Düşük Reynolds sayılı alveolar akışta partikül boyutunun aerosol dinamikleri üzerine etkisinin sayısal olarak incelenmesi

Akciğer hastalıklarında etkili bir tedavi yönteminin geliştirilmesi ve ilaç taşınımının iyileştirilmesi açısından akciğerlerin asiner bölgesindeki hava akışının ve solunan farmasötik veya zararlı partiküllerin taşınmasının incelenmesi çok önemlidir. Bu çalışmada, insan akciğerinin asiner bölgesinde etrafı alveol keseleri ile çevrilmiş bir respiratuar bronşiol modeli üzerinde alveolar hava akışı ve farklı boyutlardaki partiküllerin aerosol dinamikleri üzerine etkisi hesaplamalı akışkanlar dinamiği (CFD) kullanılarak sayısal olarak incelenmiştir. Sayısal simülasyonlar, çoklu nefes periyotları ve üç farklı solunum şartı (düşük, normal ve ağır solunum) için yapılmıştır. Her bir akış durumunda model girişinden hesap alanına farklı çaplara sahip aerosol partikülleri salınmış ve yörüngeleri sayısal olarak takip edilmiştir. Sonuçlar, hareketli alveol duvarları sayesinde alveol çukurlarına hava ve partikül girişinin olduğunu göstermiştir. Alveol çukurunda meydana gelen resirkülasyonlu akış yapılarının partikül dinamiklerini karakterize ettiği belirlenmiştir. Elde edilen sonuçlara göre model içerisinde kalan aerosol miktarı, partikül boyutu ve akış debisiyle azalmıştır. 7 µm’nin üzerinde çapa sahip aerosol partiküllerinin kanal cidarlarında ve 5 µm’nin altındaki partiküllerin ise alveol boşluklarında biriktiği belirlenmiştir. Sonuç olarak bu çalışma, solunan farmasötik veya zararlı partiküllerin alveolar bölgede davranışlarıyla ilgili önemli fizyolojik sonuçlar sunmaktadır.

Anahtar Kelimeler:

Asiner akış dinamiği, Düşük Reynolds sayılı akış, Resirkülasyon, Sonlu elemanlar

Numerical analysis of the particle size effect on aerosol dynamics in low Reynolds number alveolar flow

In order to develop an effective treatment method and improve drug delivery in lung diseases, it is very important to examine the airflow and the transport of inhaled pharmaceutical or harmful particles in the acinar region of the lungs. In this study, the alveolar airflow and the effect of particles of different sizes on aerosol dynamics were numerically investigated on a respiratory bronchiole model surrounded by alveolar sacs in the acinar region of the human lung using computational fluid dynamics (CFD). Numerical simulations were made for multiple breathing periods and three different respiratory conditions (i.e, low, normal and heavy breathing). In each flow situation, aerosol particles with different diameters from the model entry to the computational domain were released and their trajectories were tracked numerically. The results showed that there was air and particle entry into the alveolar cavities due to the movable alveolar walls. It was determined that the recirculating flow structures occurring in the alveolus characterize the particle dynamics. According to the results, the amount of aerosol remaining in the model decreased with particle size and flow rate. It was also found that aerosol particles with a diameter of more than 7 µm deposited on the duct walls and the particles below 5 µm in the alveolar cavities. Consequently, this study provides the important physiological results regarding the behavior of inhaled pharmaceutical or harmful particles in the alveolar region.

Keywords:

Acinar fluid dynamics, Low Reynolds number flow, Recirculation, Finite element,

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