An Experimental Study on Wall Effect for a Droplet Motion in a Vertical Tube
Date Issued
2011
Date
2011
Author(s)
Tsai, Hsuan-Chih
Abstract
The experiment discusses the drag and the motion of liquid droplets through anaqueous phase contained in five vertical cylinders of various diameters. The temperature is controlled between 25-28℃, and the pressure is 1 atm. To avoid the mass transition, we use water to be the droplet, and use heptane dodecane and hexadecane to be the continued fluid. The range of Reynolds numbers are between 0.34 to 350, and the rang of droplet-to-tube diameters ratio are between 0.02 to 0.74.
The present data show that the droplet drag coefficients are similar to the rigid sphere in 17.3 and 10 mm diameters, which means that the wall effect is not obvious in the range of λ from 0.08 to 0.14, but the drag line will be escape from rigid sphere line when λ is getting bigger, and it becomes more obvious in low Reynolds number range; furthermore, the droplet motion is associated with Reynolds number, the physical properties of fluids, and λ, such as when λ is smaller than 0.6, the condition for droplet could approach to the wall that its Reynolds number must come up to 200, and the lift is a attractive force at same time, but when λ is bigger than 0.7, it can be hit the walls as Reynolds number is 50, and the drop velocity become slower because of repeatedly collide with the wall.
Subjects
drag force；Reynolds number；oscillations；wall factor
Type
thesis
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