Goal-oriented reduced-order models (GOROM) have the potential to represent complex dynamics in an interpretable way. In the GOROM procedure, modes are found which when used in a Galerkin projection of the governing equations, return the desired goal function with minimum error. Determining such models leads to a high-dimensional optimisation problem, which may have multiple extrema, making purely local optimisation inapplicable.
In this thesis, a global optimisation algorithm was derived for GOROM. The optimisation response surface was approximated with a surrogate model, built using the Kriging technique. In each iteration, the surrogate model was improved by including the objective function of the three points with the highest expected improvements. This iterative process was stopped when the expected improvement fell below a threshold.
First, the performance of the algorithm was confirmed for a simple non-GOROM optimisation. Then the algorithm was applied to GOROM optimisation for the forced Burgers equation, initially using a complex forcing function giving multiple minima and later to a forcing function derived from a DNS of a turbulent channel flow. The initial forcing required on the order of tens of degrees of freedom to be optimised. The corresponding response surface proved similar to that of the simple problems, showing these optimisations to be tractable.
For the DNS forcing, hundreds of coefficients needed to be optimised. Using the developed algorithm a better optimal was found than with the local algorithm, although substantially more computational resources would be required to confirm global optimality.

This thesis proposes techniques to produce wall-shear stress estimates from three-dimensional Lagrangian particle tracking (LPT). Several works have already faced the problem of determining near-wall velocity and in particular skin friction for the case of a flat surface. Here, the problem is translated to generic three-dimensional objects. The work makes use of an experimental database, recently produced, with LPT (Hendriksen et al. 2024), that provides in-situ registration of the object, for three shapes of increasing complexity: a cube, an airfoil and a cyclist. Four techniques are examined and compared, including interpolation method as well as local data regression. The uncertainty is evaluated a-posteriori, comparing the results with a local coin-stacking technique, where applicable. All techniques yield accurate and robust representations of the skin friction lines around three-dimensional objects, allowing for an insightful inspection of the near-surface flow topology. Instead, distinct differences are found when the skin-friction magnitude is estimated.

This thesis investigates a novel load alleviation technique known as mini-tabs, small devices placed on the upper surface of wings to reduce lift. Reynolds-Averaged Navier-Stokes (RANS) simulations were conducted to analyze the impact of geometrical properties on mini-tab performance in reducing the load on a wing.

The initial simulations focused on a single mini-tab, varying parameters such as height, aspect ratio, chordwise, and spanwise positions. Results indicate that increasing height or aspect ratio leads to decreased lift due to flow deceleration at the leading edge and expansion of the separated flow region downstream of the mini-tab. This will also increase the pressure drag. Increasing the height or aspect ratio also accelerates the flow at the lower surface, further reducing the lift generated by the wing.

Placing mini-tabs closer to the wingtip exhibits similar effects on lift reduction as increasing the height of the mini-tabs. This is because the relative height of the mini-tab with the local chord length increases when the mini-tab is positioned closer to the wingtip. A maximum lift reduction is also achieved when the mini-tab is placed at a 60% chordwise position.

Subsequent simulations explored the performance of multiple mini-tabs, revealing that orienting them orthogonal to the wind direction may not be optimal due to gap formation between the mini-tabs that energizes the wake downstream of the mini-tabs and reduces the reduction in lift. Conversely, aligning the mini-tabs with the leading edge has a higher efficiency in the reduction of the lift.

Overall, the findings suggest that mini-tabs offer a viable method for reducing wing forces and for load alleviation

As the automotive industry increasingly shifts toward electrification, reducing vehicle drag becomes crucial for enhancing battery range and meeting consumer expectations. Additionally, recent European regulations require tire and car manufacturers to provide reliable drag data. A significant factor influencing vehicle drag is the highly turbulent wake generated by rotating tires. Accurate correlation between wind tunnel experiments and numerical simulations is essential, yet discrepancies often arise due to the dynamic behavior and technical challenges in measuring tire deformation, leading to inconsistencies between tire deformations observed in wind tunnels and those modelled in simulations.

This Master’s Thesis investigates the aerodynamic impact of realistic tire deformation parameters—specifically, bulge and contact patch deformations—using Computational Fluid Dynamics (CFD) simulations conducted with PowerFLOW. The deformation parameter tests are carried out in a standalone tire setup, which is validated from previous work by Dassault Systèmes and experimental results. To further assess the impact of these deformations on vehicle drag, the tests were repeated using the DrivAer model, an IP free model provided by the Technical University of Munich. Given the complexity of the flow features in a tire wake, the analysis of the results consisted of two different approaches: a statistical approach based on Principal Component Analysis (PCA), and a vortex behaviour and wake development analysis, including a vortex tracking algorithm based on the Gamma 2-Criterion and single-link hierarchical clustering.

The results identify the most influential deformation parameters based on their impact on the drag coefficient and the wake behaviour changes. Two primary wake development behaviours were identified: wake contraction and wake expansion. An analysis of the transient flow showed how these two trends resulted from changes in the unsteady behaviour introduced by certain deformation parameters. The relevance of these wake development changes was portrayed by the impact of certain deformations on the full vehicle drag as a result of
complex wake interactions.

This thesis presents a comprehensive study on Floating Offshore Wind Turbine’s (FOWT’s) modeling and simulation, focusing on the IEA 15MW wind turbine coupled to the VolturnUS-S semi-submersible platform. The primary goal was to develop the building blocks of a high-fidelity Computational Fluid Dynamics (CFD) coupled model using OpenFOAM to simulate large-scale FOWT behavior, verify, and compare each component individually against the mid-fidelity tool OpenFAST. The project builds on the frameworks of previous studies by Pere Frontera Pericàs [81] and Scarlatti [98], expanding them to accommodate the complexities of a larger turbine and more intricate environmental conditions.

The model was implemented using OpenFOAM’s waves2Foam and Moody libraries for wave and mooring modeling, respectively, while aerodynamic simulations employed the turbinesFoam package with an actuator line approach. A spatial convergence study optimized mesh parameters for computational efficiency and accuracy, ensuring reliable and stable simulation results for motions up to 24 meters in surge. Comparisons between OpenFOAM and OpenFAST using a P-Q analysis highlighted significant differences, particularly in modeling damping. OpenFAST was shown to underestimate both linear and quadratic hydrodynamic damping due to its simplified representation of fluid dynamics. Discrepancies in the equilibrium positions were found between the decay tests using CFD; their origin still needs more investigation.

In aerodynamic simulations, steady-state and prescribed motion tests revealed critical differences in thrust and power predictions between OpenFOAM and OpenFAST. OpenFAST overpredicted the reduction in axial wind speed, leading to a reduced power output for steady turbine simulations. The CFD model provided a more accurate representation of rotor wake effects and dynamic responses, particularly in high-frequency surge conditions, where OpenFAST overestimated power fluctuations. These findings underscore the importance of using high-fidelity models like OpenFOAM to improve the accuracy of performance predictions in floating wind turbines.

The study concludes by offering recommendations for future research, including model validation using experimental data and the implementation of overset mesh techniques to improve simulation stability for large motions. The work establishes a reliable CFD framework for simulating this large FOWT, offering insights into enhancing mid-fidelity models and guiding future developments in floating wind turbine design and analysis. It also builds a fully coupled CFD model in OpenFOAM to investigate its behavior.

Computational Fluid Dynamics (CFD) simulations of objects like the Kitepower V3A Leading Edge Inflatable (LEI) kite require accurate experimental data for validation. However, for these kites, particularly in steady-state simulations, such data is scarce. LEI kites are soft and deform continuously during flight, making validation complex. To address this, a unique experiment in the Open Jet Facility (OJF) at TU Delft, testing a rigidized subscale model of the V3A kite, marking the first wind tunnel test on a rigid kite.

The rigid model was made of carbon fiber reinforced polymer and mounted on a custom support structure that allowed adjustments to the kite’s angle of attack and sideslip. Aerodynamic forces and moments were measured at different wind speeds and orientations, with and without zigzag tape to study its effects on low Reynolds number flow.

The results were compared to existing CFD simulations, including Reynolds-Averaged Navier-Stokes (RANS) and vortex step methods. The experimental data aligned well with these simulations at low Reynolds numbers, validating the setup. However, some discrepancies highlighted areas for improvement, such as reducing interference from the support structure and better matching Reynolds numbers between simulations and experiments.

A 3D panel method code, named AWSM3D, is developed as an extension to the AeroModule aerodynamic software suite of TNO which includes a Blade Element Momentum theory (BEM) and a Lifting Line (LL) code. The underlying panel code method is presented along with a gradual process of simulation validation culminating in validating the code against the New MEXICO experimental dataset and an established panel code. In view of exploring the avenue of sweeping wind turbine blades as a way of increasing wind turbine efficiency, the capabilities of the three proposed aerodynamic models in solving flows about swept geometries are studied. The unmodified BEM model is incapable of adequately modeling flows over swept geometries. The limits of the cross-flow theory which the LL simulation hinges on for the simulation of swept flows are put to the test. Both a fixed wing and a conventional Horizontal Axis Wind Turbine case show that the LL solution in proximity to body extremities where the cross-flow component is prominent fails to capture smaller-scale local effects caused by said cross-flow. Despite this, the larger-scale effect is reproduced well. Although AWSM3D requires no airfoil polars and produces an accurate inviscid flow solution for more complex body geometries, it currently excludes viscosity and has a much higher computation time in comparison to an LL. A number of further AWSM3D development and research into the effects of sweep suggestions are formulated.

In response to the leading narrative of increasing sustainability in the yachting sector, a research collaboration is started between the Delft University of Technology and Dykstra Naval Architects to examine the potential use of hydro generation on board sailing superyachts. By harvesting energy from the water flow when under sail, diesel generator use can be limited, reducing overall emissions. Currently, it is not yet possible to quantify the impact of a chosen hydro generation system on the overall design during the early stages of yacht design. To assess the correct balance between the inevitable increase in system weight and size relative to, for example, emission reduction. To allow for this, a novel method is developed, presenting the designer with the opportunity to explore various hydro generation systems quickly. With the ability to complete this in an early design stage, more opportunities for hydro generation remain, and the need for a feasibility study for hydro generation is removed. In this thesis, the developed method is described, and results are presented that provide insight into its applicability. The design method considers the impact of six variables that influence hydro generation. The first three variations concern size and include the propeller diameter, battery capacity, and sail area. The remaining considerations relate to operational and design choices and include decisions on energy consumption, fixed or controllable pitch propellers, and generation in the first or third quadrant. A scenario for an ocean crossing with a sailing yacht aiming to limit fuel consumption demonstrates the influence of these considerations. The results presented in the thesis show that the method provides the basis for a later detailed design stage when an actual hydro generation system is implemented.

It is the need of the hour to focus research and development towards curbing emissions due to the growing aviation industry. Employing boundary layer Ingesting(BLI) propellers for development of propulsive fuselage concept(PFC) aircraft while utilizing hydrogen as an alternative energy source, is the idea behind project APPU(Advanced Propulsion and Power Unit). However, the empennage wake is detrimental to the propeller. This study uses chord-wise wake blowing technique to fill the empennage wake in order to mitigate the detrimental effects of the wake on the inflow of the aft mounted BLI propeller. A near complete wake filling was observed for the blown configuration, with a 99.7% uniformity in the velocity profiles for the filled empennage wake. The addition to the overall aircraft drag due to the wake blowing system was less than 2 drag counts and a mass flow rate of 0.91-1.23Kg/s was found to be required in the blown cases.

Aerodynamics has played a significant role in the industry of motorsports in improving the performance and handling of the race car. Rob Smedley, the former head of vehicle performance at Williams Racing stated that - "Where teams have problems is when their development or simulation environment – so CFD [Computational Fluid Dynamics] or wind tunnel – doesn’t describe well what happens in reality (although in truth, no-one’s wind tunnel correlates absolutely 100%)". One of the reasons for this poor correlation could be arising from the fact that, in real life on track scenarios, the race cars undergo accelerating, decelerating, or cornering motion which can have a different influence on the aerodynamics of a race car which is not accounted for in the wind tunnel and simulation environment where a steady constant flow is employed. This research aims to numerically investigate the flow past the front wing of a Formula One car in ground effect subjected to accelerating and decelerating flows to understand the trends in the aerodynamic performance.

A scaling analysis is performed to determine the relevant non-dimensional numbers that influence the flow for translationally accelerating airfoils and two dimensionless numbers are arrived at, namely, the Reynolds number and the Froude number. Numerical investigations are carried out for translationally accelerating wings in ground effect to determine the influence of these dimensionless numbers on the aerodynamic forces.

Transient simulations were performed on a two-dimensional airfoil and a three-dimensional wing in ground effect subjected to translational acceleration and deceleration. The Shear Stress Transport (SST) based on k-ω was employed to model the turbulent flow. The results from the numerical investigations revealed a temporary change in the downforce and the drag force coefficients, as the airfoil (or wing) in ground effect is subjected to translational acceleration (or deceleration). In this study, the mechanisms that contribute to this temporary change in the aerodynamic force coefficients are discussed.

During a severe accident in a water­-cooled nuclear power plant, large quantities of hydrogen can be generated in the reactor core. The hydrogen mixed with air presents a potential risk of combustion when the hydrogen concentration reaches flammability limits. If combustion occurs, pressure loads can damage safety systems and even compromise the structural integrity of the nuclear reactor walls. Thus, predicting the pressure loads is an important safety issue to ensure the reliability of critical structures in the event of a severe accident.

Computational Fluid Dynamics (CFD) codes can be used as numerical tools to assess the risks of hy­drogen combustion and predict detailed transients of the pressure loads. The scenarios simulated in nuclear safety engineering can be analyzed with low fidelity models based on reduction assumptions of the physical phenomena. Specifically, the flame gradient models are chosen to model the com­bustion phenomena based on a turbulent flame speed to which the combustion propagates. Different approaches to compute the turbulent flame speed are implemented and compared in this study, in­cluding the Turbulent Flame Closure (TFC) and the Extended Turbulent Flame Closure (ETFC). New models are proposed based on new experimental correlations specifically derived for lean mixtures of hydrogen. Other required libraries as flame radius calculation, radiative heat transfer properties determination, and axisymmetric Adaptive Mesh Refinement are implemented and evaluated. A study on the influence of the ignition source term is also carried out.

The implementation of the solver and the models is verified with the analytical solution of a planar one­-dimensional premixed flame moving into frozen turbulence. Moreover, three different experimen­tal cases, relevant to nuclear safety, are selected to perform the validation of the solver. The first one is a spherical combustion chamber which was experimentally tested with lean hydrogen mixtures and controlled measured homogeneous isotropic turbulence. The second one is the Thermal-hydraulics Hydrogen Aerosol and Iodine (THAI) facility, which is a larger vessel where effects as buoyancy be­ come more relevant. Finally, the third one is a flame acceleration enclosure called ENACCEF­2, where obstacles are placed along a cylindrical tube to promote flame acceleration and the transition from de­flagration to detonation.

Numerical results are presented in terms of the flame front location, the flame front velocity, and the pressure rise. The sensitivity of the results to mesh resolution, time discretization, and initial turbu­lence levels is assessed. The implemented combustion models are simulated with multiple turbulence models, analyzing the results and the influence on one each other. In general, the proposed mod­els represent an approach that provides good predictions in both flame development and pressure dynamics, being more robust than other models previously available

The increasing importance of climate change and stricter regulations for greenhouse gas emissions raise the pressure on the automotive industry to develop more efficient products. Besides a reduction of emissions by new combustion engines, electric vehicles are being introduced to lower the fleet fuel economy. Especially this new drivetrain technology benefits from an improved driving resistance of the vehicle, as an increase in range is highly valued for current electric vehicles. The aerodynamic drag, a considerable contribution to the driving resistance, therefore plays an important role in automotive development. With a significant contribution to aerodynamic drag, the wheels and surrounding wheelhouses are considered to have potential for possible improvements and are currently one of the focuses of research. This thesis examines the aerodynamic flow in a rear wheel arch of a low drag electric sedan to identify areas of potential improvement and derive recommendations for future developments. Three major parameters of the rear wheelhouse geometry are therefore modified and their influence on the aerodynamic drag and the flow field is assessed. These include the wheelhouse radius, wheelhouse width and the wheel track. For this purpose, Reynolds Averaged Navier Stokes (RANS) simulations are used to both calculate the effect of the variations on aerodynamic drag and analyse the origin of changes in the flow field. For parameters where it is possible, tests on a detailed full scale model are carried out in a modern full scale wind tunnel.

Due to the increasing interest in modelling floating offshore wind turbines, simulation tools need to be adapted from fixed-base applications to surge applications. In this study, an open-source inviscid 3D panel method named Vortexje was adapted for surge motion and its ability to capture the physics of severe surge motion (when the rotor velocity approaches or exceeds the incoming wind velocity) was investigated. A simple test case first found instabilities with direct surface translation, likely a result of attached wake panel placement, justifying the use of equivalent dynamic inflow conditions for subsequent simulations.

It was then found that despite validation for a fixed-base rotor, inaccuracies and numerical instabilities remain when integrating the panel method pressure values directly. Estimating the thrust through the bound circulation provided a more accurate solution, comparable to existing viscous CFD results. It was found that the rotor could, in severe surge cases, briefly operate in propeller mode. Inflow angles were also estimated using existing CFD-related techniques, which provided reasonable results for fixed-base applications but inconsistencies with moderate and severe surge. It was found that the variations in induction factor did not approach those required to induce vortex ring state.

A crosswind pumping kite power system is an Airborne Wind Energy (AWE) system that uses a flying tethered device for energy generation through a ground-based generator. The AWE research group of the TU Delft was one of the first to demonstrate the functioning of such a system. The spin-off Kitepower later on continued the technological development of this concept towards a commercial product. The system uses a leading edge inflatable (LEI) wing that operates by alternating between a traction phase and a retraction phase. Throughout these phases, the wing experiences a wide range of flow conditions with frequently changing incoming flow velocity, angle of attack and sideslip angle. As the wing is made of a flexible membrane, the shape of the wing is not fixed and will change under the aerodynamic loads applied to it. Therefore, the aerodynamic optimisation of such a wing forms a complex Fluid-Structure Interaction (FSI) problem. However, this thesis will only focus on the aerodynamic analysis of the LEI V3A wing developed by Kitepower. The analysis is done through the use of steady-state Computational Fluid Dynamics (CFD) simulations with a rigid wing geometry. Similar work that was done previously used a simplified wing geometry, which omitted the chordwise struts and only considered a limited range of flow conditions. In this study, these struts have been included in the geometry and their impact on the aerodynamic performance is assessed. In addition to this, the aerodynamic performance of the LEI wing under sideslip conditions is analysed. A hybrid meshing approach has been adopted to generate the computational domain. Simulations have been performed using a Reynolds-Averaged Navier-Stokes (RANS) solver with transition model. Comparison of the force coefficient curves showed that the impact of the struts on the total aerodynamic performance is minimal. Throughout the whole range of flow conditions considered, the force coefficient curves showed similar trends and absolute values. Locally, there are differences in the flow fields, predominantly in the tip region on the pressure side of the wing. The change in aerodynamic performance as a function of the sideslip angle was concluded to be strong. An increase in the sideslip angle led to a drop in the lift coefficient and an increase in the drag coefficient. Averaged values of the force coefficients were in line with inputs of several numerical models. Comparison of the results to available experimental data showed agreement for a limited range of flow conditions. The differences between the results of the present study and available experimental data are believed to be caused by the experimental data processing methods, in-flight deformation of the wing and steering actuation.

In dredging operation, the high-pressure water jet is widely used for the excavation of soil. To study the jetting process and optimize the dredging devices, the moving vertical water jet penetrating cohesive soil experiments were carried out by Nobel (2013). However, in terms of the design optimization for the dredging devices, it is not easy to change the jet scale and soil properties during the experiment due to time and economic constraints. Some detailed physics during the jetting process, e.g. pressure on the soil surface and shear plane inside the soil during jetting, were also not monitored during the experiment. Therefore, numerical simulation is chosen to optimize the design of dredging devices and study the physics of the jetting process. A CFD (computational fluid dynamics) numerical model is built to simulate the moving jet penetrating cohesive soil. The soil is modeled as a Bingham plastic. The sediment transport is modeled by using drift-flux model. The moving jet modeling is achieved by using dynamic mesh algorithms AMI (arbitrary mesh interface) and A/R (cell layer addition removal). The CFD numerical model has been validated with the experiment of Nobel. After the validation, an analysis of the jetting process based on this CFD model is accomplished proving that the CFD model can reveal the details of the soil failure process during jetting. This thesis work reveals that it is possible to describe the hydraulic excavation of cohesive soil with reasonable accuracy using CFD numerical model. The CFD model can also reveal the details of the soil failure process that could not be retrieved from the experiment. Since the model is generic, it can be applied for a jet bar with multiple nozzles. This is helpful to improve the design of dredging equipment, optimize the operational settings and estimate the production.

Wind energy has emerged as a promising alternative to fossil fuel energy sources over the last two decades partly due to considerable reductions in the cost of power production. A common trend towards cost reduction has been to build larger and lighter wind turbines. These produce more power per unit and use less material. Another strategy for cost reduction could be to reduce the Operations & Maintenance (O&M) costs of wind turbines by using optimal O&M strategies. O&M costs account for approximately one-fourth of the overall energy cost for the full lifetime of a wind turbine. They assume even greater significance in the wake of growing interest in offshore wind farms since offshore wind turbines operate in harsher environments compared to their onshore counterparts and are more difficult to access. Condition monitoring has been proposed as a novel preventive maintenance strategy wherein sensors are employed to collect data related to the functioning of an operational wind turbine. This data can be processed to get meaningful information about component health of the wind turbine. An aeroelastic model can be used to simulate the fault-free response of the wind turbine for given operating conditions. By comparing real-time information from the condition monitoring system and aeroelastic model, it may be possible to develop routines which can detect developing faults in the wind turbine components. This forms the basis of a model-based condition monitoring system (MOD-CMS). For purposes of model-based condition monitoring it is required to have an aeroelastic model which is computationally fast to be capable of running real-time aeroelastic load simulations, and is highly accurate in order to detect faults. Furthermore, it is also desirable to have a linear aeroelastic model since this can also be used for controller and state observer design. A state observer can help estimate states of the wind turbine which are not easily measurable. This thesis reviews state-of-the-art aeroelastic tools to get a better understanding of their limitations. A reduced-order aeroelastic model is developed using the aeroelastic module in STAS WPP (State Space Analysis of Wind Power Plants) which is an open-source aero-hydro-servo-elastic tool in the Matlab/Octave environment. The linear reduced order aeroelastic model is verified by running test cases in the frequency domain for the NREL 5MW Baseline wind turbine. The accuracy of the linearized model is demonstrated by performing a stability analysis study for the NREL 5MW Baseline wind turbine. 
Furthermore, different coupling and numerical integration schemes are studied to develop a time marching simulation tool. Two main approaches are proposed. The first involves time marching of the monolithic, strongly coupled non-linear aeroelastic model using a multistep predictor-corrector integration scheme. In the second approach, a partitioned, loosely coupled version of the linear aeroelastic model is implicitly integrated over time. In the present work a tool based on the first approach of integrating the non-linear aeroelastic model is developed and subsequently verified by running simple power production test cases. 
 In conclusion, this thesis discusses and implements a framework of strategies which can be implemented to reduce the order of a high-order aeroelastic model. It suggests coupling and numerical integration schemes to utilize this reduced-order model in a time marching simulation tool.

Flapping wings display complex flows which can be used to generate large lift forces. Flexibility in wings is widely used by natural flyers to increase the aerodynamic performance. The influence of wing flexibility on the flow can be computed using numerical analysis with Fluid Structure Interaction (FSI). However, there is a lack of open-source FSI methods. Therefore, a new implementation is developed for the well-known CFD code OpenFOAM to facilitate FSI with the multi-physics coupling library preCICE. The OpenFOAM adapter does not require changes to the OpenFOAM source code and is compatible with a variety of OpenFOAM versions. Structural modelling is performed using the open-source code CalculiX.

The method is validated using the laminar incompressible cylinder-with-a-flap benchmark for one steady and two unsteady cases. Good coherence is seen for the deflection and force generation, but the coupled method is sensitive to the eigenmodes of the structural model.

The influence of inertial, elastic and aerodynamic forces is quantified using a 2D wing. A sinusoidal flapping motion is imposed on the leading edge of the vertical wing. The inertial force on the wing dominates for high mass ratios and the wing deflection is rather independent of the flow. For a low mass ratio, the wing deformation scales with the increasing elasticity. The maximum lift and lowest drag were found for the wing with large flexibility and low mass so the passive deformation by aerodynamic forces creates a favourable shape for lift production.

Flexible translating and revolving wings at an angle of attack of 45deg show that chordwise flexibility decreases both lift and drag, however the lift over drag ratio is increased. The flow around both wings forms a coherent structure with a Root Vortex (RV), Tip Vortex (TV), Leading Edge Vortex (LEV) and Trailing Edge Vortex (TEV). The LEV on the revolving wing is stable for approximately up to half the span because vorticity is transported outward in the vortex core. The flowfield and LEV breakdown are consistent with experimental data of the same wing. The translating wing builds up circulation but the LEV detaches quickly near the centre of the wing. Chordwise bending reduces the angle of attack which decreases the distance to the core of the shed LEVs.

The Flying-V is a novel flying wing concept where the main lifting surface has been fully integrated with the passenger cabin. Previous studies have focused on the aerodynamic and structural design of the airframe; but, prior to determining which engine-airframe integration alternative is most beneficial (e.g. boundary layer ingestion, distributed propulsion, and alike), an aerodynamic analysis of the engine installation effects needs to be performed. In this sense, engine integration studies require of complex models and a multidisciplinary approach to address the physics involved in the engine-airframe interaction phenomenon. In particular, the location of the engines around the airframe has a major impact on the overall aerodynamics of the aircraft. Hence, this study focuses on determining whether the aerodynamic efficiency benefits expected from this configuration are not offset by negative interferences with the nacelle, weight penalties, or regulation constraints. In order to do so, and initial benchmark for the lift to drag ratio is obtained from a baseline Flying-V configuration, and the influence of the x, y, and z coordinates, as well as engine orientation are analysed afterwards. To carry out the simulations, an Euler pressure-based solver on a three-dimensional-unstructured grid is used to model the flow at cruise condition: M = 0.85, h = 13000 m, α = 2.9 ◦ , and T = 50 kN, and the viscous drag contribution is computed following an empirical approach. A total of forty different engine locations are tested under these conditions to build a preliminary surrogate model that predicts the aircraft’s lift to drag ratio based on the position of the nacelle. The results obtained show that misplacing the engine can lead to significant lift to drag ratio losses going as high as 55% when compared against the ideal integration configuration. Finally, a region behind the airframe’s trailing edge is identified where the interference losses due to the installation are minimized. In light of the results obtained, a location is recommended for the engines where the perturbations observed on the lift to drag ratio are near the 10%, and a good compromise is obtained among the different requirements imposed.

The current wind turbine design tools are based on aerodynamic simulations using blade element momentum (BEM) codes to calculate loads and power, see for instance the tools HAWC2, Bladed or FAST. This engineering method is computationally efficient, but theoretically valid only for steady two dimensional flow in non-yawed conditions.

To overcome these limitations engineering add-ons are used based on measurements or advanced methods. However, these include approximations which may result in introduced errors, especially in
extreme operational conditions such as yaw. Moreover, future turbines may utilize flaps or slats and experience tip speeds higher than 110 m/s leading to Mach and Reynolds number effects for which the current tools are not validated yet.

Therefore, the objective of this Master thesis is the development of an aero-servo-elastic simulation method based on an aerodynamic method with increased fidelity compared to BEM such as computational fluid dynamics (CFD). This was achieved by replacing the BEM module of NREL FAST by an OpenFOAM CFD code. Therefore, FAST and OpenFOAM were coupled by utilizing the neutral interface MpCCI.

Finally, it was investigated how such a method can be justified when compared to the state-of-the-art tools, which use BEM. The implemented coupled method was thereby validated against experimental data from the NREL phase VI experiment. The Master thesis project, which was carried out externally at the CFD department of Fraunhofer IWES, showed that there is a need for more accurate methods especially in extreme conditions such as heavy yaw.

Kite Aerodynamics Airborne Wind Energy (AWE) systems operate at high altitudes, where wind velocities are higher in magnitude and more constant with respect to lower heights at which for example wind turbines operate. The ASSET department of the Delft University of Technology uses a concept which consists of a flexible Leading Edge Inflated (LEI) kite, which is connected through a tether to a drum on a ground station. By autonomously flying the kite in crosswind patterns, high tension forces in the tether cause it to be unwound from the drum, this mechanical energy is converted into electricity via a generator. This kite power system has the potential of becoming a new player in the wind energy sector. The development of such systems creates a demand for kite models, which can be used to optimize the performance of tethered wings. By using aeroelastic models, which simulate the Fluid-Structure-Interaction (FSI), the flight dynamics of a flexible wing can be studied. In this thesis an aerodynamic analysis tool is presented, which can serve as part of a quasi-steady aeroelastic model for kites. The New Tool The Vortex Lattice Method (VLM) and 3D panel method were identified as acceptable aerodynamic modeling methods with the best balance between model complexity and computation time. Because the tethered wings in AWE systems mostly y at high angles of attack, close to stall, an extension is implemented. This extension corrects for the non-linear aerodynamic phenomena that occur at high angles of attack. A non-linear potential ow solver is used, where viscous corrections on both lift and drag are implemented by using airfoil data of the analyzed wing. The method combines the capability of a VLM and 3D panel method to incorporate effects of finite, non-planar wings with the capability of viscous airfoil analysis to predict non-linear effects, including stall. The method is implemented in an already existing analysis tool for airfoils, wings and planes, named XFLR5 which is programmed in C++. Several approaches within the method are considered where, with a trade-o_ validation procedure, the method with the best performance is selected. Because the applied corrections in the method largely depend on viscous airfoil data, an investigation is performed on the single membrane airfoils used in LEI kites. Results are compared for high-fidelity 2D CFD simulations, the 2D integral boundary layer panel method XFOIL and an existing polynomial regression model based on single membrane airfoil CFD simulations. The polynomial regression model is considered most promising, though improvements on the current available model could significantly increase accuracy of the non-linear methods. For the chordwise pressure distribution, an approach is given where XFOIL is used on-the-fly.