Capacity Testing and Local Flow Analysis of a Geometrically Complex Trim Installed within a Commercial Control Valve

Industrial control valves often handle flows with very high pressure drops (conditions often referred to as severe service). In order to cope with such pressure drops, geometrically complex valve trims with many stages of pressure drops, are designed to prevent undesirable side effects such as cavitation etc. There are many different product designs for control valve trims produced by different manufacturers. One such design uses cylindrical obstructions in the flow field to control the pressure drop. The design of these trims is based on their capacity (Cv) values. With the advent of advanced computational tools, such as Computational Fluid Dynamics based codes, it has become possible to numerically test these trims over a wide range of flow conditions. Hence, this study presents capacity testing and local flow analysis of a complex geometry trim, installed within a commercial control valve for severe service. The results show that the capacity of this particular design of trim decreases as the valve opening position decreases

The effect of manufacturing method induced roughness on severe service control valve performance

There are a number of manufacturing methods used for the manufacture of control valve trim components, some of which are expensive processes. Current market conditions and increased competition requires manufacturers to reduce costs of these components and they are investigating new technologies such as processes using Additive Layer Manufacturing (ALM) to produce these components. These processes may require or result in variations in geometrical features and surface roughness of the produced components compared to current processes, this study quantifies the effects of the selective laser melting (SLM); a form of ALM, methods induced features on the overall valve performance of the control valve via experimental measurements of valve capacity (Cv) and the roughness of the manufactured parts

H-alpha Imaging with HST+NICMOS of An Elusive Damped Ly-alpha Cloud at z=0.6

Despite previous intensive ground-based imaging and spectroscopic campaigns and wide-band HST imaging of the z=0.927 QSO 3C336 field, the galaxy that hosts the damped Ly-alpha system along this line-of-sight has eluded detection. We present a deep narrow-band H-alpha image of the field of this z=0.656 damped Ly-alpha absorber, obtained through the F108N filter of NICMOS 1 onboard the Hubble Space Telescope. The goal of this project was to detect any H-alpha emission 10 times closer than previous studies to unveil the damped absorber. We do not detect H-alpha emission between 0.05'' and 6'' (0.24 and 30 $h^{-1}$ kpc) from the QSO, with a 3-sigma flux limit of $3.70 \times 10^{-17} h^{-2}$ erg/s/cm^2 for an unresolved source, corresponding to a star formation rate (SFR) of $0.3 h^{-2}$ M_sun/yr. This leads to a 3-sigma upper limit of 0.15 M_sun/yr/kpc^2 on the SFR density, or a maximum SFR of 1.87 M_sun/yr assuming a disk of 4 kpc in diameter. This result adds to the number of low redshift damped Ly-alpha absorbers that are not associated with the central regions of Milky-Way-like disks. Damped Ly-alpha absorption can arise from high density concentrations in a variety of galactic environments including some that, despite their high local HI densities, are not conducive to widespread star formation.Comment: 18 pages, 3 figures. Replaced to match published version in ApJ, 550, 585 (Apr 1 2001

Effect of Inlet Flow Characteristics on the Volume Fraction Distribution within a Severe Service Trim and the Valve Flow Coefficient

It is well established that inlet flow characteristics may affect the performance of fluid handling systems considerably. This work focuses on the local flow analysis of a severe service control valve with a continuous resistance trim (CRT) operating under multiphase flow conditions and the effect of the inlet flow characteristics on the dispersed phase distribution within the trim and the valve flow coefficient Cv. Three dimensional CFD models, using both the mixture model and turbulence model k-omega SST, were used to simulate the flow within valve body and trim assembly under multiphase conditions. It is shown in this work that the dispersed phase distribution in the trim is strongly affected by the valve inlet conditions and thus affecting its performance. However, the valve flow coefficient is barely affected by the inlet flow conditions

The Distribution of High Redshift Galaxy Colors: Line of Sight Variations in Neutral Hydrogen Absorption

We model, via Monte Carlo simulations, the distribution of observed U-B, B-V, V-I galaxy colors in the range 1.75<z<5 caused by variations in the line-of-sight opacity due to neutral hydrogen (HI). We also include HI internal to the source galaxies. Even without internal HI absorption, comparison of the distribution of simulated colors to the analytic approximations of Madau (1995) and Madau et al (1996) reveals systematically different mean colors and scatter. Differences arise in part because we use more realistic distributions of column densities and Doppler parameters. However, there are also mathematical problems of applying mean and standard deviation opacities, and such application yields unphysical results. These problems are corrected using our Monte Carlo approach. Including HI absorption internal to the galaxies generaly diminishes the scatter in the observed colors at a given redshift, but for redshifts of interest this diminution only occurs in the colors using the bluest band-pass. Internal column densities < 10^17 cm^2 do not effect the observed colors, while column densities > 10^18 cm^2 yield a limiting distribution of high redshift galaxy colors. As one application of our analysis, we consider the sample completeness as a function of redshift for a single spectral energy distribution (SED) given the multi-color selection boundaries for the Hubble Deep Field proposed by Madau et al (1996). We argue that the only correct procedure for estimating the z>3 galaxy luminosity function from color-selected samples is to measure the (observed) distribution of redshifts and intrinsic SED types, and then consider the variation in color for each SED and redshift. A similar argument applies to the estimation of the luminosity function of color-selected, high redshift QSOs.Comment: accepted for publication in ApJ; 25 pages text, 14 embedded figure

Vegetable Shipping Line Graph Testing Survey

Survey results from both an online and in-paper survey designed to determine if how uncertainty information was displayed changed users' decisions from and interpretations of the data. Participants for the survey were recruited in different ways to target different audiences

Volcanic Ash Workshop Survey Results

Survey results from the 22 February 2016 Volcanic Ash Workshop with user groups from research and operations. Users included pilots, the civil aviation association, representatives from airlines, engine manufacturers, forecasters from the UK Met Office, and researchers from academia. Survey was a decision-making game for flight paths given different forecasts. The purpose of the survey was to see how decisions change if given different risk levels or different ways of displaying the information

Do location specific forecasts pose a new challenge for communicating uncertainty?

In the last decade, the growth of local, site-specific weather forecasts delivered by mobile phone or website represents arguably the fastest change in forecast consumption since the beginning of Television weather forecasts 60 years ago. In this study, a street-interception survey of 274 members of the public a clear first preference for narrow weather forecasts above traditional broad weather forecasts is shown for the first time, with a clear bias towards this preference for users under 40. The impact of this change on the understanding of forecast probability and intensity information is explored. While the correct interpretation of the statement ‘There is a 30% chance of rain tomorrow’ is still low in the cohort, in common with previous studies, a clear impact of age and educational attainment on understanding is shown, with those under 40 and educated to degree level or above more likely to correctly interpret it. The interpretation of rainfall intensity descriptors (‘Light’, ‘Moderate’, ‘Heavy’) by the cohort is shown to be significantly different to official and expert assessment of the same descriptors and to have large variance amongst the cohort. However, despite these key uncertainties, members of the cohort generally seem to make appropriate decisions about rainfall forecasts. There is some evidence that the decisions made are different depending on the communication format used, and the cohort expressed a clear preference for tabular over graphical weather forecast presentation