2,886 research outputs found
Characteristics of vortex packets in turbulent boundary layers
No full textStereoscopic particle image velocimetry (PIV) was used to measure all three instantaneous components of the velocity field in streamwise–spanwise planes of a turbulent boundary layer at Reτ = 1060 (Reθ = 2500). Datasets were obtained in the logarithmic layer and beyond. The vector fields in the log layer (z+=92 and 150) revealed signatures of vortex packets similar to those proposed by Adrian and co-workers in their PIV experiments. Groups of legs of hairpin vortices appeared to be coherently arranged in the streamwise direction. These regions also generated substantial Reynolds shear stress, sometimes as high as 40 times —uw‾. A feature extraction algorithm was developed to automate the identification and characterization of these packets of hairpin vortices. Identified patches contributed 28% to —uw¯ while occupying only 4% of the total area at z+ = 92. At z+ = 150, these patches occupied 4.5% of the total area while contributing 25% to —uw¯. Beyond the log layer (z+ = 198 and 530), the spatial organization into packets is seen to break down.<br/
Interview with Ellen Frankfort, women's rights activist and author
No full textEllen Frankfort, author of Vaginal Politics and health columnist for the Village Voice, is interviewed by Winifred Ryhn and Claudine Shannon. She discusses health issues and feminist politics.GrayscaleSoun
Experimental investigation of vortex properties in a turbulent boundary layer
No full textDual-plane particle image velocimetry experiments were performed in a turbulent boundary layer with Re? = 1160 to obtain all components of the velocity gradient tensor. Wall-normal locations in the logarithmic and wake region were examined. The availability of the complete gradient tensor facilitates improved identification of vortex cores and determination of their orientation and size. Inclination angles of vortex cores were computed using statistical tools such as two-point correlations and joint probability density functions. Also, a vortex identification technique was employed to identify individual cores and to compute inclination angles directly from instantaneous fields. The results reveal broad distributions of inclination angles at both locations. The results are consistent with the presence of many hairpin vortices which are most frequently inclined downstream at an angle of 45? with the wall. According to the probability density functions, a relatively small percentage of cores are inclined upstream. The number density of forward leaning cores decreases from the logarithmic to the outer region while the number density of backward-leaning cores remains relatively constant. These trends, together with the correlation statistics, suggest that the backward-leaning cores are part of smaller, weaker structures that have been distorted and convected by larger, predominantly forward-leaning eddies associated with the local shea
Dual-plane PIV technique to determine the complete velocity gradient tensor in a turbulent boundary layer
No full textSimultaneous dual-plane PIV experiments, which utilized three cameras to measure velocity components in two differentially separated planes, were performed in streamwise-spanwise planes in the log region of a turbulent boundary layer at a moderate Reynolds number (Re 1100). Stereoscopic data were obtained in one plane with two cameras, and standard PIV data were obtained in the other with a single camera. The scattered light from the two planes was separated onto respective cameras by using orthogonal polarizations. The acquired datasets were used in tandem with continuity to compute all 9 velocity gradients, the complete vorticity vector and other invariant quantities. These derived quantities were employed to analyze and interpret the structural characteristics and features of the boundary layer. Sample results of the vorticity vector are consistent with the presence of hairpin-shaped vortices inclined downstream along the streamwise direction. These vortices envelop low speed zones and generate Reynolds shear stress that enhances turbulence production. Computation of inclination angles of individual eddy cores using the vorticity vector suggests that the most probable inclination angle is 35° to the streamwise-spanwise plane with a resulting projected eddy inclination of 43° in the streamwise-wall-normal plane.<br/
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Pinch off and reconnection in liquid/liquid flows: joint experimental and numerical studies
No full textLiquid/liquid systems appear in applications involving transport, mixing, and separation of petroleum, chemical, and waste products. Breakup and coalescence transitions often determine flow regimes as well as reaction and separation rates. Because they occur over very small time and length scales compared with the larger scales that dominate the flow, they are difficult to quantify experimentally and simulate numerically. Thus far, no accurate models exist for engineers to predict these flows. Experiments and computations were performed so that accurate engineering models can be developed. Jet pinch off and drop coalescence were examined in mixtures of water/glycerin and silicone oil. Index matching, laser sheet illumination, and the PIV method were applied to obtain visualization and velocity field sequences through transitions. The computations used a novel, physically-based method that captures interface breakup and coalescence automatically without resorting to ad-hoc cut-and-connect methods. To achieve enhanced accuracy near transitions, new adaptive time and space meshes were developed. The computations were validated through direct comparison with the experiments. The detailed results should lead to improved understanding of transition behavior. This understanding is needed to develop engineering models of multiphase flows. Such predictive models will lead to extensive cost savings in device and process design
Ellen Lupton
No full textEllen Lupton is a typographer, graphic designer, author, and Curator at the Cooper-Hewitt/Smithsonian Design Museum. Link to the artist\u27s website.https://egrove.olemiss.edu/art_talks/1006/thumbnail.jp
Conversations with authors: Ellen Steinbaum
No full textA 2011 conversation with the author Ellen Steinbaum about her life and the inspiration for her work
Ellen Vincent
No full textEllen Vincent was the author of Down on the Island, Up on the Main: A Recollected History of South Bristol, Maine, an honorary citizen of the Town of South Bristol, and a founder of South Bristol Historical Society (SBHS). Born in Washington, D.C. in 1949, Ellen grew up in a Maryland suburb outside of Washington, D.C., and graduated from high school in 1967. She received a B.A. in art education from the University of Maryland at College Park in 1971, and a Masters of Fine Arts from George Washington University in 1973. She began her academic career at the Maryland College of Art and Design and in 1989 moved to Milwaukee and the Milwaukee Institute of Art and Design where she was Professor of Art until illness kept her from the classroom. Ellen was the catalyst for a group of townspeople interested in local history to carry out the idea of a historical society, leading to the formation of SBHS in 1998. She passed away February 24, 2007 from breast cancer. Click here to read more about Ellen Vincent and her legacy in South Bristol.https://digitalcommons.library.umaine.edu/songstorysamplercollectors/1003/thumbnail.jp
Pride Author event: Ellen van Neerven in conversation with Kevin Yow Yeh
No full textTo celebrate Pride Month, 2021 at QUT, QUT Library, in conjunction with Equity Services and QUT Faculty of Health held an online author talk with award winning writer Ellen van Neerven, in conversation with Kevin Yow Yeh (QUT Faculty of Health). Held 19 October, 12-1pm
Flow Visualization Using Natural Textures
No full textThe use of natural textures provides a richly diverse set of possibilities for the visualization of flow data. In this paper, we present methods that utilize the qualities and attributes of natural textures to visualize multiple scalar distributions and multiple vector fields obtained across a 2D domain in a turbulent boundary layer flow. First, we illustrate how different attributes of textures can represent scalar quantities along streamlines. We then present a technique that allows for the perception of two separate vector fields within the same image by utilizing different textures. Finally, we illustrate how textures have the ability to indicate specific regions of interest within flow images.Urness, Timothy Matthew; Interrante, Victoria; Longmire, Ellen; Marusic, Ivan. (2005). Flow Visualization Using Natural Textures. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/215655
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