With an increasing number of advanced driver assistance systems in cars, it is important to know how the driver is affected by different kinds of information signals. Many of the systems already used in cars rely on visual information, and therefore require visual attention. This can lead to an increase in inattention, as well as in cognitive and visual workload. By the use of other types of signals, the risk of overloading one sensory modality is reduced. Previous research has shown a correlation between visual inattention and unsafe driving behaviour, so the use of 3D signal sounds or spatial multisensory signals may be of importance for improving driver safety.The first study focused on the question of how driving performance and secondary task performance are affected by spatial placement of sound signals, and if the position of the sound source plays a role in the ability to capture attention correctly. Earlier studies indicated that information signals which were spatially congruent with the visual task improved response times. Furthermore, sound has been proven to be an effective means of capturing attention and re-orienting people’s attention to a specific location. The first study compared three cases of sound signals to inform the driver of a lane change task as well as a visual secondary task. The driving scenario was projected in front of the driver, and the secondary task was displayed on a computer screen at 45° to the right. In two of the cases, the sound signals’ position was congruent to one of the tasks, either driving or the secondary task. In the third case, the lane change signal was congruent with the projected driving and the secondary task signal was congruent with the secondary task screen. It was found that presenting signal sounds in front of the driver significantly improved driving performance.Previous research has shown that combining sensory modalities increases the robustness of perception. Using a driving simulator and a multisensory secondary task, the second study investigated the difference in directional attention capture capabilities with different combinations of visual, auditory and vibrotactile signals. In this study, visual signals alone, or in combination with other modalities, provided the shortest response time. Interestingly, the auditory and vibrotactile signals gave equally short response times. No significant differences in localisation error rates were observed between the different combinations.As shown in Study 1, spatially congruent signals are important in the driving environment, so can crosstalk cancellation be used to reproduce 3D sound in a car compartment? The third study evaluated how well we can reproduce 3D sound in a car compartment utilising the crosstalk cancellation technique in combination with binaural synthesis. Since the main focus is on signal sounds, these can be processed offline, reducing the need for real time filtering and allowing the use of very detailed crosstalk cancellation filters. Due to the acoustic properties of car compartments, placement of the loudspeakers plays an important role in the reproduction quality. In a listening test, the subjects were requested to judge where the sound was perceived to come from as well as the sound quality of the reproduction. This was done for three different loudspeaker positions and two distinctly different types of sound signals (speech and lane departure warning). The study showed that loudspeakers placed closely behind the driver correctly reproduced sound sources in the back hemisphere, while loudspeakers placed in front of or above the listener gave a high number of front/back confusions for all source angles. It was also found that the loudspeaker placement above the listener received a significantly higher quality rating for speech signals than the loudspeaker placement behind the ears or on the dashboard. For a typical warning sound signal, the loudspeaker positions above and behind the driver were rated equally, but still significantly higher than the dashboard position. Loudspeakers placed close to the ears produce less singularities and thereby higher reproduction quality.The first main finding from this work is that it is important to consider the placement of signal sounds in the car compartment, since a well selected signal sound position can help to focus attention, and thereby enhance driving performance and driver safety. Crosstalk cancellation can be used for implementation of virtual 3D sound in the car compartment using loudspeakers. Vibrotactile signals can be as effective in reducing reaction time as auditory signals, but it may be beneficial to combine the modalities for a more robust perception.

Due to excellent properties and relatively low material and manufacturing costs, the use of fibre reinforced polymer composites have increased during the last decades. One method that is suitable for large scale productions of e.g. lightweight vehicle components is compression moulding of sheet moulding compound (SMC). Although the technique has been considerably improved since it first was introduced, some further improvements need to be done. The main reason why it has not come in wider use in the vehicle industry is unsatisfactory conditions of the surface finish of parts manufactured due to voids. In this work, experiments and numerical simulations has been performed in order to increase the knowledge of the flow behaviour during the compression moulding process and how the flow affect the quality of the finished product. A process parameter experiment of the compression moulding phase, carried out with a design of experiment approach, was performed in order to investigate the effect of vacuum assistance, mould temperature and ram velocity on the void transport and flow behaviour for SMC. The relative amount of voids has been quantified with a high voltage insulation test and the flow behaviour has been quantified with image analysis of samples moulded with coloured SMC. In conclusion, the setting of high vacuum, low ram velocity and low mould temperature creates a homogeneous flow and minimises the amount of voids. In order to further increase the understanding of void removal during compression moulding, a model experiment was performed where a non-Newtonian fluid (grease) with added bubbles was compressed between two plates whereas the motion of the bubbles were tracked and evaluated using Particle Image Velocimetry. The bubble motion was furthermore analytically modelled and coupled to the experimental results. The experiments reveal an increase in bubble speed compared to the surrounding grease during the compression of the plates. During the latter stage of the compression, the particles change form from initially being approximately spherical, to have the characteristic form of a falling raindrop. The change in form coincides with the increase in speed of the bubble. The developed analytical model supports the shown development in the experiments. A full general solution comprising an arbitrary value of the Power Law exponent, for the velocity fraction coefficient representing the relative bubble speed, is however not covered at the present stage. Finally, the commercial software Ansys CFX were used to perform computational fluid dynamics (CFD) modelling of the flow during compression moulding with a two different multiphase models. The first model treats the flow of SMC as purely extensional and dependent on temperature, fibre volume fraction and strain rate. While the other one sees the flow as mainly extensional but also with thin shear layers near the surfaces of the moulding tool. Where the viscosity, in addition to temperature, fibre volume fraction and strain rate, also is dependant on shear strain rate. Of the two models, the latter seems to be more robust in modelling the pressure during moulding.

In the sector of mobile hydraulics, valve controlled systems are predominant. In these systems the load force and speed are adjusted by control valves. In machines where multiple drives are used in parallel at extremely varying loads the energy efficiency of such systems is often compromised over large working regions. Most valve controlled systems also lack the possibility to recuperate potential energy. A different category of hydraulic systems, called displacement controlled hydraulics are based on the manipulation of the hydraulic flow using the relative displacement of the hydraulic machines as the final control element. This type of hydrostatic power transfer, yields a resistance free velocity control, ideally leading to lossless load actuation. This thesis concerns the introduction of a new type of displacement controlled hydraulic system, adapted for construction machinery. The system decouples the hydraulic functions using one dedicated hydraulic machine for each drive. These machines are of open circuit type, capable of over center operation which enables energy recuperation. The system also comprises four separate valves that by means of switching allow the cylinder to be controlled over all four load quadrants. Depending on the selected valve hardware, the system may also include features available in a conventional valve controlled system, such as meter-out flow control. The system supports both symmetrical and asymmetrical cylinders. However, using the asymmetrical type the load may be controlled in two distinct states of operation. This yields an increased region of operation, which is otherwise generally stated as a drawback in displacement controlled systems. It also allows the selection between different control modes, where one of the modes is always more efficient than another. In this research both theoretical studies and a practical implementation demonstrate the energy related benefits of the new concept. The target application of this study is a medium-size wheel loader. Measurement results using the wheel loader in a short truck loading cycle show a 10% percent reduction in fuel consumption. According to the theoretical investigation, this corresponds to a 20% reduction in energy consumption for the hydraulicsystem itself.

Magnetic reconnection plays an important role in the transfer of mass, energy and momentum from the solar wind to the terrestrial magnetosphere. The earliest contributions to the theory of magnetic reconnection dates from the beginning of the 1930's. However, it took until the end of the 1950's when Sweet and Parker made their first reconnection model, for the concept to reach a somewhat solid ground. During the years since then magnetic reconnection has walked through the phase of reaching mythical proportions where some researchers believed in it, and some not, to the acceptance it has today where the main issue not is whether the process happens or not, but rather the main physical properties and the implications of it. During the last fifteen years much of the research due to the rapid increase in computer capacity, treats numerical simulations of magnetic reconnection. Theoretical analysis keeps though its position as a cornerstone for the understanding of the process. But also for the base of new implemented models. Much of the theoretical work accomplished to this day has its focus on magnetic reconnection itself; applications for different conditions, and the onset of the process - something which still is under much discussion among researchers. This work focuses on the implications of magnetic reconnection in combination with the outer magnetosheath flow. The analysis treats a two-dimensional and three-dimensional case. For the 3D case, the magnetosheath plasma flow is considered to be incompressible, while we for the 2D case also treat a compressible magnetosheath plasma. Magnetic reconnection is assumed to occur in a region stretching from the sub-solar point to the north, at an arbitrary point for the 2D case, and along a line parallel to the y-axis for the 3D case. The analysis is based on the MHD equations including dissipative effects such as viscosity and resistivity, where the equations are solved approximately by the use of an ordinary perturbation expansion for large Reynolds and Lundqvist numbers. The objective of the 2D study treating an incompressible plasma flow, is to get a description of the current transition layer in combination with the outer magnetosheath and boundary layer flow. The solutions are asymptotically matched with an existing model for the magnetosheath magnetic field. For the 2D compressible case and 3D analysis, the objective is to study the development of the magnetic field and total velocity during the transition from the magnetosheath to the magnetosphere. / Godkänd; 2005; 20070116 (ysko)

In a classroom an assistive listening device (ALD) is a system of external microphones that transmit sound from a sound source directly to students' hearing aids. An ALD can be a microphone close to the mouth which transmits a voice directly to listeners' hearing aids. An ALD can also be a microphone placed centrally and used by several persons at the same time. Sound quality of a listening device can be described as sound-transmission quality where maximal quality is no difference between input and output. From a wider perspective, this output can be the perceived quality of speech where a high speech quality matches given expectations, demands and necessaries. A focus on participatory learning environment in Swedish hearing impaired classes has brought out new perspectives on ALD solutions. The purpose of the studies reported in this thesis was to develop a methodical framework for the evaluation of classroom ALDs. As a basis for the evaluation of ALD communication quality is suggested. Communication quality is an extension of the sound quality concept which emphasizes student participation and peer interaction. As a pedagogical parallel, sound quality emphasizes a more cognitive view of learning whereas communication quality emphasizes participatory learning. By using room acoustic modelling and auralization in listening tests it was possible to evaluate aspects of room acoustics, signal processing techniques, speech and masking signals, and binaural advantage. A self-assessment approach was also used and a questionnaire was developed based on the Speech, Spatial and Qualities of Hearing Scale (SSQ). The studies found that students in hearing impaired classes prefer using only their hearing aids over using an ALD. Retrieving information about the acoustic environment was important aspects. Also observed was that when comparing different ALD solutions microphone distance is of importance. Listening effort correlates with hearing loss rather than with using different technologies. Today's hearing aids offer the best communication quality but it is also apparent than ALDs are preferred by students in some situations. Determining the combination of design and ALD function which can best benefit students is needed. The methodological framework described is promising for continuous studies developing and assessing classroom ALD. / <p>Godkänd; 2007; 20070315 (ysko)</p>

This thesis concerns the development of non-contact measurement methods and analysis of rotors. The methods have been verified and applied to milling machine spindles in order to investigate the speed dependency in the milling machine spindle dynamic. The research was financed by the Swedish Agency for Innovation Systems (Vinnova). Turning operations like milling are common in the automotive and aerospace industries where large metal work pieces are reduced to a fraction of their original weight when creating complex thin structures. During these operations it is important that unwanted behaviours such as excessive tool vibrations be avoided (this is normally called "chatter"). Chatter causes poor surface finish and/or material damage and can expose machine operators to annoying and/or dangerous noise levels. In order to predict processes parameters for a chatter free milling operation, knowledge of the properties of the dynamic system are essential. Normally the system dynamics are measured during no rotation; in order to include the influence of the spin speed the system must be analysed for all spindle speeds intended for the milling operation. This can be done either by measurement or modelling. Non- contact measurement techniques are however, often based on displacement sensors which do not have the same sensitivity as velocity or acceleration based methods. To improve the sensitivity in non-contact measurements of rotors a laser Doppler Vibrometry (LDV) based method has been developed. The developed LDV method is based on the reduction of the rotor surface structure and makes it possible to use single beam LDV measurements of rotors. These types of measurements were previously considered inaccurate but now have become feasible through the use of the method described in this research. Furthermore the dynamic properties of a high-speed-milling machine spindle were studied by a contactless dynamic spindle tester (CDST) developed by SKF. The measurements were substantiated by simulations using a finite element model (FEM) which confirmed the measurement results. The CDST measurements could be performed without violating safety regulations regarding human interaction with high speed spindles through the use of a magnetic excitation method. In the measurements conducted by the CDST a speed dependency in the spindle dynamic could be detected. By performing FEM simulations the major source of this dependency could be identified. The centrifugal force of the balls in the angular contact ball bearings was shown to have the largest influence on the overall dynamics compared to the gyroscopic moment of the rotor. The study performed indicates that predictions of high-speed-milling stability must include consideration of the speed dependency in the dynamic. / Godkänd; 2006; 20070109 (haneit)

Rotary kilns are industrial furnaces that have been widely used in limestone calcination, cement industry and hazardous waste incineration for centuries. In this work a rotary kiln used for the iron ore pellet sintering process in the grate-kiln pelletizing system has been studied. In order to increase the energy efficiency, a large amount of air is supplied to the kiln through air channels connected to the cooler. This air is necessary for the coal combustion process and the heat transport to the kiln bed. However, the geometry of the kiln hood connecting the air channels and the cooler is complicated. As a consequence, the jet flame is unstable. In order to improve the performance of the jet flame it is therefore necessary to study the kiln aerodynamics to reveal the flow field. Even though it is a complicated problem containing fluid dynamics, combustion and heat and mass transfer, it can be simplified into a down-scaled cold model to make it feasible to understand the flow field both experimentally and numerically. In this work, the whole kiln is generalized as a high Reynolds number turbulent round jet interacting with asymmetric co-flows. With the aid from previous PIV measurement data of a down-scaled water model of the kiln, Computational Fluid Dynamics (CFD) simulations using the commercial code ANSYS CFX 16.0 have been pursued for two main purposes: 1) To find a turbulence model that is computationally inexpensive and able to capture the main features of the mean flow field; 2) With the turbulence model chosen in 1), to study the geometrical effect on the development of the primary jet. In Paper A, three turbulence models were employed, the standard k-epsilon model, a modified k-epsilon model with slightly higher turbulence production and the SSG Reynolds stress model. Wall functions were applied since resolving the viscous wall region was not a concern in this work. It is found that the standard k-epsilon model fit the experimental data best compared to the other two models and that all three turbulence models predict an asymmetric development of the primary jet, especially far downstream, In Paper B, again using the down-scaled kiln model, isothermal cases with four different nozzle diameters were simulated with the standard k-epsilon model. The aim is to investigate the effect of initial Reynolds number on the jet development in asymmetric co-flows from the air channels. It is found that, with increasing Reynolds number, the jet becomes shorter and the mixing between the primary jet and surrounding flow is better. A low-velocity region or external recirculation zone (ERZ) form near the kiln upper wall and shrink with increased nozzle diameter or decreased initial Reynolds number. The ERZ may stabilize the flame since it is a low-velocity region and consequently attract the jet to reside predominantly in it or in the shear layer. As a conclusion, by enlarging the jet exit diameter, the jet can be prolonged, while to a certain extent, the benefit from the ERZ would need to be sacrificed. Since the asymmetric development and the ERZ in the kiln were not studied during the previous PIV measurement campaign, more experimental studies are planned to provide more experimental evidences of the details of the flow and to lay grounds for validation of the CFD simulation results.

Many new challenges in wind energy require the use of large eddy simulation for accurate modeling of wind farm flows. However, the immense computational cost hinders its use in research and industry. The lattice Boltzmann method is the most promising candidate to date to achieve the highest level of accuracy while decreasing computational cost by orders of magnitude compared to traditional methods. In this thesis, I present further development of the lattice Boltzmann method for wind energy and compile various applications, such as industrial use, generation of training data for machine learning, and analysis of wind farm control paradigms. In order to evaluate the requirements of different industrial stakeholders, we conduct a survey among industry experts on the use of large eddy simulation and show that the run time requirements indicated by many respondents can be met with the current state of the lattice Boltzmann method. In a validation study, the lattice Boltzmann method is as accurate as traditional Navier-Stokes solvers, while reducing computational cost by one to more orders of magnitude. A convolutional neural network is trained to predict average flow velocities in the wake of a single turbine. The predictions exhibit very high accuracy at execution times similar to engineering models. The lattice Boltzmann method enables the generation of larger training sets at a feasible computational cost. A proof of concept is provided for the use of reinforcement learning to discover new, cooperative wind farm control mechanisms. In an extensive analysis of the helix approach, its physical mechanisms are elucidated and a thorough parameter study of the wake of a single turbine is provided. We also study the interaction of multiple helical wakes, providing a way to extend the approach from a pair of turbines to wind farms.

Greenhouse gases and their negative effects on climate is one of the most discussed topics around the world. Globally, fossil fuel-related emissions from process industries, transportation, and electricity generation are one of the biggest contributors to greenhouse gases. One of the prime questions asked globally is how to reduce these emissions. Plasma burners can be an answer to the question. They are entirely electric-driven burners and operate at high temperatures. Presently, the available burners are small scale due to which they are not applicable in industries. So a substantial amount of interest lies in up-scaling them. However, to begin the up-scaling process, it is fundamental to clearly understand the working of the plasma burner and the various factors that affect its operation. The present thesis explains the working of a plasma burner under different operating conditions is studied experimentally, computationally, and the obtained results are validated with theoretical data. Experimentally, the temperature measurements at the plasma torch outlet were carried out using optical spectroscopy. The velocity and structure of the plasma jet coming from the outlet were studied using a high-speed camera. The experimental measurements were carried out for varied input working gases, velocities, and powers. The computational analysis was perfomed using COMSOL multiphysics software. The primary modeling was done using the equilibrium discharge interface model (EDI) in which plasma is considered to be fully ionized and at local thermal equilibrium. But considering the drawbacks of the EDI model, further computational analysis was initiated by modeling weakly ionized plasma. Different geometries of the plasma torch, working gases, velocities, and power are analyzed computationally. Further, the experimental and computational results are validated with each other and thermodynamic equilibrium data obtained using the TEC program. Finally, this thesis promises to give an overview of the plasma torches, their working under different operating conditions, and a brief discussion about the future focusing on up-scaling the plasma burners.

The automotive industry is facing ever increasing demands for reduced emissions, and lightweight solutions are thusly required. One field that has significant potential in this regard is composite materials, which can offer a good combination of weight reduction and mechanical properties. However, the rapid development cycles in the automotive industry mean that tools for numerical modeling are necessary, both regarding manufacturing processes and prediction of mechanical properties.  The material that has been of interest for this work is Sheet Moulding Compound (SMC). SMC consists of sheets of resin and chopped fibres. When used for manufacturing the sheets are cut into appropriate size and shape. The cut sheets are then placed in a pre-heated mould. When this mould is closed, the sheets melt and the fibre-filled resin flows out and fills the mould cavity; the resin then cures and solidifies. A significant advantage of SMC compared to other composite solutions is that the process has comparatively short cycle times, which is a necessity for automotive applications. However, it is a rather complicated process to model numerically for a number of reasons, including the complex rheological properties of the charge, the often rather significant temperature gradients throughout the thickness, often complicated three-dimensional effects in the flow, and the chopped fibres present in the charge. These fibres will move and change orientation as the charge is pressed, which is a significant challenge to model properly. The first part of this work is a review and discussion of the difficulties described above, and some solutions that have been suggested. The second part concerns a suggestion for a three-dimensional flow model for the compression moulding process, which takes into account factors that have been suggested to influence the flow behavior, such as temperature distribution and shear strain rate. Some simulation results are presented along with comparison to previous experimental results, and similar flow patterns are observed serving as a qualitative validation. The third part concerns the expansion of this model to include the effects of the flow on the fibre orientation.