1951 Annual Report - Veterans Farm Management Service - Northern Minnesota

Farm Management,

An effective multigrid method for high-speed flows

The use is considered of a multigrid method with central differencing to solve the Navier-Stokes equations for high speed flows. The time dependent form of the equations is integrated with a Runge-Kutta scheme accelerated by local time stepping and variable coefficient implicit residual smoothing. Of particular importance are the details of the numerical dissipation formulation, especially the switch between the second and fourth difference terms. Solutions are given for 2-D laminar flow over a circular cylinder and a 15 deg compression ramp

1951 Annual Report - Veterans Farm Management Service - Southwestern Minnesota

Farm Management,

Multigrid for hypersonic viscous two- and three-dimensional flows

The use of a multigrid method with central differencing to solve the Navier-Stokes equations for hypersonic flows is considered. The time dependent form of the equations is integrated with an explicit Runge-Kutta scheme accelerated by local time stepping and implicit residual smoothing. Variable coefficients are developed for the implicit process that removes the diffusion limit on the time step, producing significant improvement in convergence. A numerical dissipation formulation that provides good shock capturing capability for hypersonic flows is presented. This formulation is shown to be a crucial aspect of the multigrid method. Solutions are given for two-dimensional viscous flow over a NACA 0012 airfoil and three-dimensional flow over a blunt biconic

Inflation Assisted by Heterotic Axions

We explore the possibility of obtaining inflation in weakly coupled heterotic string theory, where the model dependent axions are responsible for driving inflation. This model can be considered as a certain extrapolation of $m^{2}\phi^{2}$-inflation, and is an attempt to explicitly realize the so called N-flation proposal in string theory. The instanton generated potential for the axions essentially has two parameters; a natural mass scale $M$ and the string coupling $g_{s}$. For isotropic compactifications leading to of order $\mathcal{O} (10^4)$ axions in the four dimensional spectrum we find that with $(M, g_{s})\simeq(M_{GUT}, 0.5)$ the observed temperature fluctuations in the CMB are correctly reproduced. We assume an initially random distribution for the vevs of the axions. The spectral index, $n_{s}$, is generically more red than for $m^{2}\phi^{2}$-inflation. The greater the vevs, the more red the spectral index becomes. Allowing for a wide range of vevs 55 $e$-foldings from the end of inflation, we find $0.946\lesssim n_{s} \lesssim 0.962$. The tensor-to-scalar ratio, $r$, is more sensitive to the vevs, but typically smaller than in $m^{2}\phi^{2}$-inflation. Furthermore, in the regime where the leading order theory is valid, $r$ is bounded by $r < 0.10$. The spectral index and the tensor-to-scalar ratio are correlated. For example, $n_{s}\simeq 0.951$ corresponds to $r\simeq 0.036$.Comment: 1+21 pages, 2 figures, v2: Typos corrected, v3: Typos, very minor corrections, reference added, to appear in JCA

Friction factors for smooth pipe flow

Friction factor data from two recent pipe flow experiments are combined to provide a comprehensive picture of the friction factor variation for Reynolds numbers from 10 to 36,000,000

Dynamic Properties of Charmonium

Nonrelativistic quark models of charmonia are tested by comparison of theoretical charmonium decay constants, form factors, and $\gamma\gamma$ widths with experiment and lattice gauge computations. The importance of relativistic effects, a running coupling, and the correct implementation of bound state effects are demonstrated. We describe how an improved model and computational techniques resolve several outstanding issues in previous nonrelativistic quark models such as the use of `correction' factors in quark model form factors, artificial energy prescriptions in decay constant calculations, and ad hoc phase space modifications. We comment on the small experimental value of $f_{\psi''}$ and the D-wave component of the $J/\psi$. Decay constants and $\gamma\gamma$ widths for bottomonium are also presented.Comment: 22 pages, 22 ps figures (table entries corrected, text modified

An Investigation of the Natural and Anthropogenic Contributions of Arsenic to Urban Fill Soil

Arsenic in urban/historic fill soil, originating from both natural and anthropogenic sources, is a continuing concern from a human health risk point of view. This concern is heightened in urban gardens where the soil is to be used for growing vegetables for consumption. The presentation explores the origin of arsenic present in New England urban/historic fill soil and will derive an understanding of the relative contribution of the natural and anthropogenic components using available data sets. These data sets include more than 5,000 urban soil samples from the Central Artery/Tunnel Project in Boston statistically analyzed using ProUCL 4.0. Data also includes more than 2,700 samples of a natural/rural background data set from a comprehensive study of rock and stream sediment arsenic in New England analyzed by the U.S. Geological Survey (USGS), supported by other available data sets resulting in a broad base of up to approximately 10,000 individual sample results. These multiple data sets will be reviewed and summarized such that there are a mean/median and upper values presented for natural soils and rocks and a mean/median and upper values presented for anthropogenic impacted soils, with and without outliers. From this compilation will be derived an understanding of the numerical differential between them. Finally, we will apply standard human health risk calculations, provided by the Massachusetts Department of Environmental Protection (MassDEP), to illustrate the magnitude of potential effects of the natural soil and the anthropogenic–containing soil. The derived mean, median, and upper percentage values will be considered in the context of the human health risk assessment calculations. In conclusion, the exercise will identify the risk significance of the anthropogenic contribution relative to the natural soil and provide an understanding of the overall affect associated with background in the urban environment

Who Are the Fatal Accident Drivers in Iowa?

A study of accident drivers in Iowa for five years reveals that fatal-accident drivers are mostly men. The 20-24 year and the 60-64 year groups show an excess of accident drivers. Five per cent of drivers did not carry a license. Out-of-state drivers have twice as many accidents as expected