In this study, a chemometric approach for five-peak separation analysis of the Raman spectra of diamond-like carbon (DLC) films was investigated. DLC films were deposited by high-frequency inclusion high-power impulse magnetron sputtering and alternating current high voltage burst plasma chemical vapor deposition. We used the pseudo-Voigt function as an alternative to the conventional Voigt function and applied the nonlinear least squares method. The results not only facilitate automated analysis but also guarantee highly accurate results regardless of the analyst's level of expertise. This approach is expected to lead to consistent interpretation of Raman spectral analysis of DLC films and further research and understanding of the properties of DLC films.
The flow around a circular cylinder in surfactant solution was investigated experimentally by measurement of the drag in the Reynolds number range 500 < Re < 6,000. The experiments were performed in a vertical re-circulating water tunnel. The drag coefficient was measured by the apparatus, which could measure the drag acting on the circular cylinder directly. Three cylinders of diameter d=10,19 and 25mm were tested, the ratio of length to diameter was (l/d)=11.2. Test surfactant solution was aqueous solution of Ethoquad O/12 (Lion Co.) at concentrations of 200ppm, and sodium salicylate was added as a counterion. It was cleared that the drag coefficient of a circular cylinder in surfactant solution larger than that in tap water at the Reynolds number range 500 < Re < 4,000. The value of the drag coefficient in surfactant solution was dependent on not only (l/d) but also cylinder diameter. According to the increase of the Reynolds number, the drag coefficient decreased by (Re)^<-3/2>. On the other hand, the value of the drag coefficient in surfactant solution became smaller than that in tap water at Re≅5,000.
To clarify the effects of surfactant solutions on the drag coefficient of a circular cylinder, the flow past a circular cylinder was investigated in the Reynolds number range of 10 to 7,000 by measuring the drag and by visualizing flow. In addition, the flow pattern was simulated numerically to examine the effect of the viscoelasticity of the surfactant solution. Six cylinders with diameters between 2 and 20 mm were tested, and the ratio of length to diameter (l/d) was 12~48. The test surfactant solutions were aqueous solutions of oleyl-methyldihydroxyethyl ammonium chloride (trade name: Ethoquad O/12) in the concentration range of 50 to 200 ppm and sodium salicylate was added as a counterion. It was clarified that the drag coefficient of surfactant solutions increases comparing with that of tap water in the Reynolds number range of 1,000 < Re 3,000 and drag reduction occurs when Re > 3,000 for a cylinder diameter of 20 mm. The maximum drag reduction ratio was approximately 55% for 200 ppm solution at Re = 7,000. The flow visualization results showed that the drag of surfactant solutions increases because of the existence of the wide stagnant zone around the cylinder. This zone disappeared in the Reynolds number range in which drag reduction occurred. In addition, the width of the wake of surfactant solutions decreases compared with that of tap water, and the Ka´rma´n vortex street is not found. These effects seem to be due to the elasticity caused by the micellar network in surfactant solution.
To clarify the effects of surfactant solutions on the drag coefficient of a circular cylinder, the flow past a circular cylinder was investigated at 10
To clarify the behavior of the drag coefficient of a circular cylinder in the intermediate Reynolds number range, the flow around a circular cylinder in surfactant solutions was investigated experimentally by measurement of the drag in the Reynolds number range of 3 × 102 to 7 × 103. The experiments were performed in a vertical re-circulating water tunnel. The drag coefficient was measured using an apparatus which could measure the drag acting on the circular cylinder directly. Five cylinders of diameter d = 5, 7, 10, 13 and 20 mm were tested, the ratios of length to diameter (l/d) were 12, 24 and 48. The test surfactant solutions were aqueous solutions of Ethoquad O/12 at concentrations of 50, 100 and 200 ppm, and sodium salicylate was added as a counterion. It was clarified that the drag coefficient of the cylinder in surfactant solutions increased comparing that in tap water in the Reynolds number lower approximately 103 < Re < 3 × 103. According to the increase of the Reynolds number, the drag coefficient decreased. When Reynolds number exceeded approximately 103 < Re < 3 × 103, the drag coefficient in surfactant decreased in comparison with that in tap water finally. In other ward, the drag reduction occurred in this Reynolds number range. The maximum drag reduction was about 55% for 200 ppm solution and 20mm diameter at Re ≅ 7 × 103. The value of the drag coefficient in surfactant solutions was dependent on not only (l/d) but also cylinder diameter. The drag coefficient increased with increasing cylinder diameter. The increase in the concentration of surfactant solution emphasized the characteristics of drag reduction and drag increase.
Effects of a drag reducing surfactant solution on the flow around a circular cylinder ware shown experimentally by the flow visualization method in a Reynolds number range 10
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