نوع مقاله: مقاله کامل پژوهشی

نویسندگان

1 کارشناسی ارشد مهندسی هوا فضا-آیرودینامیک، دانشکده‌ی علوم و فنون نوین، دانشگاه تهران، تهران، ایران

2 دانشیار، بخش مهندسی پزشکی، گروه مهندسی علوم زیستی، دانشکده‌ی علوم وفنون نوین، دانشگاه تهران، تهران، ایران

3 دانشجوی کارشناسی ارشد مهندسی پزشکی-بیومکانیک، دانشکده‌ی علوم و فنون نوین، دانشگاه تهران، تهران، ایران

چکیده

سطح وسیع ریه با حصارهای هوایی-خونی خود، در معرض ذرات معلق هوای ورودی قرار دارد. در این شرایط، در صورت آلوده بودن این ذرات، اثر متقابل ذرات-ریه روی هم می­تواند خطرات و صدمات قابل توجهی را برای سلامتی انسان به همراه داشته باشد. از طرفی، از این واکنش­ها برای دارورسانی به بدن انسان نیز استفاده می‌شود. در هر دو حالت، تخمین دقیق مقدار و محل نشست ذرات در مجاری تنفسی، به عنوان مبنای درک مکانوبیولوژیکی این بیماری­ها به شمار می‌رود. گردآوری تجربی داده‌ها از انتقال ذرات در ریه‌ی انسان فرایند بسیار دشواری می‌باشد. اما روش دینامیک سیالات-ذرات محاسباتی، امکان شبیه‌سازی داده­های انتقال ذرات در مدل­های واقعی را فراهم ساخته است. نشست ذرات آیروسول در ریه‌ی انسان، از طریق ترکیب برخورد در اثر اینرسی، رسوب در اثر گرانش و انتشار روی می­دهد. مکانیسم اصلی نشست ذرات در مجاری پایین دست، برای ذراتی با قطر آیرودینامیکی 5/0 تا 5 میکرومتر و در حالت انبساط ریه (در حالت دم)، رسوب ناشی از نیروی گرانش و انتقال هم‌رفتی ناشی از حرکت دیواره­ها می­باشد. در این پژوهش، جریان سیال-ذره در نسل 18-ام از مجاری تنفسی مدل­سازی شده و میزان نشست ذرات در مجاری تنفسی برای دو حالت گرانش ناچیز و نرمال، با فرض تغییر­ مکان ایزوتروپیک در دیواره‌ها و میزان دبی ورودی 1 mg/s، مورد بررسی قرار گرفته است. بررسی نتایج به دست آمده نشان می‌دهد که به دلیل توانایی نفوذ ذرات با قطر آیرودینامیکی کم‌تر از 5 میکرومتر به نواجی عمیق مجاری تنفسی، با ناچیز کردن اثر نیروی گرانش، میزان نشست ذرات در مجاری پایین­دست سیستم تنفسی تا حد بسیار زیادی کاهش می­یابد. ذرات با قطر 5 میکرومتر، تحت تاثیر برخورد اینرسی (که بیش‌تر در مجاری با قطر بزرگ و متوسط روی می­دهد) و هم‌چنین در اثر رسوب (که بیش‌تر در مجاری پایین‌دست عمل می­کند)، دچار نشست می­شوند. 

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Computational Simulation of Airflow with Aerosols in Distal Parts of a Human Respiratory System: Investigating the Effects of Gravity

نویسندگان [English]

  • Mohammad Ahmadi Alashti 1
  • Bahman Vahidi 2
  • Mahtab Ebad 3

1 M.Sc. in Aerospace Engineering-Aerodynamics, Faculty of New Sciences and Technologies (FNST), University of Tehran, Tehran, Iran

2 Associate Professor, Biomedical Engineering Department, Faculty of New Sciences and Technologies (FNST), University of Tehran, Tehran, Iran

3 M.Sc. Student of Biomedical Engineering-Biomechanics, Faculty of New Sciences and Technologies (FNST), University of Tehran, Tehran, Iran

چکیده [English]

The large surface area of the lung with its thin air-blood barrier is exposed to particles in the inhaled air. In this condition, if the inhaled pollutant aerosols are toxic, the particle-lung interaction may cause serious hazards and injuries on human’s health. On the otherhand, these interactions are also used for drug delivery to human’s body. In either case, an accurate estimation of dose and sites of deposition in the respiratory tract is fundamental for understanding mechanobiology of these deseases. Obtaining in vivo data of particle transportation in the human lung experimentally is often difficult. But, computational fluid-particle dynamics (CFPD) has provided the possibility to gain aerosol transportion data in realistic airway geometries. Aerosols deposition in the human lung mainly occurs due to combination of inertial impaction, gravitational sedimentation and diffusion. For particles with aerodynamic size of 0.5 to 5 micron and in inhalation state of lung, the main mechanisms of particle deposition in distal parts of human’s respiratory system are sedimentation, due to gravity and convective transfer due to wall movement. In this study, deposition of particles in distal part of human respiratory system, specifically 18th generation, has been modeled for two gravity conditions, normal and absent gravity, by assuming isotropic displacements on the walls and with the rate of 1 (mg/sec) for particle input. By analyzing the results, it was determined that the amount of particle deposition in distal airways reduces a great amount by omitting the effect of gravitational force because, particles smaller than 5 micron can penetrate into that airways. Particles with the diameter of 5 micron deposit under the effect of inertial impact, whereas this mechanism occurs mostly in airways with large and medium diameters and also, by sedimentation which occurs in the distal lung.

کلیدواژه‌ها [English]

  • CFPD
  • Particles deposition in acinar region
  • Alveolated duct with moving wall
  • Distal parts of respiratory system
  • Micro-Gravity

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