disk rotation
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Fluids ◽  
2022 ◽  
Vol 7 (1) ◽  
pp. 33
Author(s):  
Valerie Hietsch ◽  
Phil Ligrani ◽  
Mengying Su

We considered effective diffusion, characterized by magnitudes of effective diffusion coefficients, in order to quantify mass transport due to the onset and development of elastic instabilities. Effective diffusion coefficient magnitudes were determined using different analytic approaches, as they were applied to tracked visualizations of fluorescein dye front variations, as circumferential advection was imposed upon a flow environment produced using a rotating Couette flow arrangement. Effective diffusion coefficient results were provided for a range of flow shear rates, which were produced using different Couette flow rotation speeds and two different flow environment fluid depths. To visualize the flow behavior within the rotating Couette flow environment, minute amounts of fluorescein dye were injected into the center of the flow container using a syringe pump. This dye was then redistributed within the flow by radial diffusion only when no disk rotation was used, and by radial diffusion and by circumferential advection when disk rotation was present. Associated effective diffusion coefficient values, for the latter arrangement, were compared to coefficients values with no disk rotation, which were due to molecular diffusion alone, in order to quantify enhancements due to elastic instabilities. Experiments were conducted using viscoelastic fluids, which were based on a 65% sucrose solution, with different polymer concentrations ranging from 0 ppm to 300 ppm. Associated Reynolds numbers based on the fluid depth and radially averaged maximum flow velocity ranged from 0.00 to 0.5. The resulting effective diffusion coefficient values for different flow shear rates and polymer concentrations quantified the onset of elastic instabilities, as well as significant and dramatic changes to local mass transport magnitudes, which are associated with the further development of elastic instabilities.


2021 ◽  
Vol 34 (06) ◽  
pp. 1761-1767
Author(s):  
Anatoly Ivanovich Zavrazhnov ◽  
Aleksandr Vladimirovich Balashov ◽  
Sergey Petrovich Strygin ◽  
Nikita Yurievich Pustovarov ◽  
Andrey Anatolyevich Zavrazhnov

Mechanical and pneumatic seed drills of both domestic and foreign production are used in Russian farms. They are equipped with a mechanical drive of working tools and an electronic seeding control system. Due to the slipping of the wheels or the breakage of the chains, the sowing of seeds in individual seed dispensers interrupts. According to the results of laboratory and bench-scale studies in respect to soybean seeds, the required power for the electric drive of one seed dispenser was determined, which, depending on the disk rotation speed from 10 to 60 rpm, ranged from 30 to 120 W. By calculation, using the analytical expression, the power, required for the fan drive of a 12-row seed drill, was determined, which, depending on the disk rotation speed, ranged from 1.6 to 2.47 kW. A condition is formulated, which will eliminate the probability of shifting and rolling seeds along the furrow after their fall out of the sowing disc rotating in the opposite direction to the movement of the seeder unit, provided correspondence of the linear speed of the sowing disc and the speed of the seeder unit (the effect of zero overlaps). In this case, the trajectory length of the seeds falling to the furrow should be consistent with the speed of the seeder unit and the seeding rate according to the proposed expression.


2021 ◽  
Vol 923 (2) ◽  
pp. 251
Author(s):  
Yoshiaki Hagiwara ◽  
Shinji Horiuchi ◽  
Masatoshi Imanishi ◽  
Philip G. Edwards

Abstract We present the results of second-epoch ALMA observations of 321 GHz H2O emission toward two nearby active galactic nuclei, NGC 4945 and the Circinus galaxy, together with Tidbinbilla 70 m monitoring of their 22 GHz H2O masers. The two-epoch ALMA observations show that the strengths of the 321 GHz emission are variable by a factor of at least a few, confirming a maser origin. In the second epoch, 321 GHz maser emission from NGC 4945 was not detected, while for the Circinus galaxy the flux density significantly increased and the velocity gradient and dispersion have been measured. With the velocity gradient spanning ∼110 km s−1, we calculate the disk radius to be ∼28 pc, assuming disk rotation around the nucleus. We also estimate the dynamical mass within the central 28 pc to be 4.3 × 108 M ☉, which is significantly larger than the larger-scale dynamical mass, suggesting the velocity gradient does not trace circular motions on that scale. The overall direction of the velocity gradient and velocity range of the blueshifted features are largely consistent with those of the 22 GHz maser emission in a thin disk with smaller radii of 0.1–0.4 pc and molecular outflows within ∼1 pc from the central engine of the galaxy, implying that the 321 GHz masers could trace part of the circumnuclear disk or the nuclear outflows.


2021 ◽  
Vol 939 (1) ◽  
pp. 012033
Author(s):  
A Lee ◽  
B Utepov ◽  
E Kan ◽  
O Kuychiev

Abstract This article presents the theoretical background for the justification of the parameters of the rotating sprayer. Theoretical studies show that an increase in the rotation frequency of the disk at a constant air flow velocity leads to a minimum median mass diameter of the droplets. Therefore, when justifying the diameter of the sprayed droplets, it is necessary to consider the combination of the disk rotation speed and the axial velocity of the air flow. To obtain high-quality air-droplet flow, the initial speed of the main droplets discharged from the periphery of the spray disc should be less than the air velocity and rotational frequency Pavlovskyi spray is recommended to be applied with in ω=60… 200 c1.


Author(s):  
Анна Игоревна Пичугина ◽  
Дарья Дмитриевна Гончар

В работе представлены результаты исследования кинетики сернокислого выщелачивания никеля из его сульфидов. В качестве модельных образцов выбраны синтезированные сульфиды никеля по составу и строению идентичные природным минералам: миллериту и хизлевудиту. Получены зависимости влияния скорости извлечения металла от концентрации серной кислоты, температуры, частоты вращения диска и продолжительности взаимодействия. Рассчитаны полиномиальные модели изучаемого процесса, преобразованные в уравнения скорости. Вычислены константы скорости и эмпирические значения энергии активации. The paper presents the results of a study of the kinetics of sulfuric acid leaching of nickel from its sulfides. Synthesized nickel sulfides were selected as model samples, identical in composition and structure to natural minerals: millerite and heazlewudite. The dependences of the influence of the metal extraction rate on the concentration of sulfuric acid, temperature, disk rotation frequency and duration of interaction are obtained. The polynomial models of the process under study, transformed into velocity equations, are calculated. The rate constants and empirical values of the activation energy are calculated.


2021 ◽  
Vol 2057 (1) ◽  
pp. 012092
Author(s):  
V G Glavnyi ◽  
V V Rakhmanov ◽  
S V Dvoynishnikov ◽  
S V Krotov ◽  
V G Meledin

Abstract Primary standards for the unit of air flow velocity often use a Laser Doppler Anemometer (LDA) as the primary measurement standard. A rotating disc with a fixed diameter is used to calibrate LDA. The paper proposes calibration platform based on the precision mechanics of HDD disk. A disk rotation controller has been developed for the platform. Deviations of the disk rotation speed do not exceed 0.01% RMS in the range of angular speeds of 600-4800 rpm.


2021 ◽  
Vol 925 ◽  
Author(s):  
Scott Morgan ◽  
Christopher Davies ◽  
Christian Thomas

The control of stationary convective instabilities in the rotating disk boundary layer via a time-periodic modulation of the disk rotation rate is investigated. The configuration provides an archetypal example of a three-dimensional temporally periodic boundary layer, encompassing both the von Kármán and Stokes boundary layers. A velocity–vorticity formulation of the governing perturbation equations is deployed, together with a numerical procedure that utilises the Chebyshev-tau method. Floquet theory is used to determine the linear stability properties of these time-periodic flows. The addition of a time-periodic modulation to the otherwise steady disk rotation rate establishes a stabilising effect. In particular, for a broad range of modulation frequencies, the growth of the stationary convective instabilities is suppressed and the critical Reynolds number for the onset of both the cross-flow and Coriolis instabilities is raised to larger values than that found for the steady disk without modulation. An energy analysis is undertaken, where it is demonstrated that time-periodic modulation induces a reduction in the Reynolds stress energy production and an increase in the viscous dissipation across the boundary layer. Comparisons are made with other control techniques, including distributed surface roughness and compliant walls.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Anupam Bhandari

Abstract This paper investigates the flow of water-based Fe3O4 ferrofluid flow and heat transfer due to rotating cone and disk under the influence of the external magnetic field. The similarity approach is used to transform the governing equations of ferrohydrodynamic flow into a set of nondimensional coupled differential equations. The nondimensional coupled differential equations are solved numerically through the finite element procedure. Effect of rotation of the disk, rotation of the cone, the intensity of the magnetic field, volume concentrations, and Prandtl number are analyzed on the velocity and temperature distributions. These effects are also observed on the skin friction coefficients and local heat transfer rate. The rotation of the disk, rotation of the cone, and the intensity of the magnetic field have a major impact on the velocity profiles, temperature profiles, skin friction coefficients, and local heat transfer rate.


2021 ◽  
Vol 25 (2) ◽  
pp. 99-107
Author(s):  
S.V. Fokin ◽  
◽  
O.A. Fomina ◽  

The article describes the methodology of physical and mathematical modeling of the mechanism for ejection of chips of a disk chipper. This technique allows you to calculate and optimize the design and technological parameters of the chip ejection mechanism. To accomplish this task, the flow of chip elements was divided into separate spherical elements, and the working surfaces of the chip ejection mechanism are represented by a set of fragments of planes conjugated to each other. When creating a mathematical model for calculating and optimizing the design and technological parameters of the chip ejection mechanism, the following indicators of the efficiency of the chip ejection mechanism were analyzed: the rate of chip ejection at the exit of the chipping line, the probability of chip ejection from the first revolution of the chipping disk, the mechanical power consumed for the ejection of chips after the stage of crushing the cut residues knives. The mathematical model is implemented in a computer program in the Object Pascal language in the Delphi 7 development environment. The program allows carrying out computer experiments to analyze the movement in the casing and chipping of chips obtained from felling residues and to study the effect of the design and technological parameters of the ejection mechanism on the efficiency of the disk chipper. The computer studies carried out made it possible to determine the best numerical ranges of the chipping disk rotation frequency and the number of blades located on the chipping disk. The likelihood of chip entrainment at the first revolution of the chipping disk and the power consumption for the ejection of chips from the disk chipper were also determined.


Author(s):  
Zitao Hu ◽  
Xue-Ning Bai

Abstract It has recently been shown that the inner region of protoplanetary disks (PPDs) is governed by wind-driven accretion, and the resulting accretion flow showing complex vertical profiles. Such complex flow structures are further enhanced due to the Hall effect, especially when the background magnetic field is aligned with disk rotation. We investigate how such flow structures impact global dust transport via Monte-Carlo simulations, focusing on two scenarios. In the first scenario, the toroidal magnetic field is maximized in the miplane, leading to accretion and decretion flows above and below. In the second scenario, the toroidal field changes sign across the midplane, leading to an accretion flow at the disk midplane, with decretion flows above and below. We find that in both cases, the contribution from additional gas flows can still be accurately incorporated into the advection-diffusion framework for vertically-integrated dust transport, with enhanced dust radial (pseudo-)diffusion up to an effective αeff ∼ 10−2 for strongly coupled dust, even when background turbulence is weak α < 10−4. Dust radial drift is also modestly enhanced in the second scenario. We provide a general analytical theory that accurately reproduces our simulation results, thus establishing a framework to model global dust transport that realistically incorporates vertical gas flow structures. We also note that the theory is equally applicable to the transport of chemical species.


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