اثر میدان مغناطیسی بر حرکت، تغییر شکل و زمان جدایش قطرات سیالات نیوتنی و غیرنیوتنی در میکروکانال جریان متمرکز

نوع مقاله : مقاله پژوهشی

نویسندگان

دپارتمان مهندسی مکانیک، دانشکده فنی و مهندسی، دانشگاه خوارزمی

چکیده

در مطالعه‌ی حاضر، تأثیر میدان مغناطیسی خارجی بر فرآیند تشکیل قطرات با اندازه و فرکانسی متفاوت و همچنین تأثیر خواص غیرنیوتنی بر مشخصات این قطرات، در یک میکروکانال جریان متمرکز به روش عددی بررسی شده و از طریق دو مدل غیرنیوتنی ویسکوز کاریو و توانی، وابستگی تنش با نرخ کرنش، مورد ارزیابی گرفته است. همچنین، تحلیل معادلات پیوستگی و مومنتوم جریان دوفازی، تراکم ناپذیر و غیردائم، با استفاده از روش حجم محدود و یک الگوریتم عددی بر اساس تکنیک کسر حجمی انجام گرفته است تا تأثیر عدد باند (0 تا 0/2) و اندیس توانی (0/3، 0/6 و 1/3) بر روی فرآیند تشکیل‌شدن قطرات، اندازه و زمان جدایش آن‌ها مورد ارزیابی قرار گیرد. نتایج بدست آمده نشان می‌دهند که میان سیال نیوتنی و سیالات غیرنیوتنی با مدل‌های مختلف، قطره‌ی کاریو در عدد باند 0/2 دارای بیشترین حجم، معادل حجم بی‌بعد 1/56 بوده و تأثیر میدان مغناطیسی بر فرآیند تشکیل و جدایش قطرات، بیش از تأثیر معادله‌ی ساختاری (مدل ویسکوزیته) است. همچنین، با افزایش قدرت میدان مغناطیسی، زمان جدایش قطرات بیشتر شده و قطراتی بزرگتر با فرکانس تولیدی کمتر، حاصل شده است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effect of Magnetic Field on Motion, Deformation, and Separation Time of Newtonian and Non-Newtonian Droplets in a Flow‐Focusing Microchannel

نویسندگان [English]

  • sima mashafi
  • mostafa esmaeili
Department of Mechanical Engineering, Faculty of Engineering, Kharazmi University , Tehran, Iran
چکیده [English]

In the present study, the effect of external magnetic field on the process of droplet formation with different sizes and frequencies in a flow-focusing micro-channel is numerically studied. Moreover, the influence of non-Newtonian properties on the droplet formation characteristics is investigated using two non-Newtonian Carreau and power-law models. To solve the continuity and momentum equations for unsteady, two-phase, and incompressible flow, the finite volume method is employed. A numerical algorithm based on the volume-of-fluid technique is used to determine the effect of Bond number (0 to 0.2) and Power-law indices (0.3, 0.6, and 1.3) on the droplet formation process along with their size and separation time. To validate the numerical solution, the formation of Newtonian fluid droplets at different values of magnetic field strength is compared with the results of other studies and very good agreement was observed. The results of the numerical solution show that the Carreau fluid droplet in the Bond number of 0.2 has the highest volume, which is equivalent to the dimensionless volume of 1.56. Also, the process of droplet formation is more affected by the magnetic field than by the non-Newtonian model. Besides, with developing the field strength, droplet separation time increases and as a result, larger droplets with lower frequency will be formed.

کلیدواژه‌ها [English]

  • Microfluidic
  • droplet formation
  • magnetic field
  • Non-Newtonian fluid
  • numerical simulation
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