Kwang-Yong Kim

The enhancement of drug delivery into the lung surfactant is facilitated by research on the interaction between drugs and the lung surfactant. Drug designers must have a thorough theoretical understanding of a drug before performing clinical tests to reduce the experimental cost. The current study uses a coarse-grained molecular dynamics (MD) approach with the MARTINI force field to parameterize the corticosteroid drug mometasone furoate, which is used to treat lung inflammation. Here, we investigate the accurate parametrization of drug molecules and validate the parameters with the help of umbrella sampling simulations. A collection of thermodynamic parameters was studied during the parametrization procedure. The Gibbs free energy gradient was used to calculate the partition coefficient value of mometasone furoate, which was approximately 10.49 based on our umbrella sampling simulation. The value was then matched with the experimental and predicted the partition coefficient of the drug, showing good agreement. The drug molecule was then delivered into the lung surfactant monolayer membrane at the alveolar air–water interface, resulting a concentration-dependent drop in surface tension while controlling the underlying continual compression–expansion of alveoli that maintains the exhalation–inhalation respiratory cycle. The dynamical properties of the monolayer demonstrate that the drug’s capacity to diffuse into the monolayer is considerably diminished in larger clusters, and this effect is intensified when there are more drug molecules present in the monolayer. The monolayer microstructure analysis shows that the drug concentration controls monolayer morphology. The results of this investigation may be helpful for corticosteroid drug delivery into the lung alveoli, which can be applied to comprehend how the drug interacts with lung surfactant monolayers or bilayers.

Micromixers are important components of lab-on-a-chip systems, and also have many biological and chemical applications

In this study, a numerical investigation based on the CFD method is carried out to study the unsteady laminar flow of Newtonian fluid with a high viscosity in a three-dimensional simulation of a twisted double planetary mixer, which is composed of two agitating rods inside a moving tank. The considered stirring protocol is a “Continuous sine squared motion” by using the dynamic mesh model and user-defined functions (UDFs)to define the velocity profiles. The chaotic advection is obtained in our active mixers by the temporal modulation of rotational velocities of the moving walls in order to enhance the mixing of the fluid for a low Reynolds number and a high Peclet number. For this goal, we applied the Poincaré section and Lyapunov exponent as reliable mathematic tools for checking mixing quality by tracking a number of massless particles inside the fluid domain. Additionally, we investigated the development of fluid kinematics proprieties, such as vorticity, helicity, strain rate and elongation rate, at various time periods in order to view the impact of temporal modulation on the flow properties. The results of the mentioned simulation showed that it is possible to obtain a chaotic advection after a relatively short time, which can deeply enhance mixing fluid efficiency.

Three-dimensional numerical investigations of a novel passive micromixer were carried out to analyze the hydrodynamic and thermal behaviors of Nano-Non-Newtonian fluids. Mass and heat transfer characteristics of two heated fluids have been investigated to understand the quantitative and qualitative fluid faction distributions with temperature homogenization. The effect of fluid behavior and different Al₂O₃ nanoparticles concentrations on the pressure drop and thermal mixing performances were studied for different Reynolds number (from 0.1 to 25). The performance improvement simulation was conducted in intervals of various Nanoparticles concentrations (φ = 0 to 5%) with Power-law index (n) using CFD. The proposed micromixer displayed a mixing energy cost of 50–60 comparable to that achieved for a recent micromixer (2021y) in terms of fluid homogenization. The analysis exhibited that for high nanofluid concentrations, having a strong chaotic flow enhances significantly the hydrodynamic and thermal performances for all Reynolds numbers. The visualization of vortex core region of mass fraction and path lines presents that the proposed design exhibits a rapid thermal mixing rate that tends to 0.99%, and a mass fraction mixing rate of more than 0.93% with very low pressure losses, thus the proposed micromixer can be utilized to enhance homogenization in different Nano-Non-Newtonian mechanism with minimum energy.

Effects of the number of blades on the impeller-volute interaction and flow instability were studied for a centrifugal pump. The hydraulic performance and time-dependent flow field were analyzed by using the unsteady three-dimensional Reynolds-averaged Navier-Stokes equations with the k-ω based shear stress transport turbulence model. The grid dependence and temporal resolution were tested to evaluate the numerical uncertainties, and the numerical results were validated using experimental data. As the performance parameters, the stage total-to-static head coefficient, the impeller total-to-static head coefficient, and the volute static pressure recovery coefficient were selected to classify the cause of the impeller-volute interaction and flow instability observed inside components. Using the fast Fourier transform, fluctuations of the performance parameters were divided into three categories: the blade passing frequency and its harmonic frequencies, the fluctuations in the broadband frequency region, and the fluctuations in the low-frequency region. The results showed that the fluctuations of the performance parameters and local pressure were affected in various ways by the number of blades. The time-dependent flow structure was investigated to study the root causes of the differences in the impeller-volute interaction and flow instability by the number of blades.

본 연구에서는 경사진 출구부를 가진 유체진동기의 새로운 형상을 제안하였다. 이 진동기의 우수성을 입증하기 위해 진동수, 분사각, 최대 속도비 및 압력 강하 등의 성능을 수치적으로 평가하였다. 성능 평가를 위하여 진동기의 출구 높이와 출구부의 경사가 시작되는 위치를 변수로 하여 매개변수 연구를 수행하였다. 유동해석은 3차원 비정상 레이놀즈 평균 Navier-Stokes 방정식과 SST 난류 모델을 사용하여 수행하였다. 연구 결과 모든 경우에서 경사진 출구부는 유체진동기의 성능을 큰 압력강하의 증가 없이 전반적으로 향상시켰으며, 출구 노즐 높이가 작아지고 경사가 일찍 시작될수록 성능이 향상되었으나 출구 높이가 성능에 보다 더 민감한 영향을 미쳤다.

In this work, a design optimization study was conducted to improve the performance of a membraneless microfluidic fuel cell with a double-bridge cross-section of the flow channel. Governing equations including Navier–Stokes, mass-transport, and Butler–Volmer equations were solved numerically to analyze the electrochemical phenomena and evaluate the performance of the fuel cells. Optimization was performed to maximize the peak power density using a genetic algorithm combined with a surrogate model constructed by radial basis neural network. Two sub-channel widths of the flow channel were selected as design variables for the optimization. As a result, a large increase in the inner channel width and a small decrease in the outer channel width effectively increased the peak power density of the MMFC. The optimal design increased the peak power density by 57.6% compared to the reference design.

The present work performed a comprehensive investigation to find the effects of a dual-bleeding port recirculation channel on the aerodynamic performance of a single-stage transonic axial compressor, NASA Stage 37, and optimized the channel’s configuration to enhance the operating stability of the compressor. The compressor’s performance was examined using three parameters: The stall margin, adiabatic efficiency, and pressure ratio. Steady-state three-dimensional Reynolds-averaged Navier–Stokes analyses were performed to find the flow field and aerodynamic performance. The results showed that the addition of a bleeding channel increased the recirculation channel’s stabilizing effect compared to the single-bleeding channel. Three design variables were selected for optimization through a parametric study, which was carried out to examine the influences of six geometric parameters on the channel’s effectiveness. Surrogate-based design optimization was performed using the particle swarm optimization algorithm coupled with a surrogate model based on the radial basis neural network. The optimal design was found to increase the stall margin by 51.36% compared to the case without the recirculation channel with only 0.55% and 0.28% reductions in the peak adiabatic efficiency and maximum pressure ratio, respectively.

In this work, a numerical investigation was analyzed to exhibit the mixing behaviors of non-Newtonian shear-thinning fluids in Kenics micromixers. The numerical analysis was performed using the computational fluid dynamic (CFD) tool to solve 3D Navier-Stokes equations with the species transport equations. The efficiency of mixing is estimated by the calculation of the mixing index for different cases of Reynolds number. The geometry of micro Kenics collected with a series of six helical elements twisted 180° and arranged alternately to achieve the higher level of chaotic mixing, inside a pipe with a Y-inlet. Under a wide range of Reynolds numbers between 0.1 to 500 and the carboxymethyl cellulose (CMC) solutions with power-law indices among 1 to 0.49, the micro-Kenics proves high mixing Performances at low and high Reynolds number. Moreover the pressure losses of the shear-thinning fluids for different Reynolds numbers was validated and represented.