8,515 research outputs found
Aeroacoustics of isolated and installed jets under static and in-flight conditions
No full textIn modern aircraft configurations, the interaction between the exhausted jet with the wing and high-lift devices is set to increase substantially the total aircraft noise generated during take-off. Regarding ultra-high bypass ratio turbofan engines mounted underneath the wing, the jet plume is expected to interact strongly with rigid surfaces. The interaction between the high-speed flow and aircraft structures modifies the ‘pure’ jet mixing noise and enhance the scattered hydrodynamic field. Thus, understanding the changes to the jet turbulence flow field caused by the presence of a solid boundary is vital to predict and mitigate the engine noise produced by commercial aircraft which will be introduced imminently.In this thesis, the statistics of the streamwise component of the velocity of subsonic jets is investigated in detail. In close-coupled installed jet configurations, the interaction between the jet and a rigid surface leads to a local flow acceleration and to lower turbulence levels near the solid boundary. These effects are consistent with the conservation of momentum and the ‘beak-down’ of the eddies in that region. The characteristic length scales of these installed jet configurations are smaller than the isolated jet scales. The effects of forward flight upon the turbulence field is also considered. A stretching factor with flight velocity is obtained by considering the jet virtual origin. Models for the coherence decay, time and length scales are proposed based on experimental evidence and the assumption of frozen turbulence in the region of maximum turbulence kinetic energy. For the first time, two-point statistic models are proposed for high-subsonic and installed jet configurations. Finally, analysis of the far field of installed jets show that a strong interaction between the jet turbulence field and a solid boundary generates an additional high-frequency noise. Thus, the existence of a noise source mechanism related to the flow-structure interplay is demonstrated. It is hoped that the experimental data and analysis presented in this work provide feedback for jet noise source modelling and also future numerical and large-scale laboratory experiments
Blockage effects on the pressure field of 3D-printed small-scale jet nozzles
No full textThis paper presents a preliminary investigation into the pressure fields of jets exhausting from partially blocked nozzles. Measurements are performed for a series of asymmetric, smallscale, single stream nozzles mimicking the bypass flow from an engine-pylon-wing configuration. The hydrodynamic and acoustic pressure fields of the pylon nozzles are compared to data from an axisymmetric, annular jet baseline nozzle. For the good aerodynamic pylon designs, the isolated jet mixing noise source is slightly modified at azimuthal angles near the blockage. The blockage effects on the installed jet-wing interaction noise source are also small, even when corrections for thrust are applied. In-flight data suggest that a significant increase in the pressure levels exist at relatively high flight-to-jet-velocity ratios for the blocked configurations. For the poorly aerodynamically designed blockages, flow separation occurs close to the nozzle exit. This flow separation induces an augmentation of the jet noise sources. The near-field pressure data shows that the main effects of the pylon are, firstly, an increase in the strength of the hydrodynamic pressure field perpendicular to the pylon surface due to vortex shedding and, secondly, a fast recovery of symmetry downstream of the pylon trailing edge
Investigation into the turbulence statistics of installed jets using hot-wire anemometry
No full textThis work presents a detailed study of theturbulence flow statistics of a jet mounted with its axisparallel to a rigid flat plate. Hot-wire constant tem-perature anemometry has been used to measure thesingle-point and two-point statistics of the axial velocitycomponent at several locations within the jet flow field.Results show that the jet mean flow near the plate sur-face is subjected to a local acceleration and redirectiondue to a Coand ̆a-type effect. The propagation of theseeffects downstream of the plate trailing edge are stronglydependent on the plate position. Regarding the velocityfluctuations, the mean turbulence intensity levels areseen to decrease as the radial distance between the jetand surface decreases. Analysis of the single-point powerspectral density data on the shear layer close to the plateshows that the reduction in magnitude of the low fre-quency content of the energy spectrum is responsiblefor the decrease in turbulence intensity. Additionally,the characteristic time and length-scales computed fromtwo-point measurements reduce as the plate is mountedcloser to the jet centre-line. The axial eddy convectionvelocity is seen to increase in the region of high turbulentkinetic energy in the shear layer adjacent to the surface.Empirical models for turbulence characteristic scalesand eddy convection velocity are presented. These find-ings suggest that both the amplitude and distributionof the jet mixing noise sources are affected when closelyinstalled next to a surface. This paper is a continuationof a recent investigation on the turbulence statistics ofisolated jets presented in Proen ̧ca et al. (2019
Chapter 14: MD Anderson Publications and Publication Ethics
No full textDr. Goepfert has served on a number of editorial boards and is keenly interested in the educational dissemination of information critical to cancer research. In this section he talks about some of MD Anderson’s publications and also addresses some controversies with publication. He first raises the ethical issue of how authorship is assigned to a manuscript going out for publication. Today there are guidelines for assigning authorship, but twenty years ago, he explains, some department chairs at MD Anderson reviewed all manuscripts going for publication and insisted on being listed as first author of an article, whether they made any contribution to the research or not. Dr. Goepfert contrasts his own practice of putting his name on a paper only if he has contributed. Dr. Goepfert then shifts subjects and describes several MD Anderson educational publications, beginning with Cancer Bulletin, distributed free to all physicians across Texas.https://openworks.mdanderson.org/mchv_interviewchapters/2010/thumbnail.jp
Promise - Spring 2020
No full textRogers Award honors MD Anderson nursing assistant MD Anderson awards highest nursing honor Low-grade serous ovarian cancer survivor establishes research nonprofit Celebrity Chef Cooking Demo makes young cancer patients sous-chefs for a day Bob’s Encore: hope in the fight against pancreatic cancer Board of Visitors welcomes seven new members Board of Visitors awards highest distinction to longtime member A Conversation with a Living Legend raises 2 million for cancer research, education and prevention Get to know Advance Team’s Laura Nelson Cookbook author leaves her mark on gastric cancer researchhttps://openworks.mdanderson.org/promise/1001/thumbnail.jp
Chapter 09: Strengthening Biomedical Editing Nationwide and Within MD Anderson
No full textIn this Chapter, first briefly notes his involvement with the Southwest Chapter of the American Medical Writer’s Association and the Council of Biology Editors (with a 22-year membership). He then explains that he had his biggest impact while he served on the Board of Editors in the Life Sciences and in the late 80s worked on the Editorial Certification Examination Development Committee. He describes the examination he helped create to certify competence for editors of biomedical articles and explains the significance of certification. He notes that the Department of Scientific Publications at MD Anderson uses its own battery of tests to evaluate editors’ abilities for abstract reasoning, grammar, and other skills and talents.
Next, Mr. Pagel talks about his Department’s blog, “The Write Stuff,” and two significant projects: his role on the Historical Resources Center Steering Committee, and the development of panel discussions for the Department of Scientific Publications. To begin the discussion of the Steering Committee, he notes that Scientific Publications wrote The First Twenty Years, the first history of MD Anderson. Because of this association with the institution’s history, Mr. Pagel was asked to be part of the Steering Committee when the Historical Resources Center was formed and set as its first goal the publication of an updated institutional history. Mr. Pagel wanted the perspective to be broader than the first book, situating MD Anderson and cancer research in a larger context of other cancer institutions and the history of cancer research. Though not alone in holding this view, he says he had something to do with articulating it for the benefit of the Steering Committee. He describes how James Olsen was selected to be the author and notes other Steering Committee activities.https://openworks.mdanderson.org/mchv_interviewchapters/2275/thumbnail.jp
Experimental study on the aerodynamics of a high subsonic jet interacting with a flat plate
No full textUnderstanding the turbulent structures and noise source mechanisms resulting from the interaction between the exhausted jet with wing and high-lift devices is essential for both aerodynamic efficiency and noise reduction of the modern aircraft. This work presents an experimental investigation of the mean velocity and turbulence intensity (TI) profiles from an isolated jet and a jet installed beneath a flat plate. Both campaigns are performed in static ambient flow condition and at low and high subsonic velocity. A hot-wire anemometer was used to evaluate the mean velocity and TI for radial and axial profiles. From analysis of the mean velocity, it is evident that a Coandă effect exists in the installed jet case downstream of the trailing edge of the flat plate. The jet is seen to bend towards the plate. A comparison between isolated and installed configurations shows that the presence of the plate also serves to convect the jet asymmetrically downstream (similar to an ejector). Values of mean TI are lower along the shielded lip-line (closest to the plate) than along the unshielded lip-line. Directly after the trailing edge, there is an increase in TI. This fact supports the theory that an additional turbulent structure or wake is created
Chapter 09: Reflections on Dr. Clifton Mountain and Data Collection Roles at MD Anderson
No full textMrs. Hermes begins this chapter with memories of how much she enjoyed working for Dr. Mountain over the course of 25 years. He taught her how to think about data, she explains, and she was listed as an author on a number of publications on lung cancer [see examples below]. She explains that Dr. Mountain left MD Anderson in 1993, but she continued to work freelance for him. She recalls that he set up the first conference on mathematics at MD Anderson, early in his career sometime in the sixties.
Next she comments on how the unique openness of Houston culture fit well with the bold visions that both R. Lee Clark and Eleanor MacDonald held for oncology. She says that her most important work was on Dr. Mountain’s staging system for lung cancer and she explains why staging the disease presented challenges.
She confirms that she was always interested in the implications of basic research for clinical findings. She credits Eleanor MacDonald for helping her to develop her curiosity and questioning style.https://openworks.mdanderson.org/mchv_interviewchapters/2036/thumbnail.jp
The effects of internal nozzle blockage in a single stream jet on far-field jet mixing noise
No full textOver the last half century, major reductions in jet mixing noise from aircraft engines have been possible from the study of isolated, axisymmetric jets. However, the impact on noise due to asymmetric effects, like the presence of a pylon connecting the wing to the engine, is not yet fully understood. In this study, the authors seek to establish whether azimuthal changes to the far-field jet noise introduced by the pylon can be predicted using a method called Lighthill's analogy with Ray Tracing (LRT) which is based on a k-ε RANS CFD model. One baseline annular and three increasingly internally blocked single-stream jets are studied and compared to model-scale experimental data. The k-ε RANS model is observed to sufficiently capture the deficit in the axial velocity and turbulent intensity, to within 1 and 0.5%, respectively, from the wake that forms immediately behind the blockage. The RANS CFD does, however, slightly under-predict the TI after 5 effective diameters compared to the experiment data. The increase in pylon thickness is seen to increase the mixing noise present at a polar angle of ninety degrees. At this polar angle, the high frequency modifications to the far field sound pressure level as a function of percentage blockage are captured to within 1 dB of the experimental data. The largest blockage is seen to introduce an additional vortex noise source at mid-Strouhal numbers, which is not modelled by LRT. This blockage is also observed to locally increase the turbulence levels and, therefore, the strength of the fine-scale acoustic sources at St≥2. The authors believe this to be due to the additional mixing of counter-rotating axial vortices. RANS-based noise predictions, using LRT, are shown to be capable of both indicating and diagnosing potentially noisy geometries quickly within an industrial context at the preliminary engine design stage
Anthropological Networks
No full textNot only have anthropologists contributed to the study of social networks, they have also created their own anthropological networks in order to communicate and collaborate while conducting their study of human behaviors.Anderson, K. E. (2011). Anthropological networks. In G. A. Barnett (Ed.), Encyclopedia of social networks (pp. 44-48). Thousand Oaks, Calif.: SAGE Publications.This is the author's final version of a chapter, Anthropological Networks, in Encyclopedia of Social Networks, George A. Barnett, editor. The published two volume work is available at http://www.sagepub.com/books/Book23436
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