فرزاد فرهت فرد

The flow-focusing method is a sophisticated technique for producing small-scale droplets, particularly in microfluidic applications. The three main objectives of this study are: 1- to control jet breakup by applying artificial perturbations in the flow-focusing method to produce uniform droplets; 2- to propose a novel approach for calculating the optimal frequency for artificial perturbations using numerical simulation and the discrete Fourier transform (DFT); and 3- to eva‎luate the effects of various parameters, such as device geometry and the type of focusing gas, on the optimal frequency. Simulations are conducted using the volume of fluid (VOF) model. Results demonstrated the successful production of droplets in the tens-of-micrometer range. Applying perturbations at the optimal frequency reduced the standard deviation of dimensionless droplet diameter from 8×10^(-2) to 3.2×10⁻⁴. Four Weber numbers (We) ranging from 697 to 1760 are analyzed, revealing that the optimal frequency (f_opt) varies between 20 and 70 kHz, depending on flow conditions. Additionally, it is shown that the type of focusing gas —air, argon, and CO2— can significantly affect both the jet length and the optimal frequency (f_opt). These findings underscore the importance of considering gas properties in optimizing droplet generation systems and provide a scalable and cost-effective approach for applications requiring precise droplet control.

جريان متمركز‌كننده , قطرات تك پراكنده , ميكروسيالات قطره‌اي , تبديل فوريه گسسته , پايداري جت , شبيه‌سازي عددي

Flow-focusing , Monodisperse droplets , droplet microfluidics , Discrete Fourier Transform (DFT) , Jet stability , Numerical simulation

farzad farhatfard

Majid Siavashi