scholarly journals Numerical Simulation of Fluid Flows in Rotary Discs

2020 ◽  
Author(s):  
Dragan Mandić ◽  
◽  
◽  
Keyword(s):  
Rotational Motion ◽  
Initial Conditions ◽  
Translational Motion ◽  
Fluid Motion ◽  
Fluid Flows ◽  
Fluid Stream ◽  
Rotary Disk ◽  
Complex Fluid ◽  
Flow Diagrams ◽  
Rotating Bodies

The object of this paper is to model the complex fluid motion that is caused by the rotational motion of rotary disks. In doing so, the rotary disk occupied a normal or parallel position with respect to the fluid flow axis. Various designs of rotary bodies were also applied, with the introduction of fluid through the central opening inside the impeller of the rotating bodies and with the introduction of fluid on the outer surfaces of these impellers (surfaces limited by the largest diameters of the rotary discs). During the modeling, different initial conditions for different structures and positions of rotating bodies were adopted. For each individual stream, flow diagrams are given through a cylindrical fluid stream whose translational motion is complicated by the rotational motion of the friction disks in its flow. The results obtained give a clear picture of the disturbances and changes in the front of the fluid motion wave which can be used as a necessary experience in the design of circulating technological systems.

GPU-Based Fluid Motion Estimation Using Energy Constraint

2016 ◽  
Vol 26 (02) ◽  
pp. 1750022 ◽  
Author(s):  
Siyuan Xu ◽  
Han Zhuang ◽  
Xin Fu ◽  
Junlong Zhou ◽  
Mingsong Chen
Keyword(s):  
Motion Estimation ◽  
Graphics Processing Unit ◽  
Fluid Motion ◽  
Fluid Flows ◽  
Brightness Distribution ◽  
Processing Unit ◽  
Consistency Constraints ◽  
Distribution Matrix ◽  
Complex Fluid ◽  
Graphics Processing

Although motion estimation (ME) approaches for fluid flows have been widely studied in computer vision domain, most existing ME algorithms cannot accurately deal with regions with both slight and drastic brightness changes. To address this issue, this paper introduces a novel data structure called brightness distribution matrix (BDM) which can be used to accurately model regional brightness. Based on our proposed consistency constraints and energy function, we can obtain motion vectors from image sequences with high accuracy. Since the BDM-based ME approach requires a large number of computations when dealing with complex fluid scenarios, to reduce the overall ME time, a parallelized version of our approach is developed based on graphics processing unit (GPU). Experimental results show that our GPU-based approach not only can be used to improve the ME quality for complex fluid images, but also can reduce the overall ME processing time (up to 7.06 times improvement).

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 Probing roto-translational diffusion of small anisotropic colloidal particles with a bright-field microscope

2021 ◽  
Vol 44 (4) ◽  
Author(s):  
Fabio Giavazzi ◽  
Antara Pal ◽  
Roberto Cerbino
Keyword(s):  
Particle Size ◽  
Rotational Motion ◽  
Colloidal Particles ◽  
Aqueous Suspension ◽  
Translational Motion ◽  
Translational Diffusion ◽  
Experimental Demonstration ◽  
Bright Field ◽  
Microscopic Scale ◽  
Bright Field Microscopy

Abstract Soft and biological materials are often composed of elementary constituents exhibiting an incessant roto-translational motion at the microscopic scale. Tracking this motion with a bright-field microscope becomes increasingly challenging when the particle size becomes smaller than the microscope resolution, a case which is frequently encountered. Here we demonstrate squared-gradient differential dynamic microscopy (SG-DDM) as a tool to successfully use bright-field microscopy to extract the roto-translational dynamics of small anisotropic colloidal particles, whose rotational motion cannot be tracked accurately in direct space. We provide analytical justification and experimental demonstration of the method by successful application to an aqueous suspension of peanut-shaped particles. Graphic abstract

On the role of helicity in complex fluid flows

1985 ◽  
Vol 113 (1) ◽  
pp. 32-37 ◽  
Author(s):  
Leonid Shtilman ◽  
Evgeny Levich ◽  
Steven A. Orszag ◽  
Richard B. Pelz ◽  
Arkady Tsinober
Keyword(s):  
Fluid Flows ◽  
Complex Fluid

scholarly journals Diffusion in the aqueous compartment.

1984 ◽  
Vol 99 (1) ◽  
pp. 180s-187s ◽  
Author(s):  
A M Mastro ◽  
A D Keith
Keyword(s):  
Rotational Motion ◽  
Spin Label ◽  
Mammalian Cells ◽  
Translational Motion ◽  
Diffusion Constant ◽  
Rotational Correlation Time ◽  
Model Systems ◽  
Quiescent Cells ◽  
Spin Resonance ◽  
In Cells

Measurements of diffusion of molecules in cells can provide information about cytoplasmic viscosity and structure. In a series of studies electron-spin resonance was used to measure the diffusion of a small spin label in the aqueous cytoplasm of mammalian cells. Translational and rotational motion were determined from the same spectra. Based on measurements made in model systems, it was hypothesized that calculations of the apparent viscosity of the cytoplasm from both rotational and translational motion would distinguish between the effects of viscosity and structure on diffusion. The diffusion constant measured in several cell lines averaged 3.3 X 10(-6) cm2/s. It was greater in growing cells and in cells treated with cytochalasin B than in quiescent cells. The viscosity of the cytoplasm calculated from the translational diffusion constant or the rotational correlation time was 2.0-3.0 centipoise, about two to three times that of the spin label in water. Therefore, over the dimensions measured by the technique, 50-100 A, solvent viscosity appears to be the major determinant of particle movement in cells under physiologic conditions. However, when cells were subjected to hypertonic conditions, the translational motion of the spin label decreased threefold, whereas the rotational motion changed by less than 20%. These data suggest that the decrease in cell volume under hypertonic conditions is accompanied by an increase in cytoplasmic barriers and a decrease in the space between existing cytoplasmic components without a significant increase in viscosity in the aqueous phase. In addition, a comparison of reported diffusion values of a variety of molecules in water and in cells indicates that cytoplasmic structure plays an important role in the diffusion of proteins such as bovine serum albumin.

scholarly journals FLOW RESISTANCE DUE TO INTENSE BEDLOAD TRANSPORT

1984 ◽  
Vol 1 (19) ◽  
pp. 89
Author(s):  
Daniel M. Hanes
Keyword(s):  
Flow Resistance ◽  
Fluid Motion ◽  
Fixed Bed ◽  
Fluid Flows ◽  
Frictional Resistance ◽  
Bedload Transport ◽  
Local Pressure ◽  
Gradient Forces ◽  
Granular Fluid ◽  
Lift Off

When water flows over a stationary bed the fluid motion is retarded by both skin the friction and local pressure gradient forces related to the roughness of the bed. If the bed itself is composed of discreet movable grains, the boundary is less clearly defined and the dynamics poorly understood (see Gust and Southard, 1983). Owen (1964) proposed that saltating grains (grains which lift off the bed, move through the fluid, and fall back to the bed without colliding with other grains) have the effect of increasing the frictional resistance of the bottom. At higher flow stages, Hanes and Bowen (1984) have suggested a model for bedload transport which is based upon the dynamics of collisional grain flows following Bagnold (1954, 1956). In such a collision dominated flow, it appears that the resistance of the bed to the overlying flow can be less than the resistance of a fixed bed to the same overlying flow. This result is consistent with the dynamics of rapid granular-fluid flows, as will be discussed below.

scholarly journals Rotational Behavior of Cometary-type Bodies

1992 ◽  
Vol 152 ◽  
pp. 291-296
Author(s):  
Eric Bois ◽  
Pascal Oberti ◽  
Claude Froeschlé
Keyword(s):  
Qualitative Study ◽  
Rotational Motion ◽  
Numerical Experiments ◽  
Initial Conditions ◽  
Close Approach ◽  
Rotational Behavior ◽  
Comet Nucleus ◽  
Gravitational Perturbation ◽  
The Sun ◽  
Sensitivity To Initial Conditions

The present paper deals with a general dynamical qualitative study of the rotational motion for cometary-type bodies submitted to gravitational torques. Numerical experiments of the evolution of comet nucleus attitude have been then performed, including the Sun and Jupiter's disturbing torques in the model. Results show small effects of the solar gravitational perturbation for Halley-type orbits. Only a very close-approach with Jupiter induces notable effects. The latter configuration presents some interesting sensitivity to initial conditions.

Secondary fluid flows driven electromagnetically in a two-dimensional extended duct

2005 ◽  
Vol 461 (2058) ◽  
pp. 1659-1683 ◽  
Author(s):  
Zhi-Min Chen ◽  
W.G Price
Keyword(s):  
Steady State ◽  
Laboratory Experiments ◽  
Fluid Motion ◽  
Fluid Flows ◽  
Two Dimensional ◽  
Slip Boundary Conditions ◽  
Slip Boundary ◽  
Wave Numbers ◽  
Motion Problem ◽  
Secondary Fluid

This study focuses on two-dimensional fluid flows in a straight duct with free-slip boundary conditions applied on the channel walls y =0 and y =2 πN with N >1. In this extended wall-bounded fluid motion problem, secondary fluid flow patterns resulting from steady-state and Hopf bifurcations are examined and shown to be dependent on the choice of longitudinal wave numbers. Some secondary steady-state flows appear at specific wave numbers, whereas at other wave numbers, both secondary steady-state and self-oscillation flows coexist. These results, derived through analytical arguments and truncation series approximation, are confirmed by simple numerical experiments supporting the findings observed from laboratory experiments.

scholarly journals Determining hydrodynamic forces in bursting bubbles using DNA nanotube mechanics

2015 ◽  
Vol 112 (45) ◽  
pp. E6086-E6095 ◽  
Author(s):  
Rizal F. Hariadi ◽  
Erik Winfree ◽  
Bernard Yurke
Keyword(s):  
Fluid Motion ◽  
Fluid Flows ◽  
Elongational Flow ◽  
Breaking Waves ◽  
Primitive Form ◽  
Flow Rates ◽  
Rate Distribution ◽  
Hydrodynamic Shear ◽  
Dna Nanotube ◽  
Self Replication

Quantifying the mechanical forces produced by fluid flows within the ocean is critical to understanding the ocean’s environmental phenomena. Such forces may have been instrumental in the origin of life by driving a primitive form of self-replication through fragmentation. Among the intense sources of hydrodynamic shear encountered in the ocean are breaking waves and the bursting bubbles produced by such waves. On a microscopic scale, one expects the surface-tension–driven flows produced during bubble rupture to exhibit particularly high velocity gradients due to the small size scales and masses involved. However, little work has examined the strength of shear flow rates in commonly encountered ocean conditions. By using DNA nanotubes as a novel fluid flow sensor, we investigate the elongational rates generated in bursting films within aqueous bubble foams using both laboratory buffer and ocean water. To characterize the elongational rate distribution associated with a bursting bubble, we introduce the concept of a fragmentation volume and measure its form as a function of elongational flow rate. We find that substantial volumes experience surprisingly large flow rates: during the bursting of a bubble having an air volume of 10 mm3, elongational rates at least as large as ϵ˙=1.0×108 s−1 are generated in a fragmentation volume of ∼2×10−6μL. The determination of the elongational strain rate distribution is essential for assessing how effectively fluid motion within bursting bubbles at the ocean surface can shear microscopic particles and microorganisms, and could have driven the self-replication of a protobiont.

The flow induced by the torsional oscillations of an elliptic cylinder

1995 ◽  
Vol 290 ◽  
pp. 279-298 ◽  
Author(s):  
N. Riley ◽  
M. F. Wybrow
Keyword(s):  
Small Amplitude ◽  
Fluid Motion ◽  
Fluid Flows ◽  
Elliptic Cylinder ◽  
Minor Axis ◽  
Oscillatory Motion ◽  
Torsional Oscillations ◽  
Steady Streaming ◽  
Axis Parallel ◽  
Streaming Flow

We consider the fluid motion induced when an elliptic cylinder performs small-amplitude torsional oscillations about an axis parallel to a generator which passes through either the centre or a point on the major or minor axis of the ellipse. In common with other fluid flows dominated by oscillatory motion, a time-independent, or steady streaming flow develops. This steady streaming exhibits several unusual and unexpected features, which are confirmed by experiment.

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