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Full-Text Articles in Physics
Spontaneous Oscillations In Simple Fluid Networks, Nathaniel Karst, Brian Storey, John Geddes
Spontaneous Oscillations In Simple Fluid Networks, Nathaniel Karst, Brian Storey, John Geddes
Brian Storey
Nonlinear phenomena including multiple equilibria and spontaneous oscillations are common in fluid networks containing either multiple phases or constituents. In many systems, such behavior might be attributed to the complicated geometry of the network, the complex rheology of the constituent fluids, or, in the case of microvascular blood flow, biological control. In this paper we investigate two examples of a simple three-node fluid network containing two miscible Newtonian fluids of differing viscosities, the first modeling microvascular blood flow and the second modeling stratified laminar flow. We use a combination of analytic and numerical techniques to identify and track saddle-node and …
Spontaneous Oscillations In Simple Fluid Networks, Nathaniel Karst, Brian Storey, John Geddes
Spontaneous Oscillations In Simple Fluid Networks, Nathaniel Karst, Brian Storey, John Geddes
John B. Geddes
Nonlinear phenomena including multiple equilibria and spontaneous oscillations are common in fluid networks containing either multiple phases or constituents. In many systems, such behavior might be attributed to the complicated geometry of the network, the complex rheology of the constituent fluids, or, in the case of microvascular blood flow, biological control. In this paper we investigate two examples of a simple three-node fluid network containing two miscible Newtonian fluids of differing viscosities, the first modeling microvascular blood flow and the second modeling stratified laminar flow. We use a combination of analytic and numerical techniques to identify and track saddle-node and …
Harmonic Initial-Boundary Evolution In General Relativity, Maria Babiuc-Hamilton, B´Ela Szil´Agyi, Jeffrey Winicour
Harmonic Initial-Boundary Evolution In General Relativity, Maria Babiuc-Hamilton, B´Ela Szil´Agyi, Jeffrey Winicour
Maria Babiuc-Hamilton
Computational techniques which establish the stability of an evolution-boundary algorithm for a model wave equation with shift are incorporated into a well-posed version of the initial-boundary value problem for gravitational theory in harmonic coordinates. The resulting algorithm is implemented as a 3-dimensional numerical code which we demonstrate to provide stable, convergent Cauchy evolution in gauge wave and shifted gauge wave testbeds. Code performance is compared for Dirichlet, Neumann, and Sommerfeld boundary conditions and for boundary conditions which explicitly incorporate constraint preservation. The results are used to assess strategies for obtaining physically realistic boundary data by means of Cauchy-characteristic matching.
Laminar Flow Of Two Miscible Fluids In A Simple Network, Casey Karst, Brian Storey, John Geddes
Laminar Flow Of Two Miscible Fluids In A Simple Network, Casey Karst, Brian Storey, John Geddes
John B. Geddes
When a fluid comprised of multiple phases or constituents flows through a network, nonlinear phenomena such as multiple stable equilibrium states and spontaneous oscillations can occur. Such behavior has been observed or predicted in a number of networks including the flow of blood through the microcirculation, the flow of picoliter droplets through microfluidic devices, the flow of magma through lava tubes, and two-phase flow in refrigeration systems. While the existence of nonlinear phenomena in a network with many inter-connections containing fluids with complex rheology may seem unsurprising, this paper demonstrates that even simple networks containing Newtonian fluids in laminar flow …
Nonextensive Statistical Mechanics For Rotating Quasi-Two-Dimensional Turbulence, Sunghwan Jung, Brian Storey, Julien Aubert, Harry Swinney
Nonextensive Statistical Mechanics For Rotating Quasi-Two-Dimensional Turbulence, Sunghwan Jung, Brian Storey, Julien Aubert, Harry Swinney
Brian Storey
We have conducted experiments on an asymmetrically forced quasi-two-dimensional turbulent flow in a rapidly rotating annulus. Assuming conservation of potential enstrophy and energy, we maximize a nonextensive entropy function to obtain the azimuthally averaged vorticity as a function of radial position. The predicted vorticity profile is in good accord with the observations. A nonextensive formalism is appropriate because long-range correlations between small-scale vortices give rise to large coherent structures in the turbulence. We also derive probability distribution functions for the vorticity from both extensive and nonextensive entropies, and we find that the prediction from nonextensive theory is in better accord …
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Rebecca J. Christianson
In the search for new, more effective coolant fluids, nanoparticle suspensions have shown promise due to their enhanced thermal conductivity. However, there is a concomitant increase in the viscosity, requiring an increase in pumping power to achieve the same flow rate.Studies of flow cooling in simple geometries indicate that there is a benefit to using nanofluids, but it is difficult to justify extending these results to the far more complicated geometries. Moreover, with the variability of property measurements found in literature, it is possible to show conflicting results from the same set of flow-cooling data. In this work we present …
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Jessica Townsend
In the search for new, more effective coolant fluids, nanoparticle suspensions have shown promise due to their enhanced thermal conductivity. However, there is a concomitant increase in the viscosity, requiring an increase in pumping power to achieve the same flow rate.Studies of flow cooling in simple geometries indicate that there is a benefit to using nanofluids, but it is difficult to justify extending these results to the far more complicated geometries. Moreover, with the variability of property measurements found in literature, it is possible to show conflicting results from the same set of flow-cooling data. In this work we present …
On The Influence Of Damping In Hyperbolic Equations With Parabolic Degeneracy, Ralph Saxton, Katarzyna Saxton
On The Influence Of Damping In Hyperbolic Equations With Parabolic Degeneracy, Ralph Saxton, Katarzyna Saxton
Ralph Saxton
This paper examines the effect of damping on a nonstrictly hyperbolic 2x2 system. It is shown that the growth of singularities is not restricted as in the strictly hyperbolic case where dissipation can be strong enough to preserve the smoothness of solutions globally in time. Here, irrespective of the stabilizing properties of damping, solutions are found to break down in finite time on a line where two eigenvalues coincide in state space.