A split finite element algorithm for the compressible Navier-Stokes equations

An accurate and efficient numerical solution algorithm is established for solution of the high Reynolds number limit of the Navier-Stokes equations governing the multidimensional flow of a compressible essentially inviscid fluid. Finite element interpolation theory is used within a dissipative formulation established using Galerkin criteria within the Method of Weighted Residuals. An implicit iterative solution algorithm is developed, employing tensor product bases within a fractional steps integration procedure, that significantly enhances solution economy concurrent with sharply reduced computer hardware demands. The algorithm is evaluated for resolution of steep field gradients and coarse grid accuracy using both linear and quadratic tensor product interpolation bases. Numerical solutions for linear and nonlinear, one, two and three dimensional examples confirm and extend the linearized theoretical analyses, and results are compared to competitive finite difference derived algorithms

The sensitivity of willingness to pay to an economic downturn

Stated preference (SP) studies are typically undertaken at one point in time, while the results may be relied on in decision-making several months or even years later. This reliance is only justified if values are stable over time, an assumption which is doubtable given the onset of an economic downturn. We assess the reliability of values taken before an economic downturn for application during the downturn, via analysis of responses to two near identical surveys conducted respectively before and during the 2008-2010 economic recession. The surveys were valuing near identical sets of permanent water sector service and environmental improvements. Each survey employed a dichotomous choice and a payment card contingent valuation question. Our main result is that the economic downturn led to lower payment card responses but had no effect on the values elicited via a dichotomous choice (ie referendum-type) contingent valuation question. We explore potential explanations for this finding in light of the literature on closed-ended versus open-ended elicitation method comparisons

Analysis of boundary conditions for SSME subsonic internal viscous flow analysis

A study was completed of mathematically proper boundary conditions for unique numerical solution of internal, viscous, subsonic flows in the space shuttle main engine. The study has concentrated on well posed considerations, with emphasis on computational efficiency and numerically stable boundary condition statements. The method of implementing the established boundary conditions is applicable to a wide variety of finite difference and finite element codes, as demonstrated

Evaluation of Composite Components on the Bell 206L and Sikorsky S-76 Helicopters

Progress on two programs to evaluate structural composite parts in flight service on Bell 206L and Sikorsky S-76 commercial helicopters is described. Forty ship sets of composite parts that include the litter door, baggage door, forward fairing, and vertical fin were installed on Bell Model 206L helicopters that are operating in widely different climates. Part installation started in 1981 and selected parts are being removed and tested at prescribed intervals over a 10 yr evaluation. Four horizontal stabilizers and eleven tail rotor spars that are production parts on the S-76 helicopter are being tested after prescribed periods of service to determine the effects of the operating environment on their performance. Concurrent with the flight evaluation, materials used to fabricate the parts are being exposed in ground racks and tested at specified intervals to determine the effects of outdoor environments. Results achieved from 123,000 hrs of accumulated service on the Bell 206L parts and 53,000 hrs on the Sikorsky S-76 parts are reported. Seventy-eight Bell 206L parts were removed and tested statically. Results of 7 yrs of ground exposure of materials used to make the Bell 206L parts are presented

Developments and trends in three-dimensional mesh generation

An intense research effort over the last few years has produced several competing and apparently diverse methods for generating meshes. Recent progress is reviewed and the central themes are emphasized which form a solid foundation for future developments in mesh generation

Ground exposure of composite materials for helicopters

Residual strength results are presented on four composite material systems that were exposed for three years at locations on the North American Continent. The exposure locations are near the areas where Bell Model 206L Helicopters, that are in a NSA/U.S. Army sponsored flight service program, are flying in daily commercial service. The composite systems are: (1) Kevlar-49 fabric/F-185 epoxy; (2) Kevlar-49 fabric/LRF-277 epoxy; (3) Kevlar-49 fabric/CE-306 epoxy; and (4) T-300 Graphite/E-788 epoxy. All material systems exhibited good strength retention in compression and short beam shear. The Kevlar-49/LRF-277 epoxy retained 88 to 93 percent of the baseline strength while the other material systems exceeded 95 percent of baseline strength. Residual tensile strength of all materials did not show a significant reduction. The available moisture absorption data is also presented

The Missing Monitor in Corporate Governance: The Directors\u27 & Officers\u27 Liability Insurer

This article reports the results of empirical research on the monitoring role of directors\u27 and officers\u27 liability insurance (D&O insurance) companies in American corporate governance. Economic theory provides three reasons to expect D&O insurers to serve as corporate governance monitors: first, monitoring provides insurers with a way to manage moral hazard; second, monitoring provides benefits to shareholders who might not otherwise need the risk distribution that D&O insurance provides; and third, the bonding provided by risk distribution gives insurers a comparative advantage in monitoring. Nevertheless, we find that D&O insurers neither monitor corporate governance during the life of the insurance contract nor manage litigation defense costs once claims arise. Our findings raise significant questions about the value of D&O insurance for shareholders as well as the deterrent effect of corporate and securities liability. After exploring various explanations for these findings, we conclude that the absence of monitoring is due, at least in part, to the agency problem in the corporate context. Our analysis thus suggests that the existing form of corporate D&O insurance both results from and contributes to the relatively weak constraints on corporate managers. Corporate managers buy D&O coverage for self-serving reasons, and the coverage itself because it does not control moral hazard, reduces the extent to which shareholder litigation aligns managers\u27and shareholders\u27 incentives

The Missing Monitor in Corporate Governance: The Directors\u27 & Officers\u27 Liability Insurer

This article reports the results of empirical research on the monitoring role of directors\u27 and officers\u27 liability insurance (D&O insurance) companies in American corporate governance. Economic theory provides three reasons to expect D&O insurers to serve as corporate governance monitors: first, monitoring provides insurers with a way to manage moral hazard; second, monitoring provides benefits to shareholders who might not otherwise need the risk distribution that D&O insurance provides; and third, the bonding provided by risk distribution gives insurers a comparative advantage in monitoring. Nevertheless, we find that D&O insurers neither monitor corporate governance during the life of the insurance contract nor manage litigation defense costs once claims arise. Our findings raise significant questions about the value of D&O insurance for shareholders as well as the deterrent effect of corporate and securities liability. After exploring various explanations for these findings, we conclude that the absence of monitoring is due, at least in part, to the agency problem in the corporate context. Our analysis thus suggests that the existing form of corporate D&O insurance both results from and contributes to the relatively weak constraints on corporate managers. Corporate managers buy D&O coverage for self-serving reasons, and the coverage itself because it does not control moral hazard, reduces the extent to which shareholder litigation aligns managers\u27and shareholders\u27 incentives