A prolate spheroid submerged in water can be heated for decreasing the viscous drag because of a decrease in viscosity with increasing temperature. The heated boundary layer experiment, based on this principle, was carried out in a circulating water channel of NCKU, and the viscous drag of a spheroid, with a five-to-one ratio of length to mid-diameter, was also measured by means of wake surveys. The difference of total-head between wake and undisturbed region was measured by two total-head tubes, and the water speed in the wake area was measured by an electromagnetic flowmeter. The results indicate that the viscous drag of the model decreases with surface heating, and the decrease in viscous drag of the model is 13% when the surface temperature is 17°C above the ambient water temperature. The velocity gradient in the wake region and the total-heating differential readings between undisturbed and wake region also decrease with surface heating due to the delayed laminar-turbulent transition in the boundary layer. The values of the coefficient of viscous drag obtained without surface overheating are found to be in agreement, for the range of Froude numbers investigated, with the results obtained from previous experiments.
All Science Journal Classification (ASJC) codes
- Computational Mechanics
- Mechanics of Materials
- Physics and Astronomy(all)
- Fluid Flow and Transfer Processes