Tidal Turbine Blade Selection for Optimal Performance in an Array

2011 ◽  
Author(s):  
Rachel F. Nicholls-Lee ◽  
Stephen R. Turnock ◽  
Stephen W. Boyd
Keyword(s):  
Tidal Cycle ◽  
Free Stream ◽  
Stokes Equations ◽  
Tidal Energy ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Energy Capture ◽  
Tidal Turbines ◽  
Outer Domain ◽  
Tidal Turbine

In order to maximize tidal energy capture from a specific site free stream devices are situated in arrays. In an array the downstream evolution of the wake generated by a rotating tidal energy conversion device influences the performance of the device itself, the bypass flow to either side as well as the performance of any downstream device. As such it is important to design a turbine that can perform efficiently and effectively in these circumstances. Use of passively adaptive composite blades for horizontal axis tidal turbines has been shown to improve performance in fluctuating inflows. Active adaptation and/or bi-directional hydrofoil sections could be implemented in order to optimize performance throughout the tidal cycle. This paper considers the performance in an array of four free stream turbines implementing standard rigid blades, wholly bidirectional blades, passively adaptive blades and actively adaptive blades. The method used to evaluate the performance of tidal current turbines in arrays couples an inner domain solution of the blade element momentum theory with an outer domain solution of the Reynolds averaged Navier Stokes equations. The annual energy capture of four devices with each blade type in a staggered array is then calculated for a single tidal cycle and compared.

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.

A numerical study of the interaction between unsteay free-stream disturbances and localized variations in surface geometry

1989 ◽  
Vol 209 ◽  
pp. 285-308 ◽  
Author(s):  
R. J. Bodonyi ◽  
W. J. C. Welch ◽  
P. W. Duck ◽  
M. Tadjfar
Keyword(s):  
Numerical Solutions ◽  
Free Stream ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Surface Geometry ◽  
Navier Stokes Equations ◽  
S Waves ◽  
Tollmien Schlichting

A numerical study of the generation of Tollmien-Schlichting (T–S) waves due to the interaction between a small free-stream disturbance and a small localized variation of the surface geometry has been carried out using both finite–difference and spectral methods. The nonlinear steady flow is of the viscous–inviscid interactive type while the unsteady disturbed flow is assumed to be governed by the Navier–Stokes equations linearized about this flow. Numerical solutions illustrate the growth or decay of the T–S waves generated by the interaction between the free-stream disturbance and the surface distortion, depending on the value of the scaled Strouhal number. An important result of this receptivity problem is the numerical determination of the amplitude of the T–S waves.

Free-stream coherent structures in parallel boundary-layer flows

2014 ◽  
Vol 752 ◽  
pp. 602-625 ◽  
Author(s):  
Kengo Deguchi ◽  
Philip Hall
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Coherent Structures ◽  
Free Stream ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Homotopy Continuation ◽  
Boundary Layer Flows ◽  
Navier Stokes Equations ◽  
High Reynolds

AbstractOur concern in this paper is with high-Reynolds-number nonlinear equilibrium solutions of the Navier–Stokes equations for boundary-layer flows. Here we consider the asymptotic suction boundary layer (ASBL) which we take as a prototype parallel boundary layer. Solutions of the equations of motion are obtained using a homotopy continuation from two known types of solutions for plane Couette flow. At high Reynolds numbers, it is shown that the first type of solution takes the form of a vortex–wave interaction (VWI) state, see Hall & Smith (J. Fluid Mech., vol. 227, 1991, pp. 641–666), and is located in the main part of the boundary layer. On the other hand, here the second type is found to support an equilibrium solution of the unit-Reynolds-number Navier–Stokes equations in a layer located a distance of $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}O(\ln \mathit{Re})$ from the wall. Here $\mathit{Re}$ is the Reynolds number based on the free-stream speed and the unperturbed boundary-layer thickness. The streaky field produced by the interaction grows exponentially below the layer and takes its maximum size within the unperturbed boundary layer. The results suggest the possibility of two distinct types of streaky coherent structures existing, possibly simultaneously, in disturbed boundary layers.

Similarity Solutions for the Interaction of a Potential Vortex With Free Stream Sink Flow and a Stationary Surface

1974 ◽  
Vol 96 (1) ◽  
pp. 49-54 ◽  
Author(s):  
J. A. Hoffmann
Keyword(s):  
Boundary Layer ◽  
Differential Equations ◽  
Free Stream ◽  
Stokes Equations ◽  
Similarity Solutions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Stationary Surface ◽  
Direct Numerical Integration ◽  
Potential Vortex

Similarity equations, using an assumed transformation which reduces the partial differential equations to sets of ordinary differential equations, are obtained from the boundary layer and the complete Navier-Stokes equations for the interaction of vortex flows with free stream sink flows and a stationary surface. Solutions to the boundary layer equations for the case of the potential vortex that satisfy the prescribed boundary conditions are shown to be nonexistent using the assumed transformation. Direct numerical integration is used to obtain solutions to the complete Navier-Stokes equations under a potential vortex with equal values of tangential and radial free stream velocities. Solutions are found for Reynolds numbers up to 2.0.

Transonic flow hysteresis in a twin intake model

2018 ◽  
Vol 122 (1256) ◽  
pp. 1557-1567 ◽  
Author(s):  
A. Kuzmin
Keyword(s):  
Free Stream ◽  
Stokes Equations ◽  
Rectangular Cross Section ◽  
Navier Stokes ◽  
Stream Velocity ◽  
Order Accuracy ◽  
Navier Stokes Equations ◽  
2D Flow ◽  
Turbulent Airflow ◽  
3D Effects

ABSTRACTTurbulent airflow in a supersonic intake model of rectangular cross-section is studied numerically. Instability of shock waves formed in the intake and ahead of the entrance is examined. Solutions of the Reynolds-averaged Navier–Stokes equations are obtained with a finite-volume solver of second-order accuracy. The expulsion and the swallowing of the shocks with a variation of free-stream parameters are studied at both subsonic and supersonic conditions prescribed at the outlet. Hysteresis in the dependence of 2D flow on the free-stream velocity and angle-of-attack is documented. An influence of 3D effects on the flow is examined.

scholarly journals On the viscous hypersonic blunt body problem

1964 ◽  
Vol 20 (3) ◽  
pp. 353-367 ◽  
Author(s):  
William B. Bush
Keyword(s):  
Blunt Body ◽  
Free Stream ◽  
Stokes Equations ◽  
Viscosity Coefficient ◽  
Absolute Temperature ◽  
The Body ◽  
Navier Stokes ◽  
Nose Radius ◽  
Navier Stokes Equations ◽  
Specific Heats

The viscous hypersonic flow past an axisymmetric blunt body is analysed based upon the Navier-Stokes equations. It is assumed that the fluid is a perfect gas having constant specific heats, a constant Prandtl number, P, whose numerical value is of order one, and a viscosity coefficient varying as a power, ω, of the absolute temperature. Limiting forms of solutions are studied as the free-stream Mach number, M, and the free-stream Reynolds number based on the body nose radius, R, go to infinity, and ε = (γ − 1)/(γ + 1), where γ is the ratio of the specific heats, and δ = 1/(γ − 1) M2 go to zero.

RANS Modelling of Wake Induced Transition With the Dynamic Intermittency Concept

2006 ◽  
Author(s):  
Koen Lodefier ◽  
Erik Dick
Keyword(s):  
Turbulence Model ◽  
Free Stream ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Suction Side ◽  
Navier Stokes ◽  
Transition Model ◽  
Navier Stokes Equations ◽  
Free Stream Turbulence ◽  
Sst Turbulence Model

A transition model for describing wake-induced transition is presented based on the SST turbulence model by Menter and two dynamic equations for intermittency: one for near-wall intermittency and one for free-stream intermittency. In the Navier-Stokes equations, the total intermittency factor, which is the sum of the two, multiplies the turbulent viscosity computed by the turbulence model. The quality of the transition model is illustrated on the T106A test cascade for different levels of inlet free-stream turbulence intensity. The unsteady results are presented in space-time diagrams of shape factor, wall shear stress, momentum thickness and intermittency on the suction side. Results show the capability of the model to capture the physics of unsteady transition. Inevitable shortcomings are also revealed.

Simulations of the viscous flow normal to an impulsively started and uniformly accelerated flat plate

1996 ◽  
Vol 328 ◽  
pp. 177-227 ◽  
Author(s):  
P. Koumoutsakos ◽  
D. Shiels
Keyword(s):  
Flat Plate ◽  
Free Stream ◽  
Stokes Equations ◽  
The Body ◽  
Navier Stokes ◽  
Vorticity Field ◽  
Navier Stokes Equations ◽  
Unsteady Forces ◽  
Viscous Incompressible Flow ◽  
Experimental Works

The development of a two-dimensional viscous incompressible flow generated from an infinitesimally thin flat plate, impulsively started or uniformly accelerated normal to the free stream is studied computationally. An adaptive numerical scheme, based on vortex methods, is used to integrate the vorticity–velocity formulation of the Navier–Stokes equations. The results of the computations complement relevant experimental works while providing us with quantities such as the vorticity field and the unsteady forces experienced by the body. For the uniformly accelerated plate the present simulations capture the development of a number of centers of vorticity along the primary separating shear layer. This phenomenon has been observed in experimental works but has not been predicted by inviscid models. The present simulations suggest that this Kelvin–Helmholtz-type instability is driven by the interaction of primary and secondary vorticity near the tips of the plate and depends on the acceleration of the plate.

A study of non-parallel and nonlinear effects on the localized receptivity of boundary layers

1995 ◽  
Vol 290 ◽  
pp. 29-37 ◽  
Author(s):  
J. D. Crouch ◽  
P. R. Spalart
Keyword(s):  
Free Stream ◽  
Stokes Equations ◽  
Nonlinear Effects ◽  
Free Stream Velocity ◽  
Navier Stokes ◽  
Stream Velocity ◽  
Navier Stokes Equations ◽  
Dimensional Boundary ◽  
Instability Growth ◽  
The Difference

The acoustic receptivity due to localized surface suction in a two-dimensional boundary layer is studied using a finite-Reynolds-number theory and direct numerical simulation of the Navier-Stokes equations. Detailed comparisons between the two methods are used to determine the bounds for application of the theory. Results show a 4% difference between the methods for receptivity in the neighbourhood of branch I with low suction levels, low acoustic levels, and a moderate frequency; we attribute this difference to non-parallel effects, not included in the theory. The difference is larger for receptivity upstream of branch I, and smaller for receptivity downstream of branch I. As the peak suction level is increased to 1% of the free-stream velocity, the simulations show a nonlinear deviation from the theory. Suction levels as small as 0.1% are shown to have a significant effect on the instability growth between branch I and branch II. Increasing the acoustic amplitude to 1% of the steady free-stream velocity produces no significant nonlinear effect.

Influence of Turbulence Intensities onto Transmission Line Conductor Wind Loads

2012 ◽  
Vol 241-244 ◽  
pp. 1344-1348
Author(s):  
Hui Xue Dang ◽  
Feng Li Yang ◽  
Jing Bo Yang
Keyword(s):  
Transmission Line ◽  
Free Stream ◽  
Stokes Equations ◽  
Power Spectrum Density ◽  
Wind Loads ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Spectrum Density ◽  
Load Characteristics ◽  
Lift And Drag

The rationality of transmission line responses, tower responses, etc., are determined by the computed wind loads, which are directly correlated with the free-stream turbulences that generated at different ground roughness conditions, different terrains, etc.. Accounting for this problem, the flow fields around transmission line conductor LGJ630/45 are computed by solving Navier-Stokes equations to study the influence of Tis (turbulence intensities) onto wind load characteristics. The results show that, the peak-values of power spectrum density (PSD) results of both lift and drag are obviously influenced by TIs, while their corresponding frequencies are kept the same at different TIs; with the increase of Tis, the time-averaged value of conductor drag decreases nonlinearly and monotonically. Thus, given the influence of TIs onto wind loads, field observed free-stream values should be used as inputs for numerical simulations, and then the obtained wind loads can be adopted to accurately simulate transmission line gallopings and windage yaws.

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