| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 104 === Penetrative entrainment by a turbulent fountain has many practical applications
in nature. The examples include the cooling system in the commercial building,
recirculating a water reservoir and the process of improving the water quality.
This research studied the penetrative entrainment flow rate quantitatively. A
new experimental design was developed to estimate the penetrative entrainment
volume flow rate by a turbulent fountain.
Simulation experiments used the salt bath technique. Two sources, a salt solution source and a fresh water source, were placed in a plexiglass tank. Two
sources were located at different heights, the fresh water source at the top and the salt solution source at 2 cm above the floor of the tank. There were 9 experimental runs conducted in this research, and the flow from the fresh water source hit the floor boundary in 3 runs of them. Two data acquisition methods included the measurements of solution density and the recording of flow images.
Experiments started from the 2 layers initially with the fresh water as the
upper layer and the salt solution as the lower layer. After the experiment began,
the density in the upper dilute layer increased with the time until the steady state
and the density in the lower dense layer remained the same in the transient state
except for the cases in which the fountain flow hit the floor boundary. When the
fresh water flow hit the floor boundary, the density of the lower dense layer was less than that of the salt solution and the interface was unclear. For the experimental cases in which the fountain flow does not reach the floor, this new experimental set-up gives three independent equations to estimate the penetrative entrainment flow rate by a fountain flow. Using the numerical turbulent fountain flow model gives the Richardson number at the density interface between 0.029 and 1.816 and the entrainment rate in the range between 0.13 and 2.21, when the initial fountain momentum is 4/3 Q2f/A , and the Richardson number at the density interface between 0.044 and 14.389 and the entrainment rate in the range between 0.12 and 2.08, when the initial fountain momentum is Q2 /A .
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