Phase transitions on partially contaminated surface under the influence of thermocapillary flow

2019 ◽  
Vol 877 ◽  
pp. 495-533 ◽  
Author(s):  
A. V. Shmyrov ◽  
A. I. Mizev ◽  
V. A. Demin ◽  
M. I. Petukhov ◽  
D. A. Bratsun
Keyword(s):  
Experimental Data ◽  
Numerical Solutions ◽  
Thermocapillary Flow ◽  
Creeping Flow ◽  
Stagnant Zone ◽  
Surface Velocity ◽  
Condensed State ◽  
Flow Forming ◽  
Perfect Agreement ◽  
Linear Temperature

We study, both experimentally and theoretically, the fluid flow driven by a thermocapillary effect applied to a partially contaminated interface in a two-dimensional slot of finite extent. The contamination is due to the presence of an insoluble surfactant which is convected by the flow forming a stagnant zone by the colder edge of the interface. The thermocapillary surface stress is produced by a special optocapillary system, which makes it possible, first, to get an almost linear temperature profile along the interface and, second, to apply a surface pressure large enough to force the surfactant to experience a phase transition to a more condensed state. This enabled us for the first time since the release of the paper by Carpenter & Homsy (J. Fluid Mech., vol. 155, 1985, pp. 429–439) to test experimentally their theoretical predictions and obtain new results for the case when the contamination exists simultaneously in two phase states within the interface. We show that one part of the surface is free of surfactant and subject to vigorous thermocapillary flow, while another part is stagnant and subject to creeping flow with a surface velocity which is approximately two orders of magnitude smaller. We found that the extent of the stagnant zone theoretically predicted earlier does not coincide with the newly obtained experimental data. In this paper, we suggest analytical and numerical solutions for the position of the edge of the stagnation zone, which are in perfect agreement with the experimental data.

Attenuation estimation using sweep signals in ultrasonic laboratory measurements

Geophysics ◽  
2014 ◽  
Vol 79 (3) ◽  
pp. V115-V130 ◽  
Author(s):  
Jun Matsushima ◽  
Makoto Suzuki ◽  
Ippei Matsugi ◽  
Yoshibumi Kato ◽  
Shuichi Rokugawa
Keyword(s):  
Experimental Data ◽  
Wave Attenuation ◽  
Time Window ◽  
Ultrasonic Attenuation ◽  
Pulse Generation ◽  
Ratio Method ◽  
Spectral Amplitude ◽  
Multiple Reflections ◽  
Perfect Agreement ◽  
Attenuation Estimation

It is important to obtain reliable attenuation results from experimental data to elucidate the physical mechanism responsible for ultrasonic wave attenuation. For attenuation estimation, a time window is often used to compute the frequencies of the direct-arrival waveforms. However, the effect of windowing distorts the spectral distribution due to a spectral leakage effect, degrading the attenuation estimates. We propose a method that enables accurate measurement of ultrasonic attenuation using sweep signals under the assumptions that velocity dispersion can be ignored and the quality factor [Formula: see text] is not dependent on frequency. We obtained the spectral amplitude of the sweep signal in the frequency-time domain using the continuous wavelet transform and estimated attenuation in the time-scale spectrum domain using the spectral-ratio method. This method is independent of the effect of windowing, whereas the windowing effect underestimates the attenuation results. In the absence of noise, the estimated attenuation results using sweep signals are in perfect agreement with the given input values, and the accuracy of the estimated attenuation results from windowed pulse waveforms depends on the extraction window length. However, our numerical experiments demonstrated that the proposed method is largely influenced by the existence of overlapping sweep events such as multiple reflections between the source and receiver transducer. Thus, applicability of the proposed method is limited to highly attenuative media, in which overlapping events are much smaller than direct sweep signals because these multiple reflected events are largely attenuated. Application of the proposed method to laboratory experimental data yielded similar underestimation of the attenuation results due to the windowing effect in the case of highly attenuative media. We also evaluated the usefulness of observing compressed pulse waveforms with shorter duration from the crosscorrelation of sweep waveforms than the case of pulse generation.

Thermal Elastohydrodynamic Lubrication Analysis for Point Contact Transmission

2009 ◽  
Author(s):  
Hai-zhou Huang ◽  
Xi-chuan Niu ◽  
Xiao-yang Yuan
Keyword(s):  
Film Thickness ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Surface Velocity ◽  
Squeeze Film ◽  
Elastic Displacement ◽  
Circular Arc ◽  
Tooth Width ◽  
Contact Transmission

To investigate the thermal EHL (elastohydrodynamic lubrication) in point contact transmission, a model considering the two-dimensional surface velocity of tooth face and the running-in is proposed. The numerical solutions for pressure, temperature and film thickness distribution in the contact zone are obtained by solving equations including the Reynolds, Energy and the elastic displacement with variable dimension meshing method. The model was used to study the point contact transmission of the circular arc gear in a windlass. The main results show that it is pure rolling along the direction of tooth width, and the rolling speed plays a leading role in improving the lubricating performance and transmission efficiency of circular arc gear. The squeeze film effect makes the pressure peak tend to be gentle and the film thickness increase slightly.

Jet-to-Plate Distance Effect on Heat Transfer From a Flat Plate to an Impinging Jet at Various Reynolds Numbers

2012 ◽  
Author(s):  
Patricia Streufert ◽  
Terry X. Yan ◽  
Mahdi G. Baygloo
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Flat Plate ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Air Jet ◽  
Plate Distance

Local turbulent convective heat transfer from a flat plate to a circular impinging air jet is numerically investigated. The jet-to-plate distance (L/D) effect on local heat transfer is the main focus of this study. The eddy viscosity V2F turbulence model is used with a nonuniform structured mesh. Reynolds-Averaged Navier-Stokes equations (RANS) and the energy equation are solved for axisymmetric, three-dimensional flow. The numerical solutions obtained are compared with published experimental data. Four jet-to-plate distances, (L/D = 2, 4, 6 and 10) and seven Reynolds numbers (Re = 7,000, 15,000, 23,000, 50,000, 70,000, 100,000 and 120,000) were parametrically studied. Local and average heat transfer results are analyzed and correlated with Reynolds number and the jet-to-plate distance. Results show that the numerical solutions matched experimental data best at low jet-to-plate distances and lower Reynolds numbers, decreasing in ability to accurately predict the heat transfer as jet-to-plate distance and Reynolds number was increased.

scholarly journals The Flow of a Glacier in a Channel of Rectangular, Elliptic or Parabolic Cross-Section

1965 ◽  
Vol 5 (41) ◽  
pp. 661-690 ◽  
Author(s):  
J. F. Nye
Keyword(s):  
Cross Section ◽  
Numerical Solutions ◽  
Maximum Shear Stress ◽  
Surface Velocity ◽  
Channel Section ◽  
Ice Surface ◽  
Centre Line ◽  
Symmetry Principles ◽  
Wide Range ◽  
Flow Law

AbstractNumerical solutions are found for the steady rectilinear flow of ice, obeying Glen’s non-linear flow law, down uniform cylindrical channels of rectangular, semi-elliptic and parabolic cross-section. The results are also directly applicable to the pumping of a non-Newtonian fluid down a pipe. There is assumed to be no slip of the ice on the channel surface. Certain results on the centre-line velocity in symmetrical channels may be derived purely from dimensional and symmetry principles. An analytical solution due to Dr. W. Chester is given for a semi-elliptic channel section which departs only slightly from a semi-circle. Contrary to a view sometimes held, the maximum shear stress at the ice surface in a parabolic channel and in some elliptical channels does not always occur at the edge. With the flow law, strain-rate proportional to (stress)3, the velocity averaged across the ice surface, which is easily measured with a line of stakes, is close to the average velocity over the whole section for a wide range of parabolic sections; the hydrological importance of this result is that the discharge may be inferred without the need to measure the velocity at depth. Arguments are given to show that the result still holds when there is slipping on the bed and when the power in the flow law differs somewhat from 3, Depending on the amount of bed slip and the shape of the channel section, the kinematic wave velocity for a range of parabolic channels is between 2.0 and 2.3 times the centre-line velocity of the ice, and between 2.0 and 3.5 times the mean surface velocity of the ice.

Numerical Analysis of Heat and Mass Transfer From Fluid Spheres in an Electric Field

1986 ◽  
Vol 108 (2) ◽  
pp. 337-342 ◽  
Author(s):  
L. Sharpe ◽  
F. A. Morrison
Keyword(s):  
Mass Transfer ◽  
Electric Field ◽  
Radial Flow ◽  
Numerical Solutions ◽  
Creeping Flow ◽  
Dimensionless Temperature ◽  
Flow Heat ◽  
Steady State Heat ◽  
Transmitting Boundary ◽  
Finite Difference Techniques

Steady-state heat or mass transfer to a drop in an electric field at low values of the Reynolds number is investigated. The energy equation is solved using finite difference techniques; upwind differencing is used in approximating the convective terms. Far from the sphere, a “transmitting” boundary condition is introduced; the dimensionless temperature is held at zero for inward radial flow and the dimensionless temperature gradient is held at zero for outward radial flow at a fixed distance from the sphere’s surface. Numerical solutions are obtained using an iterative method. Creeping flow heat transfer results are obtained for Peclet numbers up to 103.

scholarly journals Application of the Method of Integral Relations to the Calculation of Two-Dimensional Incompressible Turbulent Boundary Layer

1981 ◽  
Vol 48 (4) ◽  
pp. 701-706 ◽  
Author(s):  
W.-S. Yeung ◽  
R.-J. Yang
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Numerical Solutions ◽  
Experimental Results ◽  
Two Dimensional ◽  
Incompressible Turbulent Boundary Layer ◽  
Method Of Integral Relations ◽  
Integral Relations

The orthonormal version of the Method of Integral Relations (MIR) was applied to solve for a two-dimensional incompressible turbulent boundary layer. The flow was assumed to be nonseparating. Flows with favorable, unfavorable, and zero pressure gradient were considered, and comparisons made with available experimental data. In general, the method predicted very well the experimental results for flows with favorable or zero pressure gradient; for flows with unfavorable pressure gradient, it predicted the experimental data well only up to a certain distance from the initial station. This result is due to the flow not being in equilibrium beyond that distance. Finally, the scheme was shown to be efficient in obtaining numerical solutions.

Stability of fluid flow through deformable neo-Hookean tubes

2009 ◽  
Vol 627 ◽  
pp. 291-322 ◽  
Author(s):  
GAURAV ◽  
V. SHANKAR
Keyword(s):  
Reynolds Number ◽  
Numerical Solutions ◽  
Unstable Mode ◽  
Creeping Flow ◽  
Interfacial Instability ◽  
Elastic Model ◽  
Deformable Solid ◽  
Linear Elastic ◽  
Linear Elastic Model ◽  
Flow Through

The linear stability of fully developed Poiseuille flow of a Newtonian fluid in a deformable neo-Hookean tube is analysed to illustrate the shortcomings of extrapolating the linear elastic model for the tube wall outside its domain of validity of small strains in the solid. We show using asymptotic analyses and numerical solutions that a neo-Hookean description of the solid dramatically alters the stability behaviour of flow in a deformable tube. The flow-induced instability predicted to exist in the creeping-flow limit based on the linear elastic approximation is absent in the neo-Hookean model. In contrast, a new low-wavenumber (denoted by k) instability is predicted in the limit of very low Reynolds number (Re ≪ 1) with k ∝ Re1/2 for purely elastic (with ratio of solid to fluid viscosities ηr = 0) neo-Hookean tubes. The first normal stress discontinuity in the neo-Hookean solid gives rise to a high-wavenumber interfacial instability, which is stabilized by interfacial tension at the fluid–wall interface. Inclusion of dissipation (ηr ≠ 0) in the solid has a stabilizing effect on the low-k instability at low Re, and the critical Re for instability is a sensitive function of ηr. For Re ≫ 1, both the linear elastic extrapolation and the neo-Hookean model agree qualitatively for the most unstable mode, but show disagreement for other unstable modes in the system. Interestingly, for plane-Couette flow past a deformable solid, the results from the extrapolated linear elastic model and the neo-Hookean model agree very well at any Reynolds number for the most unstable mode when the wall thickness is not small. The results of this study have important implications for experimental investigations aimed at probing instabilities in flow through deformable tubes.

Experimental Studies of Hydrodynamic Interaction of Two Bodies in Waves

2015 ◽  
Author(s):  
Quan Zhou ◽  
Ming Liu ◽  
Heather Peng ◽  
Wei Qiu
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Potential Flow ◽  
Numerical Solutions ◽  
Experimental Studies ◽  
Low Frequency ◽  
Surface Elevation ◽  
Linear Potential ◽  
Free Surface Elevation ◽  
Two Bodies

There are challenges in the prediction of low-frequency load and especially the resonant free surface elevation between two bodies in close proximity. Most of the linear potential-flow based seakeeping programs currently used by the industry over-predict the free surface elevation between the vessels/bodies and hence the low-frequency loadings on the hulls. Various methods, such as the lid technique, have been developed to suppress the unrealistic values of low-frequency forces by introducing artificial damping coefficients. However, without the experimental data, it is challenging to specify the coefficients. This paper presents the experimental studies of motions of two bodies with various gaps and the wave elevations between bodies. Model tests were performed at the towing tank of Memorial University. The objective was to provide benchmark data for further numerical studies of the viscous effect on the free surface predictions. The experimental data were compared with numerical solutions based on potential flow methods. The effect of tank walls were examined. Preliminary uncertainty analysis was also carried out.

A Model for Flow Distribution in Manifolds

1971 ◽  
Vol 93 (1) ◽  
pp. 7-12 ◽  
Author(s):  
R. A. Bajura
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Analytical Model ◽  
Distribution Systems ◽  
Numerical Solutions ◽  
Flow Behavior ◽  
Flow Distribution ◽  
Analytical Investigation ◽  
Momentum Balance ◽  
Distribution Equation

An analytical investigation of the performance of flow distribution systems was conducted for both intake and exhaust manifolds. Primary emphasis was placed on configurations in which the lateral tubes formed sharp-edged junctions at right angles to the manifold axis. A mathematical model describing the flow behavior at a discreet branch point was formulated in terms of a momentum balance along the manifold. The model was extended to the case of continuous discharge or intake for a uniformly porous manifold. Numerical solutions of the governing flow distribution equation were obtained and compared with experimental data. Dimensionless parameters characterizing the performance of manifolds were formulated from the analytical model.

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