Experimental comparison of a wind-turbine and of an actuator-disc near wake

The actuator disc (AD) model is commonly used to simplify the simulation of horizontal-axis wind-turbine aerodynamics. The limitations of this approach in reproducing the wake losses in wind farm simulations have been proven by a previous research. The present study is aimed at providing an experimental analysis of the near-wake turbulent flow...

HFSB-seeding for large-scale tomographic PIV in wind tunnels

A new system for large-scale tomographic particle image velocimetry in low-speed wind tunnels is presented. The system relies upon the use of sub-millimetre helium-filled soap bubbles as flow tracers, which scatter light with intensity several orders of magnitude higher than micron-sized droplets. With respect to a single bubble generator,...

A posteriori uncertainty quantification of PIV-based pressure data

A methodology for a posteriori uncertainty quantification of pressure data retrieved from particle image velocimetry (PIV) is proposed. It relies upon the Bayesian framework, where the posterior distribution (probability distribution of the true velocity, given the PIV measurements) is obtained from the prior distribution (prior knowledge of...

Three-dimensional flow field over a trailing-edge serration and implications on broadband noise

The three-dimensional flow field over the suction side of a NACA 0018 airfoil with trailing-edge serrations was studied by means of time-resolved tomographic particle image velocimetry. Mean flow results show that the boundary layer thickness decreases along the streamwise direction with a corresponding reduction of the size of the turbulent...

Gazing at clouds to understand turbulence on wind turbine airfoils

There are many ways to learn from data. Our first experiment consisted in reproducing the way aerodynamicists work [2] with a genetic optimizer. The data pool was too narrow and asymptotic tendencies were unreliable. Our 2nd Experiment, a simple version of [4], had a virtually unlimited data pool and used neural networks. Results were better,...

Point vortex modelling of the wake dynamics behind asymmetric vortex generator arrays

In this work, we present a simple inviscid point vortex model to study the dynamics of asymmetric vortex rows, as might appear behind misaligned vortex generator vanes. Starting from the existing solution of the in_nite vortex cascade, a numerical model of four base-vortices is chosen to represent two primary counter-rotating vortex pairs and...

Boundary layer characterization and acoustic measurements of flow-aligned trailing edge serrations

Trailing edge serrations designed to reduce airfoil self-noise are retrofitted on a NACA 0018 airfoil. An investigation of the boundary layer flow statistical properties is performed using time-resolved stereoscopic PIV. Three streamwise locations over the edge of the serrations are compared. An analysis of the results indicates that, while...

How does the presence of a body affect the performance of an actuator disk?

The article seeks to unify the treatment of conservative force interactions between axi-symmetric bodies and actuators in inviscid ow. Applications include the study of hub interference, di_user augmented wind turbines and boundary layer ingestion propeller con_gurations. The conservation equations are integrated over in_nitesimal streamtubes to...

Flow topology and acoustic emissions of trailing edge serrations at incidence

The flow past a NACA 0018 airfoil with sawtooth trailing edge serrations has been investigated using stereoscopic particle image velocimetry (PIV). The serration flap angle and airfoil incidence are varied in order to study the effect of secondary flow establishing between the suction and pressure sides of the serrations. The flow topology...

Mitigation of Pusher-Propeller Installation Effects by Pylon Trailing-Edge Blowing

This paper presents an experimental assessment of the working principles of pylon trailing-edge blowing for the mitigation of the interaction between a pusher propeller and its associated pylon. The experiments were performed at the Large Low-Speed Facility of the German–Dutch wind tunnels (DNW–LLF), using a powered propeller model and an...

Pusher-Propeller Installation Effects in Angular Inflow

Pylon-mounted pusher propellers suffer from installation effects due to the interaction between the pylon and the propeller. The impact of angular inflow on these installation effects was quantified at the Large Low-Speed Facility of the German-Dutch wind tunnels (DNW-LLF). Particle-image-velocimetry measurements showed that the pylon wake's...

Pusher-Propeller Blade Loading With and Without Pylon Trailing-Edge Blowing

The aerodynamic interaction e_ects characteristic of pusher propellers were studied at the Large Low-Speed Facility of the German{Dutch wind tunnels (DNW-LLF). A propeller model was positioned downstream of a pylon equipped with a trailing-edge blowing system. Surface-pressure transducers integrated into the propeller blades con_rmed the local...