scholarly journals Accurate RANS Simulation of Wind Turbine Stall by Turbulence Coefficient Calibration

2018 ◽  
Vol 8 (9) ◽  
pp. 1444 ◽  
Author(s):  
Wei Zhong ◽  
Hongwei Tang ◽  
Tongguang Wang ◽  
Chengyong Zhu
Keyword(s):  
Experimental Data ◽  
Wind Turbine ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Maximum Torque ◽  
Simulation Accuracy ◽  
Navier Stokes Equations ◽  
Pressure Distributions ◽  
Sst Turbulence Model ◽  
Better Than

Stall, a complex phenomenon related to flow separation, is difficult to be predicted accurately. The motivation of the present study is to propose an approach to improve the simulation accuracy of Reynolds Averaged Navier–Stokes equations (RANS) for wind turbines in stall. The approach is implemented in three steps in simulations of the S809 airfoil and the NREL (National Renewable Energy Laboratory) Phase VI rotor. The similarity between airfoil and rotor simulations is firstly investigated. It is found that the primary reason for the inaccuracy of rotor simulation is not the rotational effect or the 3-D effect, but the turbulence-related problem that already exists in airfoil simulation. Secondly, a coefficient of the SST turbulence model is calibrated in airfoil simulation, ensuring the onset and development of the light stall are predicted accurately. The lift of the airfoil in the light stall, which was overestimated about 30%, is reduced to a level consistent with experimental data. Thirdly, the calibrated coefficient is applied to rotor simulation. That makes the flow patterns on the blade properly simulated and the pressure distribution of the blade, as well as the torque of the rotor, are predicted more accurately. The relative error of the predicted maximum torque is reduced from 34.4% to 3.2%. Furthermore, the procedure of calibration is applied to the MEXICO (Model Experiments in Controlled Conditions) rotor, and the predicted pressure distributions over blade sections are better than the CFD (Computational Fluid Dynamics) results from the Mexnext project. In essence, the present study provides an approach for calibrating rotor simulation using airfoil experimental data, which enhances the potential of RANS in accurate simulation of the wind turbine aerodynamic performance.

Simulation of the Gap Resonance Between Two Rectangular Barges in Regular Waves by a Free Surface Viscous Flow Solver

2013 ◽  
Author(s):  
B. Elie ◽  
G. Reliquet ◽  
P.-E. Guillerm ◽  
O. Thilleul ◽  
P. Ferrant ◽  
...  
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Viscous Flow ◽  
Stokes Equations ◽  
Resonance Phenomenon ◽  
Navier Stokes ◽  
Regular Waves ◽  
Navier Stokes Equations ◽  
Flow Solver ◽  
Gap Resonance

This paper compares numerical and experimental results in the study of the resonance phenomenon which appears between two side-by-side fixed barges for different sea-states. Simulations were performed using SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach and results are compared with experimental data on two fixed barges with different headings and bilges. Numerical results, obtained using the SWENSE approach, are able to predict both the frequency and the magnitude of the RAO functions.

Расчетно-экспериментальное исследование влияния вдува/отсоса газа через перфорированную поверхность на пограничный слой при сверхзвуковом числе Маха

2021 ◽  
Vol 47 (21) ◽  
pp. 19
Author(s):  
П.А. Поливанов
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Stokes Equations ◽  
Numerical Data ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Navier Stokes Equations ◽  
Piv Method ◽  
Sst Turbulence Model ◽  
Method Analysis

In this paper a numerical and experimental study of the effect of blowing/suction through a perforated surface on a turbulent boundary layer at a Mach number M = 1.4 is carried out. Most of the calculations were performed by Reynolds-averaged Navier-Stokes equations with the k-w SST turbulence model. The calculated geometry completely repeated the experimental one including the perforated surface. The numerical data were compared with experimental measurements obtained by the PIV method. Analysis of the data made it possible to find the limits of applicability of the numerical method for this flow.

scholarly journals 3D Hydrodynamic Modelling Enhances the Design of Tendaho Dam Spillway, Ethiopia

Water ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 82
Author(s):  
Getnet Kebede Demeke ◽  
Dereje Hailu Asfaw ◽  
Yilma Seleshi Shiferaw
Keyword(s):  
Stokes Equations ◽  
Flow Behavior ◽  
Fluid Flows ◽  
Three Dimensions ◽  
Navier Stokes ◽  
Hydraulic Structures ◽  
Hydrodynamic Modelling ◽  
Navier Stokes Equations ◽  
Pressure Distributions ◽  
Computational Fluid Dynamics Cfd

Hydraulic structures are often complex and in many cases their designs require attention so that the flow behavior around hydraulic structures and their influence on the environment can be predicted accurately. Currently, more efficient computational fluid dynamics (CFD) codes can solve the Navier–Stokes equations in three-dimensions and free surface computation in a significantly improved manner. CFD has evolved into a powerful tool in simulating fluid flows. In addition, CFD with its advantages of lower cost and greater flexibility can reasonably predict the mean characteristics of flows such as velocity distributions, pressure distributions, and water surface profiles of complex problems in hydraulic engineering. In Ethiopia, Tendaho Dam Spillway was constructed recently, and one flood passed over the spillway. Although the flood was below the designed capacity, there was an overflow due to superelevation at the bend. Therefore, design of complex hydraulic structures using the state-of- art of 3D hydrodynamic modelling enhances the safety of the structures. 3D hydrodynamic modelling was used to verify the safety of the spillway using designed data and the result showed that the constructed hydraulic section is not safe unless it is modified.

scholarly journals Three-Dimensional Turbulent Vortex Shedding From a Surface-Mounted Square Cylinder: Predictions With Large-Eddy Simulations and URANS

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
B. A. Younis ◽  
A. Abrishamchi
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Navier Stokes Equations ◽  
Large Eddy

The paper reports on the prediction of the turbulent flow field around a three-dimensional, surface mounted, square-sectioned cylinder at Reynolds numbers in the range 104–105. The effects of turbulence are accounted for in two different ways: by performing large-eddy simulations (LES) with a Smagorinsky model for the subgrid-scale motions and by solving the unsteady form of the Reynolds-averaged Navier–Stokes equations (URANS) together with a turbulence model to determine the resulting Reynolds stresses. The turbulence model used is a two-equation, eddy-viscosity closure that incorporates a term designed to account for the interactions between the organized mean-flow periodicity and the random turbulent motions. Comparisons with experimental data show that the two approaches yield results that are generally comparable and in good accord with the experimental data. The main conclusion of this work is that the URANS approach, which is considerably less demanding in terms of computer resources than LES, can reliably be used for the prediction of unsteady separated flows provided that the effects of organized mean-flow unsteadiness on the turbulence are properly accounted for in the turbulence model.

A Numerical Study of the Hydrodynamics of Reversing Flows Around a Cylinder

1994 ◽  
Vol 116 (4) ◽  
pp. 202-208 ◽  
Author(s):  
K. Nakajima ◽  
Y. Kallinderis ◽  
I. Sibetheros ◽  
R. W. Miksad ◽  
K. Lambrakos
Keyword(s):  
Experimental Data ◽  
Finite Element Method ◽  
Stokes Equations ◽  
Numerical Study ◽  
Offshore Structures ◽  
Two Dimensions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Random Behavior ◽  
Marching Scheme

A numerical study of the nonlinear and random behavior of flow-induced forces on offshore structures and experimental verification of the results are presented. The numerical study is based on a finite-element method for the unsteady incompressible Navier-Stokes equations in two dimensions. The momentum equations combined with a pressure correction equation are solved employing fourth-order artificial dissipation with a nonstaggered grid, instead of the more commonly used staggered meshes. The solution is advanced in time with a combined explicit and implicit marching scheme. Emphasis is placed on study of reversing flows around a cylinder. Comparisons with experimental data evaluate accuracy and robustness of the method.

Laminar Source Flow Between Two Parallel Coaxial Disks Rotating at Different Speeds

1967 ◽  
Vol 34 (3) ◽  
pp. 541-547 ◽  
Author(s):  
F. Kreith ◽  
H. Viviand
Keyword(s):  
Series Expansion ◽  
Stokes Equations ◽  
Double Series ◽  
Navier Stokes ◽  
Large Radius ◽  
Laminar Regime ◽  
Navier Stokes Equations ◽  
Pressure Distributions ◽  
Flow Configurations ◽  
Source Flow

This article presents an analysis of the flow in the gap between two parallel coaxial disks rotating at different velocities, with a source in the center. The Navier-Stokes equations are solved by double series expansion about a known solution at a large radius, and velocity and pressure distributions are calculated for the laminar regime. The interaction between the source flow and the rotational effects is investigated by a method valid for small rotational Taylor numbers of the disks. Several flow configurations are shown to be physically possible, and the magnitude of the parameters delineating the different flow regimes are calculated.

OIL SPREADING UNDER ICE COVERS

1989 ◽  
Vol 1989 (1) ◽  
pp. 161-166 ◽  
Author(s):  
Poojitha D. Yapa ◽  
Tamara Chowdhury
Keyword(s):  
Experimental Data ◽  
Laboratory Experiments ◽  
Stokes Equations ◽  
Constant Volume ◽  
Navier Stokes ◽  
Discharge Mode ◽  
Navier Stokes Equations ◽  
Discharge Rates ◽  
Volume Mode ◽  
Balance Of Forces

ABSTRACT A new set of equations is presented for describing oil spreading under ice in calm waters. These equations consider the constant discharge mode, constant volume mode, and termination of spreading due to a balance of forces. Therefore, a complete description of the spreading phenomena from the time of initial spill to termination of spreading is presented. The equations are derived based on a simplified form of Navier-Stokes equations. Laboratory experiments were conducted using ice covers of different roughnesses, oils of different viscosities, and varying discharge rates. The theory agrees closely with the experimental data.

Numerical Study on Impeller Performance of Mini Hydro Turbine

2015 ◽  
Vol 772 ◽  
pp. 552-555 ◽  
Author(s):  
Kyu Han Kim ◽  
Joni Cahyono
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Hydro Turbine ◽  
Pressure Distributions ◽  
Power Outputs

The aim of this paper is to numerically explore the feasibility of designing a Mini-Hydro turbine. The interest for this kind of horizontal axis turbine relies on its versatility. In the present study, the numerical solution of the discredited three-dimensional, incompressible Navier-Stokes equations over an unstructured grid is accomplished with an ANSYS program. In this study, a mini hydro turbine (3kW) has been considered for utilization of horizontal axis impeller. The turbine performance and flow behavior have been evaluated by means of numerical simulations. Moreover, the performance of the impeller varied in the pressure distribution, torque, rotational speed and power generated by the different number of blades and angles. The results trends are similar between the highest pressure distributions at the impeller also produced highest power outputs on 6 numbers of blades at impeller. The model has been validated, comparing numerical results with available experimental data.

Dynamic Stall Control by Undulatory Deformation

2013 ◽  
Vol 444-445 ◽  
pp. 299-303
Author(s):  
Lan Ge ◽  
Wen Rong Hu
Keyword(s):  
Stokes Equations ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Reynolds Average Navier Stokes ◽  
Navier Stokes Equations ◽  
Stall Angle ◽  
Stall Control ◽  
Reynolds Average ◽  
High Angles Of Attack ◽  
Better Than

Dynamic stall can delay the stall of wings and airfoils that are rapidly pitched beyond the static stall angle. A new method of active dynamic stall control by the undulatory foil was proposed in this paper. The study was based on solving unsteady Reynolds-Average Navier-Stokes equations. Comparisons of the effectiveness of pitching foils and undulatory foils on dynamic stall control in both light stall and deep stall were conducted. The undulatory foils with various controllable parameters were further discussed. The results showed that the performance of undulatory foils is much better than that of the rigid pitching foil at high angles of attack either in the light stall or in the deep stall situation.

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