Effect of boundary conditions on thermal plume growth

Abstract

The advent of a verifiable theory allowed experimentalists to start measuring the proportionality coefficient. However, estimates of the coupling coefficient were quite different due to some reasons. First of all, laboratory setups differed in design. Difference in the nature of working fluids or in heating techniques (e.g., in dimensions and shape of measuring cells) led researchers to repeatedly differing results. Therefore, while comparing experimental results, a necessity to ascertain the influence of boundary conditions appears to be inevitable. The second problem concerning the determination of the position and shape of plumes was related to visualization techniques for temperature fields and corresponding flows.In 2003, Kaminski and Jaupart [7] mostly succeeded in combining the results determined for various liquid. To more accurately specify the coefficient, they used the asymptotic solution of Worster [8] for high Prandtl numbers. The influence of boundaries was investigated by Vatteville [9]. On the basis of experimental results and their extension to a numerical model, the authors revealed a strong dependence of the plume vertical rate on the dimensions of an experimental cell and the conditions on its upper boundary.In the works under discussion, provided that a plume is axially symmetric, the cells with a square and cylindrical base were used. Therefore, a transition to a narrow layer or, in the limit, to the Hele-Shaw approximation, where one of the cell dimensions would be significantly less than two others, may be considered as a natural generalization of the problem. This can lead to the loss of axial symmetry and, consequently, cause the variation in the plume dynamics.However, there have been practically no investigations of this kind. The transition to a thin vertical layer implies difficulties in visualizing the temperature field. Shadow and interference methods that are most frequently used for Abstract We have investigated the influence of boundary conditions on the growth rate of convective plumes. Temperature and rate fields were studied in a rectangular convective cell heated by a spot heater. The results of the full-scale test were compared with the numerical data calculated using the ANSYS CFX software package. The relationship between the heat plume growth rate and heat boundary conditions, the width and height of the cell, size of heater for different kinds of liquid was established.

Formation and evolution of laminar thermal structures: correlation to the thermal boundary layer and effects of heating time

“…According to previous studies (Moses et al 1993;Kaminski & Jaupart 2003;Bond & Johari 2005;Whittaker & Lister 2008;van Keken, Davaille & Vatteville 2013;Kondrashov, Sboev & Dunaev 2016a;Kondrashov, Sboev & Rybkin 2016b), the properties of thermal structures generated by a small heat source could be affected by several factors in laboratory experiments. These factors include mainly the dimensions and geometries of the heat source and the tank, the boundary conditions, the properties of the fluid, and the leakage of the heating power.…”

Critical transitions on a route to chaos of natural convection on a heated horizontal circular surface

“…Since the work of Batchelor (1954) and Morton, Taylor & Turner (1956) on the modelling of plumes, increasing attention has been devoted to the study of plumes. Starting plumes, which rise above a horizontal surface in a two-dimensional model (Hier et al 2004;Hattori et al 2013b;Van den Bremer & Hunt 2014), on a three-dimensional circular disk (Robinson & Liburdy 1987;Kitamura & Kimura 2008;Plourde et al 2008;Lesshafft 2015;Kondrashov, Sboev & Rybkin 2016b;Sboev, Rybkin & Goncharov 2018;Sboev & Kuchinskiy 2020), and from a line heat source (Noto 1989;Hattori et al 2013a), were studied using theoretical, experimental and numerical methods with a focus on the heat transfer and evolution of plume structures (e.g. cap and stem).…”

“…2013 b ; Van den Bremer & Hunt 2014), on a three-dimensional circular disk (Robinson & Liburdy 1987; Kitamura & Kimura 2008; Plourde et al. 2008; Lesshafft 2015; Kondrashov, Sboev & Rybkin 2016 b ; Sboev, Rybkin & Goncharov 2018; Sboev & Kuchinskiy 2020), and from a line heat source (Noto 1989; Hattori et al. 2013 a ), were studied using theoretical, experimental and numerical methods with a focus on the heat transfer and evolution of plume structures (e.g.…”

Tri-axis convective accelerometer with closed-loop heat source

“…When acceleration occurs, the detected temperatures change, but only by small amount. It has been found that the Zaxis detection accelerometer has a close relation with the natural convection of the flow inside a cavity heated from below [48][49][50][51][52][53]. In recent years, many researchers have found that boundary conditions [48,49] and heater geometry [50,51] have substantial impact on the pattern of these convective flows.…”

“…In recent years, many researchers have found that boundary conditions [48,49] and heater geometry [50,51] have substantial impact on the pattern of these convective flows. Because of the temperature distribution, the local heating of the quiescent air over the heater surface produces density gradient directed toward the decrease in the medium temperature, and convective flow occurs in the form of thermal plume when the buoyancy exceeds the viscous friction [53]. For a single local heater under heating conditions, the hot air rises upwards along the vertical axis going through the heater.…”