非飽和層中原有殘餘水( “舊水” )的多寡與分佈影響著降雨入滲、灌溉、滲漏等入侵此區域之水( “新水” )的分布型態，且地表下新舊水的互動也影響著地下水水質。
本研究藉由雙管微模型實驗探討孔隙幾何結構、排退與汲取流量，以及舊水殘餘相蒸發對氣泡形成與遷徙機制的影響。並進一步觀測氣泡的型態對於新水注入過程中，新舊水互動的影響。
實驗結果顯示，舊水在新水注入前若有蒸發過程，則會改變舊水殘餘相的位置。而舊水殘餘相位置離出入口越遠，新水注入後越容易產生氣泡。氣泡形成與否不只與殘餘相位置有關；注入流量的不同也會影響氣泡的生成。流量越慢，新水進入管內後越有機會直接與舊水接觸。而氣泡生成後將阻礙新舊水的接觸，新水僅能透過角落流與舊水進行溶質擴散及混合。若注入新水之流量過高時，舊水及氣泡在新水透過角落流接觸舊水之前，就會被推出管外，而不會有新舊水的接觸。在細管內舊水不會因新水的注入而移動，直到流量高於50μL/min，舊水才被推動。
本研究顯示舊水蒸發對於氣泡殘餘有顯著的影響。而氣泡的存在降低了新舊水混合的機率。角落流則可作為新水接觸且混合舊水的橋樑。

The unsaturated zone is an important part of the path for surface water entering groundwater. The amount and location of the residual water (old water) in the vadose zone affects the infiltration of invading water ( new water, e.g., that from rainfall, stream flow, and irrigation water etc.).
In this study, I showed the interaction between "old water" and "new water" under different pumping rates, geometry factor and evaporation level of old water, by using pore doublet micromodel experiment. Air entrapment is a key directly separating the new and old water, and promoting "old water" remaining.
I focus on the air entrapment and what influence on "new and old water interplay". The experimental results show that the evaporation process changes the position of the old water and enhances the air-bubble trapping. The air bubble entrapment reduces the new-old water interplay. And in that case, the new water can only contacted with the old water by corner flow. Under high injection flow rate, the old water and air bubbles were pushed out of the tube before the new water contacted the old water by corner flow. The old water would not be pushed until the capacity up than 50μL/min. This study shows that the evaporation process has a significant effect on the air-bubble trapping. The air bubble reduces the chance of the new-old water mixing. In addition, the corner flow is the path for new water intruding and mixing with the old water.

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