Flow with free and rough surfaces near hydropower stations is of interest for both engineering and environmental applications. Here, Computational Fluid Dynamics simulations of free surface flow and flow over rough surfaces in regulated rivers were performed in applications such fish migration, spillway design and flow over rough surfaces as in hydropower tunnels or natural channels. For all the investigated applications it is typical with very large geometrical scales, high flow rates and highly turbulent flow. Modelling boundaries such as free water surfaces and rough walls presents a challenge and was given special attention as well as the treatment of turbulence. Validation of the numerical simulations was performed in all cases with methods such as acoustic measurements with an Acoustic Doppler Current Profiler (ADCP), Acoustic Doppler Velocimeter (ADV) and optical measurements with Particle Image Velocimetry (PIV).Numerical simulations have been used to evaluate the flow downstream the Stornorrfors hydropower plant in Umeälven with regards to upstream migrating fish. Field measurements with an ADCP were performed and the measurements were used to validate the simulations. By adding a fish ladder in the simulations it was possible to investigate the attraction water created from the fishway at different positions and angles. An additional possibility to create better attraction water and improve the conditions for upstream migrating fish was simulated by guiding the spill water from the hydropower dam through a smaller passage from the old river bed.Fish population data from the same location was compared with flow fields from numerical simulations. The population data was compared with variables such as velocity, vorticity and turbulence intensity. A correlation between fish detections and turbulence intensity was shown.Simulations on the spilling from a dam were performed and compared to experimental results from a physical scale model. ADV was used to measure the velocity and validate the simulations. Two different spillway configurations were considered and simulations with both the Rigid Lid model and the Volume of Fluids method were carried out. Water levels, velocities and the shape of the water surface were compared between simulations and experiments. The simulations capture both qualitative features such as a vortex near the outlet and show good quantitative agreement with the experiments.A wall with large surface roughness was created by laser scanning a tunnel. One of the side walls was down-scaled and used to create a rough wall in a channel with rectangular cross-section for both a numerical model and an experimental model. Numerical simulations were performed and validated by PIV-measurements in the experimental model.The resolution of the geometry for the rough surface was lowered in two steps and numerical simulations were performed for flow over all three surfaces. The difference in flow fields in the bulk and near wall region was investigated as well as the difference in turbulent quantities which can provide good input for a new model for surface roughness in applications with very large surface roughness and high velocities such as flow in hydropower tunnels or natural channels and rivers. / Godkänd; 2013; 20130425 (aneane); Tillkännagivande disputation 2013-05-29 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Anders G. Andersson Ämne: Strömningslära/Fluid Mechanics Avhandling: Modelling Flow with Free and Rough Surfaces in the Vicinity of Hydropower Plants Opponent: Associate Professor Nils Rüther, Dept of Hydraulic and Environmental Engineering, Norwegian University of Science and Technology, Trondheim, Norway Ordförande: Professor Staffan Lundström, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Torsdag den 20 juni 2013, kl 13.00 Plats: E231, Luleå tekniska universitet

Godkänd; 2014; 20140307 (soflar); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Sofia Larsson Ämne: Strömningslära/Fluid Mechanics Avhandling: The Fluid Dynamics of the Cold Flow in a Rotary Kiln Opponent: Forskningsassistent Lisa Prahl Wittberg, Skolan för teknikvetenskap, Mekanik, KTH, Stockholm Ordförande: Professor Staffan Lundström, Avd för strömningslära och experimentell mekanik, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Fredag den 11 april 2014, kl 10.00 Plats: E231, Luleå tekniska universitet / Fastelaboratoriet - VINNEXC

The fluid mechanical field of rough surface flows has been developed ever since the first experiments by Haagen (1854) and Darcy (1857). Although old, the area still holds merit and a surprising amount of information have to this day yet to be fully understood, which surely is a proof of its complexity. Many equations and CFD tools still rely on old, albeit reliable, concepts for simplifying the flow to be able to handle the effects of surface roughness. This notion is, however, likely to change within a not so unforeseeable future. The advancement of computer power has opened the door for more advanced CFD tools such as Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES). It can be argued that once a given flow situation has been fully accessible by numerical simulations, it is likely to be fully understood within a few years 1 . However, DNS is still limited to small scales of roughness and relatively low Reynolds number which is in contrast with given hydropower conditions today. The hydropower industry annually supplies Sweden with about 45% of its electricity production, and tunnels of various types are regularly used for conveying water to or from turbines within hydropower stations. The tunnels are a vital part of the system and their survival is of the essence. Depending on the manner of excavation, the walls of the tunnels regularly exhibit a roughness, this roughness may range from a few mm to m, which is true especially if the tunnel have been subjected to damage. For natural roughness e.g. hydropower tunnels, there is no clear way to distinguish between rough surface flows and flow past obstacles. Yet, to be able to distinguish between the two cases has proven to be important. This work is aimed to increase the understanding of how the wall roughness affects the flow, and how to treat it numerically. Paper A employs the use of pressure sensors to evaluate local deviations in pressure as well as head loss due to the surface roughness. Paper B is aimed at using PIV to evaluate the flow using averaging techniques and characteristic length scales. Paper C Further investigates the data from the PIV and pressure measurements and Evaluates the possibility to use basic but versatile turbulence models to evaluate the flow in such tunnels.

Iron ore pellets are a highly refined product supplied to the steel making industry for use in blast furnaces or direct reduction processes. The use of pellets offers many advantages such as customer adopted products, transportability and mechanical strength yet the production is time and energy consuming. Being such, there is a natural driving force to enhance the pelletization in order to optimize production and improve quality. The aim with this thesis is to develop numerical models with which the drying zone of an induration furnace can be examined and optimized. To start with, a continuous model of velocity and temperature distribution in the up-draught drying zone, without regard to moisture transport, is developed with aid of Computational Fluid Dynamics (CFD). The results show a rapid cooling of air due to the high specific surface area in the porous material. With the global model an overall understanding of heat transfer is gained, but the heat and moisture transport should also be investigated on a smaller scale in order to account for small scale phenomena such as turbulence and dispersion. Drying of a bed of iron ore pellets is therefore considered by modeling a two-dimensional discrete system of round pellets. The system is divided by modified Voronoi diagrams and the convective heat transfer of hot fluid flow through the system including dispersion due to random configuration of the pellets is modeled. The results show that the temperature front advances much faster in the gaps between pellets than in the interior of the pellets even if all the heat energy of the air goes in heating of the pellets initially. Decrease of temperature is possible for low dew points of the input air due to evaporation. If the dew point temperature is higher than the temperature of the pellets on the other hand, there is slight condensation of the steam at the beginning of the process and the temperature increases faster than it would for pure thermal heating. An uneven distribution in temperature and moisture content between pellets is furthermore displayed in the discrete system. This phenomenon is related to the natural dispersion occurring in random system of pellets.To further investigate drying of individual pellets, forced convective heating of a cylindrical porous pellet with surrounding flow field taken into account is first examined. A model with properties similar to that of an iron ore pellet is numerically investigated and with interface heat transfer condition provided by CFD, the simulations show an increased heating rate for the porous cylinder when compared to a solid. The most plausible explanation to this is that there is less solid to heat up for the porous medium since the porous cylinder behaves as if it was impermeable from a fluid flow point of view. With diffusive liquid transport inside the two-dimensional pellet and corresponding evaporation at the surface, simulations of drying show an initial warm up phase with a succeeding constant rate drying phase. Constant drying rate will only be achieved if the surface temperature is constant, i.e. if it has reached the wet bulb temperature. The falling rate period will subsequently start at the forward stagnation point when the local moisture content approaches zero, while other parts of the surface still provide enough moisture to allow surface evaporation. The phases will thus coexist for a period of time. Experiments are carried out in order to examine the drying behavior of a single iron ore pellet with main goal to retrieve data for validation of the computational drying models. The experiments are performed with two inlet temperatures and one pellet from the experiments is scanned by an optical scanning equipment. In order to investigate the influence of surface irregularities and overall geometry on drying, simulations of the first drying period are compared for: 1) a scanned pellet 2) an oval pellet resembling the experimental one with equivalent volume 3) a spherical pellet with equivalent volume. The results show that the local moisture content at the surface is influenced by both surface irregularities and overall geometry. A smooth surface will decrease the local variation of moisture while a spherical geometry will, compared to an oval, increase the difference. A diffusive model taking into account capillary flow of liquid moisture and internal evaporation is developed to account for the whole drying process and simulations of the scanned pellet are validated with good agreement. The result clearly shows four stages of drying; i) evaporation of liquid moisture at the pellet surface, ii) surface evaporation coexisting with internal drying as the surface is locally dry, iii) internal evaporation with completely dry surface and iv) internal evaporation at boiling temperatures. A moisture front moving towards the core of the pellet will start to develop at the second drying stage and the results show that the front will have a non-symmetrical form arising from the surrounding fluid flow. With the developed drying model, simulations are then carried out on a spherical pellet with aim to investigate how the inlet air humidity affects drying. The results indicates that the effect of air dew point arise from the start of the first drying period, i.e the surface evaporation period, while the difference is reduced at the end of the period due to a prolonged stage of constant rate drying attained at high dew points. The wet-bulb temperature is increased with humidity and condensation will occur if the pellet surface temperature is below the dew point. Furthermore it is found that the moisture gradients at the surface and inside the pellet are increased with drying rate. / Godkänd; 2010; 20101103 (annlju); DISPUTATION Ämnesområde: Strömningslära/Fluid Mechanics Opponent: Professor Graham Nathan, The University of Adelaide, Australia Ordförande: Professor Staffan Lundström, Luleå tekniska universitet Tid: Onsdag den 8 december 2010, kl 09.00 Plats: F431, Luleå tekniska universitet

Iron ore pellets are a highly refined product and for companies such as LKAB it is important to constantly improve the pelletization in order to enhance production and improve product quality. A long term goal has been established to develop and considerably refine tools and techniques with which the drying zone of a pelletizing plant can be optimized. The aim with this research project is to numerically investigate how material and processing parameters influence the drying. This will be applied to several scales: i) The constituents of the pellets and their properties and geometry. ii) The geometry of the pellet, their permeability and size distribution. iii) The geometry of the bed and the processing conditions including the state of the air (ex. humidity, temperature and velocity). To start with, a pellet bed model of velocity and temperature distribution in the up-draught drying zone without regard to moisture transport is developed with aid of Computational Fluid Dynamics (CFD). Results from simulations show a rapid cooling of air due to the high specific surface area in the porous material. Following this work, heat and mass transport within a single pellet during drying is modeled. Heat transfer and convective transport of water and air through the capillaries of the porous media is computed and vaporization by boiling is taken into account. A sensitivity analysis shows that it is important to use a realistic value of the convective heat transfer coefficient when the vaporization of water is a dominating drying mechanism while the temperature of the solid and capillary movement of water is not influenced to the same extent. The derived model is applicable to a number of numerical set up such as a single pellet placed in infinite space. To further develop a single pellet model, forced convective heating of a porous media with surrounding flow field taken into account must first be examined. Therefore, a two dimensional model with properties similar to that of an iron ore pellet is numerically investigated. With interface heat transfer condition provided by CFD, the heat transfer and fluid flow around and within a porous cylinder is examined. The results lay foundation of future development of a single pellet drying model where heat and mass transfer models are combined and coupled to the surrounding flow field. / Godkänd; 2008; 20080428 (ysko)

Black liquor (BL), a by-product of the chemical pulping process, is an important liquid fuel in the pulp and paper industry. It contains almost all of the inorganic cooking chemicals along with the lignin and other organic matter separated from the wood during pulping in the digester. To recover the organic combustion heat and cooking chemicals (sodium and sulphur) from the produced black liquor in kraft pulping, Tomlinson kraft recovery boilers are traditionally used. However, the kraft recovery boiler is not thermodynamically efficient and suffers from problems with explosion phenomena, fouling, and emissions. A potential technology for improving the recovery cycle is pressurised gasification of black liquor. However, uncertainties about the reliability and robustness of the technology are preventing a large-scale market introduction. One important step towards a greater trust in the process reliability is the development of simulation tools that can provide a better understanding of the process and improve performance through optimisation. This licentiate thesis is concerned with the modelling and simulation of an entrained flow gasifier for pressurised gasification of black liquor at high temperature. The thesis comprises three papers presenting the simulation results obtained from different models using CFD (Computational Fluid Dynamics). In paper A a simplified gasification model, considering just the gas phase, is used to make a qualitative study of the effect of burner spray angle on the gas flow in the gasifier. In paper B the simulation results from a more advanced model with gas/droplet interaction, are compared to the results presented in paper A. Finally, in paper C a complex model for pressurised gasification of black liquor droplets is presented and used to study the influence of uncertainties in model parameters. / Godkänd; 2003; 20070122 (ysko)

This project aims to design and develop hydro jet which is integrated to Electric motor, whichis limited to run at 70% PWM. Which limits the efficiency of the system, to make an efficientsystem, hydro jet parameters are not defined which are desired to be defined by design fourimpellors for basic Radinn G2x Jet Pack design. The impellors will be four expected points inHydro Jet and final impellor is assumed to lie between these design points, to find the finalspecifications of the hydro jet, the hydro jet will be designed, using computational fluiddynamics they will be analysed. After analysis, they will be manufactured and tested in poolfacility where MGM controller will be used to measure the numerical data from electric circuitwhich powers the system to analyse the performance parameters to finalize the validity of 100% PWM. Microsoft Excel is used to calculate the Hydro Jet Geometric parameters, which areused in Solid Works, where parametric modelling is used to design impellors based ongeometric parameters calculated in Excel. Using Computational fluid dynamics hydro jetperformance is simulated and analysed. To validate the design further, prototypes aremanufactured and tested using workshop pool testing facility using MGM software. As a result,four hydro jet points are calculated, analysed and tested, four pumps are designed for specificflow rate, velocity and torque is calculated for four hydro jets. They are calculated and verifiedusing computational fluid dynamics, as a result flow rate, velocity and torques are calculatedfor all four hydro jets. Four impellors are manufactured and then tested in Radinn work shopand as a result current, power and rpm of the hydro jets are measured using MGM software.From power, rpm and current the torque can be calculated, while rpm is compared againstpredicted computational fluid dynamics results. The results from this project is limited toRadinn G2x jet pack, motor and other parts of the hydro jet’s Jet pack are standard parts

This Licentiate is about Whole Body Vibrations and focuses on transient vibrations with human's discomfort and motion assessment. Whole Body Vibrations occurs when a body is in contact with a vibrating surface. Whole Body Vibrations is a major problem in terrain vehicle, which affects both the physiological and psychological health and discomfort. The first study, Paper A, focus on the prediction of vibration discomfort based on r.m.s.-values in z-direction of seat. In the case of individual results, the correlation coefficient was 0.54. Based on averages for each test condition, the correlation coefficient was 0.93. Study in Paper B focus on the prediction of vibration discomfort and perceived motions. By analysis of vibration values in one-third octave bands of x-direction in the top of the seat backrest, pitch motion and vertical motions in seat, pitch alone with variable length was found to give best correlation with the vector sum of perceived motions (r=0.677). Surprisingly, one-third-octave band higher than 50Hz give a high contribution to the prediction of perceived motions. One of the background variables, "Length of driver", was found to have a statistically significant effect on perceived motions. Tall driver perceived less motion than short drivers. In Paper C, focus on evaluating the effect of two seat design (sliding and fixed) in minimizing the discomfort from transient vibrations. Results showed that sliding seat is superior in attenuating vibration that contains transient vibration in horizontal direction. Sliding seat was perceived to give less overall and low back discomfort compared to fixed seat. / Godkänd; 2002; 20070224 (ysko)

Godkänd; 1998; 20070404 (ysko)

The goal of the Turbine 99 Draft Tube experiments is to provide extensive experimental data on a well-defined sharp-heel draft-tube flow. The data bank has served as calibration data for the simulation challenge presented by the Turbine 99 workshop in Porjus in June 1999. This thesis gives some background on draft-tube flows in general and discusses in some detail the parameters and flow conditions relevant to the Turbine 99 draft tube. Some comments on the research and development conducted so far in the project and future plans are given at the end. In the three accompanying papers, details of the developments and the scientific results are presented: Paper 1. Presents the scope of the work and some initial results from the measurements Paper 2. Discusses the quality of the measurements Paper 3. Presents some of the results from the measurements / Godkänd; 2000; 20070318 (ysko)