A tidal current turbine is a device functioning in a manner similar to wind turbine for harnessing energy from tidal currents, a group of which is called a farm. The existing approaches used to predict power from tidal current turbine farms oversimplify the hydrodynamic interactions between turbines, which significantly affects the results. The major focus of this dissertation is to study the relationship between turbine distribution (the relative position of the turbines) and the hydrodynamic interactions between turbines, and its impact on the power from a farm. A new formulation of the discrete vortex method (DVM-UBC) is proposed to describe the behavior of turbines and unsteady flow mathematically, and a numerical model is developed to predict the performance, the unsteady wake and acoustic emission of a stand-alone turbine using DVM-UBC. Good agreement is obtained between the results obtained with DVM-UBC and published numerical and experimental results. Then, another numerical model is developed to predict the performance, wake and acoustic emission of a two-turbine system using DVM-UBC. The results show that the power of a two-turbine system with optimal relative position is about 25% more than two times that of a stand-alone turbine under the same conditions. The torque such a system may fluctuate 50% less than that of a stand-alone turbine. The acoustic emission of such a system may be 35% less than that of a stand-alone turbine. As an extension, a numerical procedure is developed to estimate the efficiency of an N-turbine system by using a linear theory together with the two-turbine system model. By integrating above hydrodynamic models for predicting power and a newly-developed Operation and Maintenance (O&M) model for predicting the cost, a system model is framed to estimate the energy cost using a scenario-based cost-effectiveness analysis. This model can estimate the energy cost more accurately than the previous models because it breaks down turbine’s components and O&M strategies in much greater detail when studying the hydrodynamics and reliability of the turbine. This dissertation provides a design tool for farm planners, and shed light on other disciplines such as environmental sciences and oceanography. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

An extensive technological shift is currently taking place to mitigate climate changeand this trend is particularly noticeable in the transport sector. This is interestingfrom an acoustical perspective, since it changes the noise environment in society.For example, a study in Gothenburg has shown that a complete electrification ofthe road traffic would reduce the noise levels by between 2 and 5 dB(A). In Sweden,noise emissions are calculated with a calculation model from 1996, called the Nordiskberäkningsmodell (Nordiska). Given the age of the model it is reasonable to investigate whether Sweden should change completely to the EU-common calculationmodel Common NOise aSSessment methOdS (CNOSSOS), since it is mandatory touse for national noise mapping. This master thesis has performed a computation analysis to compare and discussdifferences between CNOSSOS and Nordiska, to contribute to answering the question whether Sweden should change to CNOSSOS (or perhaps another model). Theresults show that CNOSSOS overall computes higher noise levels than Nordiska andthat the differences between them increase linearly with distance. Farthest from thenoise source the differences are up to 5 dB(A) for the road case and 9 dB(A) forthe railway case. In other words, the differences are larger for the railway trafficmodels than they are for the road traffic models, which is thought to be a result ofthe complexity of the CNOSSOS railway model. Another interesting phenomenonis that the differences behind buildings between the models are different for roadand railway traffic, which can be explained by the fact that the screening effects inNordiska’s road and railway models are different. My conclusion is that CNOSSOS is unsuitable for domestic calculations of noiseemissions. The model does not align with Swedish legislation and there is uncertaintydue to the fact that the differences between the CNOSSOS and Nordiska road andrailway models are different in size. Moreover, CNOSSOS railway model requires alot of computational power, which can delay and increase the costs of noise mappingor reduce the accuracy of the results. However, additional work is needed in whicheach calculation model is compared with measurements in situ to see which modelbest describes reality. If the conclusion thereafter is that CNOSSOS still is not asuitable option, it could be examined whether it is possible to create an updatedversion of Nord2000 (another Nordic calculation model used e.g. in Denmark) toobtain a calculation model that is more suitable for future traffic conditions. / För att minska effekterna av de pågående klimatförändringarna pågår idag ett omfattande teknikskifte för bland annat väg- och spårburen trafik. Detta skifte är intressant ur ett akustiskt perspektiv eftersom det förändrar bullermiljön i samhället.Till exempel har en studie i Göteborg visat att en full elektrifiering av vägtrafiken hade reducerat bullernivåerna med mellan 2 och 5 dB(A). Bullret beräknasmed en beräkningsmodell och i Sverige används idag Nordisk beräkningsmodell från1996 (Nordiska). Givet att modellen är gammal finns det god anledning att utredaom Sverige borde byta helt till den EU-gemensamma beräkningsmodellen CommonNOise aSSessment methOdS (CNOSSOS), som dessutom är obligatorisk vid dennationella bullerkartläggningen. Detta examensarbete har gått ut på att utföra en beräkningsanalys i syfte att jämföra och diskutera skillnader mellan CNOSSOS och Nordiska, vilket är ett steg i attbesvara frågan om Sverige borde byta till CNOSSOS (eller kanske någon annan beräkningsmodell). Resultaten visar att CNOSSOS överlag beräknar högre ljudnivåerän Nordiska och att skillnaderna dem emellan ökar linjärt med avståndet. Längstbort från bullerkällan uppgår skillnaderna som mest till 5 dB(A) för vägfallet och9 dB(A) för spårfallet. Skillnaderna är alltså större för spårmodellen än de för vägmodellen och det tros bero på komplexiteten i CNOSSOS spårmodell. Ett annatintressant fenomen är att skillnaderna bakom byggnader är olika stora för väg- ochspårtrafik, vilket förklaras med att skärmeffekten i Nordiskas väg- och spårmodellär olika. Min slutsats är att CNOSSOS inte är lämplig för inhemska beräkningar. Modellenkrockar med svensk lagstiftning samtidigt som det föreligger en osäkerhet i att skillnaderna mellan väg- och spårmodellerna är olika stora. Därutöver kräver CNOSSOSspårmodell mycket datorkraft, vilket kan fördyra och fördröja bullerutredningar ellerminska noggrannheten i beräkningsresultat. För att säkert besvara frågan anser jagdock att man behöver utföra ytterligare arbete där respektive beräkningsmodell jämförs med mätningar in situ för att se vilken modell som stämmer bäst överens medverkligheten. Kommer man därefter fram till att CNOSSOS inte är ett alternativbör man utreda om det är möjligt att skapa en uppdaterad version av Nord2000 (enannan nordisk beräkningsmodell som används bland annat i Danmark) i syfte att fåen beräkningsmodell som är bättre anpassad för framtida trafikförhållanden.

Vertical-axis wind turbines (VAWTs) have with time been outrivaled by the today more common and economically feasible horizontal-axis wind turbines (HAWTs). However, VAWTs have several advantages which still make them interesting, for example, the VAWTs can have the drive train at ground level and it has been argued that they have lower noise emission. Other proposed advantages are suitability for both up-scaling and floating offshore platforms. The work within this thesis is made in collaboration between Halmstad University and Uppsala University. A 200-kW semi-guy-wired VAWT H-rotor, owned by Uppsala University but situated in Falkenberg close to Halmstad, has been the main subject of the research although most results can be generalized to suit a typical H-rotor. This thesis has three main topics regarding VAWTs: (1) how the wind energy extraction is influenced by turbulence, (2) aerodynamical noise generation and (3) eigenfrequencies of the semi-guy-wired tower. The influence from turbulence on the wind energy extraction is studied by evaluating logged operational data and examining how the power curve and the tip-speed ratio for maximum Cp is impacted by turbulence. The work has showed that the T1-turbine has a good ability to extract wind energy at turbulent conditions, indicating an advantage in energy extraction at turbulent sites for VAWTs compared to HAWTs.The noise characteristics are studied experimentally, and models of the two most likely aerodynamic noise mechanisms are applied. Here, inflow-turbulence noise is deemed as the prevailing noise source rather than turbulent-boundary-layer trailing-edge noise (TBL-TE) which is the most important noise mechanism for HAWTs. The overall noise emission has also been measured and proven low compared to similar sized HAWTs. The eigenfrequencies of a semi-guy-wired tower are also studied. Analytical expressions describing the first-mode eigenfrequency of both tower and guy wire has been derived and verified by experiments and simulations.

This thesis deals with issue of traffic noise, its measurement and data evaluation. Theoretic part of my work concretes basic information about acoustics and also describes and analyzes traffic noise sources of tire/pavement. Next part deals with quite pavement and with measurement methods of traffic noise. Practical part of my thesis contains description, results and evaluation of realized measurement with methods CPX and SPB.

The task of the master's thesis is introduction with the problems of traffic noise, focusing on noise from road traffic. There is a description what is the noise, how it is formed, its resources and what are the methods of measuring. The following are the various noise reduction measures such as noise barriers and low noise pavements. The main attention is devoted to the noise generated at the tire / road that is reduced by these pavements. The practical part describes the implemented measurements on individual sections at various locations in our country. The measurement was carried by slightly modified method CPX with reference tire directly at the vehicle. The main aim was to evaluate the measurement data, make comparison of different low-noise surfaces with each other and with the commonly used surfaces. Then quantification of the rate reduction of the noise emission for a given section and verification of input data for noise modeling. In conclusion, the obtained results are summarized and based on them were confirmed very good acoustic properties with the recommendation to continue with measurements in the future.

reducing noise, noise in railway transport, management of application of products for modification of adhesion

It is the tyre that ensures the interaction between a wheel and road surface and it is the the tyre which also acts as a primary cushioning. Its construction, features and condition highly influence driving properties of a car and thus passenger safety as well. In motorsports the tyre is a key part of the vehicle and therefore it is necessary to make use of its complete potential for reaching the best results. The aim of this thesis is a device construction suitable for tyre parameter and their characteristics measurement. The next task is to design a measuring system for tyre pressure and temperature monitoring. With using of these devices a few real-tyre measurements and subsequent result evaluation will be done. The output of the thesis is an overview of construction details, overview of selected tyre parameters, design and drawing documentation of multipurpose measuring device and the results of my measurements.