Wings with leading-edge (LE) tubercles have gained increasing attention over the past decade. Despite their impressive aerodynamic performance, the underlying flow control mechanisms of tubercles remain controversial. In this thesis, both experimental and theoretical approaches are employed to investigate the flow patterns of a tubercled wing at pre-stall and post-stall angles of attack (AoAs).

In the experimental study, 2D Particle Image Velocimetry (PIV) was used to measure flow patterns at cross-flow planes along the chord. At a pre-stall AoA, high-vorticity regions generated by the tubercles appear in an alternating pattern near the LE. A quantitative comparison was conducted to examine the similarities between a tubercle and a delta wing. The results show that tubercles cannot be regarded as small delta wings in terms of vortex generation. The leading-edge vortex (LEV) sheets are convected downstream, where they interact with laminar separation bubbles (LSBs), creating complex flow patterns in the downstream regions. At a post-stall AoA, stall cells (SCs) appear along the span, with their formation dependent on both Reynolds number (Re) and tubercle amplitude. However, the spacing of SCs is relatively independent of AoA, Re, and amplitude, consistently ranging between 5 to 7 tubercle wavelengths.

In the theoretical study, the lifting line theory (LLT) approach was first used to predict the LEV strength but proved ineffective due to the absence of thickness effects. A subsequent analysis using the panel method in xflr5 showed that the Kutta condition should also be applied to the leading edge (LE) rather than only to the trailing edge (TE). Crow’s model was adapted by taking LEVs into consideration. However, a global description of the instability was not obtained due to difficulties in representing LEVs and related mathematical challenges.

This thesis contributes to a further understanding of the tubercle’s role in flow control. The LEVs generated by the tubercles are identified as key factors influencing flow evolution, yet these effects are not captured by LLT-based models or a conventional panel method. Future reduced-order models (ROMs) should account for the influence of LEVs to provide accurate representations of tubercled wing flow dynamics.

This thesis aims to study the effects of enhanced flow entrainment in a VAWT wind farm. This is achieved by advection of low momentum wake into the free-stream flow via lateral forces, and these forces are introduced by pitching the rotor blades.
For this study, scaled down VAWT models have been designed and setup in a wind farm layout. This wind farm model has been tested in the Open Jet Facility (OJF) of the Delft University of Technology to gather insight into the farm's flow behaviour. The wake is acquired using Tomographic Particle Tracking Velocimetry (PTV) measurement technique, where the flow is measured by acquiring images of Helium Filled Soap Bubbles (HFSB), suspended in the flow-stream. The performance of individual turbines is characterized by taking the load measurements, and comparing the thrust coefficients.

With the increased use of Advanced Driver Assistance Systems (ADAS) in modern cars, the  field of surface contamination saw a resurgence. To keep the various sensors working properly it is of utmost importance to keep them clean and free of contamination. One way to achieve this is to ensure they are mounted in areas where they can be kept free of water droplets that can cause issues themselves, or by depositing contaminants that they are carrying. Current research focuses on the resulting contami- nation pattern after a drive or test on the car, this thesis however aims to see whether state-of-the-art Particle Image Velocimetry (PIV) techniques can be used to track the water droplets themselves, and with it open up new ways of researching surface contamination. To achieve this two experiments were performed. The first one was a simple experiment to see whether the droplets are being able to be imaged with the PIV cameras. The second experiment introduced a car side mirror model to the flow and used the Shake-the-Box (STB) algorithm to track the individual water droplets. Both of these ex-periments were successful, and showed that this combination of water droplets and STB PIV has great potential for being used in surface contamination research. The main issues found were with experi-mental setups, especially in the windtunnel. As the droplets do not follow the airflow accurately, extra care needs to be taken to ensure the droplets are operating at the right conditions, and are present at the measurement domain. The actual behaviour of the droplets as tracked by the STB algorithm, seems to be accurate with respect to the expectations indicating that the tracking of the droplets is accurate. Further research should try to increase the scale of the experiments, and/or introduce contaminants to the droplets to see how, if at all, this affects the traceability of the droplets.

Wind tunnel investigations of cycling aerodynamics are conducted in air streams that are designed to have minimum turbulence. This is not representative of the true, turbulent wind environment encountered by a track cyclist in an indoor velodrome. The goal of this thesis, broadly speaking, is to assess the effects of this turbulence on cycling aerodynamics.
To address this question, two experimental campaigns were conducted. The first consisted of track measurements, to measure the turbulence intensities and spectra encountered in an indoor velodrome, by an isolated cyclist and by a cyclist in the far wake of another. This turbulence data was collected using a three-hole pressure probe. In the case of an isolated cyclist, it was observed that the airflow was dependent on the cyclist's location on track. A spectral analysis also revealed the presence of periodic components to the airflow, a result of the cyclist's cadence. When riding in the far wake of another cyclist, the turbulence encountered was stronger when the distance of separation got smaller.
The second experimental campaign was conducted in the wind tunnel. First, the measured track turbulence intensities and spectra were simulated using grids, for small scale, high frequency turbulence, and large obstacles, for large scale, low frequency turbulence. Once the simulated turbulence matched the track turbulence to acceptable levels, its effects on the drag of a cylinder model, representative of the cyclist's limb, were assessed. These drag measurements were conducted using an external force balance. It was found that for a smooth surfaced cylinder, free-stream turbulence was enough to trigger flow transitions and cause a reduction in the measured drag. For a rough surfaced cylinder, increasing the turbulence triggered flow transition earlier, and led to an increased Reynolds number range for the critical flow regime. It was also seen that large scale turbulence did not have a significant effect of the drag of the cylinder.

This thesis covers the experimental characterisation of a multi-nozzle research combustor capable of achieving flameless combustion (FC). The combustor is operated with methane as fuel and air as the oxidiser, under an overall lean equivalence ratio ranging from 0.6-0.9. The work focused on designing and applying different experimental techniques under varying operating conditions. Particle Image Velocimetry (PIV) is used to characterise the flow field for reacting and non-reacting conditions. Local gas temperature and gas composition measurements are performed to characterise the formation of NOx in the combustor. Emission data and local gas temperatures are further reported as a function of the equivalence ratio, thermal power input, and oxidiser's oxygen concentration. PIV revealed the flow field structures to be very similar between non-reacting and reacting flow conditions; the location of the recirculation zones remained unaffected. Significant differences exist in the axial flow velocities and turbulence levels in the central recirculation zone (CRZ). Radial temperature measurements near the reaction zone revealed the temperature profiles to flatten for a decrease in equivalence ratio, indicative of distributed combustion. Gas composition measurements are performed near the exhaust of the combustor. The measurements showed the combustor to perform very well from an emission standpoint. Measurements showed the NOx on the centreline to be ultra-low (<10ppm) for all cases investigated. The N2O and NNH mechanisms are identified as the major contributors to the production of NOx and not the thermal pathway, as the gas temperature is consistently below the thermal NOx threshold of 1800K. A reduction in the equivalence ratio and a reduction in the oxygen concentration both reduce NOx emissions. The measured levels of CO and CH4 were negligible near the exhaust for all operating conditions investigated, confirming that combustion is fully completed at this location. Measurements of CO and CH4 near the reaction zone indicate distributed combustion, where a reduction in the equivalence ratio below 0.7 resulted in elongation and widening of the reaction zone. Oxygen measurements near the exhaust and close to the reaction zone indicate the entrainment of cooling air into the combustion chamber, which would locally influence the equivalence ratio. It is recommended to redesign the exhaust duct connection to eliminate the entrainment of cooling air.

The main objective of this master’s thesis is to experimentally investigate the effects of dynamic inflow conditions on the wake of an actuator disc. Dynamic inflow is the unsteady wake in momentum theory. Dynamic inflow can experimentally be generated by a gust generator. During the experiments, in which Particle Image Velocimetry (PIV) was used as a flow measurement technique, the gust generator produced different gust frequencies and gust amplitudes. The oscillating gust results in the oscillating wake of the actuator disc. The oscillations of the wake cause wake expansion and compression. The expansion and compression of the wake is mainly dependent on the gust frequency. The higher the gust frequency is, the more oscillations the wake will see. So, the actuator disc’s wake was influenced by the gust.

In the last thirty years, massive improvements in flight operations and aircraft technology were implemented, reaching a 54% reduction in specific fuel consumption [1]. However, during the same period, the aviation market has tripled the number of flights per year with a consequent and direct increase in the emissions of greenhouse gasses. To fight against climate change due to the global rise in temperature, international policies are pushing towards a greener future for our society, setting specific objectives for reducing emissions, including aviation ones. In order to achieve the critical goal of climate neutrality by 2050, as stated by the European Green Deal [2], and since the number of total flights is valued will double by that year; significant development steps have to be taken in the aviation industry that has to become greener. The best way to decrease aircraft emissions is to increase its aerodynamic efficiency, so increasing the wingspan of the wing in order to reduce the lift-induced drag. Unfortunately, this has two main problems, the increased total structural weight (that will therefore reduce the payload leading to an increase in the number of flights) and the limited wingspan due to existing airport gate requirements. These issues can be solved using a Hinged Folding Wingtip (HFW) that allows an aerodynamic efficient enormous wingspan during flight operations but will fold on the ground enabling the usage of existing gates. Furthermore, the hinge mechanism improves load alleviation capabilities, particularly during gusts, consequently reducing the bending moment transferred at the root of the wing, allowing beneficial lighter structure. This thesis study focused on a precise aeroelastic characterisation (both aerodynamic and structural) of the hinged folding wingtip device using the instantaneous, non-intrusive and whole-field, large-scale Particle Image Velocimetry (PIV) technique, with the state-of-the-art Shake-The-Box (STB) Lagrangian Particle Tracking (LPT) algorithm in combination with Helium-Filled Soap Bubbles (HFSB) flow tracers and fiducial markers painted on the wing model. This new technique permits the avoidance of intrusive, conventional sensors used for aeroelastic evaluations, like strain gauges, piezoelectric accelerometers, potentiometers, and load cells that alter the structural properties of the tested object but also Pitot tubes that alter the flow behaviour. Furthermore, only pointwise measurements are possible with these devices. Through a wind tunnel campaign at the W-tunnel facility at TU Delft, using a hinged folding wingtip model in both steady and unsteady conditions, it was shown that the implementation of this device shows very promising potential. Not only from an aerodynamic efficiency (due to the increased wingspan) and energy consumption efficiency (due to lower structural weight) points of view but more significantly in the gust alleviation capacities, indeed the peak load and the corresponding root bending moment can be reduced significantly applying a correct timing on the hinge release.

The dark flight of the meteorite in the atmosphere complicates the estimation of the impact point on the Earth’s surface. The irregular shape of the meteorite affects the aerodynamic forces during the dark flight, which can influence the trajectory of the meteorite. This further complicates the meteorite recovery. Limited knowledge of the aerodynamic properties of meteorite is speculated as one of the major reasons for partial recovery of the meteorites. Therefore, this work experimentally investigates the meteorite aerodynamics during dark flight using a subsonic wind tunnel. The drag coefficient, free fall analysis from 10 km altitude and the rotational aspects were studied using a 3D printed meteorite model. Additionally, the results were implemented in a dark flight code to study the influence of these parameters for a hypothetical meteorite fall. This study proved that aerodynamic forces are very crucial in the meteorite dark flight and strongly influences the meteorite trajectory.

Optimal design of a lift dumping assembly (LDA) has been found utilizing a gapped spoiler design that consists of two separate surfaces that are placed at 0.06b-0.17b and 0.28b-0.038b spanwise locations. The gapped design allows the cross flow amplified at the hingeline of the inboard spoiler to escape through the middle gap increasing the lift dumping per area efficiency of the design by 44% while only reducing lift dumping by 4.6% compared to the full spoiler span configuration. LDA spoilers reach a projection height of 8.7% local chord and the hingeline is placed at 80% local chord. With this combination of projection height and chordwise location, there are no occurrences of adverse lift phenomena. Other tested spoilers that are either smaller in chord length, deflection angle or placed such that it is submerged in the boundary layer have shown to increase the lift coefficient at angles of attack relevant to touchdown, 17 degrees.

Control surfaces are integrated within the LDA given the spoilers do not heavily influence the authority of the control surfaces. The ground roll performance of the Flying without the LDA is already comparable to a B747-400 using spoilers. At the point of operation where ground roll is maximized, namely forward center of gravity and maximum landing weight, the Flying V can come to a stop from touchdown in 1300 m and 28.4. Introducing the LDA to the Flying V is less effective than introducing spoilers to a B747-400 as the Flying V does not have any lift from flaps that the LDA can spoil. Nonetheless at typical runway conditions LDA reduces the total ground roll by 95 m. The significance of dumping lift is amplified for adverse runway conditions as 130 m in wet runways and 500 m in icy conditions can be gained using the LDA.

At 17 degrees touchdown angle of attack the LDA only uses the spoiler to create a slight nose down moment of -0.0069 to help derotate the aircraft. Furthermore the LDA can be directly deployed at touchdown to decrease the lift coefficient by 0.057 which is approximately equal to decreasing the angle of attack by 1.5 degrees on the clean aircraft reducing the possibility of a bounce-off. At braking attitude of -2.5 degrees angle of attack, control surfaces join the spoiler in lift dumping. In this case the LDA reduces the lift coefficient by 0.21 and increases the drag coefficient by 0.028.

Vertical Axis Wind Turbine (VAWT) operation is characterized by complex and unsteady three-dimensional fluid dynamics, which presents considerable challenges. One of the crucial points to understand is the complex interaction between rotor, inflow, and wake systems. If we can demonstrate its effectiveness in the complex flow/inflow conditions, will be of great importance. To investigate the wake/wind aerodynamics validate state-of-the-art VAWT wake models, a high ¬fidelity experimental measurement in the domain of VAWT wakes is needed. Computational fluid dynamics (CFD) models for complex wind interactions are far from being feasible. These models are highly time-devouring and computationally expensive, and their cost prohibits the simulation of complex flow configurations. This is usually overcome through the implementation of simple and computationally inexpensive analytical wake models, where the flow conditions are solved through simple analytic expressions and only over specific points of interest. The work aims to realize and validate a simple and efficient analytical wake model (Abkar, 2019 [2]), (Bastankhah & Porté¬Agel, 2014 [7]) for prediction of the wind velocity profile downwind of a VAWT turbine: The best by comparing the modeling results with a set of particle image velocimetry (PIV) measurements of the wakes of an in-house designed VAWT are used as a high-fidelity reference. The present work evaluates and quantifies the influence of the wake deflection produced by the pitch angles of the blades on the scaled VAWT turbine. It reproduces the main phenomena involved in the flow pattern and identifies the general structure of the resulting wake that occurs: under the influence of pitching the blades on the upstream turbine. The configuration consists of a VAWT aligned in the direction of the incoming flow: With a class of cases for different configurations of the turbine are studied for example ¬ deflection of wake through zero pitch, positive 10 degrees pitch, Negative 10 degrees pitch angles (Mendoza et al, 2019 [32]). The available power distribution over other hypothetical downwind turbines due to the influence of wake deflection by the upstream turbine is studied and reported. These interactions are measured with the help of large ¬scale PIV experiments in OJF, TU Delft. Also, an efficacious force balance system for the VAWT rotor is studied, designed, and fabricated (in-house) to calculate the accurate lift and drag forces on the VAWT structure. The stereo particle image velocimetry results are compared with two theoretical works Jensen wake model, [21] and Gaussian-based wake model Abkar [2] and CFD simulations by Huang et al [18]. The study shows a wake shift towards the windward side (cross-flow width), Negative¬ Y direction. For all the pitch cases, maximum for the positive pitch angle and least for a negative pitch angle. The wake shift in the negative ¬Y direction can be caused by the blade rotation, with the clockwise rotation of the VAWT rotor, and the rear blade turning into the incoming flow of wind. The theoretical models especially the Gaussian-based wake model represent the wake deficit in close agreement to the experimental results but fails to account for wake shift and change in wake structure. The CFD simulations reproduce the 3D wake structures consistent with the experiment results but show an early recovery in the wake. The wake recovery with downwind available power is found higher with a positive pitch angle and least with the negative pitch. A study of in-plane velocity vectors indicates crosswind force introducing crosswind momentum to the flow and as a result would give rise to the CVPs, also according to a study by Rolin F, Porte-Agel [38]. The theoretical models do not account for any of these structural changes in wake and the deflections in them. Furthermore, the suitability of these experimental references are used to verify the CFD simulations and analytical models’ range of the fidelity

In order to assess the span-wise load distribution in an aeroelastic gust encounter, a novel method is developed which makes use of marker-based optical tracking. This allows for the prediction of the elastic force and the computation of the inertial force such that Collar's triangle may be quantified during the encounter through an iFEM optimisation approach.

Closure of Collar's triangle represents a complete framework of fluid-structure interactions (FSI) enabling the comprehensive understanding of different design elements compromising aeronautical applications. Experimental methods such as tomographic particle image velocimetry (Tomo-PIV) are proven to provide accurate acquisition opportunities of fluid properties in three dimensional domains. However, not only the closure problem requires simultaneous investigations of fluid and structure behaviors but also the maximum attainable measurement volumes for characterizing these behaviors are severely limited for conventional Tomo-PIV applications. Therefore, a large scale Tomo-PIV setup capable of measuring simultaneous flow motion via Helium Filled Soap Bubbles (HFSB) and structure motion by means of surface markers is employed for experimental investigations of turbulent boundary layer interactions with an unsteadily deforming elastic membrane. Despite the aforementioned benefits of large scale tomographic PIV/PTV techniques, available spatial resolution characteristics for time-resolved flow field measurements are significantly restricted due to the tracer particle specifications of HFSB. This restriction requires additional post-processing algorithms to be applied over the raw experimentally acquired datasets in order to mitigate the effect of experimental trade-off between the temporal and spatial resolution specifications, and allow instantaneous flow field characterization. Although state-of-the-art data assimilation approaches provide the capability of reconstructing high resolution flow features by interpolating the available scattered particle tracking information for global time-resolved flow field reconstruction, drawbacks due to the inability of resolving the viscous effects for near wall flow behavior, incapability of handling physical intrusions to the flow field and propagation of measurement errors, compromise accurate characterization of flow structures in close proximity of the FSI interface. First of all, these algorithms are developed for reconstructing flow features involved with engineering applications where the flow conditions are dominated by turbulent characteristics. However, the fluid behavior in close proximity of walls are dictated by non-negligible viscous forces. Hence, achieving dense interpolation of flow properties of near wall features requires proper characterization of viscous effects for which the thesis proposes the employment of wall function applications for appropriate boundary condition determination. Secondly, even though the available data assimilation methods are able to handle flow behavior around objects, characterization of regions in direct interaction with the object boundaries is not possible. Therefore, in order to handle non-uniform solid boundaries, computational FSI frameworks of the Arbitrary Lagrangian-Eulerian (ALE) and the immersed boundary treatment methods are utilized. Furthermore, as the local closure of Collar’s triangle demands fluid loading over the structural surfaces to be determined, surface pressure information is required to characterize the aeroelastic interactions. Hence, an alternative approach of non-intrusive surface pressure reconstruction from PIV data over unsteadily deforming non-uniform boundaries is introduced via interpreting the ALE method with boundary fitted coordinate systems. Finally, measurement and processing errors contained within the experimental procedures propagate through the data assimilation algorithms. Therefore, to enable the the mitigation of experimental measurement and processing errors, an alternative approach of governing equation based dense flow field interpolation is developed using solenoidal and irrotational radial basis functions (RBF). Capabilities of the proposed methods within the thesis project are demonstrated with various theoretical, numerical and experimental test cases. The wall function application enabled accurate characterization of average streamwise velocity profiles as well as providing slight improvements on the fluctuating velocity components compared to the no-slip boundary condition implementation. Both approaches introduced for handling of physical intrusions resulted in increased coherence levels of flow behaviors within the respective test cases, where the local variations of velocity components revealed promising improvements against the state-of-the-art assimilation algorithms favoring the developed methods in terms of providing greater agreements to the reference flow fields. The introduced surface pressure reconstruction scheme with boundary fitted coordinates yielded relative error levels confined below 4% compared to analytical flow field properties where the resultant errors are computed to be related to the numerical truncation errors rather than the discretizations of mesh deformations or vectorial transformations. The developed alternative approach of dense flow field interpolation with solenoidal and irrotational RBFs allowed inherent mass conservation for the velocity field reconstructions that significantly increased the agreement of the interpolated velocity and vorticity fields with the reference flow field information while irrotationality imposition on the material accelerations provided elevated accuracy levels for pressure field computations. Consequently, the proposed methods of wall function implementation, ALE-VIC+ and ImVIC+ are utilized for experimental characterization of surface pressure variations over the unsteadily deforming elastic membrane exposed to turbulent boundary layer conditions. The instantaneously available low density particle tracking information is assimilated towards dense interpolation of material accelerations to capture temporal evolution of static pressure values at the central membrane location. The superior accuracy specifications of both ALE-VIC+ and ImVIC+ against linear interpolation owing to the kinematic characterization of the influence of membrane motion on the flow field properties provided greater agreements of the non-intrusive time-resolved pressure field computations with the pressure tab measurements.

A proportionate controller is investigated experimentally for unsteady load alleviation purposes on a 2D wing model with a trailing edge flap. This study is supposed to be a simplified version of a Smart Rotor, a mechanism which deals with the reduction of unsteady loads acting on a wind turbine and aims to understand the behavior of this type of control under dynamic stall conditions. The controller acts on the velocity of the flaps, and pressure sensors are used to detect the unsteady loads, which are generated by actuating the wing model in a sinusoidal motion. Two different regimes are considered: attached flow (oscillations around zero angle of attack, where little flow separation is expected) and dynamic stall (oscillations close to the static stall angle). The influence of actuation frequency and controller time lag is also studied, as these parameters were found to be crucial for such a concept during the literature review. A reduction of 87.5% in the standard deviation of the lift is obtained for a frequency of 0.2Hz and time lag in the control system of 12ms for attached flow conditions. The reduction of the standard deviation of the lift deteriorates for increased frequency and time lag. The proposed controller is also able to reduce the loads during dynamic stall, although the reduction is smaller, close to 40% in the reduction of the lift coefficient. A maximum reduction of 59% in the peak-to-peak loads experienced during dynamic stall is observed, for 0.2Hz and a time lag of 12ms. Time lag is again crucial for this reduction, and larger and faster actuation systems are needed to fully compensate for the larger drop in loads. However, the active load control of the loads during dynamic stall can negatively affect the aerodynamic damping of the model, since the flap actuation is dependent on the detachment of the leading-edge vortex from the surface of the wing. The flap actuation is also shown to delay the onset of dynamic stall, by increasing the static stall angle with respect to the case without flap deflection.

The aim of this investigation is to provide an experimental volumetric visualization of the near wake topology of the vortex structures generated by a flapping-wing Micro Air Vehicle (MAV) by means of large-scale Robotic PIV. This novel technique implements coaxial illumination and imaging in combination with the use of Helium Filled Soap Bubbles (HFSB) as tracing particles to achieve large measurement volumes of the order of 10 liters. Information of different phases throughout the flapping cycle is obtained by means of a phase-locked averaging procedure. The MAV used for this study is called DelFly II. It is a platform composed a two pairs of wings attached to a slip body with horizontal and vertical tailplanes for stability and maneuverability. Measurements are performed at regular free-flight scenarios within the DelFly flying envelope. The configurations selected have different reduces frequencies which allows to analyze the effect of this important parameter. Same configurations are also measured with and without the presence of the tails to see their influence of the wake topology. In addition, experiments in both tethered and free-flight conditions have been performed, yielding an unprecedented comparison between the aerodynamics of the two conditions.
The significance of the proposed project lies on the ability of assess the complete three-dimensional wake of the DelFly II. This is the first experimental study performed that can achieve such measuring volumes for any flapping-wing platform, to the knowledge of the present author. Another major benefit of this study is the use of standard flight configuration to observe the wake structures when the MAV is able to sustain level flight. Therefore, the proposed work is expected to be a relevant addition to the understanding of the flapping-wing mechanism.

During front crawl swimming, water is driven backwards with the limbs. Drag forces generated by the limbs are consequently used for forward propulsion. The hands are responsible for approximately 60% of the generated propulsive forces. Reaching a podium place in competitive swimming is dependent on differences in finishing times smaller than 0.5%. For this reason, investigating the effects of hand configuration on swimming performance is of interest. Configurable properties of the hand are the finger spreading and hand palm cupping. It is argued that a small finger spreading leads to a larger obstruction in the fluid flow compared to closed fingers, resulting in larger generated drag forces. Similarly, a small hand cupping is expected to increase the drag forces in analogy to the drag increase experienced by cupped disks. In this thesis, an experimental investigation is carried out to look into the effects of both finger spreading and hand cupping. Furthermore, CFD simulations are used for the abstract modelling of hands with finger spreading by use of slotted disks. 
Towing tank experiments in water are performed to investigate the effects of finger spreading for five full-scale arm models. The research showed that a small finger spreading of 5° can increase the drag coefficient of the hand with 1.7%, in comparison to closed fingers. Larger spreadings were found to influence the drag coefficient disadvantageously, where a 20° finger spreading reduced the drag with 1.5%. The found effects indicate that finishing times can be reduced with 0.3% by using 5° finger spreading instead of 20° spreading.
Wind tunnel experiments are used to look into the effects of hand cupping. Dynamic scaling based on the Reynolds number is used to account for the used air flow. Effects for five full-scale arm models with different hand cuppings were investigated, these have a 5° finger spreading which was found optimal from previous research. It appeared that small rotations around the longitudinal axis of the arm have large influences on the drag coefficient, where a maximum in drag was never found for the hand palm perpendicular to the flow, but with an abducted thumb opposing the flow. The research showed that 6% more drag is generated for a flat hand in comparison to the largest investigated hand cupping. This indicates that finishing times can be reduced with 0.8% by using a flat hand instead of a large hand cupping. 
In conclusion, the research found a hand configuration with 5° finger spreading and a flat hand palm optimal for maximizing drag forces. The found effects on finishing times indicate that using this hand configuration can play an important role in reaching podium places during front crawl swimming.

Aerodynamics has become increasingly important these days in the design of automobiles due to the increased constraints placed on the emissions. In the past the focus has been primarily on the shaping of the upper body. However, due to practical requirements, further scope of improvements to the upper body has been greatly reduced. The focus has thus shifted towards the optimization of the underbody which includes the wheel and the wheelhouse. The contribution of the wheel and the wheelhouse to the total drag and lift coefficient of a body has been estimated at 30\% and 40\% respectively. Therefore, understanding the behavior of the flow in the wheelhouse would potentially result in reducing the drag coefficient of an automobile.

In the present study, the wheelhouse flow has been investigated experimentally using Particle Image Velocimetry (PIV). A generic simplified car body with a wheel and a wheelhouse has been designed and used for this purpose. The study has been done for a rotating wheel and stationary ground configuration. Planar PIV and Stereo PIV have been used to study the flow inside the wheelhouse and in the wake of the wheel respectively. The study was undertaken for the Reynolds number, based on wheel diameter, of 9000 and 72000. Measurements were taken at planes inside and outside the wheelhouse as well as upstream and downstream of the wheel. In addition to providing data for the Large Eddy Simulation (LES), the results from the PIV measurements showed that the behavior of the flow depended on the Reynolds number. Velocity profiles in the wake of the wheel highlighted a three dimensional flow in the wheelhouse.

Finally, the effect of a Vortex Generator (VG) on the flow was investigated. The VG was found to have an effect at the low Reynolds number wherein the flow inside the wheelhouse and in the underbody was found to be quite different compared to the configuration without a VG.

Even though propellers are the oldest form of propulsion, they are still a popular choice for unmanned aerial vehicles (UAVs) and passenger aircraft in certain market segments. If the propellers are mounted on the wing, strong propeller-wing interactions alter the aerodynamic efficiency of the aircraft. Using low-order numerical models, it is shown in literature that the wing chord and twist distribution can be changed to maximise this efficiency. These results are only theoretical. This thesis, therefore, aims to validate and apply a numerical model for optimisation of the wing design taking propeller-wing interactions into account.

A vortex lattice method (VLM) was adapted to include the effects of propeller-induced velocities. Comparing the results of the adapted VLM with existing experimental data already validates the numerical model for predicting the lift distribution. To validate it for changes in lift distribution due to wing design changes, a wind-tunnel experiment is set up. Two wings are tested in a tractor propeller configuration. The only difference between the wings is in the twist distribution. To find the lift distribution, the circulation is evaluated in the flow around a wing at several stations along the wingspan. Particle-image velocimetry was used to obtain this flow field. Indeed, the lift distributions measured on both wings are matched by predictions from the adapted VLM, which proofs the numerical model is suitable for qualitative optimisation studies.

For the wing and operating conditions used for the wind-tunnel experiment, an optimisation study is performed using the adapted VLM. It shows the drag can be reduced with 34% by adopting the optimal chord and twist distribution. Even though the operating conditions are not representative for full-scale aircraft or UAVs, it does show there is a great potential for taking propeller-wing interactions into account for the design of the wing.