Islanabilirlik Gradyan Yüzeylerinde Kendi Kendini Yürüten ve Birleştiren Damlacıklar: Bir Lattice Boltzmann Çalışması

Yıl 2023, Cilt: 27 Sayı: 3, 464 - 473, 25.12.2023

Mehmet Alptug Boylu , Umut Ceyhan

Öz

Damlacıkların kendi kendine taşınması ve kontrolü, mikroakışkan cihazların
geliştirilmesinde, kendi kendini temizlemede, su toplamada ve ısı transferini
geliştirmede önemli bir rol oynar. Yüzeylerde bir ıslatma gradyanı
yapılandırılmışsa, harici bir kuvvet olmadan damlacık manipülasyonu elde
edilebilir. Temas açısı histerezisi, daha çok ıslanan tarafa doğru bir itici güç
oluşturur. Bu kuvvet, hareketli temas hatlarının yakınındaki viskoz gerilimlerle
dengelenirse, bu tür yüzeyler üzerindeki damlacıklar, bu denge tarafından
belirlenen sabit öteleme hızına ulaşabilir. Bu çalışmada D2Q9 lattice Boltzmann
yöntemi, ıslanabilirlik gradyan yüzeylerinde kendiliğinden hareket eden
damlacıkların simülasyonu için kullanılmıştır. Yüzey enerjisi ve akışkan
viskoziteleri değiştirilerek, tek damlacıkların yüzeyler üzerindeki davranışı,
bunların birleştirme mekanizması ve sınırlandırılmış kanallar içindeki denge
şekilleri ve hareketleri sistematik olarak incelenmiştir. Damlacık daha viskoz bir
akışkan içinde hareket ederse, damlacık hızının ıslanma gradyanına bağlılığının
zayıfladığı gözlemlenmiştir. Büyük görünüm oranlı kanal akışları için, arayüz
hareketinin iki boyutlu tahmininin üç boyutlu D3Q19 modeli hesaplamalarına
yaklaştığı gösterilmiştir.

Anahtar Kelimeler

Arayüzey akışı, Temas hattı, Islanabilirlik gradyanı, Lattice Boltzmann metodu

Self-Driving and Merging Droplets on Wettability Gradient Surfaces: A Lattice Boltzmann Study

Öz

Self-transport and control of droplets play an essential role in the
development of microfluidic devices, self-cleaning, water harvesting, and heat
transfer enhancement. Droplet manipulation without an external force can be
accomplished if a wetting gradient is structured on surfaces. The contact angle
hysteresis generates a driving force toward the more wetting side. If this force is
balanced by the viscous stresses near moving contact lines, droplets on such
surfaces may attain constant translational speed determined by this balance. The
D2Q9 lattice Boltzmann method is employed for the simulation of the self-driven
droplets on wettability gradient surfaces. By varying the surface energy and fluid
viscosities, the behavior of single droplets on surfaces, their merging mechanism,
and equilibrium shapes and motions within confined channels are studied
systematically. If the droplet moves in a more viscous fluid, the droplet’s speed
dependence on the wetting gradient is observed to weaken. For large aspect ratio
channel flows, it is shown that two-dimensional prediction of the interface motion
approaches the three-dimensional D3Q19 model computations.

Anahtar Kelimeler

Interfacial flow, Contact line, Wettability gradient, Lattice Boltzmann method

Kaynakça

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