旅波式介電泳的數值模擬

Abstract

本文以數值方法研究一項用以驅動具導電性二項懸浮液旅波式介電泳幫浦，在此我們以血作為二項懸浮流的例子來做探討。針對前人的計算程式，本文進行了三項修改。(1)將源項計算從平面微粒顆數改成空間微粒顆數，使計算樣本變多，使微粒濃度、流速、(血液)導電度等空間結果圖變得更平滑，數值變異較小，減少數值上的誤差。(2)微粒(血球)周遭流體的黏滯係數改為隨微粒空間濃度變化的參數，修改後流速減弱，整體阻力變大。(3)將定值的材料參數 CM 因子改為隨當地微粒濃度變化的參數。經此修改之後流速比修正前變快。上述三項修改將使數值模擬更接近實況。 在本文中也利用最終改良上述三項程式結果，來模擬進行實驗比對。在平均濃度18%，流道長1300μm(290μm+720μm+290μm)，流道高60μm，工 作頻 率10MHz，電壓 5V(peak to peak)下，最後模擬結果平均流速為 28.15μm/s，實驗為 18μm/s， 比較上有 35%誤差。 針對於濃度與頻率及流道幾何進行參數分析，在10MHz情況下，微粒濃度20%時較15%時有更好的輸送效能。而同樣濃度，10MHz 和 5MHz 比較，10MHz 的平均流速較快。而前後流道加長，電極區不變下流速則減緩。

The work of the thesis is to study numerically a travelling wave dielectrophoretic pump for delivering two-phase suspension conducting fluid, with blood as a model fluid for simulation. Three modifications were made from a previous computer programe.(1)The calculation of source term for exchanging momentum between the suspension and continuum phases was modified from planar to three-dimensional situation, with randomly refill particle for steady state simulation. The samples of the particle calculation were increased by such a modification, and thus more smooth variations of the fileds were were observed.(2)The viscosity is modified by allowing it to be a variable of the local particle concentration,and the resulting pumping velocity is thus dcreased.(3)The effect of the variation of the Clausius-Mossotti factor with particle concentration is included,and the resulting pumping velocity is increased. It is expected that the modified program will provide a better simulation for the real simulation. By performing a simulation with average concerntration 18%, total channel length 1300μm(with an electrode array 720μm at the middle), channel height 60μm,frequency 10MHz, and voltage 5 volts(peak to peak), the average pumping velocity is 28.15μm/s, which is 35% higher than the experimental value, 18μm/s. A preliminary parametric study was carried out for the pump performance. The pump performs better for 20% particle concentration in comparing with 15% situation,for 10MHz frequency in comparing with that at 5MHz, and for case with shorter channel length with fixed a electrode array.