Numerical Simulated Method on Wind Environmental of Outdoor

2011 ◽  
Vol 250-253 ◽  
pp. 3815-3821
Author(s):  
Can Li ◽  
Tian Fu Deng
Keyword(s):  
Numerical Simulation ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Outdoor Air ◽  
Wind Environment ◽  
Outdoor Air Quality ◽  
Turbulent Airflow ◽  
Cfd Method ◽  
Velocity Pressure ◽  
Improve Planning

Outdoor wind environment play an important role at planning an estate. The method of simulating the wind environment of the district was conducted by two cases that had been tested and verified. The steady-state three-dimensional turbulent airflow fields were analyzed by computational fluid dynamic (CFD) method for the two cases. The distribution of velocity, pressure and turbulivity were presented. The detailed schemes on simplified physical model, mesh division, solving and boundary conditions defining were presented. Results shows that numerical simulation helps predict the details of the outdoor wind environment of estate, and it helps evaluate outdoor air quality in all its aspects or improve planning.

Hydraulic Characteristics of the New Type Bulb Turbine With Micro-Head

2013 ◽  
Author(s):  
Lingyu Li ◽  
Yuan Zheng ◽  
Daqing Zhou ◽  
Zihao Mi
Keyword(s):  
Numerical Simulation ◽  
Cfd Simulation ◽  
Guide Vane ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Three Dimensions ◽  
Guide Vanes ◽  
Runner Blade ◽  
Cfd Method ◽  
Bulb Turbine

The head of low-head hydropower stations is generally higher than 2.5m in the world, while micro-head hydropower resources which head is less than 2.5m are also very rich. In the paper, three-dimensional CFD method has been used to simulate flow passage of the micro-head bulb turbine. The design head and unit flow of the turbine was 1m and 3m3/s respectively. With the numerical simulation, the bulb turbine is researched by analyzing external characteristics of the bulb turbine, flow distribution before the runner, pressure distribution of the runner blade surface, and flow distribution of the outlet conduit under three different schemes. The turbine in second scheme was test by manufactured into a physical model. According to the results of numerical simulation and model test, bulb turbine with no guide vane in second scheme has simpler structure, lower cost, and better flow capacity than first scheme, which has traditional multi-guide vanes. Meanwhile, efficiency of second scheme has just little decrease. The results of three dimensions CFD simulation and test results agree well in second scheme, and higher efficiency is up to 77% which has a wider area with the head of 1m. The curved supports in third scheme are combined guide vanes to the fixed supports based on 2nd scheme. By the water circulations flowing along the curved supports which improve energy transformation ability of the runner, the efficiency of the turbine in third scheme is up to 82.6%. Third scheme, which has simpler structure and best performance, is appropriate for the development and utilization of micro-head hydropower resources in plains and oceans.

Numerical Simulation of Campus Wind Environment

2010 ◽  
Vol 160-162 ◽  
pp. 280-286
Author(s):  
Ri Chao Liu ◽  
Zhong Hua Tang ◽  
Wei Yang Qi
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Wind Direction ◽  
Natural Ventilation ◽  
Pressure Field ◽  
Field Analysis ◽  
Wind Environment ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Rng Turbulence Model

This paper adopted computational fluid dynamics (CFD) method, used k-ε RNG turbulence model-closed control differential equations for numerical simulation. Through numerical simulation and analysis of wind environment in a middle school campus, the round wind field under dominant wind direction was got in the summer and winter. According to the results of velocity field and pressure field, analysis the wind environment, compared the influence of wind direction and surrounding buildings space to the natural ventilation, provided guidance introduce for the layout of the school.

scholarly journals Numerical Investigation of Different Tip Clearances Effect on the Hydrodynamic Performance of Pumpjet Propulsor

2018 ◽  
Vol 15 (05) ◽  
pp. 1850037 ◽  
Author(s):  
Denghui Qin ◽  
Guang Pan ◽  
Qiaogao Huang ◽  
Zhengdong Zhang ◽  
Jiujiu Ke
Keyword(s):  
Numerical Simulation ◽  
Rotor Blade ◽  
Fluid Dynamic ◽  
Open Water ◽  
Suction Side ◽  
Close Relation ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Hydrodynamic Performance ◽  
Cfd Method

Previous studies show that the tip clearance loss limits the improvement of turbomachinery performance, and it is roughly in close relation with the gap size. In this study, a pumpjet propulsor (PJP) with different sizes of tip clearances ([Formula: see text], 0.5, 1, 2, 3[Formula: see text]mm) has been presented to investigate the influence of tip clearances on PJP. This analysis is based on computational fluid dynamic (CFD) method, and the SST k-[Formula: see text] turbulence model is applied. Calculations are carried out with a worldwide employed ducted propeller (the Ka4-70 propeller in 19A duct) to verify the numerical simulation. And the grid independence validation is discussed. The numerical simulation of PJP flow with different tip clearances is carried out. Results show that the open water efficiency decreases gradually with the increase of tip clearance. The efficiency decreasing is caused by the tip flow loss. The shape of tip vortex of PJP which consisted of tip-separation vortex and tip-leakage vortex is presented. Furthermore, the formation and spread process of tip vortex at different tip clearances are discussed. Then, the effect of different tip clearances on the pressure field of rotor blade is investigated. The main pressure area affected by different tip clearances is mainly concentrated in the area above 0.9 spanwise of the suction side of rotor blade. Beyond that, the effects of different tip clearances on the velocity field of PJP has been studied.

Three-dimensional direct numerical simulation of infrasound propagation in the Earth’s atmosphere

2018 ◽  
Vol 859 ◽  
pp. 754-789 ◽  
Author(s):  
R. Sabatini ◽  
O. Marsden ◽  
C. Bailly ◽  
O. Gainville
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Lower Thermosphere ◽  
Three Dimensional ◽  
Stratified Medium ◽  
Horizontal Wind ◽  
Physical Analysis ◽  
Strong Impact

A direct numerical simulation of the three-dimensional unsteady compressible Navier–Stokes equations is performed to investigate the infrasonic field generated in a realistic atmosphere by an explosive source placed at ground level. To this end, a high-order finite-difference method originally developed for aeroacoustic applications is employed. The maximum overpressure and the main frequency of the signal recorded at 4 km distance from the source location are about 4000 Pa and 0.2 Hz, respectively. The atmosphere is parametrized as a vertically stratified medium, constructed by specifying vertical profiles of the temperature and the horizontal wind which reproduce measurements. The computation is carried out up to 140 km altitude and 450 km range. The goal of the present paper is twofold. On the one hand, the feasibility of using a direct numerical simulation of the three-dimensional fluid dynamic equations for the detailed description of long-range propagation in the atmosphere is proven. On the other hand, a physical analysis of the infrasonic field is realized. In particular, great attention is directed towards some important phenomena which are not taken into account or not well predicted by classical propagation models. To begin with, the present study clearly demonstrates that the weakly nonlinear ray theory may lead to an incorrect evaluation of the waveform distortion of high-amplitude waves propagating towards the lower thermosphere. In addition, signals recorded in the shadow zones are investigated. In this regard, the influence on the acoustic field of temperature and wind inhomogeneities of length scale comparable with the acoustic wavelength is analysed. The role of diffraction at the thermospheric caustic is finally examined and it is pointed out that the amplitude of the source may have a strong impact on the length of the shadow zone.

Comparisons of Rotordynamic Characteristics Predictions for Annular Gas Seals Using the Transient Computational Fluid Dynamic Method Based on Different Single-Frequency and Multifrequency Rotor Whirling Models

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Single Frequency ◽  
Solution Technique ◽  
Model Parameters ◽  
Multiple Frequency ◽  
Rotordynamic Coefficients ◽  
Gas Seals ◽  
Cfd Method

The three-dimensional (3D) transient computational fluid dynamic (CFD) method was proposed to predict rotordynamic coefficients for annular gas seals. This transient CFD method uses unsteady Reynolds-Averaged Navier–Stokes (RANS) solution technique and mesh deformation theory, which requires a rotor whirling model as the rotor excitation signal to solve the transient leakage flow field in seal and obtain the transient fluid response forces on the rotor surface. A fully partitioned pocket damper seal (FPDS) was taken as the test object to validate the present numerical method. Comparisons were made between experimental data and rotordynamic coefficient predictions using the three variations of the single-frequency and multiple-frequency rotor whirling models: (1) one-dimensional whirling model, (2) circular orbit whirling model, and (3) elliptical orbit whirling model. The numerical results show that the rotordynamic coefficients predicted by the present CFD method and six different rotor whirling models all agree well with the experiment data, and nearly coincide for all rotor whirling models. The proposed transient CFD method can be used to perform a reasonably accurate prediction of the frequency-dependent rotordynamic coefficients for annular gas seals based on any one of the present six rotor whirling models, as long as ensuring the combination of these whirling model parameters captures the small perturbation theory. The rotor whirling parameters such as whirling orbit, amplitude, and frequency number are important in predicting rotor whirling motion and fluid response forces, but have almost no effect on the computed rotordynamic coefficients. The benefit of the multiple-frequency rotor whirling models is the ability to calculate accurate rotordynamic coefficients of annular gas seals in a wide frequency range with a simulation time on the order of one-tenth the cost of the single-frequency whirling models.

scholarly journals Generating Hexahedral Mesh for Wire-wrapped Fuel Assembly With RBF Mesh Deformation Method

2021 ◽  
Vol 8 ◽  
Author(s):  
X. A. Wang ◽  
Dalin Zhang ◽  
Mingjun Wang ◽  
Yapeng Liu ◽  
Lei Zhou ◽  
...  
Keyword(s):  
Nuclear Reactor ◽  
Fluid Dynamic ◽  
Rapid Development ◽  
Three Dimensional ◽  
Reactor Core ◽  
Hexahedral Mesh ◽  
Deformation Method ◽  
Fuel Assemblies ◽  
Polyhedral Cells ◽  
Cfd Method

Fuel assemblies with wire spacer are widely used in Generation IV liquid nuclear reactors. With the rapid development of computational power, the Computational Fluid Dynamic (CFD) method is becoming an effective tool to investigate the detailed three-dimensional thermal hydraulic characteristics in wire-wrapped fuel assemblies. Due to the complexity of geometry, most of the published researches are performed with large number tetrahedron or polyhedral cells. The simulation is quite time-consuming and is generally limited to assemblies with small number of fuel pins. In this paper, a hexahedron meshing strategy is developed based on the Radial Basis Function (RBF) theory in present paper. This strategy would be beneficial for the modeling for the wire-wrapped fuel assemblies in real nuclear reactor core with large number of fuel pins. To validate this strategy, two experiments are simulated and detailed flow parameter distributions within the bundle, including the pressure distribution and the temperature distribution, have been compared. Good agreements have been achieved between the simulation results and the experimental results.

The Numerical Simulation of Aerodynamic Performance for Wind Turbines’ Blade Wheel

2010 ◽  
Vol 34-35 ◽  
pp. 1761-1764
Author(s):  
Dan Dan Dai ◽  
Wen Lei Sun ◽  
Qun Zhao
Keyword(s):  
Numerical Simulation ◽  
Wind Turbines ◽  
Velocity Vector ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Visual Images ◽  
Three Dimensional Flow ◽  
Technical Parameters ◽  
Fluent Software ◽  
Cfd Method

It’s necessary to research on the interaction of blade wheel with incoming flow. The CFD method was used in this paper for numerical simulation of the aerodynamic performance for wind turbines’ blade wheel at rated wind speed. The first thing was the establishment of wind turbine dynamic model of blade wheel. Then using Fluent software to simulate the three-dimensional flow field around it. The visual images on pressure distribution，flow rate distribution and velocity vector of the blade were obtained. Also, the load and the torque of the blade were calculated. The reliability of this numerical simulation is inspected in this paper. Some technical parameters and instructional suggestions about how to design the blade as well are proposed.

Numerical Analysis of Hydrodynamic Performance of FX-83-W Hydrofoil Current Turbine

2017 ◽  
Author(s):  
Yuchen Shang ◽  
Nikolaos I. Xiros
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Open Water ◽  
Hydrodynamic Performance ◽  
Ocean Current ◽  
Thrust Coefficient ◽  
Cfd Method ◽  
Three Dimensional Coordinate ◽  
Current Turbine

Ocean current flow characteristics are relatively stable and predictable, current turbine absorbs the energy of the ocean currents by the blades with a relative stable and lower angular velocity which indicates the capacity of current turbine greater than the onshore wind turbine. In this paper, the CFD method is utilized to calculate and analyze the working principle of FX-83-W current turbine. The three-dimensional coordinate of FX-83-W Hydrofoil blade surface have been calculated by MATLAB code, and 3D model has been established in Gambit. The basic control equations of CFD and its numerical solution are described, Reynolds Averaged N-S equations is used, and the realizable k-e turbulence model is introduced to solve the Reynolds stress in the RANS equation. The numerical algorithm is the finite volume method (FVM), and the numerical simulation of CFD is used to study the open water performance, leading to thrust coefficient KT and torque coefficient KQ of FX-83-W Hydrofoil. The hydrodynamic thrust and hydrodynamic power of the ocean current turbine under different sea conditions have been obtained by numerical simulation.

Numerical Simulation and Experiment Research on Aerodynamic Characteristics of a Multi-Blade Centrifugal Fan

2011 ◽  
Vol 317-319 ◽  
pp. 2157-2161
Author(s):  
Yong Chao Zhang ◽  
Qing Guang Chen ◽  
Yong Jian Zhang ◽  
Xiang Xing Jia
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Internal Flow ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Computational Domain ◽  
Centrifugal Fan ◽  
Cfd Method

The full flow field model of a widely used multi-blade centrifugal fan was built, and unstructured grids were used to discrete the computational domain. The moving reference frame is adopted to transfer data between the interfaces of the rotating field and the stationary field. Pressure boundary conditions are specified to the inlet and the outlet. The SIMPLE algorithm in conjunction with the RNG k-ε turbulent model was used to solve the three-dimensional Navier-Stokes equations. The steady and unsteady numerical simulations of the inner flow in the fan at different working conditions were presented using the CFD method. The numerical simulation results were validated by contrasting to the experiment results. The results displayed the characteristics of the velocity field, pressure field, pressure fluctuation at two monitoring points in the centrifugal fan. The results can provide basis for optimizing the fan design and the internal flow, and have important value of engineering applications in the increase of the overall performance in operation.

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