NASA Scientific and Technical Aerospace Reports

have improved the ability to monitor and predict transient movement of water and contaminants in the vadose. One of the
advancements is the water flux meter developed by Pacific Northwest National Laboratory (PNNL). The water flux meter is
a device that, when it is buried in the subsurface, measures the flux of water infiltrating from the surface. Direct measurement
of this parameter is very useful since the flux to groundwater is generally estimated from rainfall data and assumptions related
to transpiration by vegetation, runoff, and evaporation, and their seasonal variation. Four water flux meters were installed at
the SRS to collect baseline data on the temporal variation in water flux. The flux meters were installed at locations with other
vadose zone monitoring equipment to verify operation of various pieces of equipment and to prepare a more complete analysis
of water flux in the vadose zone. The flux meters are currently in operation and collecting data.
NTIS
Flowmeters; Ground Water; Annual Variations; Contaminants
20040111150 Lawrence Livermore National Lab., Livermore, CA
Very High Resolution Simulations of Compressible, Turbulent Flows
Woodward, P. R.; Porter, D. H.; Sytine, I.; Anderson, S. E.; Mirin, A. A.; Apr. 26, 2001; In English
Report No.(s): DE2004-15005669; UCRL-JC-143626; No Copyright; Avail: National Technical Information Service (NTIS)
The steadily increasing power of supercomputing systems is enabling very high resolution simulations of compressible,
turbulent flows in the high Reynolds number limit, which is of interest in astrophysics as well as in several other fluid
dynamical applications. This paper discusses two such simulations, using grids of up to 8 billion cells. In each type of flow,
convergence in a statistical sense is observed as the mesh is refined. The behavior of the convergent sequences indicates how
a subgrid-scale model of turbulence could improve the treatment of these flows by high-resolution Euler schemes like PPM.
The best resolved case, a simulation of a Richtmyer-Meshkov mixing layer in a shock tube experiment, also points the way
toward such a subgrid-scale model. Analysis of the results of that simulation indicates a proportionality relationship between
the energy transfer rate from large to small motions and the determinant of the deviatoric symmetric strain as well as the
divergence of the velocity for the large-scale field.
NTIS
Compressible Flow; Turbulence; Computerized Simulation
20040111161 California Univ., Lawrence Berkeley National Lab., Berkeley, CA, USA
Computational Economy Improvements in PRISM
Tonse, S. R.; Brown, N. J.; 2004; 10 pp.; In English
Report No.(s): DE2004-823936; No Copyright; Avail: Department of Energy Information Bridge
The PRISM piecewise solution mapping procedure, in which the solution of the chemical kinetic ODE system is
parameterized with quadratic polynomials, is applied to CFD simulations of H(sub 2)+air combustion. Initial cost of
polynomial construction is expensive, but it is recouped as the polynomial is reused. We present two methods that help us to
parameterize only in places that will ultimately have high reuse. We also implement non-orthogonal Gosset factorial designs,
that reduce polynomial construction costs by a factor of two over previously used orthogonal factorial designs.
NTIS
Computational Fluid Dynamics; Combustion; Factorial Design
20040111177 Lawrence Livermore National Lab., Livermore, CA
Comparison of Direct Eulerian Godunov and Lagrange Plus Remap, Artificial Viscosity Schemes
Pember, R. B.; Anderson, R. W.; Mar. 30, 2001; In English
Report No.(s): DE2003-15005665; UCRL-JC-143206; No Copyright; Avail: National Technical Information Service (NTIS)
The authors compare two algorithms for solving the equations of unsteady inviscid compressible flow in an Eulerian
frame: a staggered grid, Lagrange plus remap artificial viscosity scheme and a cell-centered, direct Eulerian higher-order
Godunov scheme. They use the two methods to compute solutions to a number of one- and two-dimensional problems. The
results show the accuracy of the two schemes to be generally equivalent. In a 1984 survey paper by Woodward and Colella,
the Lagrange plus remap approach did not compare favorably with the higher-order Godunov methodology. They examine,
therefore, how certain features of the staggered grid scheme considered here contribute to its improved accuracy. The critical
features are shown to be the use of a monotonic artificial viscosity in the Lagrange step and, in the remap step, the use of a
corner transport upwind scheme with van Leer limiters in conjunction with separate advection of internal and kinetic energies.
NTIS
Viscosity; Algorithms; Compressible Flow; Computational Grids
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