Prediction of Turbulence-Generated Noise in Unheated Jets. Part 1; Jeno Technical Manual (Version 1. 0)


Book Description

The model-based approach, used by the JeNo code to predict jet noise spectral directivity, is described. A linearized form of Lilley's equation governs the non-causal Green s function of interest, with the non-linear terms on the right hand side identified as the source. A Reynolds-averaged Navier-Stokes (RANS) solution yields the required mean flow for the solution of the propagation Green s function in a locally parallel flow. The RANS solution also produces time- and length-scales needed to model the non-compact source, the turbulent velocity correlation tensor, with exponential temporal and spatial functions. It is shown that while an exact non-causal Green s function accurately predicts the observed shift in the location of the spectrum peak with angle as well as the angularity of sound at low to moderate Mach numbers, the polar directivity of radiated sound is not entirely captured by this Green s function at high subsonic and supersonic acoustic Mach numbers. Results presented for unheated jets in the Mach number range of 0.51 to 1.8 suggest that near the peak radiation angle of high-speed jets, a different source/Green s function convolution integral may be required in order to capture the peak observed directivity of jet noise. A sample Mach 0.90 heated jet is also discussed that highlights the requirements for a comprehensive jet noise prediction model.Khavaran, Abbas and Bridges, James and Georgiadis, NicholasGlenn Research CenterNOISE PREDICTION; TURBULENCE; JET AIRCRAFT NOISE; CONVOLUTION INTEGRALS; EXPONENTIAL FUNCTIONS; MACH NUMBER; MATHEMATICAL MODELS; SUPERSONIC SPEED







Grinding And Lapping


Book Description

This book is a comprehensive guide to grinding and lapping techniques. It covers everything from basic concepts to advanced tips and tricks, making it an essential resource for professionals and hobbyists alike. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.







I Have a Dog


Book Description

I have a dog. An inconvenient dog. When I wake up, my dog is inconvenient. When I'm getting dressed, my dog is inconvenient. And when I'm making tunnels, my dog is SUPER inconvenient. But sometimes, an inconvenient dog can be big and warm and cuddly. Sometimes, an inconvenient dog can be the most comforting friend in the whole wide world.




Social Work


Book Description

The second edition of this text has been thoroughly revised and updated to ensure that it continues to provide a comprehensive survey of social work practice and theory. New chapters covering the changing nature of social work and advocacy and empowerment approaches have been included, and the editors have added a new conclusion in which they reflect on the past, present and future of social work. All of the chapters have been revised to cover the most recent debates and developments in research and practice.




The Dare


Book Description

Jessica Martin is not a nice girl. As Prom Queen and Captain of the cheer squad, she'd ruled her school mercilessly, looking down her nose at everyone she deemed unworthy. The most unworthy of them all? The "freak," Manson Reed: her favorite victim. But a lot changes after high school. A freak like him never should have ended up at the same Halloween party as her. He never should have been able to beat her at a game of Drink or Dare. He never should have been able to humiliate her in front of everyone. Losing the game means taking the dare: a dare to serve Manson for the entire night as his slave. It's a dare that Jessica's pride - and curiosity - won't allow her to refuse. What ensues is a dark game of pleasure and pain, fear and desire. Is it only a game? Only revenge? Only a dare? Or is it something more? The Dare is an 18+ erotic romance novella and a prequel to the Losers Duet. Reader discretion is strongly advised. This book contains graphic sexual scenes, intense scenes of BDSM, and strong language. A full content note can be found in the front matter of the book.




Green History


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Charting the origins of the modern ecology movement over more than two thousand years, this volume gives a voice to those hidden from history, revealing "green" themes within artistic and scientific thought.




Noise Produced by Turbulent Flow Into a Rotor


Book Description

A users manual for a computer program for predicting atmospheric turbulence and mean flow and turbulence contraction as part of a noise prediction scheme for nonisotropic turbulence ingestion noise in helicopters is described. Included are descriptions of the various program modules and subroutines, their function, programming structure, and the required input and output variables. This routine is incorporated as one module of NASA's ROTONET helicopter noise prediction program. Simonich, J. C. and Caplin, B. Unspecified Center NAS1-17763; RTOP 505-63-51...




Modeling of Turbulence Generated Noise in Jets


Book Description

A numerically calculated Green's function is used to predict jet noise spectrum and its far-field directivity. A linearized form of Lilley's equation governs the non-causal Green s function of interest, with the non-linear terms on the right hand side identified as the source. In this paper, contributions from the so-called self- and shear-noise source terms will be discussed. A Reynolds-averaged Navier-Stokes solution yields the required mean flow as well as time- and length scales of a noise-generating turbulent eddy. A non-compact source, with exponential temporal and spatial functions, is used to describe the turbulence velocity correlation tensors. It is shown that while an exact non-causal Green's function accurately predicts the observed shift in the location of the spectrum peak with angle as well as the angularity of sound at moderate Mach numbers, at high subsonic and supersonic acoustic Mach numbers the polar directivity of radiated sound is not entirely captured by this Green's function. Results presented for Mach 0.5 and 0.9 isothermal jets, as well as a Mach 0.8 hot jet conclude that near the peak radiation angle a different source/Green's function convolution integral may be required in order to capture the peak observed directivity of jet noise. Khavaran, Abbas and Bridges, James Glenn Research Center NASA/TM-2004-213105, AIAA Paper 2004-2983, E-14580