Experiments and computational simulations have been performed as part of a larger project to instil trust in computational methods for design of hydraulics flows in spillways. Presented in this licenciate is one manuscript and two conference papers. The first conference paper details experiments done at Älvkarleby of a multiple outlet spillway model with an inlet channel specifically designed to contain interesting hydraulic features. The results indicate that simulations agree well with experiments. In the second conference paper acoustic doppler velocimetry measurements (ADV) were done and compared to simulations of a racetrack flume with a fish passageway at Älvkarleby. The results showed agreement but due to inlet conditions of the experiment some discrepancies were noticed. The manuscript presents experiments of a wider range of flow in the experimental flume of the first conference paper, with additional ADV measurements. Preliminary conclusions are that discrepancies can be due to inlet conditions. A short summary of further work is included.

In present thesis, the Lagrangian particle based method Smoothed ParticleHydrodynamics (SPH) is used to model two-dimensional problems associated with hydropower applications such as dam break evolution and hydraulic jumps. In the SPHmethod, the fluid domain is represented by a set of non-connected particles which possess individual material properties such as mass, density, velocity, position and pressure. Besides representing the problem domain and acting as information carriers the particles also act as the computational frame for the field function approximations. As the particles move with the fluid the material properties changes over time due to interaction with neighbouring particles. The adaptive nature of the SPH-method together with the nonconnectivity between the particles results in a method that is able to handle very large deformations as is the case for highly disordered free-surface flows such as hydraulic jumps.The dam break case was used as a model validation test case where the response of different parameter settings was explored. The SPH spatial resolution and the choice of artificial viscosity (a term in the momentum equation) constants had a major impact on the results. Increasing the spatial resolution increased the number of flow features resolved and setting the constants equal to unity resulted in a highly viscous and unphysical solution.Following the parameter study, the work focused on SPH simulations of hydraulic jumps. A hydraulic jump is a rapid transition from supercritical flow to subcritical flow characterized by the development of large scale turbulence, surface waves, spray, energy dissipation and considerable air entrainment. Several features of the jump were explored using the SPH method and good agreement with theory and experiments was obtained for e.g. the conjugate depth and the mean free surface elevation in the roller section. However, the free surface fluctuation frequencies were over predicted and the model could not capture the decay of fluctuations in the horizontal direction.

Hydropower is a versatile renewable source of power generation able to change rapidly operating conditions. Hydropower plants may today work over a larger operating range than designed for due to the introduction of renewable sources of energy and the deregulation of the electricity market. Such operating conditions may involve large stresses and losses due to complex unsteady and transient flow phenomena, which have to be taken into account under design or refurbishment phase. The use of computational fluid dynamics (CFD) in the design and refurbishment process is becoming increasingly popular due to its flexibility, detailed flow description and cost-effectiveness comparing to model testing used since a century in the development of turbines. However, issues have still to be resolved due to the combined flow physics involved in hydropower machines such as partly separated flow at curved surfaces, vortices, unsteadiness, swirl flow, strong adverse pressure gradients, convoluted geometry as well as numerical artefacts. Therefore, experimental data in such complicated systems are required to validate numerical simulations and develop more accurate models.The first part of this thesis is a numerical investigation of the three-dimensional flow of the axial Hölleforsen model spiral casing and distributor, where the influence of the penstock on the flow is analysed using different turbulence models and inlet boundary conditions. Comparisons with experimental results indicate the importance of the penstock to perform accurate simulation in the present case. Therefore, detailed inlet boundary conditions are necessary to simulate accurately the spiral casing flows if the penstock is not included in the simulation.The second part of the thesis focuses on an experimental investigation of an axial hydropower turbine model known as Porjus U9. The measurements are part of a project aiming to investigate experimentally the flow in different regions of the machine to build a data bank in order to validate numerical simulations and study scale-up efficiency between model and prototype, since the corresponding prototype is available for similar experiments. The investigation was performed at 3 different working points: part load, best efficiency point and high load. The inlet flow of the spiral casing as well as some sections in the spiral casing and draft tube are investigated with a two components laser Doppler anemometer (LDA). To improve the signal quality and measurement accuracy refractive index matching optical box was mounted on the circular pipe of the spiral casing inlet. LDA result of the mean velocities and corresponding RMS are presented to investigate the flow before the runner and at the inlet of the spiral casing, since the flow is influenced by the existence of a bend before the inlet. The results of the draft tube measurements are also presented. Good quality data are obtained for initial boundary conditions at the inlet of the casing and drafttube cone to perform numerical simulations.

Experimental fluid mechanics has for a long time been used to visualize flow phenomenon. An early pioneer was Ludwig Prandtl who used aluminum particles in water flumes to describe the flow in a qualitative manner. In line with the rapid development of Computational Fluid Dynamics, CFD, the need for new validation tools has increased. By combining Prandtls attempt to trace particles and contemporary tools in laser and computer technologies a quantitative non intruisiv whole field technique, so called Particle Image Velocity (PIV) has been developed. The PIV technique has been improved and grown in popularity through recent decades with the increase in computer capacity. This thesis describes three rather different areas of application of PIV measurements. In the first case PIV is used as pure measurement technology tool to describe the flow field inside an attraction channel in connection to fish migration. In the second case, PIV is applied as a validation tool for CFD calculations with Large Eddy Simulation (LES) including an extensive analysis of the results. Finally, a description of how PIV technique can be adopted to study the flow of complex fluids in small geometries by means of microscopy is given.The attraction channel is a U-shaped channel designed to facilitate salmonoid like fihes to migrate upstream to their spawning grounds. The attraction channel has a restriction in the downstream outlet that provides an acceleration of the attraction water up to 38% of the sourunding water velocity according to the PIV measurements. With PIV measurements it is also shown that the depth of displacement over the restriction is significant for how far downstream the acceleration is perceptible. CFD technology is constantly evolving and new methods will become the future standard in the industry. In the current situation Reynolds Avereaged Numerical Simulations (RANS) is the most used method in CFD. But development is approaching LES technology. This is, for instance, motivated by energy production units which has many applications with high turbulence and temperature fluctuations. In the current situation it is required to extend the service life of existing power plants. Therefore it is desirable to be able to estimate these fluctuations impact on thermal loads on the materials inside the plant, for example pipe walls. An LES approach is superior to applying to RANS since the large eddies are resolved. However, LES is still not mature enough to be used without validation in critical applications. Therefore, PIV has been used to create a validation database for a generic T-junction.Double Restriction Sealings (DRS) have been used in bearings and other lubricated applications since the 1940's. A DRS is intended to prevent contamination from entering and is therefore used to increase the life span of lubricated parts, i.e. hinder polutants to reach the rolling elements in bearings for example. Although it is widly applied little is known about the actual function and mechanism of the DRS. To learn more about the flow and particle tracks within a DRS, a new method to visualize and quantify grease flow within a DRS has been developed based upon micro PIV. The main result from this study is that it is possible to make quantititative measurement of the flow within a DRS.

Increasing competition has set pressure on the product development process to reduce development time and costs. Computer Aided Engineering (CAE) has been used to decrease development times by facilitating early predictions of product performances and qualities. Especially in early phases of product development, models with sufficient accuracy can provide valuable decision supports in order to pass legislations and fulfill customer expectations. Acoustic performance and sound quality are essential parts of the perceived product functionality and quality. A powerful method in product sound development is to combine recordings and simulations into auralizations. Interior vehicle noise is an important factor in the perceived product quality where tyre noise is a dominant source. The objective of this licentiate thesis was to lay the foundation for an auralization model of interior tyre noise. The aim of the model is to use the results from for example FEM simulations of tyre/road interaction and filter it through experimentally measured transfer functions into the cabin of the car. By varying compounds, components and road profiles in simulations, tyre noise can be auralized in different cars in an early design phase. Tyre noise predictions and auralizations are relevant both in tyre and car development. The vibrations generated by the tyre/road interaction are transferred through the hubs of the car and into the cabin as structure borne sound. The hub acts as the coupling element and describes the boundary condition for the rim. In paper I, the mechanical mobility of a hub was measured in 6-DOF. Measurement results showed good multiple coherences, reciprocities and low random errors in the frequency range 0-300 Hz. The measured mobilities will be used to transform operational forces and moments into velocities and will be implemented as boundary conditions in FEM simulations. For auralizations of the air-borne tyre noise contribution, knowledge of the required accuracy in positioning of sources and receivers is essential. In Paper II, variations in perceived sound caused by displacements of source and listening positions were assessed to find the smallest displacement giving a just audible differences. In addition, binaural transmissibility functions were measured from a loudspeaker near a wheel to an artificial head inside the car. Results showed that the accuracy in the positioning of the source and the receiver needed to be smaller than 2 cm to avoid audible differences. In order to generalize auralizations of interior tyre noise, audible variations in specimens of nominally identical products need to be known. In Paper III, variations in perceived interior sound between tyres of different brands and specimens of nominally identical cars were assessed. The differences between five nominally identical cars were found to be two to three times larger than the difference between two tyre models / CASTT - Centre for Automotive Systems Technologies and Testing

Fluid flow through porous media takes place in many natural processes such as ground water flows, capillary flows in plants and flow in human organs and muscles. It is also of outmost importance to have knowledge of this flow in a number of industrial processes such as paper making, making of fibre boards, composites manufacturing, filtering, forming and sintering of iron ore pellets and drying and impregnation of wood. Despite the significance of porous media flow and the vast amount of work that has been performed to investigate it, knowledge of some fundamentals is missing. Little is, for instance, known about transitional and turbulent flow in porous media on the microscopic level. On a macroscopic level Darcy law is extended to the so called Ergun or Forchheimer Equations when Re becomes larger than about 10 to fit experimental. The actual value depends both on the porous media and how Re is defined. The deviation from Darcy flow can for modest Re be explained by inertia but may, as Re increases, also be attributed to turbulence. The macroscopic way of modelling the transition from inertia dominated to turbulent flow is just to continue with the Forchheimer Equation or possibly some version of it. In any case experimental data yields that, on a macroscopic level, the transition from Darcy flow to inertia dominated and turbulent flow is smooth. To get a better understanding of this process the transition from laminar to turbulent flow in porous media is here studied with a new method. To mimic inter-connected pores, a simplified geometry is studied consisting of a pipe with a relatively large diameter that is split into two parallel pipes with different diameters. This is a pore-doublet set-up and the pressure drop over all pipes is recorded by pressure transducers for different flow rates. Statistical method and frequency analysis are performed to investigate collected data (Papers A and B). Positive skewness of pressure drop fluctuations indicates early stage of presence of turbulent patches in the flow for each pipe. The measured flow distribution and pressure drop fluctuations highlights six distinct flow patterns in the pipe network based on variation in flow regime of each pipe and the level of pressure fluctuations (Paper B). Correlation between the pressure drop between two pipes shows that two parallel pipes follow each other fluctuations much better before both of them become fully turbulent. Some detailed results are that the frequency analysis reveals two different frequency band events in the pipes. The gain factor shows that both frequency band events originate from the larger pipe until the early presence of turbulent patches in the smaller pipe (Paper B). The low frequency fluctuations makes the flow in the pipes to be out of phase while the high frequency band fluctuations try to bring the flow in the pipes back to equilibrium state.

LKAB (Luossavaara-Kiirunavaara AB) is an international company that producesiron ore products for the steel industry; their main product is iron ore pellets.The aim with this research project is to numerically investigate if it is possible to use selective non-catalytic reduction (SNCR) technologies in grate-kiln pelletizingplants for NOx reduction. The technique had, to the best knowledge of the author, never been used in this context before despite that it is commonly used in cement and waste incineration plants. The investigation is done in several stages: 1) Reveal if the technique is possible to use with the two most commonly reagents ammonia and urea. 2) Derive a chemistry model for cyanuric acid so that this reagent also can be scrutinized. 3) Compare the reagents urea and cyanuric acid in the grate-kiln pelletizing process.A CFD model of parts of the real grate was created and numerical simulations with the commercial code ANSYS CFX was carried out solving the flow field. A model for spray injection into the grate was then included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. It is shown that the SNCR technique with ammonia does not work in the grate-kiln process. Urea on the other hand can be used under some conditions and also cyanuric acid. The results lay grounds for a continued development of the proposed chemistry model.

No description available.

Water turbines are since some years widely used for grid stabilization purposes according to their exceptional load variation capability which gives them the ability to compensate grid fluctuations initiated by the customer’s consumption or intermittent electricity production systems such as wind and solar power. Different renewable power generation technologies can be combined in mini-grids to electrify isolated villages and extend existing grid networks. In these occasions, small hydro units are also a good option to reduce the overall variability of supply to low levels and provide low‑cost, local electrification solutions. Hence, initially designed hydropower turbines for steady operation at on-design operating condition experience many off-design, start/stop and load variations during their life time according to the nowadays on-demand energy market and introduction of intermittent power generation systems to the electricity market.Start/stop and load variations can be harsh for the turbines due to the time dependent forces exerted on different parts of the turbines, especially rotating parts. Off-design performance of hydropower systems may also result in unfavorable and harmful periodic forces on the rotating parts. Therefore, investigations are required to study these working conditions and consider them in design of new hydropower plants and refurbished turbines. This was the motivation for the experimental investigation of a Kaplan turbine during on-design, off-design and transient operations with focus on the turbine’s rotor. The test case was a 1:3.1 scaled model of Porjus U9; a Kaplan turbine. The first paper deals with pressure measurements on the runner blades of the model under steady state operating conditions to find and quantify the sources of pressure fluctuations exerted on the runner at different operating points. The goal was to investigate the turbine’s performance at the best efficiency point with concentration on the performance of the water supply system and compare it to operations at high load and part load for a constant blades angle. The model results are compared with prototype measurements to corroborate the findings. The second paper presents the model investigations during load acceptance and load rejection. The model was investigated with pressure measurement on the stationary and rotating parts of the turbine under different load variations between part load, high load and best efficiency point. The third paper focuses on velocity measurements in the runner blade channels and at the runner outlet under on-design and off-design operating conditions. The velocity measurements are performed with a laser Doppler anemometry (LDA) system. The results of the model investigations along two propeller curves are presented to investigate the runner blade angle effects on the turbine’s performance.

Waste hydrochloric acid (HCl) from the pickling process at SSAB EMEA in Borl¨ange, Sweden, is regenerated using a technique called spray roasting where waste HCl is sprayed into a hot reactor through four spray nozzles at the top of the reactor. The regeneration (drying) process is driven by four natural gas burners placed symmetrically along the periphery of the reactor and causes the water in the waste acid droplets to evaporate. Through chemical reactions the iron chloride is oxidized to form hematite and chloride gas; the latter to be used for manufacturing of new HCl which anew is used in the pickling process. The produced byproduct in form of hematite is sold and used in e.g. the electronic industry and as filling material for road constructions. A good quality of the hematite powder vouch for profit of the sold product, and hence an enhanced economy for the whole regeneration process which in turn motivates a continued regeneration rather than shipping away the waste acid and continuously buying new HCl.Due to the hostile environment inside the reactor, measurements and optical visualizations are difficult to perform. This limitation lead to a poor understanding of the dynamics inside the reactor as the process is a black box where waste acid is injected and hematite and chloride gas is collected; what happens in-between the two stages is not known to any larger extent. Here Computational Fluid Dynamics (CFD) is a useful tool for the modeling of the physics inside the reactor. In this licentiate thesis, the commercially available CFD software Ansys CFX has been used to model the gas flow and temperature inside the regeneration reactor as part of the main goal of modeling the whole regeneration process. As a first approach, the gas flow and temperature behavior are of certain interest as these quantities determine the dynamics of the injected droplets through their journey inside the reactor, and hence the regeneration process. The present work comprise two papers devoted to the actual application of HCl regeneration, and one paper which emphasize the importance of grid independency studies and the impact of grid element size in regions with high gradients. In the two application-focused papers (Paper A and C) the gas flow and temperature profile inside the reactor is resolved together with the particle (droplet) distribution. In Paper C the study is developed to also comprise the influence on theses quantities due to different locations and spray directions of the spray nozzles located at the top of the reactor.