The TANGO mission represents a significant leap forward in the global monitoring of greenhouse gas emission plumes, particularly CO2 and NO2. Comprising two satellites, TANGO-Carbon and TANGO-Nitro, the mission is designed to operate from 2027 to 2031, offering unprecedented capabilities through stereo (temporally separated) and high spatial res- olution emission plume images. These capabilities create a unique framework that facilitates the development of novel estimation methods for emission rates of greenhouse gas emitters. Conventional methods for estimating emission rates of CO2 and NO2 rely on combining gas concentration measurements with wind velocity fields derived from meteorological data, often introducing substantial uncertainties due to the inherent inaccuracies in wind velocity estimation. To address this challenge, this research explores alternative methods enabled by TANGO’s innovative framework, which allows for the direct measurement of emission plume velocity from concentration data. By eliminating the dependency on uncertain me- teorological inputs, these methods promise to reduce the uncertainty in emission rate estimates.
Through detailed simulations and analyses, this research demonstrates that the TANGO mission can effectively establish a framework for directly measuring emission plume velocities. By simulating the data products of the TANGO satellites using Large-Eddy Simulations and applying advanced methods such as traditional Correlation Image Velocimetry (CIV) and Computer Vision Correlation Image Velocimetry (CVision-CIV), wind velocity fields were successfully estimated from plume imagery. These estimates were found to be of promising precision across a range of conditions, including varying wind velocities, emission rates of greenhouse gasses, and levels of measurement noise in the simulations. Results revealed that the CVision-CIV method outperforms the traditional CIV method, especially in scenarios with low signal-to-noise ratios. Wind velocity fields directly estimated from plume imagery were implemented in the Cross-sectional Flux Method to estimate CO2 emission rates. The emission rate estimates indicate that direct plume velocity measure- ments provide a more accurate estimate of emission source rates than conventional methods, which rely on indirect wind velocity estimates from meteorological data. The use of wind velocity fields obtained through the CVision-CIV method resulted in CO2 emission rate estimates with ±20% accuracy in most scenarios, particularly under optimal SNR conditions. Additionally, the study highlights the impact of mission parameters such as image resolu- tion and measurement noise on the accuracy of wind velocity estimations. It was found that higher image resolution and longer time intervals between measurements enhance the precision of wind velocity field estimates by reducing the relative effects of measurement noise.
In summary, this research demonstrates that direct estimation of wind velocities from emission plume imagery, as enabled by the TANGO mission’s advanced capabilities, can accurately be performed and significantly enhance the accuracy of emission rate estimates. The improved wind velocity estimation methods proposed in this thesis offer a promising advancement in remote sensing techniques for greenhouse gas monitoring.

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.

Infiltration is the uncontrolled flow of air into the building through the envelope, which contributes to a significant amount of heat loss and is estimated to be around 30% of the heating demand. It is therefore essential to estimate the amount of infiltration, to design a suitable heating and cooling system in a building. Empirical relations which are used to determine infiltration, generally overestimate the infiltration rate, since the effects of weather, mechanical ventilation and building geometry are not taken into account. Large Eddy Simulation (LES) is used to determine the pressure distribution around a building along with an airflow network model to determine the infiltration flow rate. Validation studies of the LES model show that the pressure data at the front and back faces of a surface-mounted cube are accurately captured, whereas, the pressure at the top and side faces slightly deviate from reference data with an error of 16%-20%. This occurs due to a shift in the recirculation region at the top towards the leeward part of the cube surface. The reattachment of the flow is not observed at the top and side surfaces, which explains the deviations in pressure. The infiltration rate is analysed in the Matrix VII building using the in-house model, which combines the LES model and the airflow network model. It is then compared with other relevant standards and models like the NTA 8800 and an energy balance model. The comparison is made in terms of the cross-correlation between the models and the heat loss associated with infiltration. The in-house model shows good cross-correlation with the NTA 8800 model, with a Pearson correlation coefficient of 0.8454. The building standards which employ empirical relations, overestimate the heat loss by a factor of 10 compared to the in-house model. The in-house model is then used to develop a database of infiltration values for different building heights and airtightness values. The specific infiltration rate is observed to decrease in buildings taller than 120 m due to the minimal changes in velocity higher up the atmospheric boundary layer. The database is observed to provide values of infiltration with reasonable accuracy, compared to the existing database in the ISSO standard.

The total electrical energy consumption by all the operational data centers (located all over the world) is enormous (approx. 1% of the global electricity demand 20000TWh). This electrical energy is required 24x7 to operate and cool all the IT equipment present in the data center. The electrical energy required to cool all the servers present in the white space can range from as low as 10% to as high as 40% of the total data center electrical consumption. The server's inlet temperature has to be within the ASHRAE recommended range (18o C – 27o C), so that they can function correctly.   A simplified design of a raised floor white space with hot aisle / cold aisle configuration is considered. The tile flow rate through the floor tiles influences the server's inlet temperature. To control the tile flow rate, 11 design variables of the data center white space are identified. These are the position of the 4 perforated plates, the amount of perforations of each perforated plates, the floor tiles perforation, the raised floor height, and the CRAH distance to the cabinet. 600 design samples of the white space are generated by applying the Latin Hypercube Sampling (LHS) technique on these 11 design variables. A well-validated CFD software 6SigmaRoom by Future Facilities is used to generate the CFD results. The standard k-ε model is used to model the turbulence in the CFD simulations, in a steady-state condition. A database of 600 samples is generated by recording the cabinet's inlet temperature, flow rate of floor tiles from the CFD simulations, and the corresponding changeable design parameters generated by the LHS technique. The error due to CFD simulation is estimated at less than 4% for the tile flow rate and 1.7o C for the server inlet temperature.  Four Artificial Neural Networks (ANN) are trained on the data from the database to predict the floor tile's tile flow rate and the cabinet's inlet temperature, respectively. The average R2 prediction (testing) accuracy is 0.97 for the tile flow rate predictions and 0.92 for the cabinet's inlet temperature predictions. Their average prediction error is less than 5% for the tile flow rate and less than 20 C for the cabinet's inlet temperature. The Non-dominated Sorting Genetic Algorithm-II (NSGA-II), a variant of the genetic algorithm, is used to find the optimum values of the 11 design parameters of the white space. These optimum values are going to ensure the server's inlet temperature to be within the ASHRAE recommended range. The genetic algorithm optimizes the design variables based on the predictions made by the neural network predicting the tile flow rate. The values of the optimized design parameters are verified using the 6SigmaRoom software by comparing the server's (mean) inlet temperature of the optimized case with the non-optimized case. More number of servers have their (mean) inlet temperature below 270 C in the optimized case as compared to the non-optimized case. The electrical power required by the CRAHs to cool the white space is reduced by 10% in the optimized case as compared to the power which is required by the CRAHs in the non-optimized case. In this study, a CFD simulation of the white space took 40 minutes. The neural networks took less than a minute to make the predictions, and the NSGA-II algorithm took less than 10 minutes to find the optimized design parameters of the white space.  Thus, in this thesis, it is shown that using an artificial neural network and a genetic algorithm, in combination with computational fluid dynamics gives satisfying results in optimizing the white space design, required to keep the server's inlet temperature within the ASHRAE recommended range. The computational time required to find the optimum white space design is also reduced by using a neural network and a genetic algorithm. The prediction by the neural network and the optimization performed by the genetic algorithm can be improved further with the availability of more training data and in-depth knowledge of applying these techniques (the neural network and the genetic algorithm) in predicting and optimizing the solutions respectively.  

Wave impact tests are performed in the LNG industry to design the structure of the cargo containment system (CCS) of the vessels and to study the physics of breaking wave impacts. The state-of-the-art methodology divides the wave impact flow into two parts: the global flow and the local flow. The global flow considered as the solution of the incompressible Euler equations for the liquid and gas in the tank; and the local flow as a perturbation of the global flow. However, researchers have found it to be a challenge to generate repeatable global flows of focused breaking waves and, therefore, to draw definitive conclusion about the contribution of the global flow variability in the impact pressure variability. In this context, a new facility was designed and built at MARIN in the framework of the SLING project to further investigate the physics of sloshing impacts: the Multiphase Wave Lab (MWL), a wave flume of 10 m in length, 0.6 m in width and water depth of 400 mm.

This thesis aimed to identify and evaluate the sources of variability of the global flow of focused waves, to define the repeatability criteria and to determine the theoretical conditions that would lead to global flow repeatability in the MWL. To achieve the objectives, both theoretical and experimental work have been required.

Three main sources of global flow variability were identified: (1) water depth variation, (2) long bounded waves (seiching) and (3) currents induced by seiching. These drivers of variability were modeled in a wave generation and propagation algorithm from which the sensitivity of the global flow to the sources of variability has been addressed. The results showed that the water depth is the most critical driver of variability and that repeatability would be achieved if its difference between experiments is below 0.5 mm.

Based on the sensitivity study and the characteristics of the wave maker, a criterion to experimentally quantify global flow repeatability was derived from the Sobolev norm of the Fourier space of free surface elevations at a distance from the focal point. To validate the theoretical value, impact waves were generated using a wave focusing technique. Linear wave and wave making theories were used to compute the paddle motion generating the wave impact of interest. The breaking wave was designed using a two-parameter Ricker amplitude spectrum formulation, which defines the contribution of each frequency to the total breaking wave energy and therefore changing its characteristics (crest thickness, crest stability, gas pocket size…). Image processing techniques were used to measure wave maker motion and free surface elevations from video recordings.

While more repetitions are required to confidently conclude about the validity of the criterion, the experimental results showed that when the ‘dissimilarity’ value was below the theoretical threshold, exceptional repeatability of the global flow was obtained.

Floating breakwaters are applicable in several offshore applications to protect downstream structures from excessive wave loads and to reduce their motion response. This thesis investigates the impact of the leading platform, functionally a breakwater, on the RAOs and response of the platforms behind it in frequency domain. The structures are only hydrodynamically coupled. All models were analysed for head waves only. Variables in model design are investigated using a combination of diffraction software and solving equations of motion in six degrees of freedom for each body. The variables are the gap between the breakwater and the first platform, the width, i.e. side perpendicular to wave direction, of the breakwater and the gap between platforms. Base case dimensions for the platforms and breakwater are chosen based on the natural frequencies and wave transmission coefficients respectively. These choices are made to function well for the wave spectrum at the chosen site. Each case analysed included a breakwater and 10 platforms downstream of it. It was found that he imperfect efficiency of a breakwater means that the first few platforms behind it act as breakwaters too; albeit for much lower wave energies. Increasing the gap between the breakwater and the first platform behind it results in a decrease in RAO of the platforms due to increasing hydrodynamic coupling. The impact on pitch RAOs is greater than the impact on the heave RAOs. Increasing the width of the breakwater results in minimal reduction in RAOs of the platforms behind it at large gap sizes. At small gap sizes, there is an adverse relationship. Hydrodynamic coupling between the platforms can lead to shared natural frequencies within the design frequency range, leading to a large motion response. This can be prevented by changing the gap size and thereby the hydrodynamic coupling and moving the natural frequency outside of the design range. A breakwater and multiple platforms downstream of dimension L=100 m, B=100 m, T=5 m, with a gap of 80 m between the breakwater and platforms and 100 m between the platforms themselves was shown to effectively reduce the motions of the downstream platforms. The first few platforms exhibit higher heave than the other platforms, but similar pitch to the other platforms. Therefore, their use cases in a floating city must be chosen accordingly. The potential negative impacts of hydrodynamic coupling between the platforms means that the platforms must be further apart from each other, resulting in floating cities with a much larger footprint than previously expected. Further research into the motion response for 2D structure layout and different wave directions would be interesting follow-ups to this thesis.

Recently the interest in hydrofoil vessels using a fully submerged hydrofoil increased. Hydrofoil vessels experience a resistance hump and possible instabilities during their takeoff of which both are influence by waves. In order to determine the required power during the takeoff to overcome the resistance hump and to investigate whether the hydrofoil vessel is stable during the takeoff numerical simulations or experiments have to be performed. Experiments covering the full takeoff require a long towing tank and high towing velocities and therefore these experiments are costly. The alternative, performing numerical simulations, is favorable but requires a suitable numerical code. As no validated code is available in which a takeoff can be performed in waves, in this research Panship, a potential flow code suitable for high speed craft and adapted for use with hydrofoil craft, is validated for the takeoff of a hydrofoil vessel. In this research the results of Panship are compared with results of experiments and other numerical codes in four different stage as little validation data is present for the takeoff of a hydrofoil vessel. The four different stages are: a foil without the influence of the free surface, a foil with the influence of the free surface, two foils with the influence of the free surface and the hull and foil system near during the takeoff. In these four stages the lift and drag determined in Panship is compared with available experimental results and numerical codes. As the simulations in Panship require a vast amount of input parameters, the influence of these parameters is studied first to ensure the reliability of the results. Comparing the results of Panship for a deeply submerged foil with another potential flow solver shows that the lift is predicted correctly, but that the induced drag is underpredicted. If viscous effects are required in the solution, the quality of the results of Panship is dependent on the type of hydrofoil used. As some foils have a large viscous effect on lift, the lack of viscosity on Panship, leads to a low quality of the results for lift and induced drag as they are overpredicted. The trends for interaction of a foil with the free surface are predicted correctly but the underprediction of induced drag influences the quality of the results. Panship is able to predict the effects of foil interaction for lift correctly, but the results for foil interaction for drag are poorer. During the takeoff Panship is able to predict the lift fairly correct but the total drag is underpredicted severely. Recommendations are given to improve the results of Panship and for future work.

Accurately predicting the ship motions, is essential knowledge when operating in water. To predict the ship motions, multiple ship characteristics have to be known. For the roll motion, one of these characteristics is the roll damping coefficient. Nowadays the industry standard to determine the roll damping coefficient of a ship is by performing model tests or using empirical formulas created in the late ’70s. In recent years computational power has increased significantly. This increasemakes it possible to start using computational fluid dynamics (CFD) for practical purposes instead of solely scientific research. The roll damping coefficient is a very interesting parameter to examine with viscous flow solvers as the roll motion is heavily influenced by the viscosity of the water. Multiple studies have been performed with 3D and 2D CFD simulations. By simplifying the simulation to 2D, calculation time is reduced drastically. This simplification is performed by only simulating one cross-section of the midship. Only simulating one cross-section causes a loss of accuracy in how well the roll damping coefficients can be determined as the damping effects of the bow and stern are not taken into account, or are roughly estimated. During this research, a method to accurately determine the roll damping coefficients of a ship, while maintaining low computation time, is investigated. This method is based on performing multiple 2D CFD simulations of different cross-sections and combining the results to capture the behaviour of the entire ship. With this approach, the high accuracy of 3D simulations and the low computation time of 2D simulations are combined. The accuracy of this 2D section method is determined by comparing the results with experimental data. The experimental data is obtained through free roll decay tests of a ship from Van Oord on model scale. A 3D CFD model, which simulates a free roll decay test, is created using OpenFOAM. The results of this simulation are compared to the experimental data to determine how well a 3D simulation can predict the roll damping coefficients. Next, a 2D CFD model is created using OpenFOAM which is validated using experimental data of a structure which has a uniform cross-section along the entire length. Lastly, the validated 2D CFD model is used for the 2D section method. Multiple cross-sections of the same ship from which the experimental data is obtained and with which the 3D CFD simulation is performed, are simulated. The results of the 2D section method are compared to the experimental results in order to determine how well this method can determine the roll damping coefficient of a ship. The simulation of the 3D free roll decay test underestimated the linear damping. The non-linear damping was within the margins of the experimental data. The 2D forced oscillation simulations showed an excellent agreement in linear and non-linear damping with both the experimental data as with a comparable CFD simulation. The 2D section method slightly overestimates both the linear and non-linear damping of an entire ship but overall this method shows promising results. However, more research should be done to optimise the method further.

A tip-vortex in the wake of a finite length lift generating surface has a low pressure region near the axis of the tip-vortex. This low pressure region can trigger tip-vortex cavitation especially in ship propellers which has adverse effects by causing vibration and underwater noise production. One way of minimising the tip-vortex cavitation is by reducing the propeller blade loading but at a cost of lower operating efficiency of the propeller. An alternative passive approach, to delay the onset of cavitation, by increasing the minimum pressure in the core of the tip-vortex through modification of the tangential velocity profile of the tip-vortex is investigated in this thesis. In this thesis, the effect of upstream turbulence on the peak tangential velocity of the tip-vortex from a NACA 662-415 hydrofoil is investigated through stereo-Particle Image Velocimetry measurements. The turbulence is produced by a passive grid placed in the upstream of the hydrofoil. The tangential velocity profile at three different turbulent intensities were compared with measurements from a baseline no grid case that had nearly uniform and steady inflow to the hydrofoil. The tangential velocity profile of the vortex exhibits a reduction in the average peak tangential velocity under the influence of the grid generated turbulence compared to the no grid case. The measurements taken at two downstream locations, 0.5 and 1.3 chord length downstream from tip of the hydrofoil, showed that a significant reduction in the magnitude of the average peak tangential velocity of the tip-vortex is observed only at the latter position. Also, on examining the axial velocity profiles, a significant reduction in the magnitude of the average peak axial velocity in the core of the tip-vortex was observed under the influence of grid generated turbulence. An apparent effect of the upstream turbulence on the tangential velocity of the tipvortex is seen to appear only when sufficient time is given for a secondary vortex structure, from the upstream turbulence, to form around and be intensified by the primary tip-vortex. At 1.3 chord length downstream from the tip of the hydrofoil, the reduction in the magnitude of the peak tangential velocity is accompanied by increase core radius of the tip-vortex.

The bulbous bow is a common feature for large displacement vessels. The purpose of the bulbous bow is to reduce the bow wave, hereby making use of wave cancellation theory. The main drawback of these type of bows is that the drag reduction effect is only present for a limited range of sailing speeds. If the transit velocity is altered, the effect of the bulbous bow can even result in an increase of wave making drag. Due to this sensitivity to the sailing speed it is important to be able to predict the location of the waves generated by the protruding bulb. Computational fluid dynamics is gaining interest in commercial marine industries. The size and transit velocity at which the previously mentioned vessels that employ the protruding bulb operate, results in the common use of Reynolds averaged Navier Stokes (RANS) models. To investigate the accuracy of these RANS models, a 2D model is presented in this thesis. The bulbous bow is modeled as a shallowly submerged 2D naca0012 hydrofoil. The justification for this simplification is that the geometry and flow over a bulbous bow is too complex for the duration of this project. A submerged 2D hydrofoil can still capture the important flow dynamics for free-surface waves. In this thesis we focused on evaluating the accuracy of RANS models for simulating the wave dynamics that arise when a shallowly submerged 2D naca0012 hydrofoil moves through water. The main objective is to find which geometrical and fluid dynamic properties have an effect on the free surface wave profile. Apart from questioning if these properties have an influence on the wave profile, we also want to know how the wave profile changes by altering these properties.
The interFoam package from OpenFoam was used for simulating the flow. InterFoam adopts the volume of fluid (VOF) approach proposed by Weller (Weller, 2008) for simulating multiphase flows. Turbulence modeling was done using the k-ωSST two equationmodel from Menter et al. (Menter, 1992). In 1983 Duncan and his colleagues published a paper on the free surface wave dynamics generated by a towed naca0012 hydrofoil (Duncan, 1983). The results from their experiments are used as a benchmark for the present study. From a single phase test we found that the experiments from Duncan where performed in the regime where transition of the boundary layer from laminar to turbulent is present. The presence of this transition is expected to be one of the reasons for the disagreement in literature on wave elevation, wavelength zero point crossings and lift and drag coefficients. It is shown that the relatively small gap between the basin floor and the hydrofoil of 0.86 chord lengths has a significant impact on the wave profile and the flow at the hydrofoil. Reynolds independence is found to be at Re ¸ 2•10⁵ for a towed hydrofoil submerged at h/c = 0.955 with the basin floor located 10 chord lengths below the hydrofoil. Below this value a reduction in Reynolds number results in an decrease of the wave amplitude and an increase in the wavelength. The assumption to neglect the resistance from the hydrofoil wake made by Duncan is shown to be false. The dominating dimensionless parameters for these types of flows are: Froude based on submergence Frh, Froude based on basin to foil height Fr_D and the Reynolds number based on the chord length and the bottom fluid parameters Rec . Note that in this thesis the angle of attack (α) has been kept constant at 5° which does
effect the flow but this has not been investigated during this research. A attempt is made to simulation breaking waves in the present model. The Breaker type in the present study differs from the one found by Duncan et al. (Duncan, 1983). Even if the same breaker type was found the elevation and wavelength differ a lot. It is therefore concluded that The present model is not suited for predicting
breaking waves.

The case of the flow around a rotating circular cylinder is very complex. This thesis investigates the properties of a fluid flow for Reynolds numbers ranging from 50 to 400. Numerical simulations are performed using a combination of isogeometric analysis and the residual-based variational multiscale method, providing high accuracy. The results show how the lift and the drag generated by the cylinder are related to the spin rate and the Reynolds number. When comparing the lift and drag values to the required amount of torque which is needed to spin the cylinder, it is shown that at medium spin rates, a very high aerodynamic efficiency is obtained at a reasonable amount of torque. 3D simulations are performed and show at high spin rates strong vorticity and a wake that is dominated by vortex shedding. These results differ strongly from the 2D simulations, which leads to the question whether 2D simulations are still representative for real real at high spin rates, despite the low Reynolds number.

In the quest for renewable energy for tropical islands, Ocean Thermal Energy Conversion (OTEC) has revealed itself as one of the most promising technologies. OTEC stands or falls with the performance of the condenser. Plate Heat Exchangers (PHEs) have proven their selves as effective heat transfer
equipment for low enthalpy cycles such as OTEC. Nowadays, the design of PHEs mostly relies on models based on experimental data. This is deemed time-consuming and non-generic. Enormous successes in the application of Computational Fluid Dynamics to single-phase flows have raised the
interest to use CFD as a predictive and generic tool for the design of PHEs. Moreover, CFD yields a picture of the complete flow field, enabling the designer to better understand the fundamental flow structures that are relevant for the heat transfer and pressure drop performance of the PHE.
First, a comprehensive review of literature on condensation models is presented. Thereafter, the practicality of the phase change models in terms of real computation time needed is investigated. It is concluded that the stability issues associated with the vapor-liquid interface poses the biggest problem.
That is, for the simple Nusselt condensation problem, an extremely long computation time is needed for reasonable accuracy. Finally, the ability of the phase change models to cope with wave evolution,
flow circulation and flow separation is investigated. The multiphase model is found to properly predict the flow field. However, the heat and mass transfer predicted by the condensation models is estimated poorly.
In the end, until the stability issues of the current phase change models are solved, or a significant improvement in computational performance is made, the application of CFD to the design of condensation PHEs is questionable. Yet, using CFD only to find trends in heat transfer and pressure drop in PHEs might prove to be fruitful.

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 propulsion is caused by the momentum transfer from the rowers to the water with the help of oar blades. The design of these oar blades has also been extensively studied. However, knowledge on the effect of the air-water interface on the drag force on the oar blades is still lacking. Therefore, visualizing the flow around the oar blades will lead to better understanding of the flow structures, which would help in optimizing the drag force acting on the oar blades.

In the present study, a simplified scenario of a rectangular flat plate moving normally to its plane along a straight line and parallel to the free surface has been studied using hydrogen bubble visualization and Particle Image Velocimetry (PIV). Using a 4-axes industrial robot and a force/torque transducer, the effect of the air-water interface on the drag force on the plate has been studied at a Reynolds number, based on the longest edge of the plate, of 6×10⁴. The analysis of the drag force profiles at different plate depths led to the identification of a high drag case, which occurred at a plate depth h of 20 mm. The hydrogen bubble visualization indicated that in this specific case, the high drag was related to the formation of a compact wake behind the plate.

Hydrogen bubble visualizations were also performed at two other plate depths, h = 0 and h = 100 mm, to determine the effect of the air-water interface on the flow structures and ultimately on the drag force acting on the plate. The visualization of the deep water case (h = 100 mm) captured the formation of a vortex ring, which was found to have unique effects on the drag force. The presence of the air-water interface was found to significantly influence the drag force on the plate. Additionally, an extensive decomposition of the drag force profile showed a time-dependent added mass force and a decaying force acting on the plate.

Particle Image Velocimetry (PIV) measurements were carried out in the horizontal mid-plane of the plate. The tracking of the starting vortex and its disintegration has been identified using the swirling strength analysis. Finally, combining the hydrogen bubble visualization and PIV results, the formation and the development of the starting vortex was identified.

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.

When drilling for oil or gas, wells are typically constructed using a conventional or telescopic well design. After a section of the well has been drilled, a steel casing (or liner) is inserted into the hole preventing the collapse of the hole. The next well section has a smaller diameter as it’s casing must pass through the previously installed casing. This process leads to a stepwise reduction of the well diameter which, especially in deep or complicated wells, restricts the maximum production rate of oil and gas.

Mono-diameter technology utilizes casings which are plastically deformed after they have been placed in the well. This plastic deformation is done by pulling a conically shaped tool, known as the cone, through the newly installed casing. The plastic deformation increases the diameter of the new casing to (nearly) the same as that of the previous casing, therefore the well diameter no longer decreases with every new section.

The expansion requires a force in the order of 1000-2500[kN]. The work done by this force leads to high local heat generation due to friction and plastic deformation. This heat, poses a risk for the expansion process as the lubricant (RPSLF) decomposes above 250[C]. Decomposition of the lubricant leads to an increase of the friction, inducing more heat release and further decomposition of the lubricant. The expansion force may then exceed the pulling capacity of the drill rig or strength of the drill string, leaving the cone stuck in the well.

Previous research provides the distribution of pressure on the contact surface of the cone, the strain distribution inside the liner and the temperature dependent friction coefficient of the lubricant, by combining these the frictional heat is calculated. Heat generation from plastic deformation is a complex phenomenon
especially at low strain (-rates). The Taylor-Quinney coefficient defines the ratio between the work done on a material and the heat generated. A strain-dependent model for the Taylor-Quinney coefficient, developed by Zehnder, is used to determine the heat release from plastic deformation.

A numerical heat transfer model is built in Matlab, based on the finite volume method. The model uses a mesh based on skewed quadrilateral cells. Numerical stability of the model is verified for the cell size, time step and time integration method. Movement of the cone and the plastic deformation of the casing are modeled by taking a reference frame fixed relative to the motion of the cone and adding a ”convective” term inside the liner. Heat transfer phenomena at all boundaries are investigated using thermal resistance models.

A series of experiments is executed to verify the numerical model. The
experiments consist of full-scale expansion test using a cone equipped with 30 thermocouples placed just below the contact surface. Additionally also the temperature of the liner, expansion speed and expansion force are measured and recorded.

Comparison of the experimental and numerical results leads to the observation that the pressure profile determined in previous work is likely valid at the first onset of expansion. Over time, the forming of a lubricant film however leads to the re-distribution of roughly 20% of the force from the rear of the cone to the front. When the pressure profile is corrected for this effect; the temperatures inside the cone, temperature of the liner, expansion force and overall heat balance show a good match between the numerical and experimental results with an error of around 5%.

From the heat balance based on the experimental results, it follows that between 54% - 60% of the work done on the system is converted into heat. As all work done in the form of friction is converted into heat the remaining energy must be lost in the work done to plastically deform the casing, this provides indirect evidence for the validity of the Zehndermodel.

The validated numerical model is used to simulate a reference case field expansion, the maximum contact temperature here is 164.4[C]. This value is well below the lubricant decomposition temperature of 250[C], which leads to the conclusion that the process is safe and the expansion speed could even be increased from a thermal point of view.