Viscous-inviscid Interaction Technique Research Articles

Aerodynamic wind-turbine rotor design using surrogate modeling and three-dimensional viscous–inviscid interaction technique

In this paper a surrogate optimization methodology using a three-dimensional viscous-inviscid interaction code for the aerodynamic design of wind-turbine rotors is presented. The framework presents a unique approach because it does not require the commonly-used blade element momentum (BEM) method. The three-dimensional viscous-inviscid interaction code used here is the accurate and fast MIRAS code developed at the Technical University of Denmark. In comparison with BEM, MIRAS is a higher-fidelity aerodynamic tool and thus more computationally expensive as well. Designing a rotor using MIRAS instead of an inexpensive BEM code represents a challenge, which is resolved by using the proposed surrogate-based approach. As a verification case, the methodology is applied to design a model wind-turbine rotor and is compared in detail with the one designed with BEM. Results demonstrate that nearly identical aerodynamic performance can be achieved using the new design method and that the methodology is effective for the aerodynamic design of wind-turbine rotors.

A quasi-3D viscous-inviscid interaction code: Q3UIC

A computational model for predicting the aerodynamic behavior of wind turbine airfoils under rotation and subjected to steady and unsteady motions developed in [1] is presented herein. The model is based on a viscous-inviscid interaction technique using strong coupling between the viscous and inviscid parts. The rotational effects generated by centrifugal and Coriolis forces are introduced in Q3UIC via the streamwise and spanwise integral boundary layer momentum equations. A special inviscid version of the code has been developed to cope with massive separation. To check the ability of the code wind turbine airfoils in steady and unsteady conditions for a large range of angles of attack are considered here. Further, the new quasi-3D code Q3UIC is used to perform a parametric study of a wind turbine airfoil under rotation confined to its boundary layer.

Simulations of the Yawed MEXICO Rotor Using a Viscous-Inviscid Panel Method

In the present work the viscous-inviscid interactive model MIRAS is used to simulate flows past the MEXICO rotor in yawed conditions. The solver is based on an unsteady three-dimensional free wake panel method which uses a strong viscous-inviscid interaction technique to account for the viscous effects inside the boundary layer. Calculated wake velocities have been benchmarked against field PIV measurements, while computed blade aerodynamic characteristics are compared against the load calculated from pressure measurements at different locations along the blade span. Predicted and measured aerodynamic forces are in overall good agreement, however discrepancies appear in the root region which could be related to an underestimation of the rotational effects arising from Coriolis and centrifugal forces. The predicted wake velocities are generally in good agreement with measurements along the radial as well as the axial traverses performed during the experimental campaign.

Numerical Simulation of Transonic Flow over Wing-Mounted Twin-Engine Transport Aircraft

A numerical method has been developed for computing the e owe eld around advanced transport aircraft with wing-mounted nacelles. The method is based on a multiblock point-matched grid-generation approach combined with zonal solving strategy for complex e owe eld. In this study the e owe eld is divided into a number of nonoverlapped blocks by a cutout technique. H-type grids are generated independently in each block using an elliptic grid-generation method, in which the control of the grid quality is accomplished by the forcing-function technique of Hilgenstock. The e owe eld is simulated by solving the Euler equations. An explicit three-stage Runge ‐Kutta algorithm based on the Jameson’ s e nite volume scheme for the Euler equations has been developed that is applied to the multiregion H-type grids. The present method has been applied to isolated powered engine nacelles and complex transport aircrafts consisting of low-wing/fuselage with wing-mounted pylon/nacelles. On the wing surfaces the viscous effects are simulated by the employment of the viscous/inviscid interaction (VII) technique of two-dimensional strip boundary layer. In this study the boundary-layer program uses an integral method to calculate turbulent boundary layers. With the concept of an equivalent inviscid e ow, the model of blowing velocity is employed in the VII technique. The effect of the boundary layeron the outer inviscid e ow is represented through a transpiration boundaryconditionderived from theboundary-layerparameters.Themain benee tofthistreatment isthatthegridisgeneratedonlyonceinoverallcomputingprocedure.Computationalresultsandcomparisonswith experimental data are presented. The good agreement indicates that the present method is effective in predicting the e ows about powered engine nacelles and/or complex transport aircrafts.

Prediction of ice accretion with viscous effects on aircraft wings

A method using the viscous-inviscid interaction technique has been developed for the calculation of ice accretion on three-dimensional wings of any cross section or planform geometry. This technique matches a panel method for external potential calculation with a boundary-layer correction to calculate the flowfield. The resulting velocity field is subsequently used to compute water droplet trajectories and their impact points on the wing to obtain the quantity of ice accumulated. The method yields ice shapes that are in good agreement with numerical and experimental results in rime ice conditions.

Computation of unsteady supersonic quasi-one-dimensional viscous-inviscid interacting internal flowfields

The present steady and unsteady quasi-1D internal supersonic flowfield calculations employs a novel viscous-inviscid interaction technique directly coupling and simultaneously solving the inviscid and viscous equations. The coupled system is numerically solved using a two-stage Runge-Kutta scheme with first-order one-sided spatial differencing. Simple supersonic internal flow test cases are computed to demonstrate the capabilities of the computational procedure.

A New Technique for Computing Viscous-Inviscid Interactions in Internal Flows

A new viscous-inviscid interaction technique has been developed for computing separated flow in planar diffusers. The method couples a set of integral equations for the boundary layers to a fully elliptic potential core flow. Rapid convergence of the method is demonstrated for planar diffusers with large regions of transitory stall. For these cases, convergence of the new method is an order of magnitude faster than that obtained using the interaction schemes of Carter and Le Balleur. Good agreement between the prediction method and experimental data is obtained for diffusers that are operating near peak pressure recovery. More importantly, the onset of asymmetric detachment is successfully predicted for these cases.