926 research outputs found
Large-time behavior of the weak solution to 3D Navier-Stokes equations
No full textThe weak solution to the Navier–Stokes equations in a bounded domain D ⊂ R[superscript 3] with a smooth boundary is proved to be unique provided that it satisfies an additional requirement. This solution exists for all t ≥ 0. In a bounded domain D the solution decays exponentially
fast as t → ∞if the force term decays at a suitable rat
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Segmenting Mechanomyography Measures of Muscle Activity Phases Using Inertial Data
No full textThis dataset contains the data used in our manuscript titled "Segmenting Mechanomyography Measures of Muscle Activity Phases Using Inertial Data". Data structure is explained in the README.txt file located at the top-level of the dataset. Manuscript title in the README.txt file and contained in the title of the zip file are of a previous working title. Please contact corresponding author Richard B. Woodward for any questions.</span
Strong solutions for the Navier–Stokes–Voigt equations with non-negative density
No full textThe aim of this work is to study the Navier–Stokes–Voigt equations that govern flows with non-negative density of incompressible fluids with elastic properties. For the associated nonlinear initial-and boundary-value problem, we prove the global-in-time existence of strong solutions (velocity, density and pressure). We also establish some other regularity properties of these solutions and find the conditions that guarantee the uniqueness of velocity and density. The main novelty of this work is the hypothesis that, in some subdomain of space, there may be a vacuum at the initial moment, that is, the possibility of the initial density vanishing in some part of the space domain.All authors were supported by the Grant No. AP19676624 Ministry of Science and Higher Education of the Republic of Kazakhstan
(Kazakhstan). The first author was also partially supported by CIDMA under the Portuguese Foundation for Science and Technology MultiAnnual Financing Program for R & D Units (FCT, https://ror.org/00snfqn58).publishe
Simplified Navier-Stokes equations (SNSE)
No full textTen kinds of the simplified Navier-Stokes equations (SNSE) are reviewed and also used to calculate the Jeffery-Hamel flow as well as to analyze briefly the seven kinds of flows to which the exact solutions of the complete Navier-Stokes equations (CNSE) have been found. Analysis shows that the actual differences among the solutions of the different SNSE can go beyond the range of the order of magnitude of Re-1/2 and result even in different flow patterns, therefore, how to choose the viscous terms included in the SNSE is worthy of notice where Re=S∞u∞ L/μ∞ is the Reynolds numbers. For the aforesaid eight kinds of flows, the solutions to the inner-outer-layer-matched SNSE and to the thin-layer-2-order SNSE agree completely with the exact solutions to CNSE. But the solutions to all the other SNSE are not completely consistent with the exact solutions to CNSE and not a few of them are actually the solutions of the classical boundary layer theory. The innerouter-layer-matched SNSE contains the shear stress causing angular displacement of the inormal axis with respect to the streamwise axis and the normal stress causing expansion-contraction in the direction of the normal axis and the viscous terms being of the order of magnitude of the normal stress; and it can also reasonably treat the inertial terms as well as the relation between the viscous and inertial terms. Therefore, it seems promising in respects of both mechanics and mathematics
Geostrophic convective turbulence: The effect of boundary layers
No full textWe conduct computations of rotating Rayleigh-Bénard convection in the so-called geostrophic regime, characterized by strong thermal forcing (high Rayleigh numbers) and strong rotation (small Ekman numbers). We employ the full Navier-Stokes equations in our computations and compare no-slip and stress-free boundaries for the plates. The Ekman boundary layers, that exist in the no-slip case but not for stress-free, enhance convective heat transfer and prevent the formation of large-scale flow structures
Markov closure for the Lundgren-Monin_Novikov hierarchy of velocity increments in Burgers turbulence
No full textA central, yet unsolved issue in the longstanding problem of hydrodynamic turbulence is the closure problem of turbulence, which is due to the nonlinear character of the Navier-Stokes equation. We formulate the closure problem for the many-increment probability distributions (PDF’s) in Burgers turbulence and introduce a new method for closing the hierarchy. To this end, we rely on the experimentally and numerically verified assumption in [1] that the turbulent cascade possesses a Markov property in scale down to the so-called Einstein-Markov length. The hierarchy is closed at the stage of the two-increment PDF corresponding to a three-point closure that allows for a description of intermittency effects, not captured by other closure approximations, i.e. Gaussian closures etc. The proposed closure also opens up a possible way to a perturbative treatment of the Navier-Stokes equation beyond the Einstein-Markov length in successively taking into account a larger and larger scale “history” of the system
Dynamical properties of preferential concentration and clustering of inertial particles in turbulent flows
No full textWe analyze one-way coupling DNS of heavy particles in homogeneous turbulent flow over a large range of Stokes numbers at Rλ= 180. We focus on preferential concentration and clustering aspects, and more particularly on their dynamical properties
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