Modelagem de parâmetros fluidodinâmicos de tomates.

Abstract

This research aimed to study the physical characteristics and hydrodynamic parameters of two tomato varieties: persimmon and Italian (Solanum lycopersicum L.), in five ripening stages, from green to ripe. To achieve these results, were determined water content, firmness, physical characteristics of tomatoes, hydrodynamic parameters: terminal velocity (Vt), drag coefficient (CD), Reynolds number (Re), wall effect (KP), fruit orientation in water and shape effect analysis with determination of these parameters for spherical models of the same specific mass. For the determination of the experimental hydrodynamic parameters, twenty five samples of each fruit variety were used, as well as three spherical models, which were arranged in the experimental observation equipment, consisting of a glass column with square cross section. The terminal velocity of fruits and spherical models was recorded by a camera and were analyzed using the computational tool Quick Time Player. For the hydrodynamic parameters calculated from tomatoes, the equations for isometric particles given by Pettyjohn and Christiansen (1948), Concha and Barrientos (1986), Haider and Levenspiel (1989), Coelho and Massarani (1996); and for the spherical models, the equations for spherical particles given by Vennard (1961) through the curve (CD x Re) were considered considering the CD = 0.44, Abraham (1970), Brauer and Sucker (1976), Concha e Almendra (1979), Haider and Levenspiel (1989) and Coelho and Massarani (1996). Due to fruit irregularity, changes in size and shape during ripening were not statistically significant. For this reason, the fruits were organized and analyzed in ascending order of the form factor (sphericity) with their respective climb speeds, drag coefficients, Reynolds number and also wall effect analysis. It was concluded that the tomatoes of the Italian variety have higher number of (Re), lower values of (CD) and terminal velocity higher than the speed of persimmon tomato. The fruits of the persimmon variety had no wall effect, while the fruits of the Italian variety crashed several times on the walls, realizing that there is a great influence of the fruit shape on these parameters, since these fruits had very close density. For spherical models, the larger diameter model obtained a higher terminal velocity value and tended to be closer to the pipe wall than the smaller diameter ones. When using the literature equations for isometric and spherical particles, the obtained values do not correlate well with the experimental values. Thus, a mathematical modeling for drag coefficient, Reynolds number and terminal velocity of tomatoes was performed for sphericities ranging from 0.76 to 1.