The thermodynamic effect of a density gradient in a colder fluid as a result of a hotter plate located below it is something that is well known. However, its use as a flow field indicator using a light coil shaped body is a recent application developed by the author of this paper. The paper contributes to bring ahead this concept by a parametrical experimental analysis aimed at assessing the relationship among three of the parameters that mainly influence the whole process: the angular velocity of the coil as a dependent variable; the number of turns in the coil as the first independent variable and the weight of the coil as the second independent variable. A suitable apparatus was realized. The tests performed showed that, apart from a very few cases, an increase in the number of turns produces an increase in the angular velocity of the coil. A particular behaviour is observed for the weight of the coil: an increase in weight augments the angular velocity for small values, while for larger values the trend is opposite. Some considerations about the rotational stability can explain the entire concept, although further research will help deepen our knowledge of the process for wider parametrical ranges.
coil, density gradient, flow field, number of turns, rotation, thermodynamics
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