An Experimental Investigation of Organized Structure and Mixing in Compressible Turbulent Free Shear Layers PDF Download
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Author: Nathan Lee Messersmith Publisher: ISBN: Category : Languages : en Pages : 474
Book Description
The large scale structure and scalar transport characteristics of compressible turbulent mixing layers have been experimentally investigated at various levels of compressibility in order to study the fundamental effects of compressibility on the nature of the mixing layer. Nonintrusive optical diagnostic techniques were employed to image the large structures. Both Mie scattering from condensed ethanol droplets and laser-induced fluorescence from seeded nitric oxide were used. The LIF experiments were utilized to avoid potential particle dynamics effects associated with the Mie scattering experiments. Sizeable ensembles of digital images were collected for a variety of seeding styles, image planes and at three distinct flow conditions. Analysis of the samples provided mean and standard deviation profiles, two-dimensional spatial covariance fields and passive scalar probability density functions. In the transverse image plane, the dimensionless structure size and eccentricity increased, while the angular orientation of the structures with respect to the streamwise flow direction decreased, as the relative Mach number increased. Oblique views revealed significant three-dimensionality, and the structures imaged in this view also increased in dimensionless size with compressibility. Very little difference in the total probabilities of finding mixed fluid within the shear layer was found for flows with relative Mach numbers of 0.63 and 1.49. A relative Mach number 0.98 flow, however, demonstrated substantially lower mixed fluid probabilities, concomitant with a very high peak standard deviation. Instability mode interactions may be the cause of the disturbed nature of the mixing layer at this condition. The results from the Mie scattering and laser-induced fluorescence experiments for similar shear layer conditions were very comparable.
Author: Nathan Lee Messersmith Publisher: ISBN: Category : Languages : en Pages : 474
Book Description
The large scale structure and scalar transport characteristics of compressible turbulent mixing layers have been experimentally investigated at various levels of compressibility in order to study the fundamental effects of compressibility on the nature of the mixing layer. Nonintrusive optical diagnostic techniques were employed to image the large structures. Both Mie scattering from condensed ethanol droplets and laser-induced fluorescence from seeded nitric oxide were used. The LIF experiments were utilized to avoid potential particle dynamics effects associated with the Mie scattering experiments. Sizeable ensembles of digital images were collected for a variety of seeding styles, image planes and at three distinct flow conditions. Analysis of the samples provided mean and standard deviation profiles, two-dimensional spatial covariance fields and passive scalar probability density functions. In the transverse image plane, the dimensionless structure size and eccentricity increased, while the angular orientation of the structures with respect to the streamwise flow direction decreased, as the relative Mach number increased. Oblique views revealed significant three-dimensionality, and the structures imaged in this view also increased in dimensionless size with compressibility. Very little difference in the total probabilities of finding mixed fluid within the shear layer was found for flows with relative Mach numbers of 0.63 and 1.49. A relative Mach number 0.98 flow, however, demonstrated substantially lower mixed fluid probabilities, concomitant with a very high peak standard deviation. Instability mode interactions may be the cause of the disturbed nature of the mixing layer at this condition. The results from the Mie scattering and laser-induced fluorescence experiments for similar shear layer conditions were very comparable.
Author: Hall, Jeffery L Publisher: Ann Arbor, Mich. : University Microfilms International ISBN: Category : Electronic dissertations Languages : en Pages : 139
Book Description
Two-dimensional, compressible, turbulent shear layers are studied in a new wind tunnel facility. Both reacting and non-reacting flows are investigated, with one free stream velocity supersonic and the other subsonic. The combustion experiments are based on use of low concentrations of hydrogen, nitric oxide and fluorine gases. Side-view Schlieren photographs of these reacting and non-reacting flows appear devoid of the 2-D, large scale structures seen in incompressible flow. Comparison with all-subsonic flows produced in the same facility suggests that this lack of two-dimensional structure is due to the presence of the supersonic high-speed free stream velocity. Travelling shock and expansion waves are observed in the high compressibility flows, evidently created by turbulent structures convecting at supersonic velocities. Such waves are seen only in the low-speed fluid, with apparent convection velocities much higher than those predicted on the basis of isentropic pressure-matching arguments. The measured shear layer growth rates agree with previous results by other experiments, except for a few cases at low compressibility and low density ratio. The fast chemistry regime is attained in some of the high compressibility flows tested. 'Flip' experiments conducted in this regime indicated that the volume fraction of mixed fluid in the layer is substantially reduced as compared to previous incompressible results. These same flip experiments also reveal that compressibility significantly alters the entrainment ratio.
Author: Jeffery Lawrence Hall Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 139
Book Description
Two-dimensional, compressible, turbulent shear layers are studied in a new wind tunnel facility. Both reacting and non-reacting flows are investigated, with one free stream velocity supersonic and the other subsonic. The combustion experiments are based on use of low concentrations of hydrogen, nitric oxide and fluorine gases. Side-view Schlieren photographs of these reacting and non-reacting flows appear devoid of the 2-D, large scale structures seen in incompressible flow. Comparison with all-subsonic flows produced in the same facility suggests that this lack of two-dimensional structure is due to the presence of the supersonic high-speed free stream velocity. Travelling shock and expansion waves are observed in the high compressibility flows, evidently created by turbulent structures convecting at supersonic velocities. Such waves are seen only in the low-speed fluid, with apparent convection velocities much higher than those predicted on the basis of isentropic pressure-matching arguments. The measured shear layer growth rates agree with previous results by other experiments, except for a few cases at low compressibility and low density ratio. The fast chemistry regime is attained in some of the high compressibility flows tested. 'Flip' experiments conducted in this regime indicated that the volume fraction of mixed fluid in the layer is substantially reduced as compared to previous incompressible results. These same flip experiments also reveal that compressibility significantly alters the entrainment ratio.
Author: Steven George Goebel Publisher: ISBN: Category : Languages : en Pages : 460
Book Description
An investigation of compressible, turbulent mixing layers has been completed. The experiments were conducted using pressure measurements, schlieren photography and velocity measurements with a two-component laser Doppler velocimeter system. These diagnostic systems were developed for use with the mixing layer wind-tunnel facility. Many conditions were evaluated, and seven mixing layer cases were fully examined, with relative Mach numbers ranging from 0.40 to 1.97, which spans the region of significant compressibility effects. The spatial development and similarity of the mixing layers were examined, as well as the entrainment process and the effects of particle dynamics. Analyses to predict the mean density profiles, mean transverse velocity profiles, shape of the kinematic Reynolds stress profiles and entrainment mass fraction of a fully developed, compressible mixing layer were also developed. From the schlieren photographs, no organized, large-scale structures were observed to dominate the mixing layers under the conditions of this study. The development of the mixing layers required a Reynolds number (based on the freestream velocity difference and local mixing layer thickness) on the order of 1 $cdot$ 10$sp5$. In the fully developed regions of the mixing layers, it was found that transverse turbulence intensities and normalized kinematic Reynolds stresses decreased with increasing relative Mach number like the decreases measured in normalized growth rate, while the streamwise turbulence intensities and kinematic Reynolds stress correlation coefficients remained approximately constant. By examining the LDV velocity measurements from particles with different response characteristics, it was shown that particle dynamics effects were not a problem with these measurements. Also, by measuring velocity profiles on both sides of the wind-tunnel midplane, it was found that the flow fields were reasonably two-dimensional.
Author: Nathan Lee Messersmith
Author: Nathan Lee Messersmith![An Experimental Investigation of Structure, Mixing and Combustion in Compressible Turbulent Shear Layers [microform] PDF](https://books.google.com/books/content/images/frontcover/M51XnQEACAAJ?fife=w80-h100)
Author: Hall, Jeffery L
Author: Jeffery Lawrence Hall
Author: Steven George Goebel
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