3299

3094

كارشناسي ارشد

﴿ تبديل انرژي ﴾

اصفهان : دانشگاه صنعتي اصفهان ، دانشكده مكانيك

1385

چهارده ، 126 ، [I] ص : مصور، جدول ، نمودار

ص . ع : به فارسي

ابراهيم شيراني

محمود اشرفي زاده

محمد سعيد سعيدي ، احمد رضا پيشه ور

مهندسي مكانيك

ID3094

به فارسي و انگليسي : قابل رويت در نسخه ديجيتالي

Abstract The goal is to study the movement and deformation of a droplet on the surface fordifferent situations Multiphase flow involving droplets sitting on a surface of a channel isa common problem encountered in many engineering and scientific applications includingliquid water droplets in the channels of PEM fuel cells The existence of water dropletsreduces the cross sectional area for oxygen transport also act as additional barrier for thegas flow So it is important to study the behavior of water droplets in the channel of PEMfuel cell for different fluid properties In this work a simple phase code was modified to a two phase code The numericalsolution is based on solving Navier Stokes equations for Newtonian liquids The studyincludes the effect of interfacial forces with constant surface tension also effect ofadhesion between the wall and droplet accounted by implementing contact angle at thewall The Volume Of Fluid method is used to numerically determine the deformation offree surface The collocated grid was used in this code Results were presented for three cases In the first case we compare our results withresults obtained from other two phase code SURFER for the stationary drop in thestationary domain Then dynamic behavior of a droplet adhering to the surface of a channel has beenmodeled under the influence of surrounding fluid A comprehensive set of simulations is conducted covering a wide range of surfacetension viscosity ratios density ratios and the maximum inlet velocity The results show the droplet deformation increases as the surface tension is decreased and deformation of the droplet prevents flow separation in the channel Flow separationand recirculation eddies are observed when the viscosity and the inlet velocity of thechannel fluid are decreased Results also show that by decreasing the density ratio nosignificant change in the flow structure is occurred From the several cases that obtained with different flow properties the characteristicslength the maximum length from the center of the drop to the drop surface was obtainedand it was shown that the length when normalized with the original drop radius is wellcorrelated with the Capillary number The correlation was introduced in this work Finally the influence of the surface tension and viscosity ratios on the moving dropletis shown Results show the movement of droplet is increased by increasing the surfacetension and viscosity ratio

ابراهيم شيراني

محمود اشرفي زاده

محمد سعيد سعيدي ، احمد رضا پيشه ور