The free shear layer coming out from the lip of an asymmetric two-dimensional supersonic nozzle in a Ludweig tube wind tunnel is investigated. Newly developed procedures for Laser Induced Fluorescence (LIF) of NO$\sb2$ are utilized as the main diagnostic technique in conjunction with the new Direct Estimation Velocimetry (DEV) to produce density and velocity measurements at sampling rates in excess of 2 MHz. Both two- and three-dimensional configurations of LIF are utilized with success. Comparable measurements of density and velocity over several runs prove to be readily reproducible in their turbulent parameters. Three-dimensional LDV is used to calibrate DEV and shows excellent agreement. For the first time ever at these sampling rates, the cross-stream component of vorticity is measured and shows periodic "bursts", which is a consistent observation with other researchers. PLIF signals, recorded on an intensified framing camera equipped with a Charge-Coupled Device (CCD) using a thin sheet of laser light, show the nonturbulent nature of the flow at the beginning of the free shear layer and large streaky structures at the center of the shear layer. The characteristic scales of the existing turbulence are calculated using the spectral and dimensional analyses, and shown to be consistent with scales for the expected turbulence. Collected data are tested for the ergodic hypothesis of turbulence and the spectral indices for all different runs and different intervals of time fall in to a range of 1.65 $\pm$.05. Each component of the Reynolds stress tensor is measured and subsequently the total Reynolds stresses terms are computed; contribution of the turbulence compressibilty terms to the total Reynolds stress is measured to be 68%; the triple correlation term, $\rm\langle\rho\sp\prime u\sb{i}\sp\prime u\sb{j}\sp\prime\rangle,$ is measured for the first time / in this type of a flow and accounts only for 0.475 $\pm$ 0.325%. Seven different closure models as suggested by various researchers are evaluated using the results obtained in the present investigation. The mean value of the triple correlation terms measured is 0.029 $\pm$ 0.04 which appears to tentatively confirm the natural closure of turbulence theory which predicts vanishing triple, and higher order correlation terms. / Source: Dissertation Abstracts International, Volume: 57-02, Section: B, page: 1382. / Major Professor: Joseph A. Johnson, III. / Thesis (Ph.D.)--The Florida State University, 1996.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77660 |
| Contributors | De Silva, Upul Pradeep., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 146 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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