257 research outputs found
Stokes' first problem for some non-Newtonian fluids: Results and mistakes
The well-known problem of unidirectional plane flow of a fluid in a
half-space due to the impulsive motion of the plate it rests upon is discussed
in the context of the second-grade and the Oldroyd-B non-Newtonian fluids. The
governing equations are derived from the conservation laws of mass and momentum
and three correct known representations of their exact solutions given. Common
mistakes made in the literature are identified. Simple numerical schemes that
corroborate the analytical solutions are constructed.Comment: 10 pages, 2 figures; accepted for publication in Mechanics Research
Communications; v2 corrects a few typo
Improved shock-capturing of Jameson's scheme for the Euler equations
It is known that Jameson's scheme is a pseudo-second-order-accurate scheme for solving discrete conservation laws. The scheme contains a non-linear artificial dissipative flux which is designed to capture shocks. In this paper, it is shown that the, shock-capturing of Jameson's scheme for the Euler equations can be improved by replacing the Lax-Friedrichs' type of dissipative flux with Roe's dissipative flux. This replacement is at a moderate expense of the calculation time
Asymptotic solution of transonic nozzle flows with homogeneous condensation. I. Subcritical flows
The one-dimensional (1-D) asymptotic solution of subcritical transonic nozzle flows with nonequilibrium homogeneous condensation is presented. An algorithm based on a local iterative scheme that exhibits the asymptotic solution in distinct condensation zones is developed for transonic moist air expansions under atmospheric supply conditions. Two models that characterize the state of the condensed phase as water drops or ice crystals are employed, together with the classical nucleation theory and Hertz-Knudsen droplet growth law. It is shown that the 1-D asymptotic predictions are in good agreement with the recent static pressure measurements of moist air expansions in relatively slender nozzles when the condensed phase is assumed to consist purely of water drops. © 1993 American Institute of Physics
The mathematical theory of thermal choking in nozzle flows
The mathematical theory of sub- and supercritical nozzle flows is presented by a unified description of integro-algebraic and differential formulations of the flow equations. The critical amount of heat necessary for a thermally choked flow is defined and models which approximate this critical amount of heat are constructed for nozzle flows with both given internal heat source distributions and nonequilibrium condensation. In particular a cubic equation for an estimate of the limiting condensate mass fraction for shock free condensing flows is derived and a criterion for the existence of supercritical condensing flows based on this estimate is established. The necessary and sufficient conditions for thermal choking are then stated. It is shown that the commonly accepted view, which asserts that the flow Mach number reaches unity at thermal choking (known to be not always true in condensing flows), only exhibits a necessary condition for a thermally choked flow. © 1993 BirkhÀuser Verlag
Comments on: "Starting solutions for some unsteady unidirectional flows of a second grade fluid," [Int. J. Eng. Sci. 43 (2005) 781]
A significant mathematical error is identified and corrected in a recent
highly-cited paper on oscillatory flows of second-grade fluids [Fetecau &
Fetecau (2005). Int. J. Eng. Sci., 43, 781--789]. The corrected solutions are
shown to agree identically with numerical ones generated by a finite-difference
scheme, while the original ones of Fetecau & Fetecau do not. A list of other
recent papers in the literature that commit the error corrected in this Comment
is compiled. Finally, a summary of related erroneous papers in this journal is
presented as an Appendix.Comment: 8 pages, 2 figures (4 images), elsarticle class; accepted for
publication in International Journal of Engineering Scienc
Similitude applied to centrifugal scaling of unsaturated flow
Centrifuge experiments modeling single-phase flow in prototype porous media typically use the same porous medium and permeant. Then, well-known scaling laws are used to transfer the results to the prototype. More general scaling laws that relax these restrictions are presented. For permeants that are immiscible with an accompanying gas phase, model-prototype (i.e., centrifuge model experiment-target system) scaling is demonstrated. Scaling is shown to be feasible for Miller-similar (or geometrically similar) media. Scalings are presented for a more, general class, Lisle-similar media, based on the equivalence mapping of Richards' equation onto itself. Whereas model-prototype scaling of Miller-similar media can be realized easily for arbitrary boundary conditions, Lisle-similarity in a finite length medium generally, but not always, involves a mapping to a moving boundary problem. An exception occurs for redistribution in Lisle-similar porous media, which is shown to map to spatially fixed boundary conditions. Complete model-prototype scalings for this example are derived
Computational applications in secondary metabolite discovery (caismd): An online workshop
We report the major conclusions of the online open-access workshop âComputational Applications in Secondary
Metabolite Discovery (CAiSMD)â that took place from 08 to 10 March 2021. Invited speakers from academia and
industry and about 200 registered participants from fve continents (Africa, Asia, Europe, South America, and North
America) took part in the workshop. The workshop highlighted the potential applications of computational methâ
odologies in the search for secondary metabolites (SMs) or natural products (NPs) as potential drugs and drug leads.
During 3 days, the participants of this online workshop received an overview of modern computer-based approaches
for exploring NP discovery in the âomicsâ age. The invited experts gave keynote lectures, trained participants in handson sessions, and held round table discussions. This was followed by oral presentations with much interaction between
the speakers and the audience. Selected applicants (early-career scientists) were ofered the opportunity to give oral
presentations (15 min) and present posters in the form of fash presentations (5 min) upon submission of an abstract.
The fnal program available on the workshop website (https://caismd.indiayouth.info/) comprised of 4 keynote lecâ
tures (KLs), 12 oral presentations (OPs), 2 round table discussions (RTDs), and 5 hands-on sessions (HSs). This meeting
report also references internet resources for computational biology in the area of secondary metabolites that are of
use outside of the workshop areas and will constitute a long-term valuable source for the community. The workshop
concluded with an online survey form to be completed by speakers and participants for the goal of improving any
subsequent editions
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