50,541 research outputs found
A note on acoustic black holes in neo-Newtonian theory
Newtonian fluid dynamics allows the construction of acoustic metrics from
which black hole configurations can be studied. However, relativistic pressure
effects are neglected within Newtonian theory. We study acoustic black holes in
the framework of neo-Newtonian hydrodynamics, which is designed to take into
account relativistic inertial effects of the pressure . Within this new
hydrodynamical context we show how can influence the formation of the
acoustic horizons.Comment: Latex file, 10 pages. Some discussions extended. Accepted for
publication in MPL
Velocity contrasts enhancement for shear thinning solutions flowing in a rough fracture
Flow and transport are studied in transparent model fractures with rough
complementary self-affine walls with a relative shear displacement .
The aperture field is shown to display long range correlations perpendicular to
: for flow in that direction, the width and geometry of the front of a
dyed shear-thinning polymer solution displacing a transparent one have been
studied as a function of the fluid rheology and flow rate. The front width
increases linearly with distance indicating a convection of the fluids with a
low transverse mixing between the flow paths. The width also increases with the
flow-rate as the fluid rheology shifts from Newtonian at low shear rates towards a shear thinning behaviour at higher values. The
width also increases with the polymer concentration at high flow-rates. These
results demonstrate the enhancement of the flow velocity contrasts between
different flow channels for shear thinning fluids. The relative widths at low
and high values for different polymer concentrations are well
predicted by an analytical model considering the fracture as a set of parallel
ducts of constant hydraulic apertures. The overall geometry of the experimental
front geometry is also predicted by the theoretical model from the aperture
map
Laboratory investigation of infiltration process of nonnewtonian fluids through porous media in a non-isothermal flow regime for effective remediation of adsorbed contaminants
Thesis (M.S.) University of Alaska Fairbanks, 2019Contamination of soil and groundwater have serious health implications for man and environment. The overall goal of this research is to study a methodology of using nonNewtonian fluids for effective remediation of adsorbed contaminants in porous media under nonisothermal flow regimes. Non-Newtonian fluids (Guar gum and Xanthan gum solutions) provide a high viscous solution at low concentration and these fluids adjust their viscosities with applied shear rate and change in temperature. Adjustment of viscosity with an applied rate of shear is vital for contaminant remediation because non-Newtonian shear thinning fluids can penetrate to low permeability zones in subsurface by decreasing their viscosities due to high shear rates offered by low permeability zones. The application of non-Newtonian shear thinning fluids for contaminant remediation required the improvement in understanding of rheology and how the factors such as concentration, temperature and change in shear rate impacted the rheology of fluids. In order to study the rheology, we studied the changes in rheological characteristics (viscosity and contact angle) of non-Newtonian fluids of different concentrations (i.e., 0.5g/l, 1g/l, 3g/l, 6g/l and 7g/l) at different temperatures ranging from 0 ºC to 30 ºC. OFITE model 900 viscometer and Tantec contact angle meter were used to record the changes in viscosity of fluids for an applied range of shear rate (i.e., 17.02 s⁻¹ to 1021.38 s⁻¹) and contact angles, respectively, for different concentrations of non-Newtonian fluids. Understanding the flow characteristic of non-Newtonian fluids under low temperature conditions could help in developing methods to effectively remediate contaminants from soils. Results of rheological tests manifested an increase in the viscosity of both polymers with concentration and decrease in temperature. Mid (i.e., 3g/l) to high (i.e., 6g/l and 7g/l) concentrations of polymers manifested higher viscosities compared to 0.5g/l for both polymers. Flow of high viscous solutions required more force to pass through a glass-tube-bundle setup which represented a synthetic porous media to study the flow characteristic and effectiveness of Newtonian and non-Newtonian fluids for contaminant remediation. Low concentrations of 0.5g/l were selected for flow and remediation experiments because this concentration can flow through porous media easily without application of force. The 0.5g/l of Xanthan gum and de-ionized water were used to conduct the infiltration experiments to study the flow characteristics of Newtonian and non-Newtonian fluids at 0.6°C, 5°C and 19°C in synthetic porous media. Infiltration depth of both Newtonian and non-Newtonian fluids would decrease with the decrease in temperature because of the change in their properties like dynamic viscosity, density and angle of contact. The result of comparison of Newtonian and non-Newtonian fluids showed water to be more effective in remediating a surrogate adsorbent contaminant (Dichlobenil) from the synthetic porous media at 19°C. This result was counter-intuitive to what we began with as our hypothesis. However, it was also observed later that 0.5 g/l concentration of Guar gum behaved more like a Newtonian fluid and 0.5 g/l concentration of Xanthan gum had not shown strong non-Newtonian behavior compared to higher concentrations of Xanthan gum. Hence more analysis needs to be done to determine what concentration of non-Newtonian fluid should be more effective for remediation.USGS-National Institute of Water Resources (NIWR), National Institute of Food and Agriculture (NIFA) USDA Hatch program, University of Alaska Fairbanks Clarence Berry fellowship and Alaskan Section of American Water Resources Association scholarshipChapter 1: Introduction -- Chapter 2: Effect of temperature on rheological properties of Guar gum and Xanthan gum of different concentrations -- Chapter 3: Porous media flow characteristics of Newtonian and non-Newtonian Fluids under different thermal regimes -- Chapter 4: Comparison of Newtonian and non-Newtonian fluid for remediation of adsorbent contaminant -- Chapter 5: Conclusion
Testing Gravity in the Outer Solar System: Results from Trans-Neptunian Objects
The inverse square law of gravity is poorly probed by experimental tests at
distances of ~ 10 AUs. Recent analysis of the trajectory of the Pioneer 10 and
11 spacecraft have shown an unmodeled acceleration directed toward the Sun
which was not explained by any obvious spacecraft systematics, and occurred
when at distances greater than 20 AUs from the Sun. If this acceleration
represents a departure from Newtonian gravity or is indicative of an additional
mass distribution in the outer solar system, it should be detectable in the
orbits of Trans-Neptunian Objects (TNOs). To place limits on deviations from
Newtonian gravity, we have selected a well observed sample of TNOs found
orbiting between 20 and 100 AU from the Sun. By examining their orbits with
modified orbital fitting software, we place tight limits on the perturbations
of gravity that could exist in this region of the solar system.Comment: 20 pages, 4 figures, 2 tables, uses AASTex v5.x macro
Overcoming the Newtonian Paradigm: The Unfinished Project of Theoretical Biology from a Schellingian Perspective
Defending Robert Rosen’s claim that in every confrontation between physics and biology it is physics that
has always had to give ground, it is shown that many of the most important advances in mathematics
and physics over the last two centuries have followed from Schelling’s demand for a new physics that
could make the emergence of life intelligible. Consequently, while reductionism prevails in biology, many
biophysicists are resolutely anti-reductionist. This history is used to identify and defend a fragmented but
progressive tradition of anti-reductionist biomathematics. It is shown that the mathematicoephysico
echemical morphology research program, the biosemiotics movement, and the relational biology of
Rosen, although they have developed independently of each other, are built on and advance this antireductionist tradition of thought. It is suggested that understanding this history and its relationship to the broader history of post-Newtonian science could provide guidance for and justify both the integration of these strands and radically new work in post-reductionist biomathematics
PROCRUSTES: A computer algebra package for post-Newtonian calculations in General Relativity
We report on a package of routines for the computer algebra system Maple
which supports the explicit determination of the geometric quantities, field
equations, equations of motion, and conserved quantities of General Relativity
in the post-Newtonian approximation. The package structure is modular and
allows for an easy modification by the user. The set of routines can be used to
verify hand calculations or to generate the input for further numerical
investigations.Comment: 20 pages, 3 figures. The latest version of the package can be
obtained from http://www.thp.uni-koeln.de/~dp/procrustes.htm
The velocity dispersion and mass function of the outer halo globular cluster Palomar 4
We obtained precise line-of-sight radial velocities of 23 member stars of the
remote halo globular cluster Palomar 4 (Pal 4) using the High Resolution
Echelle Spectrograph (HIRES) at the Keck I telescope. We also measured the mass
function of the cluster down to a limiting magnitude of V~28 mag using archival
HST/WFPC2 imaging. We derived the cluster's surface brightness profile based on
the WFPC2 data and on broad-band imaging with the Low-Resolution Imaging
Spectrometer (LRIS) at the Keck II telescope. We find a mean cluster velocity
of 72.55+/-0.22 km/s and a velocity dispersion of 0.87+/-0.18 km/s. The global
mass function of the cluster, in the mass range 0.55<=M<=0.85 M_solar, is
shallower than a Kroupa mass function and the cluster is significantly depleted
in low-mass stars in its center compared to its outskirts. Since the relaxation
time of Pal 4 is of the order of a Hubble time, this points to primordial mass
segregation in this cluster. Extrapolating the measured mass function towards
lower-mass stars and including the contribution of compact remnants, we derive
a total cluster mass of 29800 M_solar. For this mass, the measured velocity
dispersion is consistent with the expectations of Newtonian dynamics and below
the prediction of Modified Newtonian Dynamics (MOND). Pal 4 adds to the growing
body of evidence that the dynamics of star clusters in the outer Galactic halo
can hardly be explained by MOND.Comment: 17 pages, accepted for publication in MNRAS; Fig. 8 surface
brightness/density data at github.com/matthiasjfrank/pal4_surface_brightnes
Interpretation of Polymer Solution Injection Fall-Off Tests
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