Similarity of the concentration field of gas-phase turbulent jets

This work is an experimental investigation of the turbulent concentration field formed when the nozzle gas from a round, momentum-driven, free turbulent jet mixes with gas entrained from a quiescent reservoir. The measurements, which were made with a non-intrusive laser-Rayleigh scattering diagnostic at Reynolds numbers of 5000, 16000, and 40000, cover the axial range from 20 to 90 jet exit diameters and resolve the full range of temporal and spatial concentration scales. Reynolds-number-independent and Reynolds-number-dependent similarities are investigated. The mean and r.m.s. values of the concentration are found to be consistent with jet similarity laws. Concentration fluctuation power spectra are found to be self-similar along rays emanating from the virtual origin of the jet. The probability density function for the concentration is also found to be self-similar along rays. Near the centreline of the jet, the scaled probability density function of jet fluid concentration is found to be nearly independent of the Reynolds number

Pekeris waveguide comparisons of methods for predicting acoustic field amplitude uncertainty caused by a spatially uniform environmental uncertainty (L)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98654/1/JAS000589.pd

On Mixing and Structure of the Concentration Field of Turbulent Jets

This work is an investigation of the mixing of the nozzle fluid of a round turbulent jet with the entrained reservoir fluid, using laser-Rayleigh scattering methods. Our measurements, at a Reynolds number of 5000, cover the axial range from 20 to 80 jet exit diameters and resolve the full range of temporal & spatial concentration scales. The measured mean & rms values of the concentration, and the mean scalar dissipation rate, when estimated from the time derivative of concentration, are consistent with jet similarity laws. Concentration fluctuation power spectra are found to be self-similar along rays emanating from the jet virtual origin. The probability density functions for the concentration, the time derivative of concentration, and the square of the time derivative of concentration, are compiled and are also self-similar along rays

Particle image velocimetry in molten plastic

Injection molding is a standard manufacturing process for plastic parts. The most important process step, mold filling, involves unsteady nonisothermal flow of a non-Newtonian molten plastic. Mold-filling flow largely determines molecular orientation within the final part and thereby influences final part properties. This article describes techniques for successfully applying particle image velocimetry (PIV) to molten plastic flow during injection molding. The primary experimental challenges include the following: engineering optical access to the molten plastic flow at elevated temperatures (230–245°C) and pressures (∼20 MPa), finding particles that survive the thermal-mechanical environment that melts the plastic, and developing experimental and data-reduction techniques that allow multiple imperfect planar PIV measurements to be combined. Here, a custom optical-access mold allowed mold center-plane PIV to be performed in molten polystyrene. Simple statistical assessments of the velocimetry data and scaled residuals of the continuity equation suggest that the PIV can be conducted in molten plastics with an uncertainty of ±2%. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics EngineersPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83457/1/21881_ftp.pd

Hijacking Journalism: Legitimacy and Metajournalistic Discourse in Right-Wing Podcasts

Whereas personal expression has become a core practice of journalism whose merits can include greater attention to context and interpretative analysis, these freedoms from the constraints of traditional broadcast conventions can pose serious risks, including the ideological hijacking of journalism by partisan actors. In popular right-wing podcasts, such as those hosted by Ben Shapiro and Dan Bongino, the element of opinion amplifies the tendency of the podcast medium to relegate news to a secondary concern behind the emotional impact. Not only do podcasters like Shapiro and Bongino contribute to a fractured media environment of hyper-partisan news and commentary, but they also utilize social media platforms and transmedia networks to undermine traditional journalism and replace it with an alternative conservative media ecosystem - a multiplatform, full-service clearinghouse of news and commentary afforded by the publishing capabilities of the internet and the distribution algorithms of social media platforms like Facebook. This study charts the evolution of conservative audio production, from the influential work of talk radio star Rush Limbaugh through the latest innovations by conservative podcasters, as exemplified by Shapiro and Bongino. Our study builds on previous scholarship on metajournalistic discourse to examine how right-wing podcasters use exclusionary language to delegitimize the institution of journalism and offer a self-contained, ideologically conservative version of journalism as a replacement

The Vortex-Boundary Element Method - New pressure methods for application to the external flow noise problem

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76655/1/AIAA-1999-3283-148.pd

Four-dimensional laser induced fluorescence study of the structure of molecular mixing in turbulent flows

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77075/1/AIAA-1994-820-515.pd

High-sensitivity photoacoustic leak testing

The photoacoustic effect may be exploited for the detection and localization of gas leaks from otherwise sealed components. The technique involves filling the test component with a tracer gas, and radiating the component to produce photoacoustic sound from any leak site where tracer gas is present. This paper describes demonstration experiments utilizing 10.6-µ radiation from a carbon-dioxide laser and sulfur hexafluoride as a tracer gas for photoacoustic leak testing at leak rates between 6×10–5 cm3/s (1 cm3 in 4.6 h) and 5×10–9 cm3/s (1 cm3 in 6.3 years). The technique may reach or exceed the capabilities of the most sensitive commercial leak test systems using helium mass-spectrometers. In addition, comparison of the measured results to a simple scaling law suggests that tracer gas cloud geometry influences the photoacoustic signal amplitude

Valuing the Pasture Resource - Importance of Perennials in Higher Rainfall Regions of South Eastern Australia

The premature decline of perennial grass based pastures in southern temperate Australia results in poor productivity and unstable pastures that allow invasion by less desirable weedy species and the potential for soil degradation. The loss of perennial species is attributed to overgrazing arising from an undervaluation of the pasture resource. Resowing pastures is largely uneconomic so maintenance of, or increasing the perennial, is dependent on improved grazing and pasture management practices. A key to changing perceptions is valuing the true worth of the perennial component. Results are presented from a model that takes into account the seasonality of production of pastures of different composition. The model uses specific metabolically energy values for the different functional groups that are typically within pastures (perennial grasses, annual grasses, legumes, broadleaf species) and livestock demand, to estimate animal performance and then gross margins for different pasture types. The results show that the value of perennial grasses is much greater than any other component and the more perennial grass, the greater the returns. The potential use of this approach to provide more useful information to landholders, permitting more appropriate management decisions to be made, is described