Aviation is responsible for a large part of the emissions due to transportation, which is why, in recent years, a trend towards implementing sustainability in aviation has emerged. In small aircraft, the concept of Leading-Edge Distributed Propulsion (LEDP) can provide aerodynamic advantages to reduce fuel consumption thanks to the ability to increase lift due to the interaction between the slipstream of the propellers and the wing.

Therefore, a wind tunnel experiment is performed to study the aerodynamic interaction in propeller-wing-flap systems when Leading-Edge Distributed Propulsion is used. The objective of this research is to gain insight into the difference in wing loading distribution between the distributed-propeller and single-propeller configurations in the flap retracted case, about the effect of flap position on the lift enhancement in LEDP and about the effect of flap deflection on the wake downstream of the system...

The design of current skating suits is based on the assumption that the flow across the skater body parts is highly similar to cylinder flow. The latter features drag crisis behaviour, resulting in significant drag reduction at the critical Reynolds number. However, whether the aforementioned assumption is valid and whether a drag crisis along the different body parts occurs, so far remains unknown.

The goal of this study is to investigate Reynolds number effects along the leg of a skater mannequin. To do so, potential drag crisis behaviour is studied via robotic Particle Image Velocimetry and Infrared Thermography for speeds ranging between 5 m/s and 25 m/s. The boundary layer state and the critical velocity distribution along the leg, based on the wake width variation, are evaluated for the bare mannequin and the mannequin wearing a skating suit optimized for ∼ 15 m/s.

Results reveal drag crisis behaviour along the knee, lower and upper leg. Furthermore, the flow topology is not only governed by the leg geometry, but also by streamwise vortices. These streamwise vortices cause an increase of the wake width below the calf and a reduced velocity deficit behind the upper leg. Most significant differences in wake width between the bare and the dressed leg are observed at 17.5 m/s. The latter observation is also supported by the Infrared Thermography results.

It can be concluded that the flow across the leg partly differs from cylinder flow, mainly because of streamwise vortices that locally affect the drag crisis behaviour.

This work follows the wind energy airfoil probabilistic design approach that allows to derive a probability density function which gives an estimation of how much the angle of attack is likely to fluctuate, according to the considered non-uniform perturbations in the wind speed. Several combinations of the perturbation sources are possible in practice as well as several extents of each perturbation source. A probabilistic design space mapping will be carried out to evaluate what wind situations are possible in practice and how much each specific wind situation is likely to occur. The proposed model will also be validated by employing the aero-elastic simulation tool: FAST. Finally, the probabilistic approach will be used to design airfoils and in particular it will be used to optimize the airfoil aerodynamic performance over the operational range of angles of attack. The airfoil optimization will be performed with the genetic multi-objective optimization tool: Optiflow, for different relative thicknesses as well as using different cost functions.

The EU has committed itself to reduce the greenhouse gas emissions with 20% by 2020 with respect to the 1990 level. This means that all industry sectors including the transport sector have to become more energy efficient. The long and short haul trucks are, with 4.95% of the total CO2 equivalent emissions, a major contributor in the transport sector. In order to achieve a reduction in emissions, the European Commission is proposing new regulations that allow for front elongation of trucks. This elongation might improve the aerodynamic efficiency and hence reduce the emissions and fuel costs. Reducing aerodynamic drag for tractor-trailer combinations has been researched for a long period of time. In 1965 Hoerner published the results of his experimental research on 3D bluff bodies and identified that the drag coefficient at the front was related to the total drag coefficient. In 1985 Cooper determined that an optimal front edge radius based on the Reynolds number and the frontal area of the vehicle exists. These two studies concerning bluff bodies formthe basis of numerous follow up studies and this thesis. This thesis analyses how the geometry of an elongated bluff body can be optimized in order to reduce the aerodynamic drag coefficient Typically the flow around a bluff body is characterized instable and separated flow. At the front of the truck the incoming flow velocity reduces to zero at the stagnation point. A high pressure region is formed at this location. Further downstream the flow reaches the front edge corners of the truck, where the flow is accelerated. Flow separation might occur at these front edge corners. At the rear a large low pressure region is formed which contributes to the total drag coefficient. In this thesis numerical simulations are performed in order to identify the relative importance of several front-end design parameters. The numerical calculations are performed by means of the steady-state RANS k ¡! turbulence model. The domain is refined near the surface model and its wake using two density boxes around the model with different cell dimensions and an inflation layer around the model. A wall model is used to approximate the flow behavior in the boundary layer. The wall model and the local refinements reduce the computational time while retaining a high level of accuracy of the numerical solution. The numerical simulation is validated using the data from an already existing wind tunnel experiment. This wind tunnel experiment has been performed on a 1:15 scale model in the Low Turbulence wind tunnel at the TU Delft. First the influence of the mesh cell size is determined by varying the cell sizes of the two density boxes surrounding the model. One density box is close to the model and has small cell dimensions, while the second density box is encapsulating a larger volume. This resulted in chosen cell dimensions with a ratio of 1:4. The discretization error is 4.1%, while the number of cells used is 4.47¤106. The second part is the validation itself. The drag coefficient of the model is 0.297 for the wind tunnel experiment and 0.300 for the simulation,while the base pressure is slightly lower for the numerical simulation. The pressure distribution at the base is not correctly captured in the simulation results. The final part of the validation is the comparison of the boundary layer development. The results of the simulation obtained in this thesis show great similarity with the results found in the wind tunnel experiment. To explore the real world effects the 1:15 scale results...

To limit the threat posed by global climate change it is vital to reduce the emissions of the transport sector in the short term. Two existing aerodynamic add-on devices for the rear-end of a heavy duty vehicle, a tail and guide vanes, are combined in an attempt to achieve a larger drag reduction. A research is performed using numerical simulations and a wind tunnel experiment in the Open Jet Facility to gain insight in the interaction between the tail and the guide vane. It was found that the guide vane is able to further increase the base pressure of the vehicle, but that the drag reduction is sensitive to the drag of the vane. Due to the interaction between the tail and the guide vane the largest drag reduction is achieved when the guide vane is operating at its minimum drag condition.

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 dominant noise source. Reduction of airfoil self-noise should therefore focus on this noise mechanism. A modified version of the semi-empirical aero-acoustic prediction code by Brooks, Pope and Marcolini is used to compute this trailing edge noise. The panel code RFOIL is used for the boundary layer computations as well as the generation of the aerodynamic polars. A quality assessment of both codes is performed based on aerodynamic and acoustic wind tunnel measurements acquired by the Institut für Aerodynamik und Gasdynamik on the NACA 643-418 airfoil. The multi-objective optimization is executed using the genetic algorithm NSGA-II. The airfoil parameterization that is used is the Class Shape Transformation (CST) method by Kulfan. The results of the optimization are captured in the Pareto front and six individuals are assessed thoroughly. It is found that airfoils can be designed that fulfill all the aerodynamic requirements. Acoustically, only marginal differences can be observed and further research should be conducted on the topic.

The need for energy is an ever increasing problem and most resources that are used today will be exhausted or no longer tolerated by the human kind in the future Omer (2008). Anticipating on the energy demand the development of wind turbines has taken a big leap and to improve the design process efficient and accurate aerodynamic modelling is required. During start-up, stopping and standstill of the turbine, the blades experience very high angles of attack. The flow physics behind this topic is not fully understood yet. In this research it is investigated what the relation is between the leading edge thickness of the airfoil and the maximum drag coefficient, this is done by means of experimental and numerical simulation.

Given the prime importance of wind tunnel setup when it comes to aero-elastic study, the main intent of this project is to devise a mechanism for supporting system of 2D aero-elasticity experiment in the Red Wind Tunnel Facility at DTU that allows three-degree-of-freedom motion of the rigid model. This project work is mainly inspired by the fact that deep stall aero-elastic
Characteristics of wind turbines, which govern the design of stall-regulated wind turbines at high wind speed, have been barely investigated in literatures so far. So in redesigning the test section of the wind tunnel facility the following sub-tasks are included: (1) Literature survey on test section design/construction for 2D aero-elastics testing of aerofoils. (2) Panel code simulation of wing/tunnel interaction. (3) Adapted design of new test section to the Red wind tunnel facility. (4) To some extent building and testing the new test section. The implementation and actual design may be too time demanding to be fulfilled within the given time slot, however a specific design for the Red tunnel facility is documented through flow analysis and drawings at the end of the project. Among which the first and third item have been addressed and the fourth item partially as well, but the second item is still to be done with the flow solver Q3UIC which was developed by Néstor in DTU. Since the aerodynamic code of this tool is only for pitching motion, extending this tool for this thesis work happened to be out of scope.