Viscous analyses for flow through subsonic and supersonic intakes

A parabolized Navier-Stokes code was used to analyze a number of diffusers typical of a modern inlet design. The effect of curvature of the diffuser centerline and transitioning cross sections was evaluated to determine the primary cause of the flow distortion in the duct. Results are presented for S-shaped intakes with circular and transitioning cross sections. Special emphasis is placed on verification of the analysis to accurately predict distorted flow fields resulting from pressure-driven secondary flows. The effect of vortex generators on reducing the distortion of intakes is presented. Comparisons of the experimental and analytical total pressure contours at the exit of the intake exhibit good agreement. In the case of supersonic inlets, computations of the inlet flow field reveal that large secondary flow regions may be generated just inside of the intake. These strong flows may lead to separated flow regions and cause pronounced distortions upstream of the compressor

Age and Growth of Hogfish (Lachnolaimus maximus) in Southeast Florida

Hogfish (Lachnolaimus maximus; Walbaum 1792) from Southeast Florida were aged using sectioned otoliths and growth rates were calculated using the von Bertalanffy growth equation. The samples were collected from Broward County (n=209); other regions of Southeast Florida (n=18), the Florida Keys (n=35) and Bahamas (n=43). Growth rates were determined for each of these areas and were then compared to previously reported growth rates from other regions including the eastern Gulf of Mexico and Florida Keys. There was significant separation at the 95% confidence level between growth rates from each reagion. The average maximum fork length increased, from the Florida Keys (336mm) to Southeast Florida (414-mm) by 78-mm. However, the annual survival rate was the same (S=61%) between these two regions and the maximum age of Southeast Florida (age 12) was still half that of the previously reported eastern Gulf (age 23). Broward County was divided into three reef zones each at different depths (5-m, 10-m, and 20-m) and growth rate and survival rate were compared between zones. Results showed a decrease in maximum fork length with reef depth (857-mm, 420-mm, 352-mm), as well as an increase in mean age (age 3, 4, 5), maximum age (9, 10, 12), and survival (42%, 65%, 73%), respectively. The decrease in observed growth rate of an area as a whole (e.g. Florida Keys) may represent an example of Lee’s phenomena caused by increased top-down selective fishing pressure. However, the growth rates of individual hogfish are most likely a result of differences in habitat and food resource availability. This study provides baseline age and growth information for hogfish in Southeast Florida prior to the recent changes to the fishery regulations, which will help fisheries management better understand the effects of alternative management strategies

Letter from A. N. Towne to Mr. Scott, 1876 Jul 5.

P.O. LOCK BOX 2328. Central Pacific Railroad Company GENERAL SUPERINTENDENT’S OFFICE San Francisco, Cal. July 5 1876.California Pacific R.R. ……………… 463 Steamer Lines ……………………….. 570 Stockton &C. and S.&V. Railroads …. 49 Southern Extension S.P.R.R. ………… 96 Central Pacific R.R. …………………. 1,219 ——— Miles ……………….. 2,097 5.16.76Mr. Scott, Supt. North Fork Mining Co [ Dutch Hill?]Dear Sir: I take much pleasure in intro- ducing the bearer, Mr. John Muir, a celebrated Geologist, of whom, no doubt, you have heard much. Mr. Muir is on his way to spend the summer in the high Sierras, and will probably call upon you to examine the gold deposits of your neighborhood. Any attention shown the Gentleman will be much appreciated by him and by Yours Truly A. N. [ Tome?] 0609

Letter from A. N. Towne to A. W. Kaddie, 1876 Jul 5.

P.O. LOCK BOX 2328. Central Pacific Railroad Company GENERAL SUPERINTENDENT’S OFFICE San Francisco, Cal. July 5 1876.California Pacific R.R. …………………. 163 Steamer Lines …………………………... 570 Stockton &C. and S.&V. Railroads …….. 49 Southern Extension S.P.R.R…………….. 96 Central Pacific R.R. …………………….. 1,219 ——— Miles …………… 2,097 5.16.76.A. W. Kaddie, Esq Supt. Cariboo Mining Co. Cariboo, Plumas Co Cal.Dear Sir: I take much pleasure in intro- ducing the bearer, John Muir, Esq., of whom no doubt you have heard much. Mr. Muir has devoted many years of hard stdy to the gold means of Cal. He is about to make a trip up north, and may reach Plumas C: to inquire into matters relative to the dead-river gravel deposits. Any attention shown the Gentleman will be much appreciated by him, and by Yours truly A. N. [illegible] 0609

Analytical modeling of circuit aerodynamics in the new NASA Lewis wind tunnel

Rehabilitation and extention of the capability of the altitude wind tunnel (AWT) was analyzed. The analytical modeling program involves the use of advanced axisymmetric and three dimensional viscous analyses to compute the flow through the various AWT components. Results for the analytical modeling of the high speed leg aerodynamics are presented; these include: an evaluation of the flow quality at the entrance to the test section, an investigation of the effects of test section bleed for different model blockages, and an examination of three dimensional effects in the diffuser due to reentry flow and due to the change in cross sectional shape of the exhaust scoop

Solutions to aliasing in time-resolved flow data

Avoiding aliasing in time-resolved flow data obtained through high fidelity simulations while keeping the computational and storage costs at acceptable levels is often a challenge. Well-established solutions such as increasing the sampling rate or low-pass filtering to reduce aliasing can be prohibitively expensive for large data sets. This paper provides a set of alternative strategies for identifying and mitigating aliasing that are applicable even to large data sets. We show how time-derivative data, which can be obtained directly from the governing equations, can be used to detect aliasing and to turn the ill-posed problem of removing aliasing from data into a well-posed problem, yielding a prediction of the true spectrum. Similarly, we show how spatial filtering can be used to remove aliasing for convective systems. We also propose strategies to avoid aliasing when generating a database, including a method tailored for computing nonlinear forcing terms that arise within the resolvent framework. These methods are demonstrated using large-eddy simulation (LES) data for a subsonic turbulent jet and a non-linear Ginzburg-Landau model.Comment: 25 pages, 14 figure

Modeling intermittent wavepackets and their radiated sound in a turbulent jet

We use data from a new, carefully validated, Large Eddy Simulation (LES) to investigate and model subsonic, turbulent, jet noise. Motivated by the observation that sound-source dynamics are dominated by instability waves (wavepackets), we examine mechanisms by which their intermittency can amplify their noise radiation. Two scenarios, both involving wavepacket evolution on time-dependent base flows, are investigated. In the first, we consider that the main effect of the changing base flow consists in different wavepacket ensembles seeing different steady mean fields, and having, accordingly, different acoustic efficiencies. In the second, the details of the base-flow time dependence also play a role in wavepacket sound production. Both short-time-averaged and slowly varying base flows are extracted from the LES data and used in conjunction with linearized wavepacket models, namely, the Parabolized Stability Equations (PSE), the One-Way Euler Equations (OWE), and the Linearized Euler Equations (LEE). All results support the hypothesized mechanism: wavepackets on time-varying base flows produce sound radiation that is enhanced by as much as 20dB in comparison to their long-time-averaged counterparts, and ensembles of wavepackets based on short-time-averaged base flows display similar amplification. This is not, however, sufficient to explain the sound levels observed in the LES and experiments. Further work is therefore necessary to incorporate two additional factors in the linear models, body forcing by turbulence and realistic inflow forcing, both of which have been identified as potentially important in producing the observed radiation efficiency

Non-Emergency Medical Transportation Needs of Middle-Aged and Older Adults: A Rural-Urban Comparison in Delaware, USA.

Background: Older adults in rural areas have unique transportation barriers to accessing medical care, which include a lack of mass transit options and considerable distances to health-related services. This study contrasts non-emergency medical transportation (NEMT) service utilization patterns and associated costs for Medicaid middle-aged and older adults in rural versus urban areas. Methods: Data were analyzed from 39,194 NEMT users of LogistiCare-brokered services in Delaware residing in rural (68.3%) and urban (30.9%) areas. Multivariable logistic analyses compared trip characteristics by rurality designation. Results: Rural (37.2%) and urban (41.2%) participants used services more frequently for dialysis than for any other medical concern. Older age and personal accompaniment were more common and wheel chair use was less common for rural trips. The mean cost per trip was greater for rural users (difference of $2910 per trip), which was attributed to the greater distance per trip in rural areas. Conclusions: Among a sample who were eligible for subsidized NEMT and who utilized this service, rural trips tended to be longer and, therefore, higher in cost. Over 50% of trips were made for dialysis highlighting the need to address prevention and, potentially, health service improvements for rural dialysis patients

Contributors to the March Issue/Notes

Notes by Nicholas T. Tsiolis, Robert B. Devine, John A. Berry, John L. Towne, John H. Logan, Jr., August P. Petrillo, Richard A. Molique, and J. Frederick Meister

Spectral analysis of jet turbulence

Informed by large-eddy simulation (LES) data and resolvent analysis of the mean flow, we examine the structure of turbulence in jets in the subsonic, transonic and supersonic regimes. Spectral (frequency-space) proper orthogonal decomposition is used to extract energy spectra and decompose the flow into energy-ranked coherent structures. The educed structures are generally well predicted by the resolvent analysis. Over a range of low frequencies and the first few azimuthal mode numbers, these jets exhibit a low-rank response characterized by Kelvin–Helmholtz (KH) type wavepackets associated with the annular shear layer up to the end of the potential core and that are excited by forcing in the very-near-nozzle shear layer. These modes too have been experimentally observed before and predicted by quasi-parallel stability theory and other approximations – they comprise a considerable portion of the total turbulent energy. At still lower frequencies, particularly for the axisymmetric mode, and again at high frequencies for all azimuthal wavenumbers, the response is not low-rank, but consists of a family of similarly amplified modes. These modes, which are primarily active downstream of the potential core, are associated with the Orr mechanism. They occur also as subdominant modes in the range of frequencies dominated by the KH response. Our global analysis helps tie together previous observations based on local spatial stability theory, and explains why quasi-parallel predictions were successful at some frequencies and azimuthal wavenumbers, but failed at others