The overarching aim of this work is to study the freezing process of a single water droplet freezing on a cold surface, which is an interesting and important phenomenon with possible applications in many areas. Understanding the freezing process of a single water droplet is for example an important step when preventing unwanted icing, e.g. in the case of airplane wings and propellers, wind turbine rotor blades, and road surfaces.As a step in understanding the freezing process, the study specifically focuses on the internal flow in the droplet during the freezing process. To do this, the study combines the use of Computational Fluid Dynamics (CFD) to build a model of the freezing process and experimental methods, i.e. Particle Image Velocimetry (PIV) to validate the numerical results. Focus is to start with the heat- and mass transfer inside the droplet using simple geometries with a rigid boundary, not modelling the outside environment as the air and the cooling plate. These components will be incorporated in the model further on.Three papers will be included in the study. In Paper A the CFD model is created and tested on a simple 2D-geometry of a droplet. The numerical result is partially compared to experimental work found in literature. In Paper B the numerical model is developed even further and a more realistic geometry of a real droplet, although with rigid boundaries, is used. The numerical results are as for Paper A validated with experimental results found in literature. In Paper C the internal flow inside the droplet has been investigated experimentally to estimate the velocities in the water, so that in the future the results can be used to validate the numerical work.The results show that is possible to work with a very simple CFD model and still capture the main flow features and freezing characteristics in a freezing water droplet. In line with previous research, this study confirms that the natural convection induced by gravity is significant for the internal flow, as compared to conduction and effects of ice creation. If studying the freezing time the internal flow has little effect. However, when estimating the velocities in the water it is crucial. It can be seen that the gravity effects are most pronounced around the density maximum for water (at T = 4◦C). The experiments show that the method used to study the flow inside the droplet is a working method, and the velocities in the water has been estimated. The next step is to further develop the CFD model and validate the numerical work with the experimental results. An interesting next step is to incorporate a moving interface to capture the volume expansion during the phase change.

The pelletizing process where the crude ore from the mine is upgraded to pellets is a process which includes several stages involving complex fluid dynamics. In this thesis, focus is on the grate-kiln pelletizing process and especially on the rotary kiln, with the objective to get a deeper understanding of the aerodynamics and its influence on the combustion process. The aim is to discover flow features taking place in the kiln, and the kiln hood, by using Computational Fluid Dynamics (CFD) on simplified models of the real kiln, and to validate the set-ups of the numerical model with physical experiments using Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV). By starting as simple as possible, studying only the cold flow field without combustion and validating the simulations, a foundation for future geometrical optimizations can be achieved. Later on more realistic geometries may be studied with the validated simulations as a base. In Paper A the initial down-scaled, simplified model of the real kiln is studied, and both numerical and experimental analyses of the flow field are performed. Paper B focuses on the turbulent secondary flow that arises in ducts with non-circular cross-section. One of the inlet ducts to the kiln of interest here is close to semi-circular in cross section, hence the focus of this work. Numerical and experimental results are reported. Paper C is a development of the model, where instead of parallel inlet ducts as in Paper A, the top one has an inclination angle to the kiln axis. A thorough experimental analysis of the flow field is performed in this case. Conclusions are that steady state simulations can be used to get an overview over the main features of the flow field. Precautions should though be taken when analyzing the recirculation zone which is important for the flame stabilization. A stable flame is safe and crucial for efficient combustion. Steady state simulations do not capture the transient, oscillating behavior of the flow seen in the physical experiment. These oscillations will under certain conditions considerably affect the size of the recirculation zone. Another parameter affecting the size of the recirculation zone is the inclination of the upper inlet duct, where a decrease in recirculation length is seen although the actual inclination of the incoming jet is only about 3-4º. The choice of turbulence model affects the prediction of turbulent secondary flow. If this flow feature needs to be revealed, a more advanced turbulence model should be used. / Fastelaboratoriet - VINNEXC

In an iron ore pelletizing plant, crude ore is upgraded to pellets to be used as feedstock in steel-making plants. As part of a grate-kiln pelletizing plant, the rotary kiln is an indurating furnace in which the pellets are sintered. The rotary kiln involves complex flow of large amounts of gas and the process is strongly coupled to the fluid dynamics, which is not well understood. The present work focuses on increasing the understanding of the aerodynamics of the rotary kiln.Though the kiln geometry is relatively simple a rather complex flow arises, which is known to occur for turbulent flows in similar geometries. In order to isolate the underlying flow mechanisms, simplified models of the kiln are studied both numerically using Computational Fluid Dynamics (CFD) and experimentally using Particle Image Velocimetry (PIV). The understanding of the flow phenomena that arises for the simplified models is essential for maintaining a solid comprehension of the fluid dynamics when increasing the complexity of the models. Computations are validated against available experimental data to evaluate the capability of the numerical procedure in capturing the underlying physics of the flow. In this way, the reliability of the predictions is improved when increasing the complexity of the model.In Paper A the unsteady non-reacting flow is computed and a preliminary coal combustion model is proposed, which is in need of further development to yield reliable predictions of the reacting flow. Paper B is an experimental investigation of a down-scaled model of the kiln and also an extension to previous experimental work by introducing an inclination of the upper inlet duct to the kiln and carrying out a more thorough analysis of the fluid dynamics. In Paper C, the periodic flow observed in Paper A is investigated further using a more sophisticated turbulence closure and carefully validating the predictions against available experimental data.For the simplified models under investigation, it is concluded that the flow is dominated by the periodic shedding and downstream convection of von-Karman-like vortices originating in the free shear layers enclosing the recirculation zone formed in the inlet end of the kiln. Both numerical and experimental investigations show a strong dependence of momentum flux ratio between the two inlet ducts on the flow field. The large-scale periodic fluctuations, which are resolved in an unsteady computation but completely neglected in a steady computation, are seen to contribute significantly to the turbulent transport in the recirculation zone. This indicates the need for unsteady computations to accurately predict the transport processes. The recirculation zone is important for flame stabilization as it feeds back hot gas to the near-burner region. Hence, a challenging requirement of the numerical model is to accurately capture the physics of the recirculating flow. The use of a second-moment turbulence closure is shown to significantly improve the predictions over the use of an eddyviscosity turbulence model and give promising results for further work on more complex models of the kiln.

A model has been developed that can be used to predict the transport of non-spherical particles in the nano- and micro scale range for different applications. This may be the flow in the lungs or flow taking place during composites manufacturing, but the model can be applied to many applications where the particle Stokes and Reynolds numbers are small. The model can, for instance, be used to simulate an evenly random distribution of particles and then follow them through a laminar flow in a straight circular tube, either to study the statistical congregation of multiple particles or to follow the path of an individual particle. Both gravitational settling and Brownian motions are included in the model and their influence was also examined. To increase the understanding of the influence of the breathing pattern on the deposition of inhaled nano- and micro-fibres simulations were done in a straight model airway. Maximum deposition rate was found when particles were released in the beginning of therespiratory cycle while a minimum when the release came at the peak of inhalation. A comparison was done of a cyclic flow field and a quasi-steady one to see if the latter could accurately be used to replace the former. A quasi-steady solution generally provides a relatively good approximation to cyclic flow if an average velocity over one residence time of the particles moving with the mean fluid velocity is used. A statistical study was done to compare the deposition rates of oblate and prolate particles of different size and aspect ratio as they travel down narrowing bronchi in a steady, fully developed parabolic flow field. The model shows a clear correlation between increased particle size and increased deposition, it also consistently yielded a higher deposition rate for oblate particles compared to prolate particles with a similar geometricdiameter. A study of the motion and orientation of single oblate and prolate particles with large aspect ratio and the same geometric diameter has also been done. To see the effect the different forces have on the particle it was first studied with only the force of the flow field acting on it. Clear Jeffery orbits were visible in the simulations, although the periods of the orbits were shorter for the oblate particles than the prolate ones. When Brownian motion was introduced the motion of the particles became less periodic. For prolate particles Jeffery orbits could still be distinguished, unlike for the oblate particles whose movements mostly resembled random tumbling. In some methods to produce fibre reinforced polymer composites a fabric is impregnatedwith a fluid that may contain particles on the micro- and nano scales. Theseparticles are aimed to give the final product additional properties. It is therefore interesting to be able to reveal how the distribution and orientation of such particles are affected by the processing condition. During the manufacturing of the fabric and during the subsequent lay-up in a mold relatively large channels are formed between bundles of fibres where the impregnating fluid flows; there is also micro channels within the bundle that are also impregnated by the fluid and the capillary action there may be modelled as a suctioning force on the walls of the channels. Therefore in this study the channel between the bundles are represented as a tube with a circular diameter and a flow fieldthat are being sucked to the sides as it travels down the tube. A random distribution of particles is introduced at the inlet of the channel and the deposition is studied and the results are compared to a case when the flow is purely driven by an applied pressure gradient without any suction on the walls.

Excessive release of phosphorus from the effluent of on-site sanitation facilities to the environment is one source of aquatic pollution. The primary effect of excess phosphorus in the aquatic environment is eutrophication. In Sweden, there are about one million private on-site wastewater treatment facilities, half of which are considered unacceptable by the Swedish Environmental Protection Agency (SEPA). Recent guidelines issued by SEPA recommended total phosphorus reduction of 70-90 % in wastewater in small scale treatment facilities. Using reactive filter materials as compact filter systems following a biological pretreatment can be a convenient option for upgrading the present on-site sewage treatment facilities. Research on reactive filter materials has been undertaken in many different ways as there is no standard method for such investigations. Therefore, there is a need to develop methods and models to evaluate the reduction capacity and predict the longevity of potential reactive filter materials.In the first part of this thesis a filter material Filtra P (Nordkalk, Finland) is investigated. The phosphorus sorption characteristics of Filtra P were investigated in batch and column experiments. The batch test method was evaluated with respect to the effects of liquid-to-solid ratio and particle size on phosphorus sorption. Column experiments were carried out at different flow rates and phosphate (PO4-P) feed concentrations. The experimental data obtained from batch and column experiments were used to investigate the feasibility of modeling PO4-P breakthrough curves in fixed-bed columns by means of the convection-dispersion equation and a Langmuir isotherm. The model successfully predicted the PO4-P breakthrough curves for the columns with low influent concentration (11 mg dm-3), which is within the range normally found in wastewater (5-15 mg dm-3). Experimental observations however yield that the possibility to combine the convection-dispersion equation with a model accounting for precipitation of calcium-phosphate compounds in the bulk should be examined.The second part of the thesis focuses on dispersion in laminar flow through a randomly packed porous-medium model. The study of dispersion in flow through porous media is an important issue in many branches of science and engineering and has direct applications in several industries. For example, dispersion occurs in the disposal of sewage waste into aquifers and flow through reactive compact-bed filters that are used for on-site sanitation systems. In order to shed light on this phenomenon, a detailed longitudinal and transverse dispersion numerical experiments were performed in two-dimensional (2D) randomly packed beds of thousands of circular particles in a laminar flow regime. The calculated longitudinal and transverse dispersion coefficients were presented as Peclet numbers based on longitudinal and transverse dispersion coefficients versus Peclet number based on molecular diffusion coefficient, and were compared to three-dimensional (3D) experimental data available in the literature. It was found that at very low superficial liquid velocities both longitudinal and transverse dispersions were governed by molecular diffusion. Based on the comparisons between numerical results obtained from the 2D model to the 3D experimental data, it was found that the present 2D approach to study the longitudinal dispersion in flow through porous media can be considered to be acceptable.The present numerical data may be used to estimate the longitudinal and transverse dispersion coefficients in a 2D process by which one fluid is displaced from a porous medium by a second fluid which is miscible with the first in a laminar flow regime.

This licentiate thesis deals with the topic of variations and uncertainties in building acoustic parameters for lightweight timber constructions. A higher safety margin to the legal requirements is needed to compensate for acoustical uncertainties, which leads to higher costs. Building costs can be reduced if the variations can be identified and controlled. The project was limited to industrially prefabricated timber frame based volumes and massive timber based plate elements. This thesis is based on the work reported in three papers (A, B and C). In paper A, the variations in impact and airborne sound insulation were assessed and quantified in 30 nominally identical volume built apartments in a four-storey building. Large variations were found and the underlying causes were investigated. A statistically significant difference between floor numbers was found as the highest floor achieved better sound insulation. This difference was assumed to be caused by the higher static load on lower floors affecting the elastic layer used to structurally connect the apartments. In paper B, three room volumes were followed and measured at different stages of completion throughout the construction process. The objective was to test if acoustical deviations in the field can be identified at earlier construction stages. An ISO tapping machine was used to excite the floors and the response was measured at 20 positions. The airborne and impact sound insulation were measured in the finished building. Deviations were found, but these could not be traced to earlier stages of completion. In Paper C, the variations in sound insulation of a cross-laminated timber (CLT) building system was investigated. The construction was based on prefabricated wall and floor plate elements which were mounted at the building site. A number of acoustical uncertainties related to the measurement procedure were also investigated. The measurement uncertainty was small in comparison to the total variations. The degree of prefabrication for the CLT system was lower compared to the volume system, which indicated a greater scope for poor workmanship. All papers indicate a higher sound insulation on the upper floors in a building. It is therefore important to carefully design the elastic layer between floor numbers. The measurement uncertainty has been continuously considered in this thesis. In order to properly identify and quantify variations, the measurement uncertainty should be minimised. Advantages and drawbacks with different measurement methods and directions for future research are discussed in the concluding chapters.

Open channel flow near hydropower stations is of interest for both engineering and environmental applications. In this research project Computational Fluid Dynamics simulations of free surface flow in regulated rivers were applied with both fish migration and validation of numerical simulations in focus. In the first paper, numerical simulations has been used to evaluate the flow downstream a hydropower plant with regards to upstream migrating fish. Field measurements with an Acoustic Doppler Current Profiler were performed and the measurements were used to validate the simulations. In the second paper ,simulations on the spilling from a dam were performed and compared to experimental results from a physical scale model. The third paper deals with more in depth analysis of field measurements where the variations in the flow downstream a hydropower plant was examined.

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.