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The issue of the effects of free stream turbulence on the flow field over a surface-mounted prism is examined through experimental and numerical investigations. In the experimental studies, particle image velocimetry measurements are conducted in the ESM water tunnel at Reynolds number of $9,600$ and under two cases of turbulent inflow conditions. The results show that the mean flow separation, reattachment and parameters such as mean velocity, root mean square, Reynolds stresses and turbulent kinetic energy are affected by the turbulence characteristics of the incident flow. The instantaneous dynamics of the interactions between the separating shear layer and the solid wall and between the shear layer and the turbulence in the incident flow are detailed. In the numerical studies, large eddy simulations of the flow over a surface-mounted prism under two inflow conditions, namely, smooth inflow and isotropic homogeneous turbulence inflow, are performed. The use of a fifth-order scheme (CUD-II-5), which is a member of a family of Compact Upwind Difference schemes, in large eddy simulations of this flow is assessed. The performance of this scheme is validated by comparing the rate of temporal decay of isotropic turbulence with available experimental measurements for grid-generated turbulence. The results show that the spectra are sensitive to the method of flux vector splitting needed for the implementation of the upwind scheme. With van Leer splitting, the CUD-II-5 scheme is found to be too dissipative. On the other hand, using the Lax-Friedrichs vector splitting yields good agreement with experiments by controlling the level of artificial dissipation. This led us to recommend a new procedure, we denote by C6CUD5 scheme, that combines a compact sixth-order scheme with the CUD-II-5 scheme for large eddy simulation of complex flows. The simulation results, including flow patterns, pressure fields and turbulence statistics show that the CUD-II-5 scheme, with Lax-Friedricks flux vector splitting, provides high resolution of local flow structures. The results present new physical aspects of the flow topology over surface-mounted prisms. The effects of the incident homogeneous turbulence on the size of the separation region and suction pressures are determined by pointing out differences in the flow topologies between the two incident flow cases. / Ph. D.

This study evaluates noise and vibrations in a heavy freight locomotive cab, and provides several measures for providing more comfort to the crew. A full-scale production cab and sill structure is used to provide the results. The cab is setup in a controlled laboratory environment in a manner similar to the installation on a locomotive. Field measurements are used to emulate actual vibration input to the cab structure. A 16-channel data acquisition system is used to collect both noise and vibration data on various parts of the cab structure and inside the cab. Upon establishing the baseline for laboratory vibration measurements and correlating them with field data, a design of experiment was conducted to evaluate the vibration contribution of various parts of the cab. This showed that the cab floor and cab roof had the largest vibrations. A series of solutions including stiffening the cab floor and damping the cab roof were investigated. The results showed that although such solutions reduce localized vibrations, the overall effect on reducing cab interior noise is minimal. As a more global solution, the cab was isolated from the sill structure through six elastomeric elements mounted at the base of the cab and at the crash post. The mounts at the base were selected such that they support the static weight of the cab, provide a resonance frequency that is below the excitation range, and offer good lateral and longitudinal stability. Two tube-form elastomeric mounts were placed between the cab structure and the crash posts which attach to the front of the sill structure. The test results showed that the soft-mounted cab had significantly lower noise and vibration than the original cab. The vibration levels were reduced 10 to 100 times at certain locations and frequency ranges. The overall noise level was reduced by approximately 6 dBA. In an attempt to provide an estimate of effectiveness of the mounts with different stiffness values, a simulation model was prepared in Matlab. Although the model did not yield accurate results, it resulted in several recommendations for future research work. / Master of Science

Research has shown that head-mounted displays can produce greater presence in a virtual environment than direct-view displays. It has also been shown that after vision, haptic response is one of the most important inputs for humans in a simulated environment. This research was designed primarily to determine the performance differences associated with different display types, levels of steering force feedback, and the interaction between these two factors in a low-to-medium fidelity, PC-based driving simulator. Participants drove on a simulated driving course during which both objective driving performance data were collected (lane deviation, speed control, steering wheel angle variance, and time to the complete course) as well as subjective self-report measures including questionnaires designed to tap immersive tendencies and perceived levels of presence. Results of the research show that the use of a head-mounted display can significantly impact driving performance in terms of speed control and lane deviation. Speed control was significantly improved (increased) and lane deviation was significantly improved (decreased) in three of the four roadway segments with the use of an HMD. Results for active steering force feedback, however, showed a significantly negative effect on driving performance with an increase in average lane deviation. Descriptive statistics showed that participants preferred the HMD and D-V equally and all but one participant preferred active steering force feedback. / Master of Science

Since the introduction of graphical user interfaces (GUI), input control devices have become an integral part of desktop computing. When interfacing with GUIs, these input control devices have become the human's primary means of communicating with the computer. Although there have been a number of experiments conducted on pointing devices for desktop machine, there is little research on pointing devices for wearable computer technology. This is surprising because pointing devices are a major component of a wearable computer system, allowing the wearer to select and manipulate objects on the screen. The design of these pointing devices will have a major impact on the ease with which the operator can interact with information being displayed (Card, English, and Burr, 1978). As a result, this research is the first in a series to investigate design considerations for pointing devices and visual displays that will support wearable computer users. Twenty soldiers participated in an experiment using target acquisition software with five pointing devices and two visual displays. The findings of the research strongly support the use of a relative mode-pointing device with rotational characteristics (i.e. trackball or thumbwheel) over other designs. Furthermore, the results also suggest that there is little difference between pointing devices operated with the thumb and index finger for target acquisition tasks. This study has also showed that there were little differences in pointing and homing time for pointing devices across the two visual displays. Finally, the study demonstrated that the Fitts' law model could be applied to hand-operated pointing devices for wearable computers. This is important because it allows the future development of pointing devices to be compared with the devices tested in this research using the Fitts' Law Index of Performance calculations. / Master of Science

No / This paper presents a numerical method for estimating the curvature, deflection and moment capacity of hybrid FRP/steel reinforced concrete beams. A sectional analysis is first carried out to predict the moment-curvature relationship from which beam deflection and moment capacity are then calculated. Based on the amount of FRP bars, different failure modes were identified, namely tensile rupture of FRP bars and concrete crushing before or after yielding of steel reinforcement. Comparisons between theoretical and experimental results of tests conducted elsewhere show that the proposed numerical technique can accurately predict moment capacity, curvature and deflection of hybrid FRP/steel reinforced concrete beams. The numerical results also indicated that beam ductility and stiffness are improved when steel reinforcement is added to FRP reinforced concrete beams. (C) 2015 Elsevier Ltd. All rights reserved,

In der Produktentwicklung nimmt die Bedeutung von Head-Mounted-Displays (HMD) stetig zu. Mit HMDs ist es möglich, virtuelle Objekte zu betrachten und mit diesen in realem oder virtuellen Kontext zu interagieren. Die Entwicklung von HMDs im Entertainment-Bereich und die nativen Augmented-Reality(AR)-Funktionen von Smartphones und Tablets (Apple Inc. 2019, Google Inc. 2019) machen AR- und Virtual-Reality(VR)-Anwendungen einer breiten Nutzerbasis zugänglich. Die individuelle Entwicklung dieser Anwendungen ist mit heutigen Software-Werkzeugen umfangreich möglich. Im Bereich der Produktentwicklung und Schulung werden die Geräte ebenfalls genutzt, bedürfen jedoch intensiver Erforschung und Anpassung an individuelle Bedürfnisse. Besondere Anforderungen kommen auf AR- und VR-Systeme zu, wenn Nutzende kollaborieren möchten. Anders als im Entertainment-Bereich spielen hier die Genauigkeit der Sensorik, eine konsistente Wahrnehmung aller Teilnehmenden und Möglichkeiten zur Vermittlung von Ideen und Anmerkungen eine tragende Rolle. Als Werkzeug für einen solchen Gedankenaustausch werden neben verbaler Kommunikation und Textverkehr meist Annotationen genutzt. Bedingt durch gerätespezifische Eingabemethoden müssen Annotationssysteme und Annotationen in AR und VR anders gestaltet werden als in klassischen Desktopanwendungen. In einem Review erzeugte Annotationen beinhalten wichtige Informationen, die in den Entwicklungsprozess integriert werden müssen. Dementsprechend bedarf es einer Möglichkeit, Annotationen auch nach dem Review verwenden zu können. Diese verschiedenen Aspekte der Kollaboration sollen im Folgenden näher untersucht werden, um wichtige Erkenntnisse für den Einsatz von HMDs als Basis einer kollaborativen Umgebung zu vermitteln. [... aus der Einleitung]

This thesis examines the flow around bluff bodies placed at the floodplain edge in a compound, open channel. The floodplain edge location is associated with a strong shear layer between lower velocity floodplain flow and high velocity flow in the main channel. The drag force exerted by a bluff body is dependant on the way in which the flow separates around the body and subsequently recovers but the drag coefficients typically used to represent the effects of bluff bodies are based on experiments on bodies in geometrically simple channels. The differences induced in the wake structures and therefore in the drag coefficients of bluff bodies when they are placed in the shear layer at the floodplain edge are little understood. In this study, experimental data is gathered that allows direct comparison of the wakes of identical bluff bodies, both emergent (surface-piercing) and submerged, in simple and compound open channels. For the compound channel scenarios, for both single and multiple block arrangements, turbulence data is also reported. These results are augmented using a computational model based on the solution of the 3D Reynolds Averaged Navier Stokes equations, using a non-linear turbulence model. The results show that the changes induced in the wake structures due to their location at the floodplain edge of the compound channel can have a significant effect on the drag coefficient. For the emergent bodies, the proximity of the deep main channel flow is shown to impact in a complex manner upon the processes of reattachment and re-separation, changing the formation of vorticity in the wake. For the submerged bodies, this is complicated by asymmetry in the same processes on the block top. For both body types, separation on the main channel side results in the creation of a strong axial circulation at the floodplain edge and the decay of the wake is asymmetrically affected by the differing behaviour of the turbulence on the two sides.

Aus Einleitung und Motivation "Die gegenwärtigen Entwicklungen von Head-Mounted Displays (HMD, hier synonym auch als Brille bezeichnet) für Virtual Reality (VR) und Augmented Reality (AR) schaffen ein nie da gewesenes Potential dieser Technologien als Werkzeuge in der Produktentwicklung. Wenngleich VR- und ARAnwendungen keineswegs neu in der Industrie sind, bringt der Fortschritt der Verbraucher-HMDs völlig neue Möglichkeiten. Immersive VR-Systeme bedeuten künftig keine hunderttausend Euro Anschaffung mehr – AR-Brillen dienen zukünftig nicht nur der Erweiterung der Realität mit zweidimensionalen Informationen. Cave Automatic Virtual Environments (CAVE), 360-Grad-Projektoren und interaktive Planungstische sind in der Fabrikplanung teilweise etabliert (Runde et al. 2015). Im Unterschied zu diesen Techniken können HMDs jedoch eine deutlich höhere Immersion ermöglichen, was auch für die Interaktion mit der virtuellen Umgebung von Vorteil sein kann. Das Gefühl der Immersion ist wichtig, um in bestimmten Entwicklungsphasen entsprechende Kriterien besser beurteilen zu können. Primär ist der VR-Einsatz für Bewertungsmerkmale sinnvoll, welche nur qualitativ und nicht quantitativ bewertbar sind (Pawellek 2014). Des Weiteren spielt auch die Eingabetechnologie eine essenzielle Rolle. Um mit virtuellen Elementen interagieren zu können, sollte das Eingabegerät echtzeitfähig und intuitiv sein. ..."