|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1995 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1994 : ¥1,700,000 (Direct Cost : ¥1,700,000)
The effects of surfactant additives on the laminar-turbulent transitions of a pipe flow and a radial liquid film flow were studied experimentally. Dodecyl-benzensulfonicacid sodium was used as the surfactant. The concentration of solution was varied from 5 to 100 wppm.
For the pipe flow experiment, stainless steel-, copper-, glass- and Teflon-tubes, which have a inner diameter of 2.5mm, were used as the test pipe. The critical Reynolds numbers were obtained under conditions of both gradual increasing and decreasing Reynolds number. These critical Reynolds numbers monotonously increased with surfactant concentration until these values came to be about ten percent higher than that of tap water at a concentration of 20 wppm, and then decreased with further increasing concentration.
For the radial liquid film flow experiment, the flow was generated by a water discharge through a gap between the top of a circular brass nozzle and the lower surface of a glass plate, flowing radially in a thin liquid film along the plate. The inner diameter of the nozzle was 15mm and the distance of the gap 1mm. Experimental results showed that the transition radius increases quickly with the concentration bellow 6 wppm, after then does not change with the further increasing concentration. Furthermore, a lot of data on the critical Reynolds number of solution under various concentrations ranging from 6 wppm to 76 wppm indicated about 1.08 times as great as that of the solvent. Consequently, a small amount of additives of surfactant suppresses evidently the transition although its amount is only 5 to 8 percents.