experimental data for four air/water bubbles with 1, 2.5, 5 and 10 mm of diameter rising in quiescent fluid. A variety of bubble sizes were tested to demonstrate the accuracy of the ISM interface tracking method. The results attained were in close agreement with experimental observations. Practical implications The results obtained show that the ISM method is a viable means for interface tracking of two-phase flow CFD simulations. Other applications of the ISM method include simulations of solid–fluid interaction and other immersed boundary flow problems. Originality/value The ISM method is a novel approach to front tracking, and the results shown are original in content.

scholarly journals NUMERICAL STUDY OF UNSTEADY SUPERCAVITATION PERTURBED BY A PRESSURE WAVE

2016 ◽  
Vol 42 ◽  
pp. 1660150
Author(s):  
J. G. ZHENG ◽  
B. C. KHOO
Keyword(s):  
Pressure Wave ◽  
Numerical Study ◽  
Cavitation Model ◽  
Supercavitating Flow ◽  
Through Flow ◽  
Material Erosion ◽  
Pressure Surge ◽  
Noise Vibration ◽  
The Impact ◽  
Compressibility Effects

The unsteady features of supercavitation disturbed by an introduced pressure wave are investigated numerically using a one-fluid cavitation model. The supercavitating flow is assumed to be the homogeneous mixture of liquid and vapour which are locally under both kinetic and thermodynamic equilibrium. The compressibility effects of liquid water are taken into account to model the propagation of pressure wave through flow and its interaction with supercavitation bubble. The interaction between supercavity enveloping an underwater flat-nose cylinder and pressure wave is simulated and the resulting unsteady behavior of supercavitation is illustrated. It is observed that the supercavity will become unstable under the impact of the pressure wave and may collapse locally, which depends on the strength of perturbation. The huge pressure surge accompanying the collapse of supercavitation may cause the material erosion, noise, vibration and efficiency loss of operating underwater devices.

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