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Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 4
1301-1305
EN
Due to solar radiation exposure, air flowing inside a thermometer screen may produce a measurement error of 0.8°C or higher. To improve the air temperature observation accuracy, a temperature error correction method is proposed. The correction method is based on a computational fluid dynamics method and a genetic algorithm method. The computational fluid dynamics method is implemented to analyze and calculate the temperature errors of a screen under various environmental conditions. Then, a temperature error correction equation is obtained by fitting the computational fluid dynamics results using the genetic algorithm method. To verify the performance of the correction equation the screen and an aspirated temperature measurement platform are characterized in the same environment to conduct the intercomparison. The aspirated temperature measurement platform serves as an air temperature reference. The mean temperature error given by measurements is 0.77°C, and the mean temperature error given by correction equation is 0.79°C. This correction equation allows the temperature error to be reduced by approximately 97.5%.
EN
Nowadays the underwater gliding after the starts and the turns plays a major role in the overall swimming performance. Hence, minimizing hydrodynamic drag during the underwater phases should be a main aim during swimming. Indeed, there are several postures that swimmers can assume during the underwater gliding, although experimental results were not conclusive concerning the best body position to accomplish this aim. Therefore, the purpose of this study was to analyse the effect in hydrodynamic drag forces of using different body positions during gliding through computational fluid dynamics (CFD) methodology. For this purpose, two-dimensional models of the human body in steady flow conditions were studied. Two-dimensional virtual models had been created: (i) a prone position with the arms extended at the front of the body; (ii) a prone position with the arms placed alongside the trunk; (iii) a lateral position with the arms extended at the front and; (iv) a dorsal position with the arms extended at the front. The drag forces were computed between speeds of 1.6 m/s and 2 m/s in a two-dimensional Fluent® analysis. The positions with the arms extended at the front presented lower drag values than the position with the arms aside the trunk. The lateral position was the one in which the drag was lower and seems to be the one that should be adopted during the gliding after starts and turns.
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