Digital Image Processing Of Hydrogen Bubble Lines For Instantaneous Velocity Profiles

Masters Theses in the Pure and Applied Sciences

Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS)* at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dis semination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the though that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volumes were handled by an international publishing house to assure improved service and broader dissemi nation. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 37 (thesis year 1992) a total of 12,549 thesis titles from 25 Canadian and 153 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this impor tant annual reference work. While Volume 37 reports theses submitted in 1992, on occasion, certain uni versities do report theses submitted in previous years but not reported at the time.

Scientific and Technical Aerospace Reports

Digital Image Processing of Hydrogen Bubble Lines for Instantaneous Velocity Profiles

Boundary layer transition and turbulence have been described as being comprised of smaller structures called turbulent spots. Many researchers have obtained ensemble averaged velocity measurements in the transition region and some attempts have been made to obtain instantaneous information. Ensemble averaging can predict the overall scales of the flow field but it fails to yield information on the flow physics of the substructures within the spot. To facilitate investigation of these flow features and to establish the spot's relationship with transition or turbulence, an experimental method to obtain instantaneous full velocity profiles has been developed. The qualitative hydrogen bubble technique of flow visualization has been augmented to yield quantitative unsteady boundary layer information. The technique has been advanced by incorporating digital image processing of videotaped boundary layer flow. The method was verified by direct comparison with a laser Doppler anemometer and an analytical uncertainty analysis was performed. The technique compared well against the LDA, in both steady and unsteady flows. Recommendations were made for effective use of this technique and for further development.