The present thesis summarizes work on developing a method for unsteady aerodynamic analysis primarily for aeroelastic simulations. In contrast to widely used prediction tools based on frequency-domain representations, the current approach aims to provide a time-domain simulation capability which can be readily integrated with possibly nonlinear structural and control system models. Further, due to the potential flow model underlying the computational method, and the solution algorithm based on an efficient boundary element formulation, the computational effort for the solution is moderate, allowing time-dependent simulations of complex configurations. The computational method is applied to simulate a number of wind-tunnel experiments involving highly flexible models. Two of the experiments are utilized to verify the method and to ascertain the validity of the unsteady flow model. In the third study, simulations are used for the numerical optimization of a configuration with multiple control surfaces. Here, the flexibility of the model is exploited in order to achieve a reduction of induced drag. Comparison with experimental results shows that the numerical method attains adequate accuracy within the inherent limits of the potential flow model. Finally, rather extensive aeroelastic simulations are performed for the ASK 21 sailplane. Time-domain simulations of a pull-up maneuver and comparisons with flight test data demonstrate that, considering modeling and computational effort, excellent agreement is obtained. Furthermore, a flutter analysis is performed for the same aircraft using identified frequency-domain loads. Results are found to deviate only slightly from critical speed and frequency obtained using an industry-standard aeroelastic analysis code. Nevertheless, erratic results for control surface hinge moments indicate that the accuracy of the present method would benefit from improved control surface modeling and coupled boundary layer analysis. / QC 20100531

With the development of the vehicle industry and the innovation of technology, driving experience is improving in all aspects. Volvo is more and more focusing on improving the comfort of driving. Part of this is to minimize squeaks and rattle (S&R) from vehicle seats. A physical measurement method was studied from component level in this thesis. The communication with the supplier has helped to better understand the definition and measurement method of play. Based on the previous work from Volvo and the supplier, a new improved algorithm has been developed to suit current production demands in this thesis work. A Graphical User Interface (GUI) has been finished for general engineers. The Study and exploration of a FEM simulation method make it possible to measure play in an economical way in the future.

The quest for more efficient machines is always ongoing in the engineering world. This project is no different. ABB are investigating a new type of propeller that seems to offer increased efficiency compared to normal screw propellers. That is a so called foil wheel propeller. The foil move in a circular pattern with the fluid stream moving in the radial direction of the propeller instead of the axial as in a screw propeller. If the propeller is placed and modeled correctly it can also be used as a thrust vectoring device. This report focuses on the fluid physics of the foil wheel propeller, or as it is called in this report radial flow propeller. First of all the movements and interactions of the blades must be understood. Both to keep the efficiency high to compete with screw propellers, but also to foresee any problems that may occur with such a new device. A scaled down version of the propeller have been commissioned by ABB and will be tested in some time after the work within this report is completed. The effects associated to this will also be analyzed. The tool to compute the flow physics of the radial flow propeller will be computational fluid dynamics. Computational fluid dynamics uses a numerical method to compute the entire fluid field in space and time. The flow around the propeller is highly complex so a detailed analysis is needed if a well functioning control system is to be constructed for instance. The differences between the downscale and the full-scale are great, even when the non dimensional coefficients are considered. The down-scale case will be less efficient, it will be difficulties predicting the performance of the full-scale since the downscale flow is much less powerful than the full-scale case. The interaction between the blades has a large effect. There is a strong relation between angle of attack and the number of blades. The forces that are large change by about 30\% so it must definitely be considered if a model is to be used for a control system.

The aerodynamic team at SCANIA has discovered the need to investigate the effect of the upstream turbulence conditions on the aerodynamics of the trucks. This need comes from the fact that there are differences between the drag coefficients obtained using computational fluid dynamics (CFD) and the on-road measurements. This difference can lead to wrong predictions of fuel consumption and emissions, which can cause incorrect evaluation of design changes. In this study the problem of modeling upstream turbulence in CFD simulations is addressed together with its effect on the aerodynamics of the trucks. To achieve this, representative values of turbulence intensity and length scale were found from the work of different researchers, who performed on-road measurements for various conditions. These values were then used in a method by Jakob Mann to generate a synthetic turbulence field. This field was then used to generate time varying velocity components, added to the mean velocity at the inlet of a CFD simulation. After the implementation of the method it was discovered that the conditions at the test section of the virtual wind tunnel were representative of the on-road measurements. The results showed drag increase and wake length decrease, similar to previous studies performed on simple geometries. It also showed that the higher mixing of the flow increases the drag by surface pressure increase of forward facing surfaces and pressure decrease at the base. These conclusions may be extended to other bluff body geometries and it shows the importance of good design around gaps. The comparison between two truck geometries showed that a truck with better aerodynamics in a smooth flow shows less drag increase with introduction of upstream turbulence.

A park lock mechanism is a device that is fitted to an automatic transmission on a vehicle. The mechanism lock up the transmission so that no rolling of the vehicle can be done when the vehicle is put in the park position. The aim of this thesis is to develop a method in order the evaluate designs on a Park Lock Mechanism (PLM) that can be found in a dual clutch transmission (DCT). A Computer Aided Engineering (CAE) tool to calculate the output that is required for an evaluation of a park lock mechanism design will be created. The CAE tool shall calculate static, dynamic, and snap torque on a ratchet wheel in a gradient, with or without a trailer, also the minimum and maximum coefficient of friction between the pawl and cone, pull out force, the maximum amount of rollback, torque needed from the return spring, preload force from actuator spring, and engagement speed. The CAE tool created uses an Excel Visual Basics for Applications (VBA) workbook for all calculations. The tool allows the user to choose different vehicles with the required specification to evaluate the values for that PLM. The CAE tool will save time and cost if lots of different PLM’s are going to be designed. The CAE tool has potential for future work when more calculations can be added that can be in use for the evaluation the PLM. The CAE tool developed by the master thesis student calculates all the required values for evaluation of a PLM design, executed in a fast, efficient, and easy to use program.

The main objective of this Master Thesis project is the development of a new methodology to perform Computational Fluid Dynamics (CFD) conjugate heat transfer simulations for internal combustion engines, at the Fluid and Combustion Simulations Department (NMGD) at Scania CV AB, Södertalje, Sweden. This new method allows to overcome the drawbacks identified in the former methodology, providing the ability to use the more advanced polyhedral mesh type to generate good quality grids in complex geometries like water cooling jackets, and integrating all the different components of the engine cylinder in one unique multi-material mesh. In the method developed, these advantages can be used while optimizing the process to perform the simulations, and obtaining improved accuracy in the temperature field of engine components surrounding the water cooling jacket when compared to the experimental data from Scania CV AB tests rigs. The present work exposes the limitations encountered within the former methodology and presents a theoretical background to explain the physics involved, describing the computational tools and procedures to solve these complex fluid and thermal problems in a practical and cost-effective way, by the use of CFD.A mesh sensitivity analysis performed during this study reveals that a mesh with low y+ values, close to 1 in the water cooling jacket, is needed to obtain an accurate temperature distribution along the cylinder head, as well as to accurately identify boiling regions in the coolant domain. Another advantage of the proposed methodology is that it provides new capabilities like the implementation of thermal contact resistance in periodical contact regions of the engine components, improving the accuracy of the results in terms of temperature profiles of parts like valves, seats and guides. The results from this project are satisfactory, providing a reliable new methodology for multi-material thermal simulations, improving the efficiency of the work to be performed in the NMGD department, with a better use of the available engineering and computational resources, simplifying all the stages of multi-material projects, from the geometry preparation and meshing, to the post-processing tasks.

The high demands on low fuel consumption and low emissions on the combustion engines of both today, and the future, is highly dependent on advanced control systems in order to fulfill these demands. The control systems and strategies are based on models which describe the physical system. The more accuratly the models describe the real world system, the more accurate the control will be, leading to better fuel economy and lower emissions. This master's thesis investigates and improves the mass flow model used for a compressible restriction, such as over the throttle valve, EGR valve, or the wastegate valve, for example. The standard model is evaluated and an improvement is proposed which does not assume isentropic flow. This seems to explain the deviation from the isentropic Psi-function shown in earlier research such as (Andersson:2005). Furthermore a throttle valve is analyzed in ANSYS in order to show the generation of entropy. The presence of pressure pulsations in a combustion engine is also evaluated, especially how they effect the otherwise assumed steady flow model. It is tested if a mean value pressure is sufficient or if one needs to take the pulsations in to account, and the result shows that a mean pressure is sufficient, at least for the throttle when typical intake manifold pulsations is present. A dynamic flow model is also derived which can be useful for pressure ratios close to one. The dynamic flow model is based on the standard equation but with an extra dynamic term, however it is not implemented and tested due to complexity and time limitation. The proposed new non-isentropic flow model has proven promising and can hopefully lead to lower emissions and better fuel economy.

A ground vehicle is a dynamic system containing many non-linear components, ranging from the non-linear engine response to the tyre-road interface. In pursuit of developing driver-assist systems for accident avoidance, as well as fully autonomous vehicles, the application of modern mechatronics systems to vehicles are widely investigated. Extensive work has been done in an attempt to model and control the lateral response of the vehicle system utilising a wide variety of conventional control and intelligent systems theory. The majority of driver models are however intended for low speed applications where the vehicle dynamics are fairly linear. This study proposes the use of adaptive control strategies as robust driver models capable of steering the vehicle without explicit knowledge of vehicle parameters. A Model Predictive Controller (MPC), self-tuning regulator and Linear Quadratic Self-Tuning Regulator (LQSTR) updated through the use of an Auto Regression with eXogenous input (ARX) model that describes the relation between the vehicle steering angle and yaw rate are considered as solutions. The strategies are evaluated by performing a double lane change in simulation using a validated full vehicle model in MSC ADAMS and comparing the maximum stable speed and lateral offset from the required path. It is found that all the adaptive controllers are able to successfully steer the vehicle through the manoeuvre with no prior knowledge of the vehicle parameters. An LQSTR proves to be the best adaptive strategy for driver model applications, delivering a stable response well into the non-linear tyre force regime. This controller is implemented on a fully instrumented Land Rover 110 of the Vehicle Dynamics Group at the University of Pretoria fitted with a semi-active spring-damper suspension that can be switched between two discrete setting representing opposite extremes of the desired response namely: ride mode (soft spring and low damping) and handling mode (stiff spring and high damping). The controller yields a stable response through a severe double lane change (DLC) up to the handling limit of the vehicle, safely completing the DLC at a maximum speed of 90 km/h all suspension configurations. The LQSTR also proves to be robust by following the same path for all suspension configurations through the manoeuvre for vehicle speeds up to 75 km/h. Validation is continued by successfully navigating the Gerotek dynamic handling track, as well as by performing a DLC manoeuvre on an off-road terrain. The study successfully developed and validated a driver model that is robust against variations in vehicle parameters and friction coefficients. / Dissertation (MEng)--University of Pretoria, 2015. / Mechanical and Aeronautical Engineering / Unrestricted

Automotive manufacturers currently face a challenge with expeditious enhancement of the vibro-acoustic properties of their vehicles. A major reason for this setback is the limited design information available during initial development stages added with limited knowledge of damping within complex structures. It is now well established that CAE studies of vibration energy flow show good correlation between power flowing into trimmed body and the interior noise produced. Aim of the dissertation is to harness this "good" correlation between power input and interior noise, by learning about the changing behaviour of system in different suspension damping scenarios. It investigates how the mechanical power input to body from suspension, interior road noise produced, and their relation is affected by changing the way damping is modelled into suspension. This is being done to make stronger design decisions from NVH point of view during the concept phases of vehicle development. The investigation is for vehicle programs during early development phases, and hence a simplified vehicle CAE model was chosen, that contains a trimmed body with cavity fluid, and wheel suspension to capture all relevant effects of varying damping. Then, a detailed flowchart of suspension and trimmed body connections was prepared to understand how power flows into the trimmed body through suspension. Using results of power flow study, the most relevant paths and their frequency ranges were identified (to reduce the number of parts in study, yet results relevant and easily extrapolatable to a larger system). Lastly, responses are analyzed for various damping cases of suspension and trimmed body.  Results obtained show a reducing trend in mechanical input power and interior noise values with increasing damping in system. Whereas, for good correlation between power and noise, a great inclination towards structural damping localized into bushings is observed compared to other damping cases. Additionally, a strong dependency of noise, active power and reactive power is observed on trimmed body and cavity fluid damping. Active power is reduced when trimmed body damping is decreased to zero, and more so when cavity fluid damping is put to zero. On the other hand, noise and reactive power have an exact opposite correlation compared to active power and noise. These results suggest that although active mechanical input power is the cause of interior noise, their correlation starts to deteriorate with reducing damping within the system, and instead it is the reactive power that starts to correlate better at very low damping values. But, it is physically impossible to have no damping or very low damping, so a modelling of damping within suspension that provides relatively better correlation between (active) input power and noise is when structural damping is localized within connectors.

Fatigue failure is one of the most critical issues in industry nowadays as 60 to 90 percent of failures in metals are due to fatigue. Therefore, different methods and approaches are developed to estimate the fatigue life of metallic parts. In this research, a case-hardened steel splined shaft is studied to estimate the fatigue life that the shaft will withstand before failure. The purpose of the research is to develop an advanced fatigue prediction method for splines.A static experimental test was performed on the splined shaft for analyzing the load-strain behavior of the shaft and determining the suitable load cases of the study. A dynamic test of pure torsional load was carried out to collect experimental results for validating the generated fatigue methods and investigating the failure behavior of the shaft. Stress analysis was performed on the part for investigating critical areas and the effect of the different spline teeth designs on the resulting stress. Two finite element models were analyzed using two software, MSC Marc software with a geometry of straight spline teeth and Spline LDP with an involute spline teeth model. DIN 5466-1 spline standard’s analytical solution was used for verification purposes. Stress and strain-based approaches were used to estimate fatigue life. The most suitable method was evaluated against experimental test results.The research findings show that the most critical stress areas on the shaft are the spline root fillet and relief. When the part fails due to fatigue the crack initiates at the root fillet and propagates to the relief. It is also shown that involute teeth spline gives higher stress than straight teeth for the same load due to less contact area.The conclusion of the research could be summarized in: the stress-based method (Wöhler curve) is giving good accuracy and proved a reliable method. While among six different approaches used of strain-based methods, four-point correlation method is giving the best correlation to test results. Hence, it is recommended to use four-point correlation method for fatigue analysis for its accuracy and for considering both elastic and plastic behavior of the material.