An Experimental Study of Wall Effect on a Hot Settling Sphere in a Newtonian-Fluid-Contained Block Using Photography

In this study, the effect of temperature on the velocity and trajectory of a hot sphere falling in a water block was experimentally investigated. The sphere, 12 mm in diameter, was thrown through the water inside an enclosure at the ambient temperature by an electromagnetic attachment mechanism, and the particle velocity was recorded by a high-speed camera at 2000 fps. Then, using an image-processing algorithm, the real-time particle location was extracted and its velocity was measured. The results of the cold sphere falling test were compared with those obtained from the numerical solving by the governing equations. An electric heater was used to heat the sphere up to 100, 200, and 300 degrees C in order to investigate the effect of temperature on the sphere. The sphere was thrown upon reaching the desired temperature. By increasing the temperature, the sphere's velocity was increased up to around 40% of the velocity of the cold sphere. Further, the sphere was thrown from a point in the vicinity of the wall to investigate the wall impact on the particle movement. This led the sphere to deviate from its trajectory, with the deviation in the cold sphere being negligible, i.e., around 30% of the sphere's diameter. However, the rate of deviation was much more notable upon increasing the temperature. The deviation start point varied depending on the sphere's temperature, with the highest deviation that was observed for a sphere with a temperature of 100 degrees C. Ultimately, the sphere traveled in a more extended way, with no deviation from the main trajectory, when its temperature was increased.