Two-Dimensional Periodic Natural Convection in a Rectangular Enclosure of Aspect Ratio One

Abstract

A two-dimensional rectangular cavity of aspect ratio one is studied experimentally using a laser-doppler velocimeter. The enclosure is air filled and consists of two vertical walls at unequal isothermal temperatures and two connecting horizontal walls with temperatures varying linearly between the two vertical surfaces. This study clearly defines the existence of periodic laminar flow regimes detectable at Ra numbers above 0.3 × 107. These periodic variations in velocity are induced by the upper and lower boundary conditions. The envelopes of vertical and horizontal velocity fluctuations are reported as a function of position for Rayleigh numbers of 0.25 × 107, 0.50 × 107, and 0.85 × 107. In addition, the effect of Ra number on frequency of flow is reported.

Numerical computation of buoyant airflows confined to attic spaces under opposing hot and cold wall conditions

“…Using a time-dependent finite-difference code, these authors found that the onset of oscillations occurs at a Rayleigh number between 2 × 10 6 and 2.2 × 10 6 . Parallel to this, in an experimental study of a square cavity with conducting horizontal walls, Briggs and Jones [18] found a transition from steady to oscillatory flow behavior at a Rayleigh number of 3 × 10 6 . It was proclaimed in this work that the regime of periodic convective flows persisted to a Rayleigh number of at least 1.2 × 10 7 .…”

Numerical and experimental study of natural convection in tilted parallelepipedic cavities for large Rayleigh numbers

“…Let us quote also those of Briggs et al [10] and Penot et al [11] both dealing with the thermal exchanges occurring in parallelepipedic cavities with two active vertical walls, the rest being adiabatic. The study in [10] is in particular devoted to the analysis of the multicellular flows which take place in these cavities.…”

“…The study in [10] is in particular devoted to the analysis of the multicellular flows which take place in these cavities.…”

Hopf Bifurcation in the Double-Glazing Problem With Conducting Boundaries

“…Yet all convective flows become turbulent at sufficiently high Rayleigh number, and many are oscillatory over a range of Rayleigh numbers which usually lies between the laminar and turbulent regimes. This question of the reality of the steady solutions was addressed recently by Briggs and Jones (1985) in an experimental study of the double-glazing problem with conducting horizontal surfaces. They found a transition from steady to oscillatory free convection in a square, air-filled cavity at a Rayleigh number of 3 x 10 s with a simple periodicity of about 0.5 Hz at onset.…”