Experimental calibration of thermal particles to study natural and mixed convective flow fields*

Turbulence plays a primary role in many naturally occurring processes, such as atmospheric and oceanic currents. It is also present in the vast majority of industrial processes, including industrial mixers. In these systems, in addition to mechanically forced turbulence, a difference in temperature is instrumental in their evolution. This fact provokes research on mixed convective flows.

This experimental study aims to know better the transport of heat and momentum in natural thermal convective flows and mixed convention where the convection is enhanced by mechanically forced turbulent flow.

For that, we have different octagonal convection water tanks. The temperature difference is set by heating/cooling plates at the bottom and top. Mechanical turbulence is created by oscillating mesh grids in the bulk region of the flow.

Temperature detection is done by seeding the fluid with thermochromic liquid crystals particles (TLCs) that change their color with the temperature and are recorded by a color camera in 2D. The correct interpretation of their color is crucial to obtain the temperature field, and thus advanced calibration method is performed to get their behavior under different experimental conditions. In addition, tracers are added and tracked in 2D or 3D by different monochromatic cameras to get the velocity and acceleration fields.