液體中存在數量及尺寸不等之微小汽泡核,當液體壓力小於閾值時,汽泡核的體積隨壓力之減少而增加,汽泡內之壓力則快速降低。在液體壓力回升後,汽泡內外之壓力差導致汽泡崩裂,崩裂時汽泡內部產生極高的溫度和壓力,稱為空蝕現象。在工程上會遇到許多空蝕相關的問題,包含聲化學反應器、船隻螺旋槳在水中產生的汽泡對槳面造成侵蝕,以及利用空蝕效應對材料進行表面處理等等,因此準確預測空蝕汽泡的生成是很重要的。就聲化學反應器之分析與設計而言,反應器中的聲場模擬通常忽略汽泡的影響或假設單一汽泡尺寸,本研究探討尺寸非均勻分布的汽泡對聲場之影響,以期建立更為準確的聲場分析模型,有效提升聲化學反應器的效率。本研究使用有限元素分析模型模擬聲波穿過流體時汽泡對聲場分布的影響。首先計算操作頻率下的壓力閾值,再根據此閾值模擬無汽泡、單一汽泡尺寸以及非均質汽泡尺寸下的聲場分布並加以比較。聲場分布經過計算能求得空泡比的分布。接著利用基因演算法設計聲化學反應器之最佳化尺寸,以提升聲化學反應器之聲化學效率,最後以實驗驗證之。

If the pressure amplitude is less than a threshold in liquid, the bubble nuclei volume will expand rapidly. When subjected higher pressure, the bubbles collapse and generate high pressure, high temperature and shock wave. This phenomenon is called “Cavitation”. “Sonochemistry” is applying ultrasound to form cavitation, and the extreme environment caused by cavitation can enhance or initiate chemical activities in solution. Sonochemistry is relevant to cavitation, so we design sonochemical reactors to form intense cavitation field. Present researches commonly ignore the damping effect of bubbles when design sonochemical reactors, therefore, we introduce the inhomogeneous bubbles model to compute the sound field in sonochemical reactors. At first, calculate the pressure threshold (Blake threshold) and employ the COMSOL to compute sound field. Then, the genetic algorithm is employed to optimize the sonochemical reactor size, in order to generate better sonochemical efficiency. Finally, conduct experiments to confirm the accuracy of the computational model.

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