A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item DEVELOPMENT OF KRYPTON PLANAR LASER INDUCED FLUORESCENCE METHODS FOR THE MEASUREMENT OF HYPERSONIC FLOW CONDITIONS(2021) Standage, Chase; Gupta, Ashwani; Yu, Kenneth; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Conventional wind tunnel flow measurement techniques typically involve the use of intrusive sensor systems, such as Pitot-probes and transducers which come in contact with the flow. Intrusive methods become impractical for high Mach number flows, as such methods can cause considerable disruption to the integrity of flow measurements. Therefore, it is desirable to utilize non-intrusive methods in such experiments, especially as hypersonic flow conditions are achieved. Schlieren and shadowgraph imaging methods have been used successfully for decades as a method of non-intrusive flow visualization. However, these methods become obsolete when the path of light is obstructed, which is a common problem when analyzing concave surfaces and complex geometries. The goal of this project was to develop a scalable krypton planar laser induced fluorescence flow visualization system for use on curved-surface geometries in sup- port of the hypersonic Boundary Layer Transition (BOLT) program. The system was designed to fit multiple wind-tunnel facilities, including the AEDC Tunnel 9 hypersonic test facility and UMD Ludwieg Tube. In order to design and test the system, the AEDC Mach 3 Calibration wind tunnel was utilized and Kr-PLIF measurements were taken about a 0.50” spherical model and 2” BOLT model. A wide variety of equipment and methods were assessed for their suitability of this project, including 3 cameras and 7 sheet combinations. A beam from a single-diode Ti-Sapphire laser was amplified, modulated, and shaped in order to create a thin laser-sheet of 0.25-1.0” width and 0.01”-0.025” thickness, frequency of 1 kHz, and pulse width of 40 fs. The flow was seeded with 5% krypton, and tests were conducted at Mach 3. The results were compared to Schlieren imaging tests conducted onsite in the same Mach 3 wind tunnel. The Kr-PLIF method was moderately successful in finding regions of relatively high flow density, such as boundary layers and leading edges at an angle-of-attack. Additionally, Kr-PLIF was able to make measurements about the curved region of the BOLT model, which was previously unobservable by Schlieren imaging.Item Characterization of Fire Induced Flow Transport Along Ceilings Using Salt-Water Modeling(2006-04-27) Yao, Xiaobo; Marshall, André W.; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research provides a detailed analysis of turbulent mixing and heat transfer in canonical fire plume configurations by using a quantitative salt-water modeling technique. The methodology of quantitative salt-water modeling builds on the analogy between salt-water flow and fire induced flow, which has been successfully used in the qualitative analysis of fires. Non-intrusive laser diagnostics, Planar Laser Induced Fluorescence (PLIF) and Laser Doppler Velocimetry (LDV), have been implemented to measure the dimensionless density difference and velocity in salt-water plumes. In the implementation of the PLIF technique, the salt-water concentration is measured through tracking a fluorescent dye tracer within the entire spatial domain of a planar section of the salt-water flow, which is diluted at the same rate as the salt water. The quantitative salt-water modeling technique has been validated by comparing it with real fire experiments and theoretical data. The scaling laws are also proved by varying the initial source strength or ceiling height in the impinging plume configuration. The detailed salt-water measurements provide insight into of the wall interactions and laminarization effects in the impinging plume configuration. Additionally, highly resolved measurements provide mean profiles and turbulent statistics which will be useful for validating and developing sub-grid scale models in Computational Fluid Dynamics (CFD) codes. Furthermore, an engineering heat transfer model is developed to predict the convective ceiling heat transfer from impinging plumes using the quantitative salt-water modeling technique along with an adiabatic wall modeling concept. The successful application of the adiabatic wall heat transfer model illustrates a well controlled method for studying the heat transfer issues in more complex fire induced flow configurations by using the quantitative salt-water modeling technique.Item Predicting Smoke Detector Responce Using a Quantitative Salt-Water Modeling Technique(2004-06-16) jankiewicz, sean; Marshall, Andre; Roby, Richard; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This investigation provides a detailed analysis of the hydraulic analogue technique used as a predictive tool for understanding smoke detector response within a complex enclosure. There currently exists no collectively accepted method for predicting the response of smoke detectors; one of the most important elements in life safety. A quantitative technique has been developed using salt-water modeling and planar laser induced fluorescence (PLIF) diagnostics. The non-intrusive diagnostic technique is used to temporally and spatially characterize the dispersion of a buoyant plume within a 1/7th scale room-corridor-room enclosure. This configuration is geometrically similar to a full-scale fire test facility, where local conditions were characterized near five ionization type smoke detectors placed throughout the enclosure. An evaluation of the scaled local conditions and dispersive event times for both systems was used to formulate a preliminary predictive detector response model for use with the hydraulic analogue.