Sprays are used in a wide range of engineering applications, in the food and pharmaceutical industry in order to produce certain materials in the desired powder-form, or in internal combustion engines where liquid fuel is injected and atomized in order to obtain the required air/fuel mixture. The optimization of such processes requires the detailed understanding of the breakup of liquid structures. In this work, we focus on the secondary breakup of medium size liquid drops that are the result of primary breakup at earlier stages of the breakup process, and that are subject to further breakup. The fragmentation of such drops is determined by the competing disruptive (pressure and viscous) and cohesive (surface tension) forces. In order to gain a deeper understanding on the dynamics of the deformation and breakup of such drops, numerical simulations on single drops in uniform and shear flows, and on dual drops in uniform flows are performed employing a Volume of Fluid method. The studied parameter range corresponds to an intermediate Weber number of 20, sufficiently high so that breakup occurs, but much lower than the limit for catastrophic breakup, and a range of Reynolds numbers covering the steady wake regime for liquid drops, Re = 20-200. In order to account for liquids in various applications, a set of different density and viscosity ratios are considered, ρ*=20-80, and μ*=0.5-50 respectively. Single drop simulations show that depending on the Reynolds number and density and viscosity ratios, various breakup modes besides classical bag and shear breakup may be observed at a constant Weber number. The characteristics of the deformation process and the time required for breakup are considerably different for these modes; furthermore, both are significantly altered by velocity gradients in the flow. Dual drop simulations show that the relative position of the two drops, in addition to the Reynolds number and density and viscosity ratios, plays a crucial role in determining the interaction scenario. It is found that the behaviour of drops in tandem may be predicted based on data obtained for single drops: the breakup time and the length of the wake behind the drop. The region where collision is most likely to occur is identified as a two diameters wide and eight diameters long streak, however, weaker forms of interaction may occur up to twenty diameters behind the drop. Results presented in this thesis may be applied to formulate enhanced breakup models regarding the deformation, breakup, and interaction of liquid drops employed in spray simulations. / <p>QC 20170825</p>

The thesis comprises six papers with the overall theme of measurement, assessment and control of diesel engine noise, with an emphasize on control. The radiation of noise is shown to be dominated by the low end of the engine sides and by the engine front. The mode shapes of the crankcase, the oil sump and the timing transmission cover are investigated. The vibrations are measured and analysed through running mode, modal analyses and SEA. The noise radiation is explored in detail with near-field measurements of sound intensity. In the engine front, the noise radiation is shown to have contributions from the timing casing, the oil-sump front and the crankshaft torsion vibration damper. The radiation from the torsion damper is analysed by a regression analysis of measured intensity data and the vibrations of the damper are investigated with a laser-doppler vibrometer. The results show that the damper vibrates in the axial directions with vibration modes that both radiate noise and interfere with the radiation from the engine structure. It is shown that there in the engine front are strong coupled vibration modes between the timing cover and the oil sump front m the frequency range 500 Hz - 1 kHz. The importance of the strong vibration modes in the crankcase and the oil-sump sides is shown. The propagation paths of noise and vibration to the engine front have been examined with an SEA powerflow analysis and by opening the front cover to measure the sound power from the timing gears. The main excitations of the front cover are found to be by engine block vibrations below 1.25 kHz and by tuning gears noise above 2 kHz. Various constructions to control the noise are tested. Two stiffeners are designed and tested to reduce vibrations m the engine low end, one ladder frame introducing stiffness at the crankcase flange and one bearing beam introducing stiffness at the main bearing caps. The stiffeners have hem evaluated by sound intensity measurements and mobility measurements. The ladder frame gave good noise reductions but the bearing beam merely caused frequency shifts of the bearing modes. A decoupling of the oil sump resulted in significant noise and vibration reductions. The timing cover is modified by increasing the damping and by decrease the radiation efficiency. Various interior panels are tested, like plexiglass and aluminium panels of different thicknesses, a rubber damping layer and a combined rubber/steel-sheet damping layer. A thin plastic sheet has low radiation efficiency and may thereby lower the noise emission. A slightly improved model for calculation of radiation efficiency of small irregularly shaped plates is suggested. The traditional SEA prediction model is shown to be ill-conditioned for engine applications. An improved model using geometric averaging is suggested and evaluated. The results show that the new SEA model is working well for frequencies down to 800 Hz for predictions of damping treatments, decoupling of the oil sump and for power-flow determinations. The concept of equivalent mass is found valuable and validations are made according to the consistency and reciprocity theories. A hemi-anechoic engine laboratory is constructed and evaluated. New efficient low-cost diffusing absorbers have been designed, the performance is evaluated with standard deviation analysis of sound pressure measurements. The performance of the absorbers is found to be compeatable with much more expensive commercial designs. Measured sound intensity in three-dimensional vectors is a powerful tool to identify and illustrate sound fields. When used in near-fields to identify complex noise sources large errors may occur. It is shown that the low relative levels of vector components and the reactivity of the sound field give large errors m repeated measurements. Analyses and comparisons are performed on a simple source and on an engine. A two- and a six-microphone probe were used that were hand-held and robot-controlled. It is concluded dig in point-intensity measurements on engineering noise sources, a 4-6 microphone probe and a precision positioner should be used to get reliable measurements. / Godkänd; 1994; 20061214 (biem)

This thesis covers research in the floor vibration field. Although lightweight steel framed constructions have been in focus, many results are applicable to floors in common and to some extent also to vibrations in general. Whether a floor is treated as "good" or "bad" by the occupants is an interaction of a) the dynamic properties of the floor and of b) human vibration perception. Both these factors are covered. Two steel framed floors were tested in laboratory condition with respect to its dynamic. Modal testing was used to obtain the modal parameters, i.e. natural frequencies, damping and mode shapes. Both floors were tested for numerous set-ups where for example the effect of different supports, top layers, ceiling joists and simulated partitions were investigated. For one of the floors, subjective opinions were collected for correlation with the measured data. The research of floor dynamic has lead to a creative new method that utilizes strategically positioned small pieces of visco-elastic material to increase the damping of the floor. It was found out that this economic and proportionally easy method significantly increases the damping for some specific type of modes. The human vibration sensitivity was tested in a new developed motion simulator. Absolute threshold values for single sinusoidals were tested in the frequency range of 5-31.5 Hz. For validation of the test setup, the results were compared with data from other similar studies. The obtained thresholds agreed satisfactorily with previously reported results. More innovated tests were performed concerning multiple frequency signals of two to five discrete frequency components. The results show that a signal's composition in terms of number of frequency components and their mutual amplitude relation significantly affect the subjective perception. Therefore, it can be argued that multiple natural frequencies of a floor should be considered when it comes to design rules. This is in opposition to many floor design criteria of today since these often rely upon the fundamental frequency only. A prediction model, where the acceptance is calculated as a function of the frequency weighted total acceleration amplitude in combination with the fundamental frequency is suggested. The presented model does take into account the presence of possible multiple response frequencies. / Godkänd; 2006; 20061205 (haneit)

Godkänd; 2002; 20070110 (biem)

The increasing demands from governments on the engine manufactures to lower the fuel consumption, lower the exhaust emissions and to reduce the noise have lead to an intensive research in the combustion process. Measurement of the combustion process inside the cylinder is only suitable in laboratory environment due to a number of limitations; the pressure transducer needed to measure the pressure is expensive, difficult to mount in the cylinder and has a limited lifetime that is much shorter than the engine's lifetime. Demands of on-board diagnostics where the combustion process is continuously monitored, on production vehicles have created a need for a method to indirectly measure the combustion process. The two main indirect methods are vibration measurement based reconstruction and crankshaft angular speed measurement reconstruction. The combustion process give rise to vibrations in the engine body that in the former method is measured with an accelerometer and the pressure can be reconstructed by using inverted transfer functions. The idea behind the latter method, the crankshaft angular speed reconstruction method, is that when one cylinder fires the produced torque is higher than the load torque and the crankshaft accelerates. As next cylinder goes into compression the total load torque increases and the crankshaft speed will decrease. This is repeated when the next cylinder fires and the produced crankshaft speed fluctuations will then contain information about the combustion and compression that caused it. In this thesis an indirect method to predict the maximum cylinder pressure is developed based on the crankshaft speed fluctuations combined with neural networks. The speed fluctuations were measured on a 6-cylinder inline diesel engine at 9 speed-load-combinations. A two layer (one hidden and one output layer) feedforward neural network was trained with the backpropagation algorithm. The prediction accuracy for pmax was found to be better than ±5 % at 95%-confidence interval for the validation set. Another important parameter for the engine control and for optimising the fuel efficiency at the same time as the exhaust emissions are kept to a minimum, is the position of the pistons most upper position, TDC (top dead centre). The TDC position is normally measured mechanically with means that need access to the cylinders (the cylinder head has to be removed). This method is time consuming and therefore expensive and because of that not used on production engines. Several indirect methods to measure the TDC- positions have been suggested. Either based on measured cylinder pressures, that again need a pressure transducer mounted in the cylinder, or on the crankshaft speed fluctuations. An indirect method based on the speed fluctuations, that are measured when the starter motor rotates the engine with turned off ignition, is developed. From the measured crankshaft speed fluctuations the TDC-positions can be determined either by curve fitting or with neural networks. The TDC position determined by curve fitting has a bias error, due to the out-of-phase acceleration component in the crankshaft that are induced by the starter motor, but also caused by heat exchange between the compressed gas and the cylinder walls and gas. The results from the neural network were found to be better and the TDC-position for all 6 cylinders was determined within ±0.1 degree crank angle at 95%-confidence interval. / <p>Godkänd; 2001; 20070110 (biem)</p>

På grund av allt hårdare miljökrav från EU och nedläggningen av kärnkraften så kommer vattenkraft, vilket redan spelar en stor roll för dagens energiproduktion, behöva utökas. På grund av detta behövs en hållbarare och billigare lösning på tekniska fiskvägar, vilka idag oftast gjuts i betong. En av lösningarna som företaget Composite Service Europe AB föreslår är att göra detta i komposit, då det är lättare att underhålla och specialdesigna. För att enklare kunna specialdesigna och se så den uppfyller alla krav som ställs så kommer detta examensarbete presentera en simulering av en dessa fiskrännor samt validering av denna simulering. En ränna modellerades upp i Siemens NX vilken sedan simulerades med ANSYS CFX. Från denna simulering togs sedan flödesfältet och hastighetskonturen från den tredje bassängen ut och jämfördes mot experimentella flöden. De experimentella flödena är framtagna i kursen Experimentella Metoder och gav en indiktation för hur flödet borde se ut i bassängen. Då det experimentella arbetet var gjort på ett sådant sätt att inga hastigheter eller andra kvantiteter för flödet fanns, så kan inte flödet räknas som helt validerat utan vidare experimentellt arbete krävs. Men det som jämförelsen tyder på är att det simulerade flödet följer det experimentella. Vidare måste simuleringstiden sänkas då denna simuleringen tog 21 dagar, vilket inte är gångbart ute i industrin. Några sätt att göra det på som föreslås är att göra en nätstudie och se om det går att simulera en bassäng.

The present research focuses on flow properties of the elbow draft tube. This element has a major function in low head turbines, since up to half of the losses may arise there at part load. The use of computational fluid dynamic (CFD) to redisign a draft tube necessitates detailed knowledged of the boundary conditions. They are generally not available and qualified guesses must be made. This applies in particular to the radial velocity at the inlet. A method to estimate this component in swirling flow from experimental values of the axial and tangential velocities is derived. The method uses a two dimensional non- viscous description of the flow, the Squire-Long formulation. It is tested against swirling flow in a diffuser and applied to the Turbine-99 draft tube flow. As several other boundary conditions are difficult to estimate and many input parameters are available to perform a simulation, the use of factorial design is proposed as an alternative to design simulations in a systematic, objective and quantitative way. The method allows the deternmination of the main and joint effects of input parameters on the numerical simulation. The input parameters may be experimental uncertainty on boundary conditions, unknown boundary conditions, grid and turbulence models. The method is applied to the Turbine-99 test case, where the radial velocity, the surface roughness, the turbulence length scale and the grid were the factors investigated. The inlet radial velocity is found to have a major effect on the pressure recovery. The flow in water turbines is highly unsteady due to the runner blade rotation, guide vanes and stay vanes. Unsteady pressure measurements on a Kaplan prototype point out unsteadiness in the high and low pressure regions of the turbine. Since model and prototype are not running in dynamically similar conditions, the influence of unsteadiness on the losses is of interest. The derivation of the variation of the mechanical energy for the mean, oscillating and turbulent fields point out the contribution of unsteadiness to the losses and the turbulent production. Application to turbulent channel flow reveals that the contribution is a function of the amplitude of the oscillation, the frequency and the friction velocity. Turbulent pulsating flow in a generic model of the rectangular diffuser found at the end of elbow draft tube is studied in detail with laser Doppler anemometry (LDA). Three frequencies, corresponding to the quasi-steady, relaxation and quasi-laminar regimes with an amplitude of about 10% are investigated. The results indicate no alteration of the mean flow by the excitation of a single frequency. Furthermore. the existence of the different regimes, as found in turbulent pulsating turbulent pipe and channel flows, is confirmed. / Godkänd; 2003; 20061108 (haneit)

A model has been developed to predict the movement of oblate and prolate particles on amicro- and nano-scale in laminar channel flow, both for purposes of statistical aggregationand to study motion of single particles. For the purpose of this thesis the model has beenadapted to examine particle deposition patterns in the human lung and the filtration ofparticles during manufacturing of composites, but the possibilities of the model extendto all areas where the particle Stokes and Reynolds numbers are small.To examine the influence the breathing pattern has on the deposition of inhalednano- and micro-fibres deposition rates were compared at different injection points ofthe breathing cycle, where maximum deposition was found when the particles releasedat the beginning of the respiratory cycle while minimum deposition occurred when therelease came at peak inhalation. A comparison between a quasi-steady flow and a cyclicflow was done and it was found that a quasi-steady solution provides a reasonably goodapproximation if the velocity used is a mean of the velocity during the residence time ofthe simulations.A statistical study was done to compare the deposition rates of oblate and prolateparticles of different size and aspect ratio as they travel down narrowing bronchi in asteady, fully developed parabolic flow field. The model shows a clear correlation betweenincreased particle size and increased deposition, it also consistently yielded a higherdeposition rate for oblate particles compared to prolate particles with a similar geometricdiameter. A study of the motion and orientation of single oblate and prolate particleswith large aspect ratio and the same geometric diameter has also been done.In liquid moulding of fibre reinforced composites the resin can be enhanced by nanoandmicro-particles to give the final product additional properties. This is a processthat can be simulated by approximating the gap formed between the fibre bundles to achannel flow with a radially suctioning component caused by the capillary pressure in themicro channels in the bundles. First this flow field is described with a radial componentthat is constant over the length of the channel and compared with a flow purely drivenby an applied pressure gradient without radial forces. Particle size showed a small butstill noticeable influence, particularly for larger particles under the influence of gravity.The second flow field used is time dependent where the flow front in the bundlesand channel mimics that of previous observations. There is initially a period where theflow front in the channel is leading but the radial capillary fluid transport causes thisto retreat and be overtaken by the flow front in the bundles. Particles mixed in theresin will in general travel with a velocity greater than that of the fluid front until theradial velocity component at that point filters the particles by transporting them to thechannel wall. Particle geometry has a smaller impact on the deposition rates in compositemanufacturing than in inhalation since the effect of Brownian forces and gravity are muchsmaller, although there is still some discernible patterns such as a higher deposition ratefor spherical particles during the transport to the flow front.

A constantly increasing number of advanced driver assistance systems are implemented in cars.The driver is required to interpret the data reported by these systems while driving, and thereforeit is important to know how the information signals provided by such systems affect the driver.Driving relies to a large extent on vision, and most current advanced driver assistance systemsuse visual information, requiring visual attention from the driver. This conflicts with the drivingtask and leads to an increase in inattention and in cognitive and visual workload. Off-loadingvisually demanding tasks to other sensory modalities should be beneficial in terms of the driver’sability to divide attention resources. The aim of this thesis is to gain knowledge on how the driveris affected by information and interaction with driver assistance systems utilising 3D auditorydisplays. The goal is to provide knowledge of how to create robust interfaces that assist the driverwhile maintaining the necessary safety aspects while driving.The first paper investigated the importance of sound source placement within the car compartment.Since sound can be a very effective means of capturing attention, it could cause dangeroussituations if used in the wrong way. If sound is used to draw attention, one must be sure to notdraw the driver’s attention away from something more critical. The study showed that soundcan improve attention to the road when the sound source location is in front of the driver.Previous research has shown that a combination of sensory modalities increase the robustnessof perception. To avoid additional load on the visual modality, the second paper investigatedthe usefulness of vibrotactile information, in combination with auditory and/or visual signals.There was no significant increase in performance when adding vibration to a sound signal, butvibration and sound on their own led to similar performance. It can be argued, however, thatcombinations are still useful since they reduce the risk of an important signal being missed orneglected. In this investigation, all signals containing a visual component provided the fastestresponse time.The third paper investigated the usefulness of a 3D auditory display applied on a parking assistancesystem. A user study was conducted to evaluate drivers’ workload and performancewhen using different system implementations. It was found that a 3D auditory display was wellreceived as long as the sound only came from one direction at a time. Providing too much informationto the driver by using simultaneous sound sources at different locations was perceived asconfusing and annoying. In some cases, the effort required to perform a successful parking wassignificantly reduced when using a 3D auditory display system compared to a traditional parkingassistance system using only two sound sources. There were also indications that 3D soundcan reduce drivers’ mental workload and frustration with parking assistance systems.Placing sound sources in the car where they are most suitable can be difficult, especially if soundsources outside the car are required. The fourth paper investigated if it would be possible to use acrosstalk cancellation technique in combination with binaural recordings to reproduce 3D audiousing only two loudspeakers in the car compartment. It was found that when the loudspeakersare placed close to the ears of the driver, crosstalk cancellation can be effective inside the car compartment by avoiding strong reflections. Closely placed loudspeakers reduce filter creationcomplexity and improve sound quality.The fifth paper tackles the problems of within-the-head perception and front-back confusion,commonly found in binaural recordings and synthesis. It has been shown that reverberant binauralsounds are perceived more externalised than anechoic sounds, and tend to suffer less fromfront-back confusion. However, information sound signals should rarely be reverberant. Theidea was to create an image-source model with focus on early reflections and compare it withtraditional artificial head recordings. The image-source model performed better than the artificialhead recordings in terms of front-back confusion, and at the same time considerably limitedthe inherent room acoustics in the sound.In conclusion, meaningful and informative sound signals can raise driving performance if theyare placed in front of the driver. This encourages the driver to maintain focus on the road, byusing the attention capture capabilities of sound. A 3D auditory display can be beneficial forsystems such as parking assistance, since it helps lowering driver effort, mental workload andfrustration. Also, 3D auditory displays increase the drivers’ sense of safety and comfort, by augmentingthe drivers’ surrounding and thereby increasing their situational awareness. If a 3Dauditory display should be implemented in the car, a transaural system with crosstalk cancellationshowed promise for virtual sound source reproduction. However, binaural synthesis hasinherent problems that need to be addressed, specifically front-back confusion. It is hard to recommendusing crosstalk cancellation with binaural synthesis at the current state for locationcritical signals due to localisation confusion. However, using more than one modality for informationsignals makes the signals difficult to miss and could also help with the front-back confusionproblem, but further research is needed. If a transaural system with crosstalk cancellationis chosen as reproduction format, make sure to carefully select the loudspeaker placementsin order to avoid as many problems with filter generation as possible, since this will cause errorsin crosstalk suppression and affect the reproduction sound quality. Directive loudspeakersmounted in the neck rest, or ceiling, are good candidates for implementation.

Before presenting the Sheet Moulding Compound (SMC) process, which is the primarily focus of this work, a literature survey is carried out to deal with fibre reinforced polymer composites in general. Then the first part of this work is presented and is primarily focused on experimental visualisation of the flow during mould closure of SMC. Circular plates are manufactured with industry scale equipment at close to production conditions. Special attention is given to the advancing flow front, for which the full complexity is captured by means of continuous high resolution close-up monitoring. From the experimental visualisation of the flow front, three phases are defined, namely squish, flow, and boiling. During the initial phase, squish, outer layers do not remain outer layers, the actual flow is very complex and air is likely to be entrapped. The governing process parameters during this phase are mould temperature, mould closing speed and amount of preheating in the mould. During the second phase, flow, the flow is stable and seemingly viscous. During the last phase, boiling, bubbles are observed in the low pressure region at the flow front, favouring the void content both internally and on the surface. Based on a chemical analysis including mass spectrometry and thermogravimetry, the gas is probably styrene. In the second part it is investigated if an inverse modelling approach by proportional regularisation can be applied to mimic the pressure distribution during compression moulding of SMC. The process is simulated with Computational Fluid Dynamics and the mastered parameter, the viscosity of the SMC, is allowed to vary as a function of time. A grid refinement study of two ways to model the process and for three fictitious pressure scenarios yields that the suggested approach work very well and that the numerical errors can be minimised as desired. Finally a validation process is carried out showing that to get quantitative agreements of the whole pressure field more advanced viscosity models must be used. In order to verify the inverse modelling system have to important errors are studied. Firstly the error between calculated and experimental pressure, secondly the discretisation error due to solving the problem for many small volumes. Both have to be minimized and the later is studied with Richardson's extrapolation. The conclusions are that the initial guess is very important for predictions in the beginning of the simulation. / Godkänd; 2005; 20070108 (haneit)