SPATIOTEMPORAL INTERMITTENCE OF FLOW IN A HORIZONTAL CYLINDRICAL CONDUCT - DETERMINATION OF THE EXTERNAL TEMPERATURE-FIELD BY INFRARED THERMOGRAPHY AND STUDY OF THE BEHAVIOR

The influence of mixed convection due to buoyancy in the case of flow in a heated horizontal conduct has been observed. This effect is characterized by the gradient of the temperature between the top and the bottom in a cross section measured by infrared thermography. An increasing of the flowrate leads to an intermittency phenomenon which is occuring with fluctuation in time of this gradient. The amplitude of these oscillations depend on the test section position and the fluid velocity. In this paper, we try to characterize this phenomenon as a transition from the laminar to the turbulent.