Browsing by Subject "Thermography"
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Item A laser-induced surface flow visualization technique using liquid crystal thermography(Texas Tech University, 2002-12) Hunt, Emily McFatherObservation of flow field characteristics such as flow separation and reattachment are important in many industries. Current methods for flow visualization can be difficult to implement, expensive, and highly intrusive. The objective of this project is to develop an inexpensive, user-friendly, non-intrusive measurement technique useful to engineers interested in surface flow visualization. This is accomplished using liquid crystals in conjunction with a laser heat source to generate a thermal tuft. The shape and size of the thermal tuft is used to characterize the flow field. Wind tunnel experiments are conducted to validate this concept and examine flow behavior over a flat plate in a low Reynolds number environment. The plate is coated with liquid crystals of one-degree and fivedegree bandwidths. A 150-mW infrared, diode laser provides a constant heat source and generates a high temperature thermal spot on the model. The results obtained during the wind tunnel experimentation show that an irradiated spot on a liquid crystal coated surface will produce a tuft. The shape and size of the thermal tuft is indicative of the direction and magnitude of the flow conditions. As the wind speed increases from 2 to 10 m/s, it was shown that the length of the thermal tuft increases linearly. The tail of the tuft was also found to follow the direction of flow. Turbulent and laminar flow conditions can be distinguished; however, the angle of attack could not be realized with this technique. Developing a technique for generating a matrix of heated spots on the model indicates that the results of using this method can be viewed over a large area. Overall, it was shown that this is an easy, inexpensive, and non-intrusive technique for visualizing flow on the surface of an object.Item Experimental investigation of the performance of a fully cooled gas turbine vane with and without mainstream flow and experimental analysis supporting the redesign of a wind tunnel test section(2013-12) Mosberg, Noah Avram; Bogard, David G.This study focused on experimentally determining the cooling performance of a fully cooled, scaled-up model of a C3X turbine vane. The primary objective was to determine the differences in overall effectiveness in the presence and absence of a hot mainstream flowing over the vane. Overall effectiveness was measured using a thermally scaled matched Biot number vane with an impingement plate providing the internal cooling. This is the first study focused on investigating the effect of removing the mainstream flow and comparing the contour and laterally-averaged effectiveness data in support of the development of an assembly line thermal testing method. It was found that the proposed method of factory floor testing of turbine component cooling performance did not provide comparable information to traditional overall effectiveness test methods. A second experiment was performed in which the effect of altering the angle of attack of a flow into a passive turbulence generator was investigated. Measurements in the approach flow were taken using a single wire hot-wire anemometer. This study was the first to investigate the effects such a setup would have on fluctuating flow quantitates such as turbulence intensity and integral length scale rather than simply the mean quantities. It was found that both the downstream turbulence intensity and the turbulence integral length scale increase monotonically with approach flow incidence angle at a specified distance downstream of the turbulence generator.Item Sleeping in a society : social aspects of sleep within colonies of honey bees (Apis mellifera)(2010-05) Klein, Barrett Anthony; Gilbert, Lawrence E.; Mueller, Ulrich G.; Seeley, Thomas D.; Ryan, Michael J.; Abbott, John C.Sleep is a behavioral condition fraught with mystery. Its definition—either a suite of diagnostic behavioral characters, electrophysiological signatures, or a combination of the two—varies in the literature and lacks an over-arching purpose. In spite of these vagaries, sleep supports a large and dynamic research community studying the mechanisms, ontogeny, possible functions and, to a lesser degree, its evolution across vertebrates and in a small number of invertebrates. Sleep has been described and examined in many social organisms, including eusocial honey bees (Apis mellifera), but the role of sleep within societies has rarely been addressed in non-human animals. I investigated uniquely social aspects of sleep within honey bees by asking basic questions relating to who sleeps, when and where individuals sleep, the flexibility of sleep, and why sleep is important within colonies of insects. First, I investigated caste-dependent sleep patterns in honey bees and report that younger workers (cell cleaners and nurse bees) exhibit arrhythmic and brief sleep bouts primarily while inside comb cells, while older workers (food storers and foragers) display periodic, longer sleep bouts primarily outside of cells. Next, I mapped sleep using remote thermal sensing across colonies of honey bees after introducing newly eclosed workers to experimental colonies and following them through periods of their adult lives. Bees tended to sleep outside of cells closer to the edge of the hive than when asleep inside cells or awake, and exhibited caste-dependent thermal patterns, both temporally and spatially. Wishing to test the flexibility of sleep, I trained foragers to a feeder and made a food resource available early in the morning or late in the afternoon. The bees were forced to shift their foraging schedule, which consequently also shifted their sleep schedule. Finally, I sleep-deprived a subset of foragers within a colony by employing a magnetic “insominator” to test for changes in their signaling precision. Sleep-deprived foragers exhibited reduced precision when encoding direction information to food sources in their waggle dances. These studies reveal patterns and one possible purpose of sleep in the context of a society.