Browsing by Subject "Turbulence intensity"

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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.
Turbulent jet breakup : theory and data
(2020-08-14) Trettel, Benjamin M.; Ezekoye, Ofodike A.; Goldstein, David B; Hall, Matthew J.; Ling, Stanley; Moser, Robert D.
Understanding the breakup of turbulent liquid jets is important for many applications including spray combustion, fire suppression, and water jet cutting. Turbulent jet breakup models are rarely fully predictive, and typically require re-calibration to experimental data for different cases. In this work the existing models for turbulent jet breakup are reviewed, highlighting the successes and shortcomings of existing and new approaches. A critical shortcoming of most existing models is the neglect of a measure of the strength of the turbulence like the turbulence intensity. New models are developed to address this shortcoming and others. Existing and new models are compared against a large experimental compilation, primarily from the archival literature. Because the physical mechanisms causing breakup can vary, a new regime diagram was developed in this work, allowing the breakup regime and consequently how to model a particular jet to be determined. Problems common in the validation of turbulent jet breakup models are detailed. A model for the turbulence intensity at the outlet of a nozzle is developed. Finally, a theoretical model is developed and validated for the range of a large firefighting water jet including the effects of jet breakup and air entrainment