Convection, Evaporation, and Condensation of Simple and Binary Fluids in Confined Geometries

2012 ◽  
Author(s):  
Tongran Qin ◽  
Roman O. Grigoriev
Keyword(s):  
Free Surface ◽  
Phase Change ◽  
Concentration Field ◽  
Major Effect ◽  
Binary Fluids ◽  
Homogeneous Fluid ◽  
Evaporation And Condensation ◽  
Numerical Studies ◽  
Alcohol Water ◽  
Convection Problem

Rayleigh-Bénard and Marangoni convection in a layer of a homogeneous fluid with a free surface in the absence of phase change is a classic (and extensively studied) problem of fluid mechanics. Phase change has a major effect on the convection problem. Most notably, significant latent heat generated at the free surface as a result of phase change can dramatically alter the interfacial temperature, and hence, the thermocapillary stresses. Furthermore, differential evaporation in binary fluids can lead to considerable variation in the concentration field, producing solutocapillarity stresses, which can compete with thermocapillarity and buoyancy. This talk describes numerical studies of convection in alcohol and alcohol-water mixtures due to a horizontal temperature gradient in the presence of phase change. We illustrate how the composition of the liquid and the presence of non-condensable gases (e.g., air) can be used to alter the balance of the dominant forces. In particular, by adding or removing air from the test cell, the direction of the flow can be reversed by emphasizing either the thermocapillary or the solutocapillary stresses.

Experimental Studies of Nonisothermal Binary Fluids With Phase Change in Confined Geometries

2012 ◽  
Author(s):  
Yaofa Li ◽  
Benjamin M. Chan ◽  
Minami Yoda
Keyword(s):  
Surface Tension ◽  
Mass Transport ◽  
Phase Change ◽  
Experimental Studies ◽  
Liquid Density ◽  
Binary Fluids ◽  
Vapor Interface ◽  
Evaporation And Condensation ◽  
Alcohol Water ◽  
Liquid Vapor

Evaporative cooling, which exploits the large latent heats associated with phase change, is of interest in a variety of thermal management technologies. Yet our fundamental understanding of thermal and mass transport remains limited. Evaporation and condensation can change the local temperature, and hence surface tension, along a liquid-vapor interface. The resulting thermocapillary stresses are dominant at small length scales in many cases. For the vast majority of single-component coolants, surface tension decreases as temperature increases, resulting in thermocapillary stresses that drive the liquid away from hot regions, leading to dryout, for example. The direction of flow driven by thermocapillary stresses is therefore consistent with that driven by buoyancy effects due to changes in the liquid density with temperature. However, a number of binary “self-rewetting fluids,” consisting of water-alcohol mixtures, have surface tensions that increase with temperature, leading to thermocapillary stresses that drive liquid towards hot regions, improving cooling performance. Although not all binary coolants are self-rewetting, all such coolants are subject to solutocapillary stresses, where differential evaporation of the two fluid components leads to changes in local species concentration at the liquid-vapor interface, and hence in surface tension. Given the lack of general models of thermal and mass transport in nonisothermal two-phase flows, experimental studies of convection in simple fluids and binary alcohol-water mixtures due to evaporation and condensation driven by a horizontal temperature gradient were performed. In these initial studies, both the simple and binary fluids have thermocapillary stresses that drive liquid away from hot regions. However, the binary fluid also has solutocapillary stresses that drive liquid towards hot regions. Particle-image velocimetry (PIV) is used to nonintrusively measure the velocity and temperature fields in a layer of liquid a few mm in depth in a 1 cm × 1 cm × 4.85 cm sealed and evacuated cuvette heated on one end and cooled on the other end.

scholarly journals Impact of a Localized Source of Subglacial Discharge on the Heat Flux and Submarine Melting of a Tidewater Glacier: A Laboratory Study

2016 ◽  
Vol 46 (10) ◽  
pp. 3155-3163 ◽  
Author(s):  
Claudia Cenedese ◽  
V. Marco Gatto
Keyword(s):  
Free Surface ◽  
Laboratory Study ◽  
Heat Budget ◽  
Discharge Rate ◽  
Circulation Pattern ◽  
Freezing Temperature ◽  
Buoyant Plumes ◽  
Localized Source ◽  
Numerical Studies ◽  
Glacier Front

AbstractIdealized laboratory experiments have been conducted in a two-layer stratified fluid to investigate the leading-order dynamics that control submarine melting and meltwater export near a vertical ice–ocean interface as a function of subglacial discharge. In summer, the discharge of surface runoff at the base of a glacier (subglacial discharge) generates strong buoyant plumes that rise along the glacier front entraining ambient water along the way. The entrainment enhances the heat transport toward the glacier front and hence the submarine melt rate increases with the subglacial discharge rate. In the laboratory, the effect of subglacial discharge is simulated by introducing freshwater at freezing temperature from a point source at the base of an ice block representing the glacier. The circulation pattern observed both with and without subglacial discharge resembles those observed in previous observational and numerical studies. Buoyant plumes rise vertically until they find either their neutrally buoyant level or the free surface. Hence, the meltwater can deposit within the interior of the water column and not entirely at the free surface, as confirmed by field observations. The heat budget in the tank, calculated following a new framework, gives estimates of submarine melt rate that increase with the subglacial discharge and are in agreement with the directly measured submarine melting. This laboratory study provides the first direct measurements of submarine melt rates for different subglacial discharges, and the results are consistent with the predictions of previous theoretical and numerical studies.

A Data-Driven Exploratory Approach for Level Curve Estimation With Autonomous Underwater Agents

2017 ◽  
Author(s):  
Hsien-Chung Lin ◽  
Eugen Solowjow ◽  
Masayoshi Tomizuka ◽  
Edwin Kreuzer
Keyword(s):  
Concentration Field ◽  
Real Data ◽  
Support Vector ◽  
Level Curve ◽  
Data Set ◽  
Curve Estimation ◽  
Numerical Studies ◽  
Exploratory Approach ◽  
Vector Machines ◽  
Myopic Strategy

This contribution presents a method to estimate environmental boundaries with mobile agents. The agents sample a concentration field of interest at their respective positions and infer a level curve of the unknown field. The presented method is based on support vector machines (SVMs), whereby the concentration level of interest serves as the decision boundary. The field itself does not have to be estimated in order to obtain the level curve which makes the method computationally very appealing. A myopic strategy is developed to pick locations that yield most informative concentration measurements. Cooperative operations of multiple agents are demonstrated by dividing the domain in Voronoi tessellations. Numerical studies demonstrate the feasibility of the method on a real data set of the California coastal area. The exploration strategy is benchmarked against random walk which it clearly outperforms.

Numerical Solution of Thermal and Fluid Flow With Phase Change by VOF Method

2000 ◽  
Author(s):  
Hidemi Shirakawa ◽  
Yasuyuki Takata ◽  
Takehiro Ito ◽  
Shinobu Satonaka
Keyword(s):  
Fluid Flow ◽  
Free Surface ◽  
Phase Change ◽  
Calculation Result ◽  
Bubble Growth ◽  
Present Method ◽  
Spherical Shape ◽  
Superheated Liquid ◽  
One Dimensional ◽  
Solidification Problem

Abstract Numerical method for thermal and fluid flow with free surface and phase change has been developed. The calculation result of one-dimensional solidification problem agrees with Neumann’s theoretical value. We applied it to a bubble growth in superheated liquid and obtained the result that a bubble grows with spherical shape. The present method can be applicable to various phase change problems.

Recent Analytical and Numerical Studies on Phase-Change Heat Transfer

2014 ◽  
pp. 187-248 ◽  
Author(s):  
Ping Cheng ◽  
Xiaojun Quan ◽  
Shuai Gong ◽  
Xiuliang Liu ◽  
Luhang Yang
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Numerical Studies ◽  
Phase Change Heat Transfer

scholarly journals Modeling for Free Surface Flow with Phase Change

2005 ◽  
Vol 47 (4) ◽  
pp. 1187-1191 ◽  
Author(s):  
Xiaoyong Luo ◽  
Mingjiu Ni ◽  
Alice Ying ◽  
M. Abdou
Keyword(s):  
Free Surface ◽  
Phase Change ◽  
Free Surface Flow ◽  
Surface Flow

Identification of a Steady-State Flow in Porous Media Using Artificial Neural Networks

2012 ◽  
Author(s):  
Marek J. Lefik ◽  
Daniela P. Boso ◽  
Bernhard A. Schrefler
Keyword(s):  
Neural Networks ◽  
Porous Media ◽  
Artificial Neural Networks ◽  
Steady State ◽  
Concentration Field ◽  
Flow In Porous Media ◽  
Homogeneous Field ◽  
Steady State Flow ◽  
Convection Problem ◽  
Artificial Neural

For a steady state convection problem, assuming given concentration field values in a few measurement points and hydraulic head values in the same piezometers, the source of the concentration, and its intensity are deduced using Artificial Neural Networks (ANNs). ANNs are trained with data extracted from Finite Difference (FD) solution of a classical convection problem for small Peclet number. The numerical analysis is exemplified for vanishing, homogeneous and non-homogeneous field of velocity. It is shown that the diffusivity vector can also be identified. The complexity of the problem is discussed for each studied case.

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