EXPERIMENTS ON THE STABILIZATION OF THE NO-MOTION STATE OF A FLUID LAYER HEATED FROM BELOW AND COOLED FROM ABOVE

It is demonstrated experimentally that through the use of feedback con trol, it is possible to stabilize the no-motion (conductive) state of a fluid layer confined in a circular cylinder heated from below and co oled from above (the Rayleigh-Benard problem), thereby postponing the transition from a no-motion state to cellular convection. The control system utilizes multiple sensors and actuators. The actuators consist of individually controlled heaters microfabricated on a silicon wafer which forms the bottom of the test cell. The sensors are diodes instal led at the fluid's midheight. The sensors monitor the deviation of the fluid temperatures from preset, desired values and direct the actuato rs to act in such a way as to eliminate these deviations.