scholarly journals LXI. On the stability of steady and of periodic fluid motion (continued from May number).—Maximum and minimum energy in vortex motion

1887 ◽  
Vol 23 (145) ◽  
pp. 529-539 ◽  
Author(s):  
William Thomson
Keyword(s):  
Minimum Energy ◽  
Fluid Motion ◽  
Vortex Motion ◽  
The Stability

4D Investigation of Vortex Fluid Motion Inside the Eyeball

2021 ◽  
pp. 73-88
Author(s):  
S.A. Skladchikov ◽  
N.P. Savenkova ◽  
P.I. Vysikaylo ◽  
S.E. Avetisov ◽  
D.V. Lipatov ◽  
...  
Keyword(s):  
Numerical Models ◽  
Fluid Motion ◽  
Vortex Motion ◽  
Dissipative System ◽  
Fluid Flows ◽  
Vitreous Cavity ◽  
Posterior Chamber ◽  
Medicinal Substance ◽  
Fluid Transfer ◽  
And Diffusion

The eye is a complex system of boundaries and fluids with different viscosities within the boundaries. At present, there are no experimental possibilities to thoroughly observe the dynamic 4D processes after one or another method of eye treatment is applied. The complexity of cumulative, i.e., focusing, and dissipative, i.e., scattering, convective and diffusion 4D fluxes of fluids in the eye requires 4D analytical and numerical models of fluid transfer in the human eyeball to be developed. The purpose of the study was to develop and then verify a numerical model of 4D cumulative-dissipative processes of fluid transfer in the eyeball. The study was the first to numerically evaluate the values of the characteristic time of the drug substance in the vitreous cavity until it is completely washed out, depending on the injection site; to visualize the paths of the vortex motion of the drug in the vitreous cavity; to determine the main parameters of the 4D fluid flows of the medicinal substance in the vitreous cavity, depending on the presence or absence of vitreous detachment from the wall of the posterior chamber of the eye. The results obtained are verified by the experimental data available to doctors. In the eye, as a partially open cumulative-dissipative system, Euler regions with high rates of cumulative flows and regions with low speeds or stagnant Lagrange flow zones are defined

scholarly journals Approaching Bulk from the Nanoscale: Extrapolation of Binding Energy from Rock-Salt Cuts of Alkaline Earth Metal Oxides

2021 ◽  
Vol 74 ◽  
Author(s):  
Susanne G.E.T. Escher ◽  
Helen D. Duncan ◽  
Alexey A. Sokol ◽  
Scott M. Woodley
Keyword(s):  
Metal Oxides ◽  
Rock Salt ◽  
Alkaline Earth ◽  
Global Minimum ◽  
Minimum Energy ◽  
Earth Metal ◽  
Alkaline Earth Metal ◽  
Bulk Rock ◽  
Alkaline Earth Metal Oxides ◽  
The Stability

ABSTRACT A systematic DFT study is performed on (MgO)B, (CaO)n, (SrO)n, and (BaO)n clusters with 6 < n < 50, and which display a cuboid 2X2X2 atomic motif seen in the bulk, rock-salt, configuration. The stability and energy progression of these clusters are used to predict the energies of infinitely long nanorods, or nanowires, slabs, and the bulk global minimum energy. Keywords: Alkaline earth metal oxides, nanoclusters, nanorods, DFT.

An investigation on the instability of a flexible liquid-filled rotor

2019 ◽  
Vol 234 (2) ◽  
pp. 165-172
Author(s):  
Guangding Wang ◽  
Huiqun Yuan ◽  
Hongyun Sun
Keyword(s):  
Stokes Equations ◽  
Fluid Motion ◽  
Coupling Model ◽  
Frequency Equation ◽  
Rotor System ◽  
System Stability ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Continuity Equations ◽  
The Stability

In this paper, the stability of a flexible rotor partially filled with liquid is investigated. On the basis of the Navier-Stokes equations for the incompressible flow, a two-dimensional analytical model is developed for fluid motion. Applying the perturbation method, the linearized Navier-Stokes and continuity equations of fluid particles are obtained. Using the boundary conditions of fluid motion, the fluid forces exerted on the rotor are calculated. According to the established fluid-structure coupling model of the rotor system, the whirling frequency equation, which is applied to determine the stability of the system, is derived. The analysis results of the system stability are compared with the theoretical ones reported in the previous study. Good agreement is shown between the results of the present analysis and the literature results. The influences of the main parameters on the dynamic stability of the rotor system are discussed.

A Theoretical Discussion of a Menisci Micropump Driven by an Electric Field

2006 ◽  
Vol 129 (4) ◽  
pp. 404-411 ◽  
Author(s):  
Alexandru Herescu ◽  
Jeffrey S. Allen
Keyword(s):  
Electric Field ◽  
Fluid Motion ◽  
Liquid Interfaces ◽  
Vapor Bubbles ◽  
Liquid Phases ◽  
The Stability ◽  
Novel Concept ◽  
Enhanced Boiling ◽  
Stability Limits ◽  
Induced Dipoles

The potential for miniaturization of analytical devices made possible by advances in micro-fabrication technology is driving demand for reliable micropumps. A wide variety of micropumps exist with many types of actuating mechanisms. One such mechanism is electrohydrodynamic (EHD) forces which rely upon Coulomb forces on free charges and/or polarization forces on induced dipoles within the liquid to induce fluid motion. EHD has been used to pump liquid phases and to displace gas–liquid interfaces for enhanced boiling heat transfer as well as to displace gas/vapor bubbles. A novel concept for using EHD polarization forces to deflect a stationary meniscus in order to compress and pump a gaseous phase is described. The pumping mechanism consists in alternative compression of two gas volumes by continuous deflection of the two pinned menisci of an entrapped liquid slug in an electric field. Using the Maxwell stress relations, the electric field strength necessary to operate the pump is determined. The operational limits are determined by analyzing the stability limits of the two menisci from inertial and viscous standpoints, corroborated with the natural frequencies of the gas–liquid interfaces.

Thermodynamics and the stability of fluid motion

1967 ◽  
Vol 25 (5) ◽  
pp. 321-341 ◽  
Author(s):  
Bernard D. Coleman ◽  
James M. Greenberg
Keyword(s):  
Fluid Motion ◽  
The Stability

scholarly journals The steady motion and stability of a helical vortex

1928 ◽  
Vol 120 (786) ◽  
pp. 670-690 ◽  
Keyword(s):  
Reynolds Number ◽  
Vortex Motion ◽  
Steady Motion ◽  
Vortex Rings ◽  
Cross Sectional ◽  
Flow Past A Cylinder ◽  
Two Dimensional Flow ◽  
The Stability ◽  
Sectional Shape ◽  
Stable Formation

1. Introductory .—This is the third of a series of papers dealing with the stability or instability of certain forms of vortex motion associated with the wake of a body moving in a fluid. In the earlier papers we examined the case of a system of equal vortex rings in parallel planes, as they might form in the rear of a sphere in steady motion. Nisi and Porter have shown that the lowest speed at which the vortex ring forms is 8·14 v / d where v is the kinematic viscosity of the fluid and d is the diameter of the sphere. Such a system of vortices has been proved to be only partially stable, and it is therefore to be inferred that their production occurs at a transition stage to a more stable type of flow. Now it is well known that in the case of two dimensional flow past a cylinder of any cross-sectional shape, eddies are formed in symmetrical pairs at low values of Reynolds' number, whereas at higher values asymmetry sets in and the eddying is formed alternately at one side of the cylinder and then at the other with regular periodicity. This latter stage occurs over a range of values of Reynolds’ number extending from about 70 to 10 5 . Detailed explorations of the field for some distance behind the cylinder have established that the centres of eddying approximately assume the stable formation which has come to be known as the “Kármán vortex street."

On the spin-up and spin-down of a rotating fluid. Part 2. Measurements and stability

1976 ◽  
Vol 77 (4) ◽  
pp. 709-735 ◽  
Author(s):  
Patrick D. Weidman
Keyword(s):  
Stability Boundary ◽  
Fluid Motion ◽  
Azimuthal Velocity ◽  
Laser Doppler Velocimeter ◽  
Rotating Fluid ◽  
Constant Acceleration ◽  
Centrifugal Instability ◽  
The Stability ◽  
Theoretical Results

Measurements of the azimuthal velocity inside a cylinder which spins up or spins down at constant acceleration were obtained with a laser-Doppler velocimeter and compared with the theoretical results presented in part 1. Velocity profiles near the wave front in spin-up indicate that the velocity discontinuity given by the inviscid Wedemeyer model is smoothed out in a shear layer whose thickness varies with radius and time but scales with hE1/4Ω. The spin-down profiles are always in excellent agreement with theory when the flow is stable. Visualization studies with aluminium tracers have made possible the determination of the stability boundary for Ekman spiral waves (principally type II waves) observed on the cylinder end walls during spin-up. For spin-down to rest the flow always experienced a centrifugal instability which ultimately disrupted the interior fluid motion.

scholarly journals A possible quantum fluid-dynamical approach to vortex motion in nuclei

2017 ◽  
Vol 26 (04) ◽  
pp. 1750020
Author(s):  
Seiya Nishiyama ◽  
João da Providência
Keyword(s):  
Fluid Dynamics ◽  
Rotational Motion ◽  
Collective Motion ◽  
Rotational Velocity ◽  
Fluid Motion ◽  
Vortex Motion ◽  
Representation Formula ◽  
Essential Point ◽  
Quantum Fluid ◽  
Long Time

The essential point of Bohr–Mottelson theory is to assume an irrotational flow. As was already suggested by Marumori and Watanabe, the internal rotational motion, i.e., the vortex motion, however, may exist also in nuclei. So, we must take the vortex motion into consideration. In classical fluid dynamics, there are various ways to treat the internal rotational velocity. The Clebsch representation, [Formula: see text] is very powerful and allows for the derivation of the equations of fluid motion from a Lagrangian. Making the best use of this advantage, Kronig–Thellung, Ziman and Ito obtained a Hamiltonian including the internal rotational motion, the vortex motion, through the term [Formula: see text]. Going to quantum fluid dynamics, Ziman and Thellung finally derived the roton spectrum of liquid Helium II postulated by Landau. Is it possible to follow a similar procedure in the description of the collective vortex motion in nuclei? The description of such a collective motion has not been considered in the context of the Bohr–Mottelson model (BMM) for a long time. In this paper, we will investigate the possibility of describing the vortex motion in nuclei on the basis of the theories of Ziman and Ito together with Marumori’s work.

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