Navier-Stokes flow field analysis of compressible flow in a high pressure safety relief valve

The objective of this study is to investigate the complex three-dimensional flowfield of an oxygen safety pressure relieve valve during an incident, with a computational fluid dynamic (CFD) analysis. Specifically, the analysis will provide a flow pattern that would lead to the expansion of the eventual erosion pattern of the hardware, so as to combine it with other findings to piece together a most likely scenario for the investigation. The CFD model is a pressure based solver. An adaptive upwind difference scheme is employed for the spatial discretization, and a predictor, multiple corrector method is used for the velocity-pressure coupling. The computational result indicated vortices formation near the opening of the valve which matched the erosion pattern of the damaged hardware

Navier-Stokes Flow Field Analysis of Compressible Flow in a Pressure Relief Valve

The present study was motivated to analyze the complex flow field involving gaseous oxygen (GOX) flow in a relief valve (RV). The 9391 RV, pictured in Figure 1, was combined with the pilot valve to regulate the actuation pressure of the main valve system. During a high-pressure flow test at Marshall Space Flight Center (MSFC) the valve system developed a resonance chatter, which destroyed most of the valve body. Figures 2-4 show the valve body before and after accident. It was understood that the subject RV has never been operated at 5500 psia. In order to fully understand the flow behavior in the RV, a computational fluid dynamics (CFD) analysis is carried out to investigate the side load across the piston sleeve and the erosion patterns resulting from flow distribution around piston/nozzle interface

Generation of out-of-plane polarized spin current by spin swapping

The generation of spin currents and their application to the manipulation of magnetic states is fundamental to spintronics. Of particular interest are chiral antiferromagnets that exhibit properties typical of ferromagnetic materials even though they have negligible magnetization. Here, we report the generation of a robust spin current with both in-plane and out-of-plane spin polarization in epitaxial thin films of the chiral antiferromagnet Mn3Sn in proximity to permalloy thin layers. By employing temperature-dependent spin-torque ferromagnetic resonance, we find that the chiral antiferromagnetic structure of Mn3Sn is responsible for an in-plane polarized spin current that is generated from the interior of the Mn3Sn layer and whose temperature dependence follows that of this layer's antiferromagnetic order. On the other hand, the out-of-plane spin polarized spin current is unrelated to the chiral antiferromagnetic structure and is instead the result of scattering from the Mn3Sn/permalloy interface. We substantiate the later conclusion by performing studies with several other non-magnetic metals all of which are found to exhibit out-of-plane polarized spin currents arising from the spin swapping effect.Comment: 17 pages, 4 figure

LDC Export Diversification, Employment Generation and the 'Green Economy': What Roles for Tourism Linkages?

Pro-poor tourism is arguably one of the best green options for addressing LDC poverty, employment and economic diversification initiatives. Although often neglected as a serious policy option - and consequently most of its potential still remains untapped - tourism is the leading export for at least 11 LDCs, and the 2nd or 3rd largest export for another 11 or more. It is also a major source of new employment, especially for women, youth and the rural poor in general. While difficult to measure accurately, tourism's pro-poor impacts are directly related to the achieved level of inter- and intra-sectoral linkages. Taking export diversification, employment generation and the green economy in turn, the working paper analyzes feasible LDC alternatives, reaching the conclusion (within the limits of data availability) that - in contrast with the current overemphasis on agriculture and manufacturing - green tourism is demonstrably one of the areas of greatest current comparative advantage and development potential for the majority of LDCs, via its extensive upstream and downstream linkages/multiplier effects, employment-generating and poverty alleviation capacities, opportunities for export test marketing of new products, sustainability, and largely untapped export opportunities. An economy wide, primarily private-sector approach is an essential element for maximizing tourism benefits - including its multiple linkages with agriculture and manufacturing - together with a significant coordinating governmental role to minimize negative externalities. Unfortunately, there is no automatic guarantee that expanding tourism will significantly increase poverty alleviation or local employment generation: the necessary mechanisms must be explicitly included in tourism planning and implementation

The Wall Street Walk when Blockholders Compete for Flows

An important recent theoretical literature argues that the threat of exit can represent an effective form of governance when the blockholder is a principal. However, a significant fraction of equity blocks is held by delegated portfolio managers. How do agency frictions arising from the delegation of portfolio management affect the ability of blockholders to govern via the threat of exit? We show that when blockholders are sufficiently career concerned exit will fail as a disciplining device. Our results have testable implications on the relative degree to which different classes of delegated portfolio managers use exit as a form of governance