Buoyancy Driven Turbulence Beyond Self-Similar Equilibrium

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0967672BanerjeeSelf similarity is an important concept that arises in the study of turbulent flows, in which an assumption is often made that memory of initial conditions (ICs) are lost at late time and the turbulence develops to a equilibrium (i.e. self similar) state. However, recent studies have indicated that only special turbulent flows are truly self similar. Experiments and computations in buoyancy driven turbulence have indicated that late time turbulence can be affected by ICs seeded into the flow and memory of these ICs are not lost. This presents a remarkable opportunity to predict and design late time buoyancy driven turbulence that leaves behind the fully developed equilibrium concept, and embrace late time turbulence through prescribed ICs that either enhance, or suppress, or maintain turbulence intensity/structure in these flows. The objective of the proposed research program is to evaluate late-time signatures of ICs that will result in a better understanding of mix dominated buoyancy problems with widespread applications in heat exchangers, chemical reactors, climate dynamics, pollutant dispersion, inertial confinement fusion, and, astrophysical flows. The research includes experiments and simulations. The experimental thrust will involve a novel two wheel high acceleration experiment that uses controlled ICs to experimentally study the late time turbulent material (molecular) mixing for RT flows. High fidelity diagnostics which include a combined fast-Particle Imaging Velocimetry/Planar Laser Induced Fluorescence (f-PIV/PLIF). This will provide detailed data of ICs in each experiment, and field measurements of flow velocities, statistical probability density functions of density, velocity fluctuations and associated turbulence correlations and cross correlations. In addition, implicit Large Eddy Simulations (ILES) are planned to cross-couple with the experiment via validation and verification (V&V) of the simulation and therefore provide additional detailed data sets to study the late-time effect of designed ICs. Intellectual Merits:The intellectual merits of the proposed work involve usage of the experimental and computational data sets to: (a) examine the role of ICs to control the molecular mixing dynamics; (b) provide valuable information on active control of turbulent mixing as occurs in various applications of such flows. In addition, the proposed research is expected to result in new discoveries about the mixing process which can also be used to extend turbulence theory beyond the traditional ideas of Kolmogorov which is related to the existence of inertial range dynamics and small scale universality. Broader Impacts:The proposed research extends well beyond our interest in buoyancy driven flows and incorporates the possibility of systematically designing initial and boundary conditions for passive control of late time turbulence. On the educational front, it will help support two graduate students and will introduce students to cutting edge research ideas in a graduate level course on Turbulent Flows. Undergraduate researchers will be included through the Missouri S&T-OURE (Opportunities for Undergraduate Research Experience) program. The students who will perform the bulk of this research will be actively recruited from underrepresented groups (women and minority) at Missouri S&T through the Women in Science & Engineering (WISE) program on campus. In addition, active collaboration with Los Alamos National Laboratory (LANL) will aid in the potential impact of this work and is expected to result in future research opportunities for graduate students upon completion of their degrees.