729 research outputs found
The measurement of boundary layers on a compressor blade in cascade. Volume 1: Experimental technique, analysis and results
Measurements were made of the boundary layers and wakes about a highly loaded, double-circular-arc compressor blade in cascade. These laser Doppler velocimetry measurements have yielded a very detailed and precise data base with which to test the application of viscous computational codes to turbomachinery. In order to test the computational codes at off-design conditions, the data were acquired at a chord Reynolds number of 500,000 and at three incidence angles. Moreover, these measurements have supplied some physical insight into these very complex flows. Although some natural transition is evident, laminar boundary layers usually detach and subsequently reattach as either fully or intermittently turbulent boundary layers. These transitional separation bubbles play an important role in the development of most of the boundary layers and wakes measured in this cascade and the modeling or computing of these bubbles should prove to be the key aspect in computing the entire cascade flow field. In addition, the nonequilibrium turbulent boundary layers on these highly loaded blades always have some region of separation near the trailing edge of the suction surface. These separated flows, as well as the subsequent near wakes, show no similarity and should prove to be a challenging test for the viscous computational codes
Old and young leaves on plane trees
A leaf of a plane tree is called an old leaf if it is the leftmost child of
its parent, and it is called a young leaf otherwise. In this paper we enumerate
plane trees with a given number of old leaves and young leaves. The formula is
obtained combinatorially by presenting two bijections between plane trees and
2-Motzkin paths which map young leaves to red horizontal steps, and old leaves
to up steps plus one. We derive some implications to the enumeration of
restricted permutations with respect to certain statistics such as pairs of
consecutive deficiencies, double descents, and ascending runs. Finally, our
main bijection is applied to obtain refinements of two identities of Coker,
involving refined Narayana numbers and the Catalan numbers.Comment: 11 pages, 7 figure
Using Community-Generated Data for Water Management Policy
This Policy Notes documents the experience of Lantapan, a watershed community in Bukidnon, where data collected by a community-based group to monitor its watershed's quality through the years helped alert the local government on the critical state of their water resources, thereby helping avert a possible water crisis. At the same time, the findings indicate the urgency to have a consistency of policies at both the national and local levels in order to ensure a more effective, efficient and sustainable management of natural resources, especially water resources.watershed, water resource management, water quality
The measurement of boundary layers on a compressor blade in cascade. Volume 2: Data tables
Measurements were made of the boundary layers and wakes about a highly loaded, double-circular-arc compressor blade in cascade. These laser Doppler velocimetry measurements have yielded a very detailed and precise data base with which to test the application of viscous computational codes to turbomachinery. In order to test the computational codes at off-design conditions, the data have been acquired at a chord Reynolds number of 500,000 and at three incidence angles. Average values and 95 percent confidence bands were tabularized for the velocity, local turbulence intensity, skewness, kurtosis, and percent backflow. Tables also exist for the blade static-pressure distributions and boundary layer velocity profiles reconstructed to account for the normal pressure gradient
Evaluation of Remedial Actions at Coal Combustion Residuals (CCR) Sites through Coupled Hydrogeological-Geochemical Reactive Transport Modeling
Spatial Distributions of Multiple Dust Components in the PPN/PN Dust Shells
We investigate spatial distributions of specific dust components in the
circumstellar shells of a proto-planetary nebula candidate, HD 179821, and a
planetary nebula, BD3639, by means of spectral imaging. With
high-resolution ground-based images and ISO spectra in the mid-infrared, we can
derive ``dust feature only'' maps by subtracting synthesized continuum maps
from the observed images at the feature wavelength. Such spatially detailed
information will help to develop models for the evolution of dust grains around
evolved stars.Comment: 4 pages + 7 figures, to appear in the proceedings of the conference,
"Post-AGB Objects (proto-planetary nebulae) as a Phase of Stellar Evolution",
Torun, Poland, July 5-7, 2000, eds. R. Szczerba, R. Tylenda, and S.K. Gorny.
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