Biomedical subjects

Wm G Hoover

Publications and source records attributed to Wm G Hoover.

3 recordsLinked to original sources

PubMed2006

Smooth-particle phase stability with generalized density-dependent potentials.

Stable fluid and solid particle phases are essential to the simulation of continuum fluids and solids using smooth particle applied mechanics. We show that density-dependent potentials, such as Phi rho=1/2 Sigma(rho-rho 0)2, along with their corresponding constitutive relations, provide a simple means for characterizing fluids and that special stabilization potentials, with density gradients or curvatures, such as Phi inverted Delta rho=1/2 Sigma(inverted Delta rho)2, not only stabilize crystalline solid phases (or meshes) but also provide a surface tension which is missing in the usual density-dependent-potential approach. We illustrate these ideas for two-dimensional square, triangular, and hexagonal lattices.

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PubMed2004

Smooth-particle applied mechanics: Conservation of angular momentum with tensile stability and velocity averaging.

Smooth-particle applied mechanics (SPAM) provides several approaches to approximate solutions of the continuum equations for both fluids and solids. Though many of the usual formulations conserve mass, (linear) momentum, and energy, the angular momentum is typically not conserved by SPAM. A second difficulty with the usual formulations is that tensile stress states often exhibit an exponentially fast high-frequency short-wavelength instability, "tensile instability." We discuss these twin defects of SPAM and illustrate them for a rotating elastic body. We formulate ways to conserve angular momentum while at the same time delaying the symptoms of tensile instability for many sound-traversal times. These ideas should prove useful in more general situations.

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PubMed2002

Fluctuations, convergence times, correlation functions, and power laws from many-body Lyapunov spectra for soft and hard disks and spheres.

The dynamical instability of many-body systems is best characterized through the time-dependent local Lyapunov spectrum [lambda(j)], its associated comoving eigenvectors [delta(j)], and the "global" time-averaged spectrum [ ]. We study the fluctuations of the local spectra as well as the convergence rates and correlation functions associated with the delta vectors as functions of j and system size N. All the number dependences can be described by simple power laws. The various powers depend on the thermodynamic state and force law as well as system dimensionality.

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