An integral boundary layer method for modelling the effects of vortex generators

In this work, the measured modulated integral boundary layer (IBL) characteristics of low-profile vortex generators (VGs) are used to validate new developments in a viscousinviscid interaction code which is modified to incorporate the effect of the passive mixing devices. The motivations are laid out and sample validation data is presented...

Modeling of particle imaging through shock waves

In compressible flows particle imaging, as done in Particle Image Velocimetry (PIV), is far from trivial. The inhomogeneous refractive index field can cause aero-optical aberrations including blurring of the image, especially near optical interfaces such as shock waves. The understanding of the process causing particle image blur (or blurring of...

Image based measurement techniques for aircraft propeller flow diagnostics: Propeller slipstream investigations at high-lift conditions and thrust reverse

The aim of the thesis is to measure the propeller slipstream properties (velocity and vorticity) and to assess the unsteady and instantaneous behavior of the propeller flow field at high disk loadings, zero thrust and thrust reverse using the image based measurement techniques. Along with its implementation of the techniques in industrial...

Adaptive image interrogation for PIV: Application to compressible flows and interfaces

As an experimental tool, Particle Image Velocimetry has quickly superseded traditional point-wise measurements. The inherent image processing has become standardized though the performances are strongly dependent on user experience. Moreover, the arduously selected image interrogation parameters are applied uniformly throughout the image...

On the scaling and unsteadiness of shock induced separation

Shock wave boundary layer interactions (SWBLI) are a common phenomenon in transonic and supersonic flows. The presence of shock waves, induced by specific geometrical configurations, causes a rapid increase of the pressure, which can lead to flow separation. Examples of such interactions are found in amongst others rocket engine nozzles and on...

Surface pressure and aerodynamic loads determination of a transonic airfoil based on particle image velocimetry

The present investigation assesses a procedure to extract the aerodynamic loads and pressure distribution on an airfoil in the transonic flow regime from particle image velocimetry (PIV) measurements. The wind tunnel model is a two-dimensional NACA-0012 airfoil, and the PIV velocity data are used to evaluate pressure fields, whereas lift and...

An adaptive sampling and windowing interrogation method in PIV

Effects of micro-ramps on a shock wave/turbulent boundary layer interaction

Stereoscopic particle image velocimetry is used to investigate the effects of micro-ramp sub-boundary layer vortex generators, on an incident shock wave/boundary layer interaction at Mach 1.84. Single- and double-row arrangements of micro-ramps are considered. The micro-ramps have a height of 20% of the unperturbed boundary layer thickness and...

Vortex velocimetry of air flows using Helium Filled Soap Bubbles (HFSB)

This thesis work illustrates the first of its kind solution to this problem of lack of seeding at vortex core in air flows, by the use of Helium Filled Soap Bubble (HFSB) which is a neutrally buoyant tracer particle in air flows. To analyse the lack of seeding in the vortex core, a 2D numerical simulation of particle motion in vortex flow is...

Going against the flow: An experimental investigation into the flow mechanics of dimpled surfaces in turbulent boundary layers

Any reduction in vehicle drag or fluid resistance provides a potential of substantial energy savings, with obvious benefits to the economy, environment and overall industrial competitiveness. Although various experimental studies have confirmed the potential drag reduction of dimpled surfaces in a turbulent boundary layer (BL), the working...

Estimation and reduction of peak-locking errors in PIV measurements

In PIV, the systematic tendency of the measured sub-pixel displacement to be biased towards the integral pixel values is called peak-locking. This occurs when the particle image diameter is less than a pixel. The bias error causes inaccuracy in the measured PIV data which does not reduces with increase in the sample size. Recently developed...

Experimental analysis of the flow around a cylinder with a square cross-section

The present work investigates the flow around a two-dimensional square section object at varying angles of incidence. The experimental approach employs Particle Image Velocimetry for the determination of the time-averaged velocity field and the unsteady large scale coherent variations (e.g. vortex shedding) as well as turbulent fluctuations. The...

Stereoscopic PIV on a delta wing in supersonic flow

Ever since the 1950s delta wings are being used as an efficient planform for supersonic flight. Over time extensive research on the aerodynamics of this type of wings has been performed using many different measurement techniques. Due to technical difficulties, measurements on delta wings in a supersonic flow are still scarce and often limited...

On the tracing fidelity of helium-filled soap bubbles for PIV experiments

This thesis follows a previous study on the aerodynamic characterization of helium-filled soap bubbles (HFSBs) for large-scale PIV measurements and aims at characterizing statistically the tracing fidelity of HFSBs in PIV experiments, considering the statistical distribution of the bubbles diameter, slip velocity, relaxation time and density....

Experimental study on the energy deposition of an ns-DBD plasma actuator and its effect on a laminar boundary layer

An experimental study aimed at the influence of different barrier materials on the energy deposition of nanosecond pulsed dielectric barrier discharge (ns-DBD) plasma actuator was carried out. Additionally, the direct effect of the discharge of an ns-DBD plasma actuator on a low velocity laminar boundary layer was investigated. Three barrier...