Abstract:

The semi-open upwelling flow caused by air bubbler is one of the most important ways to generate artificial upwelling flow. The distance between the bubbler and nearby wall impacts the efficiency of the upwelling system greatly. In order to measure flowrate of upwelling flow at various altitudes, various gas flowrates when various distances between bubbler and wall being set based on various bubblers with various holes size, an experimental setup concluding bubbler, linear guideway, rope, live screw, ruler and weight were established. The experimental results show that: The flowrate of upwelling flow decreases slightly with the increasing of the bubble size. The distance between bubbler and wall doesn’t affect the bubble size, but affects the upwelling flowrate obviously because of the induced variation of plume width. The most important factor to influence upwelling flowrate is the altitude of the bubbler. The upwelling flowrate at a certain altitude decreases with the decreasing of the distance between bubbler and wall when the bubbler being at the altitude ranging of 0.8-1.6 m. The flowrate difference of upwelling flow with different bubbler-wall distance reduces at low altitude. Moreover, no influence on the upwelling flowrate exists when the altitude of the bubbler lower than 0.8 m, while violent influence when higher than 1.6 m. After overall consideration of the bubbler-wall distance and bubbler altitude, a moderate modification of theoretical formula is carried out. Good agreements between theoretical results and experimental results are found. It is beneficial to design artificial upwelling system.

Key words: artificial upwelling flow, bubbler altitude, flowrate, plume width, bubbler-wall distance