Unsteady Interacting Boundary Layer Method

Özdemir, Hüseyin; Garrel, A. van; Ravishankara, Akshay Koodly; Passalacqua, F.; Seubers, Henk

doi:10.2514/6.2017-2003

Cited by 8 publications

(8 citation statements)

References 25 publications

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“…In parallel to the development of a panel method for threedimensional unsteady flows 36 , Özdemir and co-workers performed various studies to solve the unsteady form of the integral boundary layer equations employing a high-order discontinuous Galerkin method with a non-conservative flux scheme 37,38 together with the quasi-simultaneous interaction method of Veldman 34,39 . In a recent publication Özdemir et al demonstrated a proof-of-concept of this method 40 . A fully 3D approach for steady flows is currently also investigated by Drela and fellow researchers 41,42 .…”

Section: Wind Turbine Aerodynamics -Reviving Aerospace Aerodynammentioning

confidence: 99%

Wind Turbine Aerodynamics from an Aerospace Perspective

Garrel

Pas

Venner

et al. 2018

2018 Wind Energy Symposium

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The current challenges in wind turbine aerodynamics simulations share a number of similarities with the challenges that the aerospace industry has faced in the past. Some of the current challenges in the aerospace aerodynamics community are also relevant for today's wind turbine aerodynamics community and vice versa. This paper sketches these similarities in broad strokes and points out the possibilities to revive solutions from the aerospace aerodynamics community from the 1960's onward that, with some modifications, can be applied to wind turbine aerodynamics problems. Opportunities are indicated where both the wind turbine and the aerospace aerodynamics communities can benefit from collaborative research. Nomenclature BEM = Blade-Element-Momentum CFD = Computational Fluid Dynamics Cp = Power coefficient CoE = Cost of Energy IBL = Integral Boundary Layer LES = Large Eddy Simulation RaNS = Reynolds-averaged Navier Stokes VII = Viscous-Inviscid Interaction λ = Tip speed ratio (rotor tip speed/wind speed)

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Section: Wind Turbine Aerodynamics -Reviving Aerospace Aerodynammentioning

confidence: 99%

Wind Turbine Aerodynamics from an Aerospace Perspective

Garrel

Pas

Venner

et al. 2018

2018 Wind Energy Symposium

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“…Performing such (three-dimensional) CFD simulations during the design phase of wind turbines is prohibitively expensive and a simpler solution is desired. Current wind turbine design tools are based on Blade Element Momentum (BEM) theory [8] and other local blade aerodynamic methods based on the solution of integral boundary layer equations together with the inviscid potential equations coupled with an appropriate viscous-inviscid interaction scheme [9][10][11] (also called interacting boundary layer method). Incorporating the effects of blade add-ons like VGs into such tools will allow for better and more efficient designs at a fraction of the cost compared to full three-dimensional CFD methods.…”

Section: Introductionmentioning

confidence: 99%

“…The boundary layer profiles extracted from the CFD simulations of flow over a flat plate with and without VGs and are used to derive an algebraic model for the IBL method and presented in VII. The flat plate models are implemented in an in-house integral boundary layer method [11].…”

Section: Introductionmentioning

confidence: 99%

Towards a Vortex Generator Model for Integral Boundary Layer Methods

Ravishanara

Özdemir²,

Franco

2019

AIAA Scitech 2019 Forum

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In this study a new approach to model the effect of vortex generators in integral boundary layer equations is described. Vortex generators (VGs) are commonly used on wind turbine blades to avoid early separation of flow which helps not only to increase the lift but also delays the stall. Delaying the stall angle of wind turbine blades will allow for operation over larger range of angle of attacks and thus increase power production from wind turbines. Typically, VGs are submerged in the boundary layer and generate vortices that mix high-energy fluid from outer flow with the slow-moving boundary layer. Within this study the effect of the VGs on the 2-D boundary layers are modeled as additional mixing. The presence of a new shear layer will lead to additional viscous dissipation and affect the wall shear stress. To model these effects new terms are introduced into the integral boundary layer equations to account for the extra mass and momentum flux and turbulence production. The additional unknowns introduced into the system of equations are derived using CFD simulations. Initial CFD simulations on a flat plate with body fitted meshes around VGs are used to obtain an algebraic model. The new model is implemented in an aerodynamic analysis and design tool and preliminary results are presented. The theory developed here will be extended for flows over airfoils.

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“…A 3D integral boundary layer (IBL) method is recommended as it keeps the problem, like the panel method, restricted to the surface of the blades and the wake surfaces. For wind turbine applications, unsteady flow and the effects of rotation on the development of the boundary layer should be taken into account (see [36], [83]- [86], [103], [105]). …”

Section: Discussionmentioning

confidence: 99%

“…This particular combination of models for the inviscid external flow and the viscous flow in the boundary layer keeps the mathematical problem restricted to the surface of the configuration for both models and thus avoids a timeconsuming volume discretization. The development of an unsteady 3D IBL method has been started by Özdemir [83], [84], [85], [86] and an investigation into a 3D viscous-inviscid interaction algorithm has been performed by Bijleveld [12], [13] in collaboration with Veldman (see [107], [108], [109]) at the University of Groningen.…”

Section: Challengesmentioning

confidence: 99%

Multilevel panel method for wind turbine rotor flow simulations

Garrel¹

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SummaryThe ongoing trend in wind turbine development is towards larger rotors because of the resulting lower cost of energy. These large rotors lead to relatively flexible structures that are more susceptible to the unsteady aerodynamic loading occurring in normal operating conditions. An accurate prediction of these loadings is important for the design of an economically viable and technically reliable wind turbine. Simulation methods of wind turbine aerodynamics currently in use mainly fall into two categories: the first is the group of traditional low-fidelity engineering models and the second is the group of computationally expensive CFD methods based on the Navier-Stokes equations.For an engineering environment the search is for "medium fidelity" wind turbine simulation methods that bridge the gap between the computationally inexpensive low-fidelity methods and the computationally expensive CFD methods. The ultimate goal is a balanced mixture of higher accuracy of the representation of the physics and shorter simulation times for wind turbine aerodynamics simulation methods. This can be found in the combination of the theories for panel methods, integral boundary layer methods, strong viscous-inviscid coupling, and fluid structure interaction.The present study focuses on the development of the theory and the practical implementation of a fast multilevel integral transform in a computer program. We utilize this multilevel scheme in a low-order panel method. It is demonstrated that for the simulation of the wake flow of wind turbine rotors the computational burden is reduced from O(N 2 ) for a conventional panel method to O(N ) for the present method. This implies that the computational effort is reduced to grow linearly with problem size N , with N the number of panels.We consider the unsteady, incompressible flow around wind turbine rotors and assume the effects of viscosity to be confined to infinitesimal thin boundary layers and wake regions and assume irrotational flow elsewhere. These assumptions allows us to reduce the flow problem to the problem of solving the Laplace equation for a (scalar) velocity potential function. This makes it possible to reformulate the problem as an integral equation over the surface of the rotor and the wakes that emanate from the trailing edges of the rotating wind turbine blades.The mathematical model is discretized in the form of a low-order panel iii Multilevel Panel Method method. The implementation of the panel method is verified by considering the flow over a stationary ellipsoid in a uniform onset velocity field, the flow over a rotating ellipsoid in a fluid at rest, and by considering the flow over a high aspect ratio wing with elliptic planform with as cross-section a von Kármán-Trefftz airfoil. For the first two test cases the numerical results are compared with analytical solutions. The error in the velocity potential is shown to be O(h 2 ), with h a characteristic panel size. The third test case uses the analytical solution for the 2D von Kármán-Trefftz airfoil ...

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Unsteady Interacting Boundary Layer Method

Cited by 8 publications

References 25 publications

Wind Turbine Aerodynamics from an Aerospace Perspective

Wind Turbine Aerodynamics from an Aerospace Perspective

Towards a Vortex Generator Model for Integral Boundary Layer Methods

Multilevel panel method for wind turbine rotor flow simulations

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