Submitted - Analytical_and_Experimental_Investigation_of_a_Turbulent_Mixing_Layer...Manuel_R._Rebollo.pdf

", "abstract": "An analytical and experimental study has been made of the\nturbulent mixing layer in a pressure gradient. Theory predicts the possible existence of equilibrium flows, and this was confirmed experimentally for turbulent shear layers between streams of helium and nitrogen.\n\nThe only case for which similarity is possible is for\n\u03c1_2U_2%2 = \u03c1_1U1^2, since then P_2(x) = P_1(x). These equilibrium flows are of the form U_1 ~ x^\u03b1 and \u03b4 ~ x where \u03b1 = u/U-1 dU_1/dx is a non-dimensional pressure gradient parameter.\n\nThe experimental investigation was conducted in the facility\ndesigned by Brown to produce turbulent flows at pressures up to 10 atmospheres. The adjustable walls of the test section of the apparatus were modified in order to set the pressure gradient.\n\nShadowgraphs of the mixing zone for \u03b1 = 0 and \u03b1 = - 0.. 18, at different Reynolds numbers, revealed a large scale structure noticeably different for each \u03b1.\n\nThe similarity properties of the shear layer were established from mean profiles of total head and density. In addition, the rms density fluctuations were found to be self-preserving. From the mean profiles, the spreading rate, turbulent mass diffusion, Reynolds stress\nand Schmidt number distributions were calculated from the equations of motion.\n\nThe experimental results show that the spreading rate for the adverse pressure gradient is 60% greater than for the \u03b1 = 0 case. The maximum shearing stress is 70% larger and the maximum value of the turbulent mass diffusion is 20% larger than their \u03b1 = 0 counterparts. The maximum rms density fluctuations are approximately O.2 in both\nflows.\n\nSurprisingly low values of turbulent Schmidt numbers were\nfound; e.g. , at the dividing streamline Sc_t ~ 0.16 for \u03b1 = 0 and Sc_t = 0.33 for \u03b1 = -0.18.", "date": "2015-12-03", "date_type": "published", "publisher": "California Institute of Technology", "id_number": "CaltechAUTHORS:20151130-142322868", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151130-142322868", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Office of Naval Research (ONR)", "grant_number": "N00014-67-A-0094-0001" } ] }, "primary_object": { "basename": "Analytical_and_Experimental_Investigation_of_a_Turbulent_Mixing_Layer...Manuel_R._Rebollo.pdf", "url": "https://authors.library.caltech.edu/records/mckmn-apd82/files/Analytical_and_Experimental_Investigation_of_a_Turbulent_Mixing_Layer...Manuel_R._Rebollo.pdf" }, "resource_type": "monograph", "pub_year": "2015", "author_list": "Rebollo, Manuel R." } ]