117 research outputs found
Emissivity: A Program for Atomic Emissivity Calculations
In this article we report the release of a new program for calculating the
emissivity of atomic transitions. The program, which can be obtained with its
documentation from our website www.scienceware.net, passed various rigorous
tests and was used by the author to generate theoretical data and analyze
observational data. It is particularly useful for investigating atomic
transition lines in astronomical context as the program is capable of
generating a huge amount of theoretical data and comparing it to observational
list of lines. A number of atomic transition algorithms and analytical
techniques are implemented within the program and can be very useful in various
situations. The program can be described as fast and efficient. Moreover, it
requires modest computational resources.Comment: 20 pages, 0 figures, 0 table
Analytical solutions for the flow of Carreau and Cross fluids in circular pipes and thin slits
In this paper, analytical expressions correlating the volumetric flow rate to
the pressure drop are derived for the flow of Carreau and Cross fluids through
straight rigid circular uniform pipes and long thin slits. The derivation is
based on the application of Weissenberg-Rabinowitsch-Mooney-Schofield method to
obtain flow solutions for generalized Newtonian fluids through pipes and our
adaptation of this method to the flow through slits. The derived expressions
are validated by comparing their solutions to the solutions obtained from
direct numerical integration. They are also validated by comparison to the
solutions obtained from the variational method which we proposed previously. In
all the investigated cases, the three methods agree very well. The agreement
with the variational method also lends more support to this method and to the
variational principle which the method is based upon.Comment: 27 pages, 6 figure
One-Dimensional Navier-Stokes Finite Element Flow Model
This technical report documents the theoretical, computational, and practical
aspects of the one-dimensional Navier-Stokes finite element flow model. The
document is particularly useful to those who are interested in implementing,
validating and utilizing this relatively-simple and widely-used model.Comment: 46 pages, 1 tabl
Modeling the Flow of Yield-Stress Fluids in Porous Media
Yield-stress is a problematic and controversial non-Newtonian flow
phenomenon. In this article, we investigate the flow of yield-stress substances
through porous media within the framework of pore-scale network modeling. We
also investigate the validity of the Minimum Threshold Path (MTP) algorithms to
predict the pressure yield point of a network depicting random or regular
porous media. Percolation theory as a basis for predicting the yield point of a
network is briefly presented and assessed. In the course of this study, a
yield-stress flow simulation model alongside several numerical algorithms
related to yield-stress in porous media were developed, implemented and
assessed. The general conclusion is that modeling the flow of yield-stress
fluids in porous media is too difficult and problematic. More fundamental
modeling strategies are required to tackle this problem in the future.Comment: 27 pages and 5 figure
Variational approach for the flow of Ree-Eyring and Casson fluids in pipes
The flow of Ree-Eyring and Casson non-Newtonian fluids is investigated using
a variational principle to optimize the total stress. The
variationally-obtained solutions are compared to the analytical solutions
derived from the Weissenberg-Rabinowitsch-Mooney equation and the results are
found to be identical within acceptable numerical errors and modeling
approximations.Comment: 18 pages, 2 figure
Flow of Navier-Stokes Fluids in Converging-Diverging Distensible Tubes
We use a method based on the lubrication approximation in conjunction with a
residual-based mass-continuity iterative solution scheme to compute the flow
rate and pressure field in distensible converging-diverging tubes for
Navier-Stokes fluids. We employ an analytical formula derived from a
one-dimensional version of the Navier-Stokes equations to describe the
underlying flow model that provides the residual function. This formula
correlates the flow rate to the boundary pressures in straight cylindrical
elastic tubes with constant-radius. We validate our findings by the convergence
toward a final solution with fine discretization as well as by comparison to
the Poiseuille-type flow in its convergence toward analytic solutions found
earlier in rigid converging-diverging tubes. We also tested the method on
limiting special cases of cylindrical elastic tubes with constant-radius where
the numerical solutions converged to the expected analytical solutions. The
distensible model has also been endorsed by its convergence toward the rigid
Poiseuille-type model with increasing the tube wall stiffness.
Lubrication-based one-dimensional finite element method was also used for
verification. In this investigation five converging-diverging geometries are
used for demonstration, validation and as prototypes for modeling
converging-diverging geometries in general.Comment: 31 pages, 9 figures, 2 table
Special Relativity: Scientific or Philosophical Theory?
In this article, we argue that the theory of special relativity, as
formulated by Einstein, is a philosophical rather than a scientific theory.
What is scientific and experimentally supported is the formalism of the
relativistic mechanics embedded in the Lorentz transformations and their direct
mathematical, experimental and observational consequences. This is in parallel
with the quantum mechanics where the scientific content and experimental
support of this branch of physics is embedded in the formalism of quantum
mechanics and not in its philosophical interpretations such as the Copenhagen
school or the parallel worlds explanations. Einstein theory of special
relativity gets unduly credit from the success of the relativistic mechanics of
Lorentz transformations. Hence, all the postulates and consequences of Einstein
interpretation which have no direct experimental or observational support
should be reexamined and the relativistic mechanics of Lorentz transformations
should be treated in education, academia and research in a similar fashion to
that of quantum mechanics.Comment: 12 page
Flow of non-Newtonian Fluids in Converging-Diverging Rigid Tubes
A residual-based lubrication method is used in this paper to find the flow
rate and pressure field in converging-diverging rigid tubes for the flow of
time-independent category of non-Newtonian fluids. Five converging-diverging
prototype geometries were used in this investigation in conjunction with two
fluid models: Ellis and Herschel-Bulkley. The method was validated by
convergence behavior sensibility tests, convergence to analytical solutions for
the straight tubes as special cases for the converging-diverging tubes,
convergence to analytical solutions found earlier for the flow in
converging-diverging tubes of Newtonian fluids as special cases for
non-Newtonian, and convergence to analytical solutions found earlier for the
flow of power-law fluids in converging-diverging tubes. A brief investigation
was also conducted on a sample of diverging-converging geometries. The method
can in principle be extended to the flow of viscoelastic and
thixotropic/rheopectic fluid categories. The method can also be extended to
geometries varying in size and shape in the flow direction, other than the
perfect cylindrically-symmetric converging-diverging ones, as long as
characteristic flow relations correlating the flow rate to the pressure drop on
the discretized elements of the lubrication approximation can be found. These
relations can be analytical, empirical and even numerical and hence the method
has a wide applicability range.Comment: 36 pages, 14 figures, 5 table
Reply to "Comment on Sochi's variational method for generalised Newtonian flow" by Pritchard and Corson
In this article we challenge the claim that the previously proposed
variational method to obtain flow solutions for generalized Newtonian fluids in
circular tubes and plane slits is exact only for power law fluids. We also
defend the theoretical foundation and formalism of the method which is based on
minimizing the total stress through the application of the Euler-Lagrange
principle.Comment: 9 page
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