This thesis presents a complete method of modeling the autospectra of turbulence in closed form via an expansion series using the von Kármán model as a basis function. It is capable of modeling turbulence in all three directions of fluid flow: longitudinal, lateral, and vertical, separately, thus eliminating the assumption of homogeneous, isotropic flow. A thorough investigation into the expansion series is presented, with the strengths and weaknesses highlighted. Furthermore, numerical aspects and theoretical derivations are provided. This method is then tested against three highly complex flow fields: wake turbulence inside wind farms, helicopter downwash, and helicopter downwash coupled with turbulence shed from a ship superstructure. These applications demonstrate that this method is remarkably robust, that the developed autospectral models are virtually tailored to the design of white noise driven shaping filters, and that these models in closed form facilitate a greater understanding of complex flow fields in wind engineering. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2013.

Thesis (MScEng (Department of Mechanical and Mechatronic Engineering))--Stellenbosch University, 2006. / ENGLISH ABSTRACT: Wind conditions in South Africa determine the need for a small-scale wind turbine to produce useable power at windspeeds below 7m/s. In this project, a range of windspeeds, within which optimal performance o the wind turbine is expected, was selected. The optimal performance was assessed in terms of the Coefficient of Power(Cp), which rates the turbines blade's ability to extract energy form the avalible wind stream. The optimisation methods employed allowed a means of tackling the multi-variable problem such that the aerodynamic characteristics of the blade were ideal throughout the wind speed range. The design problem was broken down into a two-dimensional optimisaion of the airfoils used at the radial stations, and a three-dimensional optimisation of the geometric features of the wind rotor. by means of blending various standard airfoil profiles, a new profile was created at each radial station. XFOIL was used for the two-dimensional analysis of these airfoils. Three-dimensional optimisn involved representation of the rotor as a simplified model and use of the Blade Element Momentum(BEM) method for analysis. an existimg turbine blade, on which the design specifications were modelled, was further used for comparative purposes throughout the project. The resulting blade design offers substantial improvements on the reference design. The application of optimisation methods has successfully aided the creation of a wind turbine blade with consistent peak performance over a range of design prints. / Sponsored by the Centre for Renewable and Sustainable Energy Studies, Stellenbosch University

Thesis (PhD) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: With increasing environmental concerns and the drive for a greener economy comes an increased desire to improve turbine engine fuel efficiency and reduce emissions. Unfortunately weight reduction techniques used increase the blade loading, which in turn increases the losses. Non-axisymmetric endwall contouring is one of several techniques being investigated to reduce loss in a turbine. An investigation at Durham University produced a non-axisymmetric endwall design for a linear cascade. An adaption of the most promising endwall was investigated in an annular rotating test rig at the CSIR using steady state instrumentation. The current investigation extends those investigations into the unsteady time domain. Previous investigations found that a generic rotor endwall contour improved efficiency by controlling the endwall secondary flow vortex system in both a linear cascade and an annular 1½ stage rotating test turbine. The current research was aimed at determining if there were any unsteady effects introduced by the contoured endwall. The approach was unique in that it investigated the unsteady effects of an endwall contour originally designed for a linear cascade both experimentally and numerically at three incidence angles (positive, zero and negative to represent increased load, design load and decreased load respectively), the results of which are openly available. Unsteady experimental hotfilm results showed that the endwall contour made the velocity profile more radially uniform by reducing the strength of the endwall secondary flow vortex system. The fluctuations in the velocity were also reduced producing a more temporally uniform velocity profile. The FFT magnitude of the velocity at the blade passing frequency below midspan was also reduced. It was found that the reduction in the endwall secondary flow vortex system due to the contour increased with increasing loading. Numerical results showed that the oscillations in the flow were small and did not penetrate the boundary layer. The contoured rotor was forward and aft loaded when compared to the annular rotor, resulting in a weaker cross passage pressure gradient which allowed the endwall secondary flow vortex system to be less tightly wrapped. Numerical results did not show a significant difference in the oscillations observed in the annular and contoured rotor. A new objective function for use in the endwall optimisation process was proposed that acts as a proxy for efficiency, but is less prone to uncertainty in the results. When used on the current results it shows the same trend as efficiency. It remains to be used to design an endwall for full validation. / AFRIKAANSE OPSOMMING: Met ’n toenemende omgewingsbesorgdheid en die strewe na ’n groener ekonomie kom ’n toenemende behoefte om turbine enjin brandstofdoeltreffendheid te verbeter en vrystellings te verlaag. Ongelukkig het gewigsbesparingstegnieke wat gebruik is die lemlading verhoog, wat op sy beurt die verliese verhoog. Nie-assimmetriese endwandprofilering is een van verskeie tegnieke wat ondersoek word om verliese in ’n turbine te verminder. ’n Ondersoek by die Universiteit van Durham het ’n nie-assimmetriese endwandontwerp vir ’n lineêre kaskade gelewer. ’n Aanpassing van die mees belowende endwand is in ’n annulêre roterende toetsopstelling by die WNNR getoets, deur gebruik te maak van bestendige toestand instrumentasie. Die huidige ondersoek brei daardie ondersoeke uit na die nie-bestendige verwysingsraamwerk . Vorige ondersoeke het bevind dat die generiese rotor endwandprofiel doeltreffendheid verbeter as gevolg van die beheer van die endwand sekondêre vloei draaikolkstelsel in beide ’n lineêre kaskade sowel as ’n annulêre 1½ stadium roterende toetsturbine. Die huidige navorsing was daarop gemik om vas te stel of die endwandprofiel enige onbestendige effekte tot gevolg gehad het. Die benadering was uniek in die sin dat dit die onbestendige effekte ondersoek het van ’n endwandprofiel wat oorspronklik ontwerp is vir ’n lineêre kaskade beide eksperimenteel en numeries op drie invalsshoeke (positief, nul en negatief om onderskeidelik verhoogde lading, ontwerplading en verlaagde lading te verteenwoordig), waarvan die resultate algemeen beskikbaar is. Onbestendige eksperimentele warmfilm resultate het getoon dat die endwandprofiel die snelheidsprofiel meer radiaal uniform gemaak het deur die vermindering van die sterkte van die endwand sekondêre vloei werwelstelsel. Die skommelinge in die snelheid is ook verminder wat ’n meer tyduniforme snelheidsprofiel gelewer het. Die FFT (Fast Fourier Transform) grootte van die snelheid van die lem verbygaan frekwensie onder lem midbestek het ook verminder. Daar was bevind dat die vermindering in die endwand sekondêre vloei draaikolkstelsel as gevolg van die endwandprofiel toeneem met toenemende lading. Numeriese resultate het getoon dat die ossilasie in die vloei klein was en nie die grenslaag binnegedring het nie. Die rotor met gevormde wand het ’n voor- en agterlading gehad in vergelyking met die rotor met annulêre wand, wat tot ’n laer drukgradient dwarsop die vloeirigting gelei het, die endwand sekondêre vloei draaikolkstelsel minder beperk het. Numeriese resultate het nie ’n beduidende verskil in die ossilasies tussen die annulêre en gevormde rotorwand getoon nie. ’n Nuwe doelwitfunksie vir gebruik in die endwand optimersproses is voorgestel wat dien as ’n plaasvervanger vir doeltreffendheid, maar minder geneig is tot onsekerheid in die resultate. Wanneer dit gebruik word op die huidige resultate toon dit dieselfde tendens as doeltreffendheid. Dit moet nog gebruik word in die ontwerp van ’n endwand vir volledige bevestiging.

An Ocean Current Turbine (OCT) numerical simulation for creating, testing and tuning flight and power takeoff controllers, as well as for farm layout optimization is presented. This simulation utilizes a novel approach for analytically describing oceanic turbulence. This approach has been integrated into a previously developed turbine simulation that uses unsteady Blade Element Momentum theory. Using this, the dynamical response and power production of a single OCT operating in ambient turbulence is quantified. An approach for integrating wake effects into this single device numerical simulation is presented for predicting OCT performance within a farm. To accomplish this, far wake characteristics behind a turbine are numerically described using analytic expressions derived from wind turbine wake models. These expressions are tuned to match OCT wake characteristics calculated from CFD analyses and experimental data. Turbine wake is characterized in terms of increased turbulence intensities and decreased mean wake velocities. These parameters are calculated based on the performance of the upstream OCT and integrated into the environmental models used by downstream OCT. Simulation results are presented that quantify the effects of wakes on downstream turbine performance over a wide range of relative downstream and cross stream locations for both moored and bottom mounted turbine systems. This is done to enable the development and testing of flight and power takeoff controllers designed for maximizing energy production and reduce turbine loadings. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Indiana University-Purdue University Indianapolis (IUPUI) / A wave rotor constant volume combustor (WRCVC) was designed and built as a collaborative work of Rolls Royce LibertyWorks, Indiana University-Purdue University at Indianapolis (IUPUI), and Purdue University, and ran experimental tests at Purdue's Zucrow Laboratories in 2009. Instrumentation of the WRCVC rig inlet flow included temperature and pressure transducers upstream of the venturi and at the fuel delivery plane. Other instrumentation included exhaust pressures and temperatures. In addition, ion sensors, dynamic pressure sensors, and accelerometers were used to instrument the rotating hardware. The rig hardware included inlet guide vanes directly in front of the rotating hardware, which together with concern for damage potential, prevented use of any pressure transducers at the entrance to the rotor. For this reason, a complete understanding of the conditions at the WRCVC inlet is unavailable, requiring simulations of the WRCVC to estimate the inlet pressure at a specific operating condition based on airflow. The operation of a WRCVC rig test is a sequence of events over a short time span. These events include introduction of the main air flow followed by time-sequenced delivery of fuel, lighting of the ignition source, and the combustion sequence. The fast changing conditions in the rig inlet hardware make necessary a time-dependent computation of the rig inlet section in order to simulate the overall rig operation. The chosen method for computing inlet section temperature and pressure was a time-dependent lumped volume model of the inlet section hardware, using a finite difference modified Euler predictor-corrector method for computing the continuity and energy equations. This is coupled with perfect gas prediction of venturi air and fuel flow rates, pressure drag losses at the fuel nozzles, pressure losses by mass addition of the fuel or nitrogen purge, friction losses at the inlet guide vanes, and a correlation of the non-dimensional flow characteristics of the WRCVC. The flow characteristics of the WRCVC are computed by varying the non-dimensional inlet stagnation pressure and the WRCVC's operational conditions, assuming constant rotational speed and inlet stagnation temperature. This thesis documents the creation of a computer simulation of the entire WRCVC rig, to understand the pressure losses in the inlet system and the dynamic coupling of the inlet section and the WRCVC, so that an accurate prediction of the WRCVC rotor inlet conditions can be computed. This includes the computational development of the WRCVC upstream rig dynamic model, the background behind supporting computations, and results for one test sequence. The computations provide a clear explanation of why the pressures at the rotor inlet differ so much from the upstream measured values. The pressure losses correlate very well with the computer predictions and the dynamic response tracks well with the estimation of measured airflow. A simple Fortran language computer program listing is included, which students can use to simulate charging or discharging of a container.