Numerical Modeling and Optimization of Hydrokinetic Turbine

2011 ◽  
Author(s):  
Nitin Kolekar ◽  
Suchi Subhra Mukherji ◽  
Arindam Banerjee
Keyword(s):  
Numerical Modeling ◽  
Transient Analysis ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Coefficient Of Performance ◽  
Speed Ratio ◽  
Turbine Performance ◽  
Design Variables ◽  
Hydrokinetic Turbine

Hydrokinetic turbines, unlike conventional hydraulic turbines are zero head energy conversion devices which utilize the kinetic energy of flowing water for power generation. The basic operational principle of the horizontal axis hydrokinetic turbine (HAHkT) is same as the wind turbine, the only difference being change in working media: water instead of air. This paper discusses the hydrodynamic design of HAHkT via numerical modeling. Presently these turbines suffer from low coefficient of performance (Cp) which is governed by several design variables such as tip-speed ratio, chord distribution, solidity and number of blades. The numerical modeling is performed for both constant and varying chord geometries using commercially available computational fluid dynamics software (CFX/FLUENT) to understand the effect of each of the design variable on turbine performance. Since the flow Reynolds number is large (≥ 105), both one- and two-equation turbulence models are applied to solve Reynolds Averaged Navier Stokes equations. In addition, a three dimensional analysis of HAHkT is performed to give a better insight into the effect of tip vortices and flow separation phenomenon on turbine performance; the results are then compared with Blade Element Momentum (BEM) theory analysis. In addition, a procedure for a multivariate optimization scheme is discussed that aims at maximizing Cp for a constant flow velocity while maintaining optimum values of critical design variables listed above. Finally, the effect of variation of angle of attack on the flow around a hydrofoil is investigate using both static and transient analysis, the transient analysis being performed by subjecting the airfoil to periodic oscillations.

Shape Optimization of Forward-Curved-Blade Centrifugal Fan with Navier-Stokes Analysis

2004 ◽  
Vol 126 (5) ◽  
pp. 735-742 ◽  
Author(s):  
Kwang-Yong Kim ◽  
Seoung-Jin Seo
Keyword(s):  
Response Surface ◽  
Stokes Equations ◽  
Computing Time ◽  
Relative Size ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Fan ◽  
Navier Stokes Equations ◽  
Design Variables ◽  
Curved Blade

In this paper, the response surface method using a three-dimensional Navier-Stokes analysis to optimize the shape of a forward-curved-blade centrifugal fan is described. For the numerical analysis, Reynolds-averaged Navier-Stokes equations with the standard k-ε turbulence model are discretized with finite volume approximations. The SIMPLEC algorithm is used as a velocity–pressure correction procedure. In order to reduce the huge computing time due to a large number of blades in forward-curved-blade centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models. Four design variables, i.e., location of cutoff, radius of cutoff, expansion angle of scroll, and width of impeller, were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and a linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. Effects of the relative size of the inactive zone at the exit of impeller and momentum fluxes of the flow in scroll on efficiency were further discussed. It was found that the optimization process provides a reliable design of this kind of fan with reasonable computing time.

Performance study of twisted Darrieus hydrokinetic turbine with novel blade design

2021 ◽  
pp. 1-37
Author(s):  
Mabrouk Mosbahi ◽  
Mouna Derbel ◽  
Mariem Lajnef ◽  
Bouzid Mosbahi ◽  
Zied Driss ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Maximum Power ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Small Scale ◽  
Performance Study ◽  
Hydrokinetic Turbine ◽  
Blade Shape ◽  
Water Turbine ◽  
Water Canals

Abstract Twisted Darrieus water turbine is receiving growing attentiveness for small-scale hydropower generation. Accordingly, the need for raised water energy conversion incentivizes researchers to focalise on the blade shape optimization of twisted Darrieus turbine. In view of this, an experimental analysis has been performed to appraise the efficiency of a spiral Darrieus water rotor in the present work. To better the performance parameters of the studied water rotor with twisted blades, three novel blade shapes, namely U-shaped blade, V-shaped blade and W-shaped blade, have been numerically tested using a computational fluid dynamics three-dimensional numerical model. Maximum power coefficient of Darrieus rotor reaches 0.17 at 0.63 tip-speed ratio using twisted blades. Using V-shaped blades, maximum power coefficient has been risen up to 0.185. The current study could be practically applied to provide more effective employment of twisted Darrieus turbines and to improve the generated power from flowing water such as river streams, tidal currents, or other man made water canals.

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.

scholarly journals Performance of Pre-Swirl Rotating-Disc Systems

1999 ◽  
Author(s):  
Hasan Karabay ◽  
Robert Pilbrow ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Turbulence Models ◽  
Cover Plate ◽  
Swirl Ratio ◽  
Rotating Disc ◽  
Blade Cooling ◽  
Cooling Air

This paper summarises and extends recent theoretical, computational and experimental research into the fluid mechanics, thermodynamics and heat transfer characteristics of the so-called cover-plate pre-swirl system. Experiments were carried out in a purpose-built rotating-disc rig, and the Reynolds-averaged Navier-Stokes equations were solved using 2D (axisymmetric) and 3D computational codes, both of which incorporated low-Reynolds-number k-ε turbulence models. The free-vortex flow, which occurs inside the rotating cavity between the disc and cover-plate, is controlled principally by the pre-swirl ratio, βp: this is the ratio of the tangential velocity of the air leaving the nozzles to that of the rotating disc. Computed values of the tangential velocity are in good agreement with measurements, and computed distributions of pressure are in close agreement with those predicted by a one-dimensional theoretical model. It is shown theoretically and computationally that there is a critical pre-swirl ratio, βp,crit, for which the frictional moment on the rotating discs is zero, and there is an optimal pre-swirl ratio, βp,opt, where the average Nusselt number is a minimum. Computations show that, for βp < βp,opt, the temperature of the blade-cooling air decreases as βp increases; for βp > βp,opt, whether the temperature of the cooling air increases or decreases as βp increases depends on the flow conditions and on the temperature difference between the disc and the air. Owing to the three-dimensional flow and heat transfer near the blade-cooling holes, and to unquantifiable uncertainties in the experimental measurements, there were significant differences between the computed and measured temperatures of the blade-cooling air. In the main, the 3D computations produced smaller differences than the 2D computations.

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.

Strongly Coupled Fluid-Structure Interactions via a New Navier-Stokes Method for Prediction of Vortex-Induced Vibrations

2005 ◽  
Author(s):  
Yannis Kallinderis ◽  
Hyung Taek Ahn
Keyword(s):  
Stokes Equations ◽  
Computational Cost ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Design Tool ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Vortex Induced Vibrations ◽  
Offshore Industry

Numerical prediction of vortex-induced vibrations requires employment of the unsteady Navier-Stokes equations. Current Navier-Stokes solvers are quite expensive for three-dimensional flow-structure applications. Acceptance of Computational Fluid Dynamics as a design tool for the offshore industry requires improvements to current CFD methods in order to address the following important issues: (i) stability and computation cost of the numerical simulation process, (ii) restriction on the size of the allowable time-step due to the coupling of the flow and structure solution processes, (iii) excessive number of computational elements for 3-D applications, and (iv) accuracy and computational cost of turbulence models used for high Reynolds number flow. The above four problems are addressed via a new numerical method which employs strong coupling between the flow and the structure solutions. Special coupling is also employed between the Reynolds-averaged Navier-Stokes equations and the Spalart-Allmaras turbulence model. An element-type independent spatial discretization scheme is also presented which can handle general hybrid meshes consisting of hexahedra, prisms, pyramids, and tetrahedral.

Numerical Analysis of Blockage Ratio Effect on a Portable Hydrokinetic Turbine

2016 ◽  
Author(s):  
Cosan Daskiran ◽  
Jacob Riglin ◽  
Alparslan Oztekin
Keyword(s):  
Free Stream ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Power Coefficient ◽  
Stream Velocity ◽  
Blockage Ratio ◽  
Ratio Effect ◽  
Turbine Performance ◽  
Hydrokinetic Turbine

Three-dimensional steady state Computational Fluid Dynamics (CFD) analyses were performed for a pre-designed micro-hydrokinetic turbine to investigate the blockage ratio effect on turbine performance. Simulations were conducted using a physical turbine rotor geometry rather than low fidelity, simplified actuator disk or actuator lines. The two-equation k-ω Shear Stress Transport (SST) turbulence model was employed to predict turbulence in the flow field. The turbine performance at the best efficiency point was studied for blockage ratios of 0.49, 0.70 and 0.98 for three different free stream velocities of 2.0 m/s, 2.25 m/s and 2.5 m/s. Distinct blockage ratio results at a free stream velocity of 2.25 were compared to a previous numerical study incorporating the same rotor geometry within an infinite flowing medium. The pressure gradient between turbine upstream and turbine downstream for blocked channel flows elevated the turbine performance. The increment in blockage ratio from 0.03 to 0.98 enhanced power coefficient from 0.437 to 2.254 and increased power generation from 0.56 kW to 2.86 kW for the present study.

Design Optimization of Forward-Curved Blades Centrifugal Fan With Response Surface Method

2004 ◽  
Author(s):  
Seoung-Jin Seo ◽  
Kwang-Yong Kim
Keyword(s):  
Response Surface ◽  
Flow Rate ◽  
Stokes Equations ◽  
Computing Time ◽  
Three Dimensional ◽  
Optimization Method ◽  
Design Flow ◽  
Navier Stokes ◽  
Centrifugal Fan ◽  
Design Variables

This paper presents the response surface optimization method using three-dimensional Navier-Stokes analysis to optimize the shape of a forward-curved blades centrifugal fan. For numerical analysis, Reynolds-averaged Navier-Stokes equations with k-ε turbulence model are discretized with finite volume approximations. In order to reduce huge computing time due to a large number of blades in forward-curved blades centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models. Three geometric variables, i.e., location of cut off, radius of cut off, and width of impeller, and one operating variable, i.e., flow rate, were selected as design variables. As a main result of the optimization, the efficiency was successfully improved. And, optimum design flow rate was found by using flow rate as one of design variables. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time.

scholarly journals A Study of RANS Turbulence Models in Fully Turbulent Jets: A Perspective for CFD-DEM Simulations

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 271
Author(s):  
Dustin Weaver ◽  
Sanja Mišković
Keyword(s):  
Stokes Equations ◽  
Near Field ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Turbulent Jets ◽  
Navier Stokes ◽  
Straight Tube ◽  
Developed Turbulence ◽  
Similar Work ◽  
Tube Geometry

This paper presents an analysis of linear viscous stress Favre averaged turbulence models for computational fluid dynamics (CFD) of fully turbulent round jets with a long straight tube geometry in the near field. Although similar work has been performed in the past with very relevant solutions, considerations were not given for the issues and limitations involved with coupling between an Eulerian and Lagrangian phase, such as in fully two-way coupled CFD-DEM. These issues include limitations on solution domain, mesh cell size, wall modelling, and momentum coupling between the two phases in relation to the particles size. Therefore, within these considerations, solutions are provided to the Navier–Stokes equations with various turbulence models using a three-dimensional wedge long straight tube geometry for fully developed turbulence flow. Simulations are performed with a Reynolds number of 13,000 and 51,000 using two different tube diameters. It is found that a modified k-ε turbulence model achieved the most agreeable results for both the velocity and turbulent flow fields between these two flow regimes, while a modified k-ω SST/BSL also provided suitable results.

Flow Analysis of the M151 Aircraft Model Using the Academic CFD Code Galatea

2017 ◽  
Author(s):  
Dimitrios A. Inglezakis ◽  
Georgios N. Lygidakis ◽  
Ioannis K. Nikolos
Keyword(s):  
Turbulent Flows ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Research Association ◽  
Navier Stokes Equations ◽  
Aircraft Model ◽  
Short Period

CFD (Computational Fluid Dynamics) solvers have become nowadays an integral part of the aerospace manufacturing process and product design, as their implementation allows for the prediction of the aerodynamic behavior of an aircraft in a relatively short period of time. Such an in-house academic solver, named Galatea, is used in this study for the prediction of the flow over the ARA (Aircraft Research Association) M151/1 aircraft model. The proposed node-centered finite-volume solver employs the RANS (Reynolds-Averaged Navier-Stokes) equations, combined with appropriate turbulence models, to account for the simulation of compressible turbulent flows on three-dimensional hybrid unstructured grids, composed of tetrahedral, prisms, and pyramids. A brief description of Galatea’s methodology is included, while attention is mainly directed toward the accurate prediction of pressure distribution on the wings’ surfaces of the aforementioned airplane, an uncommon combat aircraft research model with forward swept wings and canards. In particular, two different configurations of M151/1 were examined, namely, with parallel and expanding fuselage, while the obtained results were compared with those extracted with the commercial CFD software ANSYS CFX. A very good agreement is reported, demonstrating the proposed solver’s potential to predict accurately such demanding flows over complex geometries.

Sign in / Sign up

Export Citation Format

Share Document