## THERMAL SCIENCE

International Scientific Journal

### RAYLEIGH-BéNARD CONVECTION INSTABILITY IN THE PRESENCE OF TEMPERATURE VARIATION AT THE LOWER WALL

**ABSTRACT**

This paper analyzes the two-dimensional viscous fluid flow between two parallel plates, where the lower plate is heated and the upper one is cooled. The temperature difference between the plates is gradually increased during a certain time period, and afterwards it is temporarily constant. The temperature distribution on the lower plate is not constant in x-direction, and there is longitudinal sinusoidal temperature variation imposed on the mean temperature. We investigate the wave number and amplitude influence of this variation on the stability of Rayleigh-Benard convective cells, by direct numerical simulation of 2-D Navier-Stokes and energy equation.

**KEYWORDS**

PAPER SUBMITTED: 2012-05-05

PAPER REVISED: 2012-09-20

PAPER ACCEPTED: 2012-09-25

**THERMAL SCIENCE** YEAR

**2012**, VOLUME

**16**, ISSUE

**Supplement 2**, PAGES [S281 - S294]

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