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.

Numerical Simulation and Optimal Design Investigation on Air Duct of Floor Standing Air-Conditioner

2011 ◽  
Vol 308-310 ◽  
pp. 563-567
Author(s):  
Zhong Min Wan ◽  
Zu Yi Zheng ◽  
Huan Xin Chen ◽  
Jun Liu ◽  
Ting Xiang Jin
Keyword(s):  
Numerical Simulation ◽  
Flow Rate ◽  
Aerodynamic Characteristic ◽  
Volume Flow Rate ◽  
Structural Characteristics ◽  
Flow Characteristics ◽  
Volume Flow ◽  
Numerical Results ◽  
Air Conditioner ◽  
Duct Flow

According to the structural characteristics of floor standing air-conditioner，three dimensional numerical model of air duct system for a certain floor standing air-conditioner is developed to simulate aerodynamic characteristic of the air duct. Flow characteristics and deficiency of air duct for original floor standing air-conditioner are analyzed, and the optimal schemes of air duct are raised and numerical simulation has been carried on to obtain aerodynamic characteristic of the new air duct. The numerical results show that the volume flow rate of air-conditioner with new air duct is increased by 6.1%. The experimental results of air-conditioner with new air duct show the volume flow rate of new air duct is promoted by 5.6% at the same approximate noise level. The numerical results agree well with the previous experiment.

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 Numerical modeling of turbulent flow in a plane channel on the basis of the Cabaret scheme

2019 ◽  
pp. 356-362
Author(s):  
Д.Г. Асфандияров
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Plane Channel ◽  
Classical Problem ◽  
Flow Characteristics ◽  
Pseudospectral Method ◽  
Numerical Results ◽  
Mean Flow ◽  
Cabaret Scheme

Представлены результаты моделирования классической задачи течения вязкой несжимаемой жидкости в плоском канале по схеме Кабаре при числах Рейнольдса, равных 5600, 13750 и 21900. Расчеты выполнены как при полном (прямое численное моделирование DNS Direct Numerical Simulation), так и неполном разрешении спектра турбулентных пульсаций. Во втором случае для расчетов используются сетки, характерные для моделирования пристенных течений методом крупных вихрей. Для более точного моделирования потока импульса на стенки при грубом разрешении пристенной области вводятся специальные искусcтвенные граничные условия. Это позволяет повысить точность определения средних характеристик течения. Проведено сравнение полученных результатов по схеме Кабаре с результатами прямого численного моделирования по псевдоспектральному методу. Some results of modeling the classical problem of flow of a viscous incompressible fluid in a plane channel at the Reynolds numbers equal to 5600, 13750, and 21900 using the Cabaret scheme are discussed. The computations are performed for the complete turbulence spectrum resolution (direct numerical simulation) and for the incomplete resolution. In the latter case, the grids typical for the large eddy simulation of nearwall turbulent flows are used. In order to obtain a more accurate representation of the momentum transfer toward the wall, some artificial boundary conditions are introduced. This allows us to model the mean flow characteristics with a higher accuracy. The numerical results obtained by the Cabaret scheme are compared with the numerical results obtained by the pseudospectral method.

Numerical Simulation of the Launching of Underwater Vehicle

2014 ◽  
Vol 556-562 ◽  
pp. 4404-4407
Author(s):  
Hai Long Huang ◽  
Wei Cao ◽  
Cong Wang
Keyword(s):  
Numerical Simulation ◽  
Surface Pressure ◽  
Pressure Coefficient ◽  
Flow Characteristics ◽  
Underwater Vehicle ◽  
Vehicle Body ◽  
Cavity Shape ◽  
Movement Process ◽  
Movement Characteristic

The numerical simulation of multipahse flow characteristics during the launch process from the tube of the submarine vehicle are investigated, obtains the variation rules of the movement characteristic of the gas inside the tube, the cavity shape of around the vehicle body, the surface pressure coefficient during the movement process. The resluts show that the launch depth and velocity have significiant impact on the shouder cavitation of the submarine vehicle, the smaller values of the depth and the velocity are, the more obvious shouber cavitation, and which led to the distribution difference of the surface pressure coefficient

Numerical Simulation of Cavitation Flow Field in a Francis Turbine Runner with Attached Blades

2014 ◽  
Vol 700 ◽  
pp. 637-642
Author(s):  
Si Qing Zhang ◽  
Guo Hua Ma ◽  
Jing Qian
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Mixture Model ◽  
Volume Fraction ◽  
Francis Turbine ◽  
Correction Algorithm ◽  
Cavitation Flow ◽  
Cavitation Model ◽  
Two Phase ◽  
Turbine Runner

The numerical simulation of cavitation flow field in a Francis turbine runner with attached blades was conducted based on the no-slip mixture model in the Euler approach and the Singhal cavitation model. The RNG model after correcting viscosity and the pressure correction algorithm (SIMPLE) were supplemented. The distributions of the water-vapor volume fraction under non-design conditions were obtained. The results show that the method based on two-phase mixture model can be used to simulate the position and degree of cavitation flow in Francis turbine.

scholarly journals Hydraulic Characteristics and Numerical Simulation of the Entrance Section of Ladder-Shaped Spillway

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
X. B. Gu ◽  
Q. H. Wu ◽  
Y. Wang ◽  
H. X. Zhao
Keyword(s):  
Numerical Simulation ◽  
Energy Dissipation ◽  
Dissipation Rate ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Energy Dissipation Rate ◽  
Numerical Results ◽  
Experimental Results ◽  
Flow State ◽  
Hydraulic Characteristics

The ladder-shaped spillway in a certain reservoir junction is set as the engineering background in the paper. The hydraulic similarly model experiment and three-dimensional numerical simulation of hydraulic characteristics of water flow are performed. The outflow capacity, flow state analysis, velocity distribution, water surface line, pressure, and the energy dissipation rate are analyzed, and experimental results are compared with the numerical results. The conclusions demonstrate that the numerical results of the flow characteristics are very proximate to actual experimental results, the changeable law is the same, and their energy dissipation rate is basically consistent; it shows the feasibility of three-dimensional numerical simulation; the conclusions can provide the basis for the optimization about the flow state of the ladder-shaped spillway in the future.

scholarly journals Effect of RANS Turbulence Model on Aerodynamic Behavior of Trains in Crosswind

2019 ◽  
Vol 32 (1) ◽  
Author(s):  
Tian Li ◽  
Deng Qin ◽  
Jiye Zhang
Keyword(s):  
Numerical Simulation ◽  
Turbulence Model ◽  
Surface Pressure ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Experimental Result ◽  
Force Coefficient ◽  
Simulation Based ◽  
Aerodynamic Performances ◽  
Side Force Coefficient

Abstract The numerical simulation based on Reynolds time-averaged equation is one of the approved methods to evaluate the aerodynamic performance of trains in crosswind. However, there are several turbulence models, trains may present different aerodynamic performances in crosswind using different turbulence models. In order to select the most suitable turbulence model, the inter-city express 2 (ICE2) model is chosen as a research object, 6 different turbulence models are used to simulate the flow characteristics, surface pressure and aerodynamic forces of the train in crosswind, respectively. 6 turbulence models are the standard k-ε, Renormalization Group (RNG) k-ε, Realizable k-ε, Shear Stress Transport (SST) k-ω, standard k-ω and Spalart–Allmaras (SPA), respectively. The numerical results and the wind tunnel experimental data are compared. The results show that the most accurate model for predicting the surface pressure of the train is SST k-ω, followed by Realizable k-ε. Compared with the experimental result, the error of the side force coefficient obtained by SST k-ω and Realizable k-ε turbulence model is less than 1 %. The most accurate prediction for the lift force coefficient is achieved by SST k-ω, followed by RNG k-ε. By comparing 6 different turbulence models, the SST k-ω model is most suitable for the numerical simulation of the aerodynamic behavior of trains in crosswind.

Investigations on the effects of obstacles on the surfaces of blades of the centrifugal pump to suppress cavitation development

2021 ◽  
pp. 2150327
Author(s):  
Weiguo Zhao ◽  
Bao Guo
Keyword(s):  
Numerical Simulation ◽  
Kinetic Energy ◽  
Centrifugal Pump ◽  
Cavitation Flow ◽  
Cavitation Model ◽  
Cavitation Performance ◽  
Simulation Results ◽  
Specific Speed ◽  
And Control ◽  
Good Agreement

This paper proposes a new method that obstacles are attached to both the suction and pressure surfaces of the blades to suppress cavitation development. A centrifugal pump with a specific speed of 32 is selected as the physical model to perform the external characteristic and cavitation performance experiments. SST [Formula: see text] turbulence model and Zwart cavitation model were employed to simulate the unsteady cavitation flow in the pump. The results indicate that the numerical simulation results are in good agreement with the experimental counterparts. After the obstacles are arranged, the maximum head decrease is only 1.37%, and the relative maximum drop of efficiency is 1.12%. Obstacles have minimal impacts on the variations of head and efficiency under all flow rate conditions. The distribution of vapor volume in the centrifugal pump is significantly reduced after obstacles are arranged and the maximum fraction reduction is 53.6%. The amplitude of blade passing frequency decreases significantly. While obstacles decrease the intensity of turbulent kinetic energy near the wall in the impeller passages to effectively reduce the distribution of cavitation bubbles, and control the development of cavitation. After the obstacles are set, the strength of the vortex in the impeller passages is weakened significantly, the shedding of the vortex is suppressed, flow in the impeller becomes more stable.

scholarly journals Numerical Simulation of Static Seal Contact Mechanics Including Hydrostatic Load at the Contacting Interface

Lubricants ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 1
Author(s):  
De Huang ◽  
Xiang Yan ◽  
Roland Larsson ◽  
Andreas Almqvist
Keyword(s):  
Numerical Simulation ◽  
Contact Pressure ◽  
Fluid Pressure ◽  
Surface Profile ◽  
Element Model ◽  
Pressure Profile ◽  
Sealing Performance ◽  
Hydrostatic Load ◽  
The Difference ◽  
Maximum Contact

A finite element model of a static seal assembled in its housing has been built and is utilized to study how the seal deforms under varying loading conditions. The total contact load on the sealing surface is balanced by the sealed fluid pressure and the friction between the seal and the housing sidewall perpendicular to the sealing surface. The effect of the sealed fluid pressure between the sealing surfaces was investigated and the simulation showed that the surface profile is distorted due to the hydrostatic pressure. We study the distorted contact profile with varying sealed fluid pressure and propose five parameters to describe the corresponding contact pressure profile. One of these parameters, overshoot pressure, a measure of the difference between maximum contact pressure and the sealed fluid pressure, is an indicator of sealing performance. The simulations performed show different behaviors of the overshoot pressure with sealed fluid pressure for cosinusoidal and parabolic surfaces with the same peak to valley (PV) value.

Study on the Flow Characteristics of Rope and Cylinder With Large-Eddy Simulation

2018 ◽  
Author(s):  
Hui Cheng ◽  
Liuyi Huang ◽  
Yi Ni ◽  
Fenfang Zhao ◽  
Xinxin Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Numerical Results ◽  
Hydrodynamic Characteristics ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Smooth Cylinder ◽  
Force Calculation

Three-strand rope is the dominant material in fishing net and fish cage. Smooth cylinder is a common numerical model of net twines in the drag force calculation. This paper studied the hydrodynamic characteristics of ropes and smooth cylinders. Large Eddy Simulation was applied to the numerical simulation. Numerical results indicated that the drag coefficient of rope was much smaller than that of smooth cylinder when Re = 3900. The detailed analysis and comparison of their flow characteristics explained the reason. The specific of eddy shedding and wake pattern were presented in the numerical results.

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