Experimental study on a round tube jet in a vertical water tunnel

• Main Authors: Yuan-wei Lai, 賴元偉
• Other Authors: Yi-Jiun Peter Lin
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/75575402485483606483

碩士 === 國立臺灣科技大學 === 機械工程系 === 98 === The purpose of this research is to study the flow fields caused by a round tube jet in a crossflow within the near-wake region. The experiments of a crossflow passing around a cylindrical tube and a round tube jet under different static pressures are observed by using flow visualization and Particle Image Velocimeter (P.I.V.) techniques. Crossflow is produced by a vertical water tunnel, with ReD = 250 1080. The jet is supplied and controlled by pumping water through a rotameter into the cylindrical tube, with Rej = 260 ~ 2200. Experimental observations on crossflow passing around a cylindrical tube are divided into vertical longitudinal and cross sections. Vertical longitudinal section of the flow field is located at Z/D = 0. When ReD increases, the bifurcation line of downwash barely changes, but the region of the lee-side of cylindrical tube close to the tip has some variations. Vertical cross sections of the flow field are located at X/D = 0, -2.5, -5, -10, respectively. At X/D = 0, ambient fluid around the cylindrical tube tends to move toward the center region of the lee-side of cylindrical tube. There is no vortex observed. At X/D = -2.5, there is a stronger shear layer to confine the wake region. Wake tends to move toward the central region of the lee-side of the cylindrical tube. At X/D = -5, low ReD case shows vortices are created periodically and switch between left and right. For high ReD cases, periodical appearing vortices seem to be disturbed by stronger downwash crossflow. At X/D = -10, both high and low ReD cases show vortices appear periodically and interchange between left and right. Wakes move in S-shape pattern. For experiments of various Rej at two different water levels in stationary fluid. When Rej < 1330, jet breakdown position in the high water level is more close to the jet nozzle source, but when Rej > 1330, the comparison results are reversed. When Rej = 1330, jets in the low and the high water levels show a similar breakdown point position.