Whirl and Stall Flutter Simulation Using CFD

This paper presents recent research on numerical methods for whirl and stall flutter using computational fluid dynamics. The method involves coupling of the HMB3 CFD solver of the University of Glasgow and a NASTRAN derived structural model. Based upon a literature survey, a significant amount of research has been conducted on the numerical investigation of tiltrotors, with a focus on the XV-15 and V-22 aircraft. Within this paper, the coupling procedure is presented along with a steady CFD computation to highlight the accuracy of the high-fidelity method. In addition to this, a simple method is used to investigate the whirl flutter boundary of a standard propeller and the XV-15 blade

Parallel Performance for a Real Time Lattice Boltzmann Code

The paper will present the details of a Lattice Boltzmann solver running in real time for unsteady wake computations. In addition to algorithmic implementation, computational results, single core and parallel optimization of the methods are also discussed

Computational aeroelastic analysis of a hovering W3 Sokol blade with gurney flap

This paper demonstrates the potential effect of a gurney flap on the performance of the W3-Sokol rotor blade in hover. A rigid blade was first considered and the calculations were conducted at several thrust settings. The gurney flap was extended from 46%R to 66%R and it was located at the trailing edge of the main rotor blade. Four different sizes of gurney flaps were studied, 2%, 1%, 0.5% and 0.3% of the chord. The biggest flap proved to be the most effective. A second study considered elastic blades with and without the gurney flap. The results were trimmed at the same thrust values as the rigid blade and indicate an increase of aerodynamic performance when the gurney flap is used, especially for high thrust cases

Transient aeroelastic response control of a shipboard rotor during engagements by active Gurney flaps

No abstract available

Numerical investigation of a two-bladed propeller inflow at yaw

The development of faster computing power and nonintrusive experimental techniques has allowed for the advancement in computational fluid dynamics (CFD) validation and the greater understanding of aerodynamic conditions previously deemed too extreme to accurately measure. To this end, a numerical study is conducted that focuses on a propeller at yaw. Current low-order methods are reliant upon an accurate inflow profile to determine overall blade loading patterns. To improve such methods, CFD can be used to determine an initial inflow profile from which to conduct additional lower-order calculations. Therefore, to ensure that CFD is able to accurately capture yawed inflow profiles, a validation study is conducted that compares numerical simulations against experiments. Good agreement is found between the two methods, and subsequently the azimuthal variation in skin friction and induced angle of attack, as a result of the yawed conditions, is analyzed

A Time-Marching Aeroelastic Method Applied to Propeller Flutter

A time-marching aeroelastic method developed for the study of propeller flutter is presented and validated. Propeller flutter can take many forms with stall, whirl and classical flutter being the primary responses. These types of flutter require accurate capture of the non-linear aerodynamics associated with propeller blades. Stall flutter in particular, due to the highly detached nature of the flow, needs detailed unsteady flow modelling. With the development of modern propeller designs potentially adjusting the flutter boundary and the development of faster computing power, CFD is required to ensure accurate capture of aerodynamics. This paper focuses on the validation of the aeroelastic method using the Commander propeller blade

Processing and analysis methods for transonic cavity flow

This paper focuses on the localisation of noise sources in transonic cavity flows. Beamforming is used to estimate the pressure fluctuations inside a resonant transonic cavity, showing the localisation of the main sources of noise using an acoustic array and also combining it with a mean flow-field. The influence of the microphone array position, density, and shape is investigated. The presented method models the noise propagation with simple assumptions that are easily applicable to wind tunnel testing and may help localise the noise sources from complex geometries without intrusive methods

Latest results from the EU project AVATAR: aerodynamic modelling of 10 MW wind turbines

This paper presents the most recent results from the EU project AVATAR in which aerodynamic models are improved and validated for wind turbines on a scale of 10 MW and more. Measurements on a DU 00-W-212 airfoil are presented which have been taken in the pressurized DNW-HDG wind tunnel up to a Reynolds number of 15 Million. These measurements are compared with measurements in the LM wind tunnel for Reynolds numbers of 3 and 6 Million and with calculational results. In the analysis of results special attention is paid to high Reynolds numbers effects. CFD calculations on airfoil performance showed an unexpected large scatter which eventually was reduced by paying even more attention to grid independency and domain size in relation to grid topology. Moreover calculations are presented on flow devices (leading and trailing edge flaps and vortex generators). Finally results are shown between results from 3D rotor models where a comparison is made between results from vortex wake methods and BEM methods at yawed conditions

Final results from the EU project AVATAR: aerodynamic modelling of 10 MW wind turbines

This paper presents final results from the EU project AVATAR in which aerodynamic models are improved and validated for wind turbines on a scale of 10 MW and more. Special attention is paid to the improvement of low fidelity engineering (BEM based) models with higher fidelity (CFD) models but also with intermediate fidelity free vortex wake (FVW) models. The latter methods were found to be a good basis for improvement of induction modelling in engineering methods amongst others for the prediction of yawed cases, which in AVATAR was found to be one of the most challenging subjects to model. FVW methods also helped to improve the prediction of tip losses. Aero-elastic calculations with BEM based and FVW based models showed that fatigue loads for normal production cases were over predicted with approximately 15% or even more. It should then be realised that the outcome of BEM based models does not only depend on the choice of engineering add-ons (as is often assumed) but it is also heavily dependent on the way the induced velocities are solved. To this end an annulus and element approach are discussed which are assessed with the aid of FVW methods. For the prediction of fatigue loads the so-called element approach is recommended but the derived yaw models rely on an annulus approach which pleads for a generalised solution method for the induced velocities

Study of Blade/Vortex interaction using Computational Fluid Dynamics and Computational Aeroacoustics

Abstract A parametric study of the aerodynamics and the acoustics of parallel BVI has been carried out for different aerofoil shapes and vortex properties. Computing BVI using Computational Fluid Dynamics is challenging since the solution scheme tends to alter the characteristics of the vortex which must be preserved until the interaction. The present work uses the Compressible Vorticity Confinement Method (CVCM) for capturing the vortex characteristics, which is easier to implement and has minimal overhead in the performance of existing CFD solvers either in terms of CPU time or robustness during convergence. Apart from applying the CVCM method with an upwind solver, something not encountered in the literature, the present work couples CFD with Computational Aeroacoustics (CAA) and uses the strengths of both techniques in order to predict the nearfield and farfield noise. Results illustrate the importance of the aerofoil shape at transonic flow and show that the magnitude of the BVI noise depends strongly on the vortex strength and the miss-distance. The effect of the vortex core radius was also found to be important