7260

6766

كارشناسي ارشد

تبديل انرژي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1391

پانزده، 85ص: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

سعيد مرتضوي

احمدرضا پيشه ور

21/8/91

احمد صابونچي، احمد سوهانكار اصفهاني

1396/09/21

كتابنامه

مكانيك

مهندسي مكانيك

ID6766

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

86Abstract The numerical simulation of sedimenting deformable drops inside a vertical channel under gravity hasbeen performed at finite Reynolds numbers The three dimensional channel is confined in x direction by twovertical walls and is periodic in y and z directions Results are obtained using a finite difference fronttracking method The main dimensionless parameters are Reynolds number Bond number and ratio of thelength of channel to the diameter of drops The effect of these parameters on lateral migration of drops isinvestigated In the case of one drop the wall repulsion is the main mechanism of the lateral migration of the drop andcenterline of the channel is the steady state equilibrium lateral position of drop When the Reynolds numberis below 60 0 two different lateral migration regimes are observed migration with monotonic approach andmigration with damped oscillations These regimes are affected by dimensionless parameters When the Bondnumber increases the oscillations of drop around the centerline of channel are stronger and so the timerequired for damping these oscillations is longer If the length of the channel in x direction increases or thediameter of the drop decreases drop is less influenced by the walls of channel As a result the oscillations ofdrop around the centerline of the channel are damped Results of lateral migration of one drop are consistentwith perturbation theory of Cox et al and two dimensional numerical simulations performed by Feng et al forsolid circular cylinders Drag coefficient also has been calculated and effect of various parameters has been discussed It is foundthat drag on a viscous drop is different from rigid spherical drops because of two effects effect of internalcirculation of drop and effect of drop deformation The internal circulation of drop is basically related to theviscosity ratio and is weaken by increasing the viscosity of the drop fluid or decreasing the viscosity of theambient fluid Generally the internal circulation of the drop decreases the drag coefficient of the drop andaccording to the steady state shape of drop deformation of the drop can increase or decrease the dragcoefficient of the drop Drag coefficient of the drop is also affected by ratio of the length of the channel in x direction to the diameter of the drop If length of the channel in x direction decreases or diameter of the dropincreases the drag coefficient will increase In the case of two and four drops drops are initially placed in tandom with a specific separation distance The study of two drops is similar to that done by Feng et al for solid circular cylinders In all simulations oftwo drops drops finally get a symmetric configuration with respect to channel axis with equal spacing fromthe walls The mechanism of interaction is basically same as that defined by Feng et al which is drafting kissing and tumbling DKT As the Reynolds number or ratio of the length of the channel to the diameter ofthe drop increases Drops move slightly towards the walls This result is consistent with experimental resultsof Wu et al for two spherical particles sedimenting in a vertical channel Depending on the ratio of the lengthof the channel in x direction to the diameter of the drops four drops sediment in two or four columns withthe same settling velocity Key wordsDeformable drops Lateral migration Wall repulsion Reynolds number Bond number Drag coefficient

سعيد مرتضوي

احمدرضا پيشه ور

احمد صابونچي، احمد سوهانكار اصفهاني