WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7150

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Subject: search.filters.subject.Flow of fluids

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  • Article
    Citation - WoS: 24
    Citation - Scopus: 27
    Visualization of Diffusion and Convection Heat Transport in a Square Cavity With Natural Convection
    (Elsevier Ltd., 2010) Mobedi, Moghtada; Özkol, Ünver; Özkol, Ünver; Mobedi, Moghtada; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this study, the total heatfunction equation which includes diffusion and convection transport is divided into the corresponding heatfunction equations. The superposition rule is used to obtain the mathematical definitions of diffusion and convection heatfunctions and corresponding boundary conditions. It is observed that the separate visualization of diffusion and convection heatlines provides significant information on understanding of the mechanism of heat transfer in a convective flow. The direction of the diffusion and convection heat transport as well as the strength of convection compared to the conduction in entire or in a portion of a domain can be visualized. The diffusion heatlines demonstrate a potential flow like behavior while convective heat flow rotates due to the source term of the convection heatfunction equation, similar to the rotation of fluid flow generated by fluid flow vorticity. The similarity between the streamfunction and the total heatfunction yields a concept of heat flow vorticity, Ωt. The obtained results show that the maximum absolute value of the convection heatfunction may be an appropriate parameter for determination of the convection strength. The diffusion and convection heatfunction equations for natural convection in a differentially heated square cavity for four different length of the heated surface on the right vertical wall as sp = L/4, L/2, 3L/4 and L and a fixed length of the cooled surface on the right vertical wall as L/4 are obtained and corresponding heatlines are drawn. The values of the conduction heatfunction are positive while the sign of convection heatfunction values is negative for the studied cases. Based on the distribution of total heatlines, two regions are detected in the cavity, an active region with the positive values of heatlines signifying dominant conduction heat transfer and a passive region with the negative heatfunction values in where convection heat flow is dominant and heat only rotates in a closed contour pattern. The variations of average Nusselt number, average of heat flow vorticity, maximum absolute values of convection heatfunction and streamfunction at different Rayleigh numbers and lengths of the heated surface are presented.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 6
    Surfactant Adsorption and Marangoni Flow in Liquid Jets. 2. Modeling
    (American Chemical Society, 2004) Weiss, Michael; Darton, Richard C.; Battal, Turgut; Bain, Colin D.; 01. Izmir Institute of Technology
    This paper is concerned with the interfacial behavior of surfactant solutions on short time scales. A gravity-driven laminar liquid jet is used to create a rapidly expanding liquid surface, which exposes the surfactant solution to highly nonequilibrium conditions. This expansion causes the surface tension to differ locally from its equilibrium value, generating a (Marangoni) shear stress that acts on the jet surface and retards the surface acceleration. A theory for the flow very near the nozzle shows that the cube-root dependence of the surface velocity on the distance traveled is altered through the adsorption of surfactant. In a boundary-layer treatment, both the surface velocity and the surface concentration increase linearly from the nozzle exit over a short distance, which we term the detachment region. The length of the detachment region is found to vary with the bulk concentration raised to the power 3/2. A numerical model of the surfactant adsorption process in the jet has been developed within the framework of the CFD code FIDAP. The numerical solution confirms the general features of the theory and shows that the maximum reduction in surface velocity occurs very close to the nozzle exit, except at high concentrations. A comparison with experiments on C16TAB at concentrations below the critical micelle concentration, which are described in part 1 of this series of papers, shows good agreement.