Drag Reduction for a Rotating Disk with Highly Water Repellent Wall in Newtonian Fluids.

1997 ◽  
Vol 63 (612) ◽  
pp. 2752-2756 ◽  
Author(s):  
Keizo WATANABA ◽  
Satoshi OGATA
1999 ◽  
Vol 121 (3) ◽  
pp. 541-547 ◽  
Author(s):  
Keizo Watanabe ◽  
Takashi Akino

Laminar drag reduction has been shown for the flow of a Newtonian fluid in the space between two vertical coaxial cylinders. Experiments were carried out to measure the torque of a bob with a highly water-repellent wall to clarify the effect of the contact surface of the bob on the flow behavior. The basic material of the highly water-repellent wall is fluorine alkane modified acrylic resin with added hydrophobic silica, and the contact angle of the wall is about 150 degree. The radius rations of the bob were 0.932 and 0.676. Test fluids were Newtonian aqueous solutions of 60, 70, and 80 wt% glycerin and polymer solutions. The maximum drag reduction ratio was about 12% for 80 wt% glycerin solution at a radius ratio of 0.932. The moment coefficient of the coaxial cylinder in Newtonian fluids was analyzed for fluid slip, and it was shown that the analytical results agreed well with the experimental data. For the case of non-Newtonian fluids, the fluid slip velocity of polymer solutions is not proportional to the shear stress and the relationship is approximated by power-law equations.


1998 ◽  
Vol 41 (3) ◽  
pp. 556-560 ◽  
Author(s):  
Keizo WATANABE ◽  
Satoshi OGATA

2014 ◽  
Vol 7 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Ke Zhang ◽  
Zheng-Chuang Wang ◽  
Ya-Nan Zhang ◽  
Fang-Fang Zhang ◽  
Yi-Fan Hou ◽  
...  

2017 ◽  
Vol 26 (4) ◽  
pp. 096369351702600 ◽  
Author(s):  
Xiaodong Dai ◽  
Guicai Zhang ◽  
Bing Li ◽  
Jijiang Ge ◽  
Xuewu Wang ◽  
...  

In this paper, nanocomposite was synthesized with nano silica and poly-α-olefin, and the effects of surface modification to the nano silica on its drag reduction performance were investigated. The dosage coupling agent, Y-aminopropyltriethoxysilane, and the modification temperature were studied intensively through surface hydroxyl and oil adsorption analysis. The test results indicated that the hydroxyl number of the silica was decreased by Y-aminopropyltriethoxysilane modification, with improved lipophilicity and oil adsorption. At 50°C, the optimum Y-aminopropyltriethoxysilane dosages were 15% for Nano-Si-10, 5% for Nano-Si-20, and 10% for Degussa-R972. The modification significantly changed the nano silica surface properties and enhanced the interaction with poly-α-olefin. Through drag reduction and shear resistance tests by rotating disk 40 mins degradation and testing loop 2 times shearing, it was shown that the nanocomposite possessed good drag reduction and excellent shear resistance properties.


1978 ◽  
Vol 33 (11) ◽  
pp. 1463-1470 ◽  
Author(s):  
P. Mishra ◽  
Prakash Chandra Singh

2018 ◽  
Vol 36 (13) ◽  
pp. 981-986
Author(s):  
Xiaodong Dai ◽  
Lei Li ◽  
Shuming Yin ◽  
Guicai Zhang ◽  
Jijiang Ge
Keyword(s):  

1999 ◽  
Author(s):  
Keizo Watanabe ◽  
Hiroshi Udagawa

Abstract By applying a highly water-repellent wall pipe in the drag reduction of polymer solutions, a flow system in which drag reduction is obtained in both laminar and turbulent flow ranges has been realized. Experiments were carried out to measure the pressure drop in pipes with a highly water-repellent wall and an acrylic resin wall by means of a pressure transducer. The diameter of the pipe was 6mm. The polymer solutions tested were PE015 aqueous solutions in the concentration range of 30ppm∼1000ppm. The drag reduction ratio for laminar flow was about 11∼15%. To understand this effect, the pressure drop was measured by using surfactant solutions and degassed water, and by pressurizing tap water in the pipeline. It was shown that the laminar drag reduction does not occur in the case of surfactant solutions although degassed water and pressurizing tap water in the pipeline have no effect on the reduction. In the laminar flow range, the friction factor of a power-law fluid with fluid slip was analyzed by applying the modified boundary condition on fluid slip at the pipe wall, and the analytical results agree with the experimental results in the low Reynolds number range.


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