Ivan Marusic - US grants

The objective of the proposed reserch is to develop a new class of data analysis methods. This will involve on-the-fly identification of physically-important events selectively store the data. This database will then be interrogated by feature extraction algorithms to yield an additional object database, which is a compact representation of the physically important space-time object trajectories. These database objects will be used as input to novel data mining methods to discover causal relationships between the objects. This approach will result in efficient storage of data, visualization of the important events within the data set, and methods for the high-level analysis of relationships between objects in the data.

The zero pressure gradient turbulent boundary layer, the subject of this study, is the prototype flow for a vast number of technologically important devices (aircraft/ship/vehicle drag, industrial processes, etc.). It will receive a "fresh look' in this research as the PI brings focus to a plausible and an evolving theoretical construct of the of the basic mechanics which are responsible for the important attributes of this ubiquitous flow field. The experiments to be executed will also involve a significant perturbation: a moving belt as the wall boundary, that will dramatically alter the hypothesized source effect for the coherent motions in the flow.

It is expected that this research will provide quite significant data and insight for this very important flow field.

Abstract
Information Technology Research (ITR) Medium Proposals


Proposal Number: CTS-0324898
Principal Investigator: Ivan Marusic, Victoria Interrante, and Ellen Longmire
University/Institution: University of Minnesota

ITR: Dynamic methods for Identifying, Visualizing and Tracking Eddy Evolution in Experimental Turbulent Flows
This research program unites data visualization and experimental fluid mechanics specialists to investigate and understand the dynamic evolution of key physical mechanisms in turbulent flows. To accomplish this, the evolving nature of eddies, or vortex structures, fundamental building blocks in wall-bounded turbulent flows, will be examined. Experiments will track, in real time, vortex packets, which are structures that have been identified as a key mechanism in producing skin-friction drag in these flows. A dual stereo-PIV system will be traversed along the length of a water channel flow while implementing a feature-identification scheme based on visualization tools to generate a feedback signal. The experiments and feature detection strategies will provide answers to unique and challenging questions about the generation, development, merging and interaction, and breakdown of vortex packet structures and other dominant flow features in wall turbulence. Multivariate visualization methods appropriate for the novel experimental data will be developed. The methods will be applied to see what structures exist, and how they develop and decay. Because vortex packets are characterized by several parameters, the challenge is to present the visualization in a meaningful and useful way to turbulence practitioners. The multivariate visualizations will be optimized with special attention paid to quantifying how and why different visual features, such as color, texture, topography, and motion, work to convey information efficiently and effectively.
This research will provide, direct insight into the dynamic evolution processes of key physical mechanisms in wall turbulence at moderate to high Reynolds numbers. The new insight will constitute a major advance in the fundamental understanding of turbulent boundary layer flows and can lead to new drag reduction strategies and new turbulence simulation schemes. Also, visualization methods suited to complex turbulent flows will be developed that will prove useful to the broader turbulence community as well in researchers in additional fields. This research will lead to unique movies of vortex evolution that will be developed into an educational resource for graduate programs and broader scientific audiences. In addition to graduate students, undergraduates and high school physics teachers will participate in short-term investigations during the summers. The teachers are expected to bring their experiences with cutting edge measurement techniques and engineering applications back to the classroom.

Proposal No. CTS-0320327
Principal Investigator: E. Longmire, University of Minnesota

This grant is for a unique instrumentation system to be developed for simultaneous characterization of microscopic and macroscopic flow evolution. The system will first be used to examine two flows, which by their nature are characterized by a wide range of scales: turbulent and interfacial flows. The system, which will be developed in collaboration with LaVision, Inc, will include the required illumination and imaging optics to apply the Stereo-Particle Imaging velocimetry technique simultaneously at two magnifications and at repetition rates high enough to characterize the flow evolution. In addition, custom calibration targets and software as well as custom analysis software will be developed in order to achieve results of high accuracy in the overlapping smaller and larger fields of view. In the smaller field of view, the system will be able to resolve velocity vectors in areas of (100 square micrometer) or less, while the larger field of view may cover an area of (10 square cm) or more. These aspects will allow for observation and characterization of the evolving microscopic scales in the context of the macroscopic behavior. After the system is developed, it will be employed immediately in studies of turbulent boundary layers and drop coalescence.

The instrumentation described will provide revolutionary advances in the understanding of both coalescence at interfaces and the interaction of eddies in turbulent boundary layers. Also, the availability this system will allow for novel and groundbreaking research in additional areas of fluid dynamics including, for example, laminar/turbulent transition, control of macroscopic flows with MEMS, liquid jet and drop break up, three-dimensional instabilities, and turbulent separated flows.

The proposed system, which could become a product supported by multiple vendors, is expected to be useful to researchers in many areas of fluid dynamics. At the University of Minnesota, several graduate students will be involved with the proposed system. One will design, develop, and integrate the system hardware and software, and others will use the system for the research projects described above. Also, undergraduate researchers and high school physics teachers, funded by REU and RET supplements, will perform and participate in short-term investigations during the summers. The teachers are expected to bring their experiences with cutting edge measurement techniques and engineering applications back to the classroom.

This project will study ways of substantially increasing the efficiency of a novel way of generating electricity from the wind. Flag-like elements (termed piezoelements) composed of flexible piezoelectric materials will be positioned in the wind, which will cause the element to flap in a manner similar to a waving flag. The stresses induced in the piezoelectric material by the flapping will generate a voltage (due to the piezoelectric material properties) between the electrodes positioned on the surfaces of the piezoelement and thus electrical power in a connected load. Three specific areas of research will be addressed to increase the overall generation efficiency (output electrical power divided by input wind power). First, the geometry (length, width, thickness, and stiffness) of the piezoelement will be optimized in order to obtain the maximum flapping amplitude (and thus conversion of incident wind energy to strain energy in the piezoelectric material). Second, several different flexible piezoelectric materials will be characterized to find the material that most efficiently converts strain energy in the material into electrical energy. Third, a variety of interface electronic circuits whose function is to convert the voltages generated by the piezoelement into the amplitudes and frequencies needed for a particular application will be studied in order to develop a very efficient interface circuit. The proposed scheme is mechanically simple and potentially low cost. The amount of power that could potentially be generated will scale with the size and number of piezoelements placed in the wind. This source could supplement existing sources such as solar cells, batteries, and gasoline generators in military, industrial, and consumer environments and for temporary emergency power.