Numerical Study of Performances of Vertical Axis Tidal Turbines

2012 ◽  
Vol 455-456 ◽  
pp. 296-301
Author(s):  
Yan Liu ◽  
Peng Fei Zhao ◽  
Xiao Hui Su ◽  
Guang Zhao
Keyword(s):  
Flow Field ◽  
Turbulent Flows ◽  
Stokes Equations ◽  
Numerical Study ◽  
Vertical Axis ◽  
Negative Influence ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Tidal Turbines ◽  
Central Shaft

Numerical simulations of flows over two-dimensional vertical axis tidal turbines are carried out. Unsteady Reynolds averaged Navier-Stokes Equations are applied to model turbulent flows. Influence of the central shaft and number of blades on flow field and thus performances of turbines are investigated. Performances in terms of torque and power coefficients are obtained for different types of turbines. Results demonstrates that the central shaft has a negative influence on flow field and power coefficients. Solidity and tip speed ratio are two important factors to affect turbine’s performances. This paper provides useful information for future studies.

Performance Improvements for a Vertical Axis Wind Turbine by Means of Gurney Flap

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Yan Yan ◽  
Eldad Avital ◽  
John Williams ◽  
Jiahuan Cui
Keyword(s):  
Wind Turbine ◽  
Stokes Equations ◽  
Numerical Study ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Performance Improvements ◽  
Gurney Flap

Abstract A numerical study was carried out to investigate the effects of a Gurney flap (GF) on the aerodynamics performance of the NACA 00 aerofoil and an associated three-blade rotor of a H-type Darrieus wind turbine. The flow fields around a single aerofoil and the vertical axis wind turbine (VAWT) rotor are studied using unsteady Reynolds-averaged Navier–Stokes equations (URANS). The height of GF ranges from 1% to 5% of the aerofoil chord length. The results show that the GF can increase the lift and lift-to-drag ratio of the aerofoil as associated with the generation of additional vortices near the aerofoil trailing edge. As a result, adding a GF can significantly improve the power coefficient of the VAWT at low tip speed ratio (TSR), where it typically gives low power production. The causing mechanism is discussed in detail, pointing to flow separation and dynamic stall delay.

scholarly journals Numerical Study of the Internal Flow Field of a Centrifugal Impeller

1994 ◽  
Author(s):  
Mou-jin Zhang ◽  
Chuan-gang Gu ◽  
Yong-miao Miao
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Internal Flow ◽  
Staggered Grid ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
High Reynolds

The complex three-dimensional flow field in a centrifugal impeller with low speed is studied in this paper. Coupled with high–Reynolds–number k–ε turbulence model, the fully three–dimensional Reynolds averaged Navier–Stokes equations are solved. The Semi–Implicit Method for Pressure–Linked Equations (SIMPLE) algorithm is used. And the non–staggered grid arrangement is also used. The computed results are compared with the available experimental data. The comparison shows good agreement.

Significant of Isothermal Flow Studies for High Swirling Flow in Unconfined Burner

2015 ◽  
Vol 789-790 ◽  
pp. 477-483
Author(s):  
A.R. Norwazan ◽  
M.N. Mohd Jaafar
Keyword(s):  
Flow Field ◽  
Combustion Chamber ◽  
Turbulent Flows ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Numerical Study ◽  
Tangential Velocity ◽  
Radial Distance ◽  
Navier Stokes ◽  
Reacting Flow

This paper is presents numerical simulation of isothermal swirling turbulent flows in a combustion chamber of an unconfined burner. Isothermal flows of with three different swirl numbers, SN of axial swirler are considered to demonstrate the effect of flow axial velocity and tangential velocity to define the center recirculation zone. The swirler is used in the burner that significantly influences the flow pattern inside the combustion chamber. The inlet velocity, U0 is 30 m/s entering into the burner through the axial swirler that represents a high Reynolds number, Re to evaluate the differences of SN. The significance of center recirculation zone investigation affected by differences Re also has been carried out in order to define a good mixing of air and fuel. A numerical study of non-reacting flow into the burner region is performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) realizable k-ε turbulence approach method was applied with the eddy dissipation model. An attention is focused in the flow field behind the axial swirler downstream that determined by transverse flow field at different radial distance. The results of axial and tangential velocity were normalized with the U0. The velocity profiles’ behaviour are obviously changes after existing the swirler up to x/D = 0.3 plane. However, their flow patterns are similar for all SN after x/D = 0.3 plane towards the outlet of a burner.

Numerical Investigation of an Optimised Horizontal Axis Tidal Stream Turbine

2019 ◽  
Author(s):  
Hassan El Sheshtawy ◽  
Ould el Moctar ◽  
Thomas E. Schellin ◽  
Satish Natarajan
Keyword(s):  
Output Power ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Navier Stokes Equations ◽  
Tidal Turbines ◽  
Tidal Turbine ◽  
Sst Turbulence Model ◽  
Tidal Stream ◽  
Tidal Stream Turbine

Abstract A tidal stream turbine was designed using one of the optimised hydrofoils, whose lift-to-drag ratio at an angle of attack of 5.2 degrees was 4.5% higher than that of the reference hydrofoil. The incompressible Reynolds-averaged Navier Stokes equations in steady state were solved using k-ω (SST) turbulence model for the reference and optimised tidal stream turbines. The discretisation errors and the effect of different y+ values on the solution were analysed. Thrust and power coefficients of the modelled reference turbine were validated against experimental measurements. Output power and thrust of the reference and the optimised tidal turbines were compared. For a tip speed ratio of 3.0, the output power of the optimised tidal turbine was 8.27% higher than that of the reference turbine of the same thrust.

Numerical Simulations of Flows Inside a Partially Filled Centrifuge

2003 ◽  
Vol 125 (6) ◽  
pp. 1033-1042 ◽  
Author(s):  
Fang Yan ◽  
Bakhtier Farouk
Keyword(s):  
Flow Field ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Complex Geometry ◽  
Numerical Study ◽  
Navier Stokes ◽  
Multiphase Model ◽  
Rotating Circular Cylinder ◽  
Radial Profiles ◽  
Liquid Flows

A numerical study was conducted to predict the dynamics of gas/liquid flows in a partially filled cylinder undergoing moderate to rapid rotation. Two specific problems were considered: spinup from rest of a partially filled circular container and the steady flow field in a partially filled rotating circular cylinder with an overrotating lid. Numerical solutions of the time-dependent axisymmetric Navier-Stokes equations were obtained by using a homogeneous multiphase model. The evolution of the free surface along with the flow fields in both the gas and liquid phases are predicted. The computed results were compared with available experimental data. Details of flow field structures are examined by studying the numerical solutions. Radial profiles of axial and azimuthal velocities for both the liquid and gas phases are also presented. The model developed can be used for analyzing flows and mixing problems in complex-geometry centrifuges.

scholarly journals Study of Three-Dimensional Viscous Flow Field in Axial-Flow Fan

1996 ◽  
Author(s):  
Moming Su ◽  
Chuan-gang Gu ◽  
Yong-miao Miao
Keyword(s):  
Boundary Condition ◽  
Flow Field ◽  
Turbulent Flows ◽  
Stokes Equations ◽  
Interpolation Method ◽  
Three Dimensional ◽  
Axial Flow ◽  
Computational Procedure ◽  
Navier Stokes ◽  
Moving Wall

The complex three-dimensional flow field in an axial-flow impeller incorporating high-Reynolds-number k-ε turbulence model is studied in this paper. The fully three-dimensional Reynolds averaged Navier-Stokes equations are solved. A computational procedure has been developed for predicting three-dimensional incompressible separated turbulent flows in the impeller. The SIMPLE-like algorithm is used. Convective terms are approximated with higher-order upstream-weighted approximations and a TVD-type MUSCL scheme. Physical covariant velocity components are selected as dependent solving variables. The non-orthogonal boundary-fitted coordinate system and collocated grid arrangement are also employed. Rhie and Chow’s momentum interpolation method is adopted to eliminate the non-physical pressure and velocity oscillations. Periodic boundary condition and moving wall boundary condition are considered to simulate truthfully the turbulent flow field in impeller. Two types of axial-flow impellers are computed. The first one is designed by ordinary method and the other is a improved design that has been considered with eliminating flow separation and viscous vortex in the first design. The computed results show that the fully tree-dimensional turbulent flows computation can efficiently predict three-dimensional separated flows and viscous vortex in axial-flow impeller and vaneless clearance. Using the program, a designer can improve passage geometric design to enhance the performance of the fan.

scholarly journals Analysis of the Dynamic Characteristics of the Muzzle Flow Field and Investigation of the Influence of Projectile Nose Shape

2020 ◽  
Vol 10 (4) ◽  
pp. 1468 ◽  
Author(s):  
Ye Luo ◽  
Da Xu ◽  
Hua Li
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Numerical Study ◽  
Axisymmetric Flow ◽  
Numerical Algorithms ◽  
Separated Flow ◽  
Ambient Air ◽  
Navier Stokes ◽  
Dynamic Processes ◽  
Shock Interactions

In the present work, a numerical study of the dynamic processes occurring during projectile ejection from the open-end of a gun into ambient air was performed. The two-dimensional unsteady Navier–Stokes equations, assuming axisymmetric flow, were solved using an AUSM+ discrete scheme implemented with dynamic mesh boundary conditions. Five cases were carried out in the present study. First, two test cases were simulated to validate the numerical algorithms. The last three cases were used to investigate the blast flow field induced by the projectile nose shapes of flat-nosed, cone-nosed, and blunt-nosed projectiles. The study shows that some wave processes, such as shock–shock interactions, separated flow generation, and the Richtmyer–Meshkov Instability, are changed obviously with the change of projectile shape. The present study aims to deepen the understanding of the dynamic processes of unsteady muzzle flow during the projectile ejection.

Aerodynamic Design Optimization of Elliptical-Bladed Savonius-Style Wind Turbine by Numerical Simulations

2016 ◽  
Author(s):  
Nur Alom ◽  
Satish Chandra Kolaparthi ◽  
Sarath Chandra Gadde ◽  
Ujjwal K. Saha
Keyword(s):  
Flow Field ◽  
Numerical Simulations ◽  
Wind Turbine ◽  
Numerical Study ◽  
Low Cost ◽  
Vertical Axis ◽  
3D Simulation ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine

Savonius-style wind turbine (SSWT), a class of vertical-axis wind turbine, appears to be promising for off-shore applications because of its design simplicity, good starting ability, insensitivity to wind direction, relatively low operating speed, low cost and easy installation. Various blade shapes have been used over the years to improve the performance of this class of turbine. In the recent past, an elliptic-bladed profile with sectional cut angle of 50° has shown its potential to harness the wind energy more efficiently. The present study aims to optimize this profile by numerical simulations. In view of this, the elliptical-bladed profiles are tested at different sectional cut angles of θ = 45°, 47.5°, 50° and 55°. The shear stress transport (SST) k-ω turbulence model is used to simulate the flow field, and thereafter, the torque and power coefficients are obtained at the rotating conditions. From 2D simulation, pressure and velocity contours are generated and analyzed. 2D simulations are also carried out for a semi-circular bladed profile in order to have a direct comparison. The numerical study demonstrates an improved flow characteristics, and hence the power coefficient of the elliptical-bladed profile at = 47.5°. Finally, 3D simulation is carried out to visualize and analyze the flow field around the optimum elliptical-bladed rotor at a tip speed ratio of 0.8. The aspect ratio of the rotor for the 3D simulation is kept at 0.7.

Numerical Study of Turbulent Flows Over Vibrating Blades with Positive Interblade Phase Angle

2007 ◽  
Vol 23 (2) ◽  
pp. 149-158 ◽  
Author(s):  
S.-Y. Yang ◽  
K.-H. Chen
Keyword(s):  
Turbulent Flows ◽  
Phase Angle ◽  
Stokes Equations ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Navier Stokes ◽  
Triangular Meshes ◽  
Solution Approach ◽  
Present Solution ◽  
Interblade Phase Angle

AbstractIn this paper, a locally implicit scheme on unstructured dynamic meshes is presented to study transonic turbulent flows over vibrating blades with positive interblade phase angle. The unsteady Favre-averaged Navier-Stokes equations with moving domain effects and a low- Reynolds-number k-ε turbulence model are solved in the Cartesian coordinate system. To treat the viscous flux on quadrilateral-triangular meshes, the first-order derivatives of velocity components and temperature are calculated by constructing auxiliary cells and Green's theorem for surface integration is applied. The assessment of accuracy of the present scheme on quadrilateral-triangular meshes is conducted through the calculation of the turbulent flow around an NACA 0012 airfoil. Based on the comparison with the experimental data, the accuracy of the present approach is confirmed. From the distributions of magnitude of the first harmonic dynamic pressure difference coefficient which include the present solution and the related experimental and numerical results, it is found that the present solution approach is reliable and acceptable. The unsteady pressure wave, shock wave and vortex-shedding phenomena are demonstrated and discussed.

Numerical Study on a Flow Field in the Rinsing Process of a Beverage Can Transported With a Constant Velocity

2021 ◽  
Author(s):  
Tatsuma Kawachi ◽  
Takuto Sasaki ◽  
Aya Kaneko ◽  
Yu Nishio ◽  
Takanobu Ogawa
Keyword(s):  
Flow Field ◽  
Constant Velocity ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Side Surface ◽  
Front Surface ◽  
Experimental Result ◽  
Navier Stokes ◽  
Navier Stokes Equations

Abstract The present study investigates the flow field in a rinsing process of a beverage can numerically and experimentally. The three-dimensional Navier-Stokes equations are solved with a finite volume method along with the volume of fluid (VOF) method for free surface. The beverage can set upside down is transported with a constant velocity and rinsed with a water jet ejected from a nozzle below the can. The case of a can at rest is also simulated. The result shows that the ejected water impinges on the can bottom and spreads along the side surface of the can. Then, as it flows down toward the can mouth, its front surface forms splashes. For the stationary can case, after the jet impinges on the can bottom, it almost evenly spreads over the side surface. The water flows downward and becomes branched flows by fingering. The time average of VOF is calculated to visualize the regions rinsed by water. For the case of a moving can, only the top region of the can is rinsed, and the ratio of the rinsed region drops to 29% from 69% for the stationary case. The computed water surfaces qualitatively agree with the experimental result, but the shape of the front surface, such as splashes and fingerings, cannot be resolved with the simulation.

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