Spanwise forcing for turbulent drag reduction: An experimental investigation into active and passive flow control

Turbulent drag reduction (DR) is a crucial research area, as this can contribute to significant energy and emission reductions in various industrial and transportation applications. One such technique is the active flow control method of spanwise forcing. Spanwise forcing introduces a spatio-temporal spanwise wall oscillation as a boundary...

A Bio-inspired Sensing Approach to in-Gust Flight of Flapping Wing MAVs

Flapping wing micro aerial vehicles (FWMAVs) are known for their flight agility and maneuverability. However, their in-gust flight performance and stability is still inferior to their biological counterparts. To this end, a simplified in-gust dynamic model, which could capture the main gust effects on FWMAVs, has been identified with real in...

Aerodynamics of trailer wheels in tandem: Experimental investigation into the effects of wheel rotation, trailer side-skirts, and wheel cavity covers

The increasing importance of drag reduction in commercial vehicles, traditionally motivated by rising energy costs, and more recently accelerated through policymaking in a bid to reduce emissions, has resulted in the development of increasingly sophisticated add-on aerodynamic devices for the semi-trailer. Of these devices, the greatest uptake...

Turbulent boundary layers over surfaces with streamwise-preferential permeability: Experimental investigation into the drag and flow mechanics

Turbulent drag is the largest source of fuel consumption in aviation and forms a significant contribution to climate warming. Recent numerical studies have suggested the ability of surfaces with streamwise-preferential permeability to reduce turbulent friction, and a theoretical framework behind the working mechanism has been proposed. This work...

An aerodynamic analysis of Hyperloop breach using a scaled physical test setup and background oriented schlieren

This master thesis investigates the aerodynamic response of the Hyperloop breach failure scenario. Using a scaled physical test setup, the air pressure inside a Hyperloop tube is lowered to 10 mbar, emulating Hyperloop conditions. By opening a breach hole inside the tube, air will flow into the tube due to the pressure difference with the...

Submerged Supersonic Intakes: An experimental investigation by means of PIV, Schlieren and pressure measurements

Supersonic intakes are essential in assuring proper combustion for operating ramjet engines on cruise missiles. However, due to increasing threats and a rapidly changing service environment, today's intakes do not fit anymore to comply with the new set of requirements to tackle the above challenges. Therefore, a novel supersonic intake design is...

Experimental investigation of ramp-induced shock–boundary-layer interactions in the presence of a sinusoidal roughness strip

Of the many challenges involved in developing reliable and sustainable spaceflight, perhaps none are so dangerous and difficult to study as the aerothermodynamic conditions involved when re-entering the atmosphere. These dangerous conditions typically occur due to a variety of flow phenomena, one of which is shock—boundary-layer interactions ...

Investigation of Hypersonic Transitional Shock Wave Boundary-Layer Interactions

The control surfaces of hypersonic lifting vehicles are some of the hardest parts to design. The reason for this is the very strong shock wave boundary-layer interactions present in front of the control surface. These interactions cannot only reduce the controllability of the vehicle, but they also cause considerable aerodynamic heating. It can...

Model-Based Control of Tollmien-Schlichting Waves using DBD Plasma Actuators: An Experimental Study

One of the main goals of laminar flow control is to reduce skin-friction drag by delaying the onset of laminar to turbulent transition. Over unswept wings, the leading cause of this is the growth of flow instabilities called Tollmien-Schlichting(TS) waves. This thesis aims to test the feasibility and performance of a designed Linear Quadratic...

Towards Practical Hybrid Laminar Flow Control: Boundary Layer Stability with Suction and Scalability of Pressure Losses across Perforated Sheets

Hybrid laminar flow control (HLFC) reduces skin friction drag, by combining boundary layer suction with pressure gradient tailoring to delay boundary layer transition. This research addresses two key developments required to perform the aerodynamic design of suction-type HLFC components. First, an existing numerical transition prediction tool...

Experiments on the drag of a flat plate moving parallel to an air-water interface

Rowing is a competitive sport where victory is determined by fine margins. In the past, the focus has been on optimizing the shell. Due to the increasing regulations placed on the shell design, the scope for manoeuvring in this area is greatly limited. This increases the necessity to focus on the less explored option of propulsion in rowing. The...

Investigation of the Effect of a Surface Protuberance on a High Speed Boundary Layer

One of the major challenges that engineers face when designing a high speed vehicle is aerodynamics heating. While ideally the external surfaces are expected to maintain a smooth profile, this is not the case in most vehicles, which might be laden with discontinuities like steps, gaps, and other protrusions. These could alter the local flow...

Submerged Ramjet Intake Modeling

To evaluate the performance of proposed submerged intakes in an early design phase, a performance analysis model able to evaluate a range of intake geometries is required. This document details how such a model was developed with the use of available sub-models for specific flow features. A formulation of the method of characteristics suitable...

Characterization of junction flow under the influence of passive flow control devices: An experimental study with large-scale tomographic PTV technique

Junction flow denotes the fluid phenomenon where the flow on a flat surface encounters a protuberance. This type of flow, which is highly three-dimensional, turbulent and unsteady, usually leads to the generation of a Horseshoe vortex at the obstacle's leading edge. Existing extensive experimental and numerical studies focus on the inception of...

Rotor noise and aero-acoustic optimization of wind turbine airfoils

The thesis is focused on designing a tip-region airfoil for a multi-MW wind turbine. It is approached with the objective of optimizing the geometry of the airfoil for the best trade-off between aero-acoustics and aerodynamic requirements. Using the wind turbine noise prediction tool SILANT it is established that trailing edge noise is the most...