Three-Dimensional Effects on an Oscillating-Foil Hydrokinetic Turbine

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Thomas Kinsey ◽  
Guy Dumas
Keyword(s):  
Three Dimensional ◽  
Navier Stokes ◽  
Practical Consideration ◽  
Power Extraction ◽  
Aspect Ratios ◽  
Hydrokinetic Turbine ◽  
High Reynolds ◽  
Oscillating Foil ◽  
Yaw Angle ◽  
Upstream Flow

Three-dimensional hydrodynamic losses are assessed in this investigation for a foil oscillating sinusoidally in a combined heave and pitch motion with large amplitudes. Simulations are performed using a unsteady Reynolds-Averaged-Navier-Stokes (URANS) solver on an oscillating foil in a power-extraction mode; thus acting as a hydrokinetic turbine at high Reynolds number. Foils of various aspect ratios (span to chord length ratio) are considered, both with and without endplates for one representative operation point. Hydrodynamic forces and extracted power are compared with results from the equivalent two-dimensional (2D) computations. It is found that the relative drop of performance (cycle-averaged power extracted) due to 3D hydrodynamic losses can be limited to 10% of the 2D prediction when endplates are used on a foil of aspect ratio greater than ten. The practical consideration of an oscillating-foil hydrokinetic turbine operating in an imperfectly-aligned upstream water flow is also addressed with simulations considering an upstream flow at a yaw angle up to 30° with respect to the foil chord line. Effects on performance are found to be proportional to the projected kinetic energy flux.

Hydrokinetic turbine array modeling for performance analysis and deployment optimization

2018 ◽  
Vol 42 (4) ◽  
pp. 370-381 ◽  
Author(s):  
Sébastien Bourget ◽  
Olivier Gauvin-Tremblay ◽  
Guy Dumas
Keyword(s):  
Cfd Simulation ◽  
Three Dimensional ◽  
Free Surface Flows ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Power Extraction ◽  
Hydrokinetic Turbine ◽  
Wake Interactions ◽  
Array Optimization ◽  
Turbine Wake

The promising preliminary results of an ongoing investigation aimed at developing a turbine array optimization tool are presented. This tool uses three-dimensional Reynolds-averaged Navier–Stokes (3D RANS) CFD simulations of free-surface flows to capture blockage effects and turbine-wake interactions present in dense river arrays. Turbines are represented individually into the river model using actuating regions inside which momentum source terms are distributed non-uniformly and scaled with turbine force coefficients (defined with regards to a local velocity scale). These data are derived from a high-fidelity CFD simulation of the specific turbine operating near maximum power extraction.

scholarly journals Triglobal infinite-wing shock-buffet study

2021 ◽  
Vol 925 ◽  
Author(s):  
Wei He ◽  
Sebastian Timme
Keyword(s):  
Stability Analysis ◽  
Three Dimensional ◽  
Base Flow ◽  
Sweep Angle ◽  
Aspect Ratios ◽  
Spatially Periodic ◽  
Time Marching ◽  
High Reynolds ◽  
Limiting Case ◽  
Base Flows

This article uses triglobal stability analysis to address the question of shock-buffet unsteadiness, and associated modal dominance, on infinite wings at high Reynolds number, expanding upon recent biglobal work, aspiring to elucidate the flow phenomenon's origin and characteristics. Infinite wings are modelled by extruding an aerofoil to finite aspect ratios and imposing a periodic boundary condition without assumptions on spanwise homogeneity. Two distinct steady base flows, spanwise uniform and non-uniform, are analysed herein on straight and swept wings. Stability analysis of straight-wing uniform flow identifies both the oscillatory aerofoil mode, linked to the chordwise shock motion synchronised with a pulsation of its downstream shear layer, and several monotone (non-oscillatory), spatially periodic shock-distortion modes. Those monotone modes become outboard travelling on the swept wing with their respective frequencies and phase speeds correlated with the sweep angle. In the limiting case of very small wavenumbers approaching zero, the effect of sweep creates branches of outboard and inboard travelling modes. Overall, triglobal results for such quasi-three-dimensional base flows agree with previous biglobal studies. On the contrary, cellular patterns form in proper three-dimensional base flow on straight wings, and we present the first triglobal study of such an equilibrium solution to the governing equations. Spanwise-irregular modes are found to be sensitive to the chosen aspect ratio. Nonlinear time-marching simulations reveal the flow evolution and distinct events to confirm the insights gained through dominant modes from routine triglobal stability analysis.

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.

An Assessment of Turbulence Models for Predicting the Fluid Flow in Spiral Casing of a Hydraulic Turbomachine Using SUPG-Finite Element Method

2013 ◽  
Author(s):  
N. Parameswara Rao ◽  
K. Arul Prakash
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Spatial Discretisation ◽  
High Reynolds ◽  
Spiral Casing ◽  
Element Method

Numerical simulation of complex three-dimensional flow through the spiral casing has been studied using a finite element method. An explicit Eulerian velocity correction scheme has been employed to solve the Reynolds averaged Navier-stokes equations. The simulation has been performed to describe the flow in high Reynolds number (106) regime and two k-ε turbulence models (standard k-ε and RNG k-ε) have been used for computing the turbulent flow. A streamline upwind Petrov Galerkin technique has been used for spatial discretisation. The velocity field and the pressure distribution inside the spiral casing has been studied. It has been observed that very strong secondary flow is evolved on the cross-stream planes.

Multigrid Computation of Incompressible Flows Using Two-Equation Turbulence Models: Part II—Applications

1997 ◽  
Vol 119 (4) ◽  
pp. 900-905 ◽  
Author(s):  
X. Zheng ◽  
C. Liao ◽  
C. Liu ◽  
C. H. Sung ◽  
T. T. Huang
Keyword(s):  
Turbulent Flows ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Time Stepping ◽  
Grid Algorithm ◽  
High Reynolds

In this paper, computational results are presented for three-dimensional high-Reynolds number turbulent flows over a simplified submarine model. The simulation is based on the solution of Reynolds-Averaged Navier-Stokes equations and two-equation turbulence models by using a preconditioned time-stepping approach. A multiblock method, in which the block loop is placed in the inner cycle of a multi-grid algorithm, is used to obtain versatility and efficiency. It was found that the calculated body drag, lift, side force coefficients and moments at various angles of attack or angles of drift are in excellent agreement with experimental data. Fast convergence has been achieved for all the cases with large angles of attack and with modest drift angles.

Three-Dimensional Simulation of Laminar Rectangular Impinging Jets, Flow Structure, and Heat Transfer

1999 ◽  
Vol 121 (1) ◽  
pp. 50-56 ◽  
Author(s):  
I. Sezai ◽  
A. A. Mohamad
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Streamwise Velocity ◽  
Impinging Jets ◽  
Navier Stokes ◽  
Aspect Ratios ◽  
Laminar Jets ◽  
Nusselt Number Distribution ◽  
Dimensional Simulation ◽  
Energy Equations

The flow and heat transfer characteristics of impinging laminar jets issuing from rectangular slots of different aspect ratios have been investigated numerically through the solution of three-dimensional Navier-Stokes and energy equations in steady state. The three-dimensional simulation reveals the existence of pronounced streamwise velocity off-center peaks near the impingement plate. Furthermore, the effect of these off-center velocity peaks on the Nusselt number distribution is also investigated. Interesting three-dimensional flow structures are detected which cannot be predicted by two-dimensional simulations.

scholarly journals Heat Transfer Predictions for Two Turbine Nozzle Geometries at High Reynolds and Mach Numbers

1997 ◽  
Vol 119 (2) ◽  
pp. 270-283 ◽  
Author(s):  
R. J. Boyle ◽  
R. Jackson
Keyword(s):  
Heat Transfer ◽  
Turbulence Modeling ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Gas Temperature ◽  
Algebraic Models ◽  
Pressure Distributions ◽  
Nozzle Geometries ◽  
High Reynolds ◽  
Computational Analyses

Predictions of turbine vane and endwall heat transfer and pressure distributions are compared with experimental measurements for two vane geometries. The differences in geometries were due to differences in the hub profile, and both geometries were derived from the design of a high rim speed turbine (HRST). The experiments were conducted in the Isentropic Light Piston Facility (ILPF) at Pyestock at a Reynolds number of 5.3 x 106, a Mach number of 1.2, and a wall-to-gas temperature ratio of 0.66. Predictions are given for two different steady-state three-dimensional Navier–Stokes computational analyses. C-type meshes were used, and algebraic models were employed to calculate the turbulent eddy viscosity. The effects of different turbulence modeling assumptions on the predicted results are examined. Comparisons are also given between predicted and measured total pressure distributions behind the vane. The combination of realistic engine geometries and flow conditions proved to be quite demanding in terms of the convergence of the CFD solutions. An appropriate method of grid generation, which resulted in consistently converged CFD solutions, was identified.

Numerical Study of the Tip Clearance Flow Development in a Propulsion Pump Stage

1996 ◽  
Author(s):  
Yu-Tai Lee ◽  
Chunill Hah ◽  
James Loellbach
Keyword(s):  
Vortex Structure ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
High Reynolds

This paper summarizes a numerical investigation of the fundamental structure of the rotor tip-clearance vortex and its interaction with a passage trailing-edge vortex in a single-stage stator-rotor pump. The flow field of a highly-loaded rotor measured in a high Reynolds number pump facility (HIREP) is used for comparison. The numerical solution was obtained by solving the three-dimensional Reynolds averaged Navier-Stokes equations. The calculated results are visualized in order to understand the details of the tip-vortex structure. The study shows that the tip geometry should be accurately represented to predict the tip-vortex structure correctly.

Wake and Performance Predictions of Two- and Three-Bladed Wind Turbines Based on the Actuator Line Model1

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Sebastian Henao Garcia ◽  
Aldo Benavides-Morán ◽  
Omar D. Lopez Mejia
Keyword(s):  
Wind Turbine ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Power Extraction ◽  
Low Incidence ◽  
And Performance ◽  
Turbine Design ◽  
Simulation Parameters

Abstract This paper challenges the standard wind turbine design numerically assessing the wake and aerodynamic performance of two- and three-bladed wind turbine models implementing downwind and upwind rotor configurations, respectively. The simulations are conducted using the actuator line model (ALM) coupled with a three-dimensional Navier Stokes solver implementing the k−ω shear stress transport turbulence model. The sensitivity of the ALM to multiple simulation parameters is analyzed in detail and numerical results are compared against experimental data. These analyses highlight the most suitable Gaussian radius at the rotor to be equal to twice the chord length at 95% of the blade for a tip-speed ratio (TSR) of ten, while the Gaussian radius at the tower and the number of actuator points have a low incidence on the flow field computations overall. The numerical axial velocity profiles show better agreement upstream than downstream the rotor, while the discrepancies are not consistent through all the assessed operating conditions, thus highlighting that the ALM parameters are also dependent on the wind turbine's operating conditions rather than being merely geometric parameters. Particularly, for the upwind three-bladed wind turbine model, the accuracy of the total thrust computations improves as the TSR increases, while the least accurate wake predictions are found for its design TSR. Finally, when comparing both turbine models, an accurate representation of the downwind configuration is observed as well as realistic power extraction estimates. Indeed, the results confirm that rotors with fewer blades are more suitable to operate at high TSRs.

Unsteady Reynolds-averaged Navier–Stokes investigation of free surface wave impact on tidal turbine wake

2021 ◽  
Vol 477 (2246) ◽  
pp. 20200703
Author(s):  
Zhisong Li ◽  
Kirti Ghia ◽  
Ye Li ◽  
Zhun Fan ◽  
Lian Shen
Keyword(s):  
Free Surface ◽  
Surface Wave ◽  
Surface Waves ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Wave Impact ◽  
Power Extraction ◽  
Tidal Turbine ◽  
Turbine Wake

Tidal current is a promising renewable energy source. Previous studies have investigated the influence of surface waves on tidal turbines in many aspects. However, the turbine wake development in a surface wave environment, which is crucial for power extraction in a turbine array, remains elusive. In this study, we focus on the wake evolution behind a single turbine and its interaction with surface waves. A numerical solver is developed to study the effects of surface waves on an industrial-size turbine. A case without surface wave and two cases with waves and different rotor depths are investigated. We obtain three-dimensional flow field descriptions near the free surface, around the rotor, and in the near- and far-wake. In a comparative analysis, the time-averaged and instantaneous flow fields are examined for various flow characteristics, including momentum restoration, power output, free surface elevation and vorticity dynamics. A model reduction technique is employed to identify the coherent flow structures and investigate the spatial and temporal characteristics of the wave–wake interactions. The results indicate the effect of surface waves in augmenting wake restoration and reveal the interactions between the surface waves and the wake structure, through a series of dynamic processes and the Kelvin–Helmholtz instability.

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