It is important to understand the aerodynamic properties of tensioned cables (e.g. used in suspension bridges and yacht riggings), both for drag reduction and vibrational suppression purposes. In this study, the cross-sectional shape and surface structure of solid cables were investigated in order to improve the performance of sailing racing yachts. The apparent wind angle range 15-60° was identified as the most important for drag reduction. Thereafter, the aerodynamic properties of different shapes and surfaces were investigated in the Reynolds number range 5 x 10^3 ≤ Re ≤ 4 x 10^4, by performing computational fluid dynamics simulations and wind tunnel tests (the aerodynamic forces were measured using load cells). No significant effect of changing the surface roughness could be found for the investigated Reynolds number range. The results were compared to literature values for validation. Elliptical shapes with a fineness ratio between 1:1-3:1, together with three complex shapes, were tested. It could be shown that the largest performance gain was obtained for cables with more sail-like aerodynamic properties (for apparent wind angles below 90° a large lift/drag ratio is sought). This study was performed in collaboration with Carbo-Link AG, as an outlook, the manufacturability of carbon fiber reinforced polymer cables in the most aerodynamically efficient shape was explored.

This report focuses on the utilisation of flight mechanics in the context of aircraftconceptual design to assess stability, control, and motion characteristics. The pri-mary objective is to acquire the equations of motion and implement longitudinalstability and control criteria using Pacelab Aircraft Preliminary Design 8.1, a com-mercial software tool. The equations and criteria employed in this study are derivedfrom an extensive review of relevant literature.By incorporating a dedicated Flight Mechanics chapter within the software, it be-comes possible to evaluate aircraft concepts under varying conditions. To ensureaccuracy and validity, DATCOM+ and OpenVSP were employed for testing andverification purposes.The key aspects covered in this report include flight mechanics, its implementationin Pacelab APD 8.1, determination of aerodynamic derivatives, formulation of equa-tions of motion, and their application to the B747 aircraft model. The emphasis liesin assessing longitudinal stability and control, including specific characteristics suchas the phugoid and short period modes.This report provides valuable insights into the integration of flight mechanics withinthe Pacelab APD 8.1 software for aircraft conceptual design. The results contributeto a better understanding of stability and control parameters and their impact onaircraft performance.

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Hydrodynamic drag testing was conducted for eleven different configurations of IsoTruss® lattice structures. Flow visualization of prototypical IsoTruss® wind towers was also performed using Particle Image Velocimetry instrumentation. The drag test and flow visualization specimens included 6-node and 8-node configurations, single and double-grid geometries, thick and thin member sizes, smooth and rough surface finishes, a helical-only structure, and a smaller outer diameter test specimen. Three sets of hydrodynamic drag tests were conducted in a closed-circuit water tunnel: 1) orientation drag tests, 2) water velocity drag tests, and 3) height variation drag tests. The orientation drag tests measured the hydrodynamic drag force of the IsoTruss® test specimens at five different orientations with an average water velocity of 1.43 mph (0.64 m/s). The water velocity drag tests measured the maximum drag for each IsoTruss® test specimen at water velocities ranging from 0.0 to an average 1.43 mph (0.64 m/s). Based on the average outer structure diameter of the IsoTruss® specimens, the water velocities corresponded to a Reynolds number range of 7,000 to 80,000. Based on the average member diameter, the corresponding Reynolds number spanned from 600 to 3,000. In addition, the height variation drag tests were performed by vertically extracting the IsoTruss® test specimens from the test section at four different immersed height levels, with a maximum immersed height of 7.22 in (18.1 cm). The height variation testing corresponded to a Froude number range of 0.40 to 0.90. The IsoTruss® specimens exhibited an average lower drag coefficient based on the projected cylindrical area than the smooth circular cylinder data throughout the Reynolds number and Froude number ranges. The drag coefficient based on solid member area showed no correlation when shown as a function of the solidity ratio. However, for the drag coefficient calculated from the solid member projected area, the data for all IsoTruss® test specimens collapsed to a 2nd order polynomial when presented as a function of the Froude number, with an R2 of 0.99. Conversely, no significant relationship was shown when the drag coefficient based on projected cylindrical area was plotted versus the Froude number. The hydrodynamic data was compared to aerodynamic data, and the orientation testing results were identical. The hydrodynamic data differed by an average of 17% compared to the non-dimensional aerodynamic results. The flow visualization research revealed that the velocity returned to 2% of the freestream velocity at 1.24 diameters upstream from the prototypical IsoTruss® wind tower. Likewise, the velocity returned to a maximum 4% of the freestream velocity at 0.94 diameters sidestream of the model IsoTruss® wind tower.

Forced response which is blade vibration due to an external excitation can lead to blade failure. The estimation of the level of vibration is dependent on the determination of aerodynamic damping. This thesisinvestigates the determination of aerodynamic damping at high reduced frequencies in turbomachines. The aerodynamic damping was calculated by a linearized Navier-Stokes flow solver with exact 3D non-reflecting boundary conditions. The method was validated using the two-dimensional test cases (Standard Configuration 5 and 8). Thereafter, two 3D profiles were also investigated: an aeroelastic turbine rig (AETR) which is a subsonic turbine case, and a virtual integrated compressor (VINK) which is a transonic compressor case. In AETR case, the first bending mode with reduced frequency 2.0 was studied. The 3D acoustic modes were calculated and the rate of decay was plotted as a function of nodal diameter and radial order. This plot identified six acoustic resonant points which included two points corresponding to the first radial order. The six resonance points correspond to six peaks in the damping curve. In VINK case, the fifth mode (1854 Hz, reduced frequency 3.1) was investigated. Acoustic resonance was predicted to occur for the first and second radial orders at the inlet. It was concluded that the higher order resonance points are influencing the damping curve. There were some inconsistencies in the results and grid convergence was not achieved. These inconsistencies were due to the difficulty in calculating the acoustic modes at the transonic inlet with an impinging shock. / Aerodynamiskt påtvingade vibrationer, som är bladvibrationer på grund av en extern excitation kan leda till haveri. Prediktering av vibrationen är beroende av bestämning av aerodynamisk dämpning. I detta arbete undersöks bestämningen av aerodynamisk dämpning vid höga reducerade frekvenser i turbomaskiner. Den aerodynamiska dämpningen beräknades genom en linjäriserad Navier-Stokeslösare med exakta 3D icke-reflekterande gränsvillkor. Metoden validerades med hjälp av de tvådimensionella testfallen (Standardkonfiguration 5 och 8). Därefter undersöktes två 3D-profiler: en aeroelastisk turbinrigg (AETR), som är en subsonisk turbinenhet och en virtuell integrerad kompressor (VINK) som är ett transoniskt kompressorfall. I AETRfallet undersöktes det första böjningsformen med reducerad frekvens 2.0. 3D akustiska lägen beräknades och graden av förfall visades som en funktion av noddiameter och radiell grad. Denna metod identifierade sex akustiska resonanspunkter som innehöll två punkter som motsvarade den första radiella graden. De sex resonanspunkterna motsvarar sex toppar i dämpningskurvan. I VINK-fallet undersöktes den femte svängningsformen (1854 Hz, reducerad frekvens 3.1). Akustisk resonans förutspåddes inträffa för första och andra radiella graden vid inloppet. Slutsatsen drogs att de högre ordningens resonanspunkter påverkar dämpningskurvan. Det fanns vissa inkonsekvenser i resultaten och gridkonvergens uppnåddes inte. Dessa inkonsekvenser berodde på svårigheten att beräkna de akustiska svängningsformerna vid det transoniska inloppet med en stötvåg.

Разработаны рекомендации, позволяющие достоверно оценить воздействие ветровой нагрузки на пространственные решетчатые конструкции. Сформулирована гипотеза о том, что расхождения значений коэффициента использования сечения элемента конструкции при различных вариантах задания ветровой нагрузки могут достигать 20%. / Recommendations have been developed to reliably assess the impact of wind load on spatial lattice structures. The hypothesis is formulated that the discrepancies in the values of the coefficient of use of the section of the structural element with different options for setting the wind load can reach 20%.

Уточнена методика определения ветровых нагрузок на здания в ANSYS CFX на основе анализа сходимости полученных результатов с результатами физического моделирования. / The method for determining wind loads on buildings in ANSYS CFX has been refined based on the analysis of the convergence of the obtained results with the results of physical modeling.

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