Journal of Advanced Research in Experimental Fluid Mechanics and Heat Transfer

A Hybrid RANS/LES Model for Predicting the Aerodynamics of Small City Vehicles

Mohammad Arafat — 2024-09-15

Electric city vehicles are vital for reducing pollution in urban areas due to their zero emissions and high energy efficiency, significantly improving air quality and reducing the carbon footprint. This study investigates the aerodynamic behavior of simplified city vehicle models using computational fluid dynamics (CFD) simulations based on Reynolds-Averaged Navier-Stokes (RANS) and Detached Eddy Simulation (DES) turbulence model. The models are tested at speeds of 10 m/s, 15 m/s, and 20 m/s, with a grid independence study to ensure reliable results. ANSYS Fluent is used for the simulations, comparing the results from RANS and hybrid RANS/LES or DDES in terms of aerodynamic forces and flow patterns around the vehicle. Results show that the drag coefficient (Cd) decreases with increasing speed for both RANS and DDES models. At 10 m/s, the drag coefficients are 0.541 for RANS and 0.524 for DDES, a 3.14% reduction. At 15 m/s, the drag coefficients are 0.539 for RANS and 0.518 for DDES, a 3.89% reduction. At 20 m/s, the drag coefficients are 0.538 for RANS and 0.514 for DDES, a 4.46% reduction. Flow visualizations show that DDES simulations capture more detailed and complex flow structures, particularly in the wake region, compared to the smoother RANS patterns. These findings are essential guidelines for optimizing vehicle design to enhance aerodynamic performance and contribute to the development of more efficient, environmentally friendly urban transportation solutions.

Solute Dispersion in Casson Blood Flow through a Stenosed Artery with the Effect of Temperature and Electric Field

Nur Husna Amierah Mohd Zaperi — 2024-09-15

This study develops a mathematical model to address solute dispersion in arterial blood flow, particularly considering the effects of temperature and electric fields using the Casson fluid model. Given the physiological importance of drug delivery within the human vascular system, understanding these dynamics is crucial, especially in the presence of cardiovascular diseases (CVD). The Generalized Dispersion Model (GDM) is employed to simulate the dispersion function. Results demonstrate that elevated temperatures and electric fields enhance drug uptake and distribution by increasing blood flow. The model accurately predicts drug behavior in narrowed arteries, optimizing dosage regimens and improving therapeutic outcomes. Visual representations and detailed discussions of these findings are presented in the subsequent sections. The results are validated against a previous study that did not consider the effects of stenosis height, temperature and electric field. The findings suggest a strong agreement between the two studies. Additionally, an increase in mean absorption leads to an increase in velocity. When mean absorption increases, the functions of steady dispersion and overall dispersion decrease, while the function of unsteady dispersion increases. The reverse behavior is observed for the electric field. The study concludes that integrating temperature and electric field effects into drug delivery systems can significantly enhance treatment efficacy and reduce side effects, providing a valuable tool for advanced targeted therapies in CVD and cancer management.

Temperature Condition Impact on the Onset of Rayleigh-Benard Convection in a Binary Fluid Saturated Anisotropic Porous Layer

Nurul Hafizah Zainal Abidin — 2024-09-15

Rayleigh-Benard convection in a saturated anisotropic porous media is investigated numerically. The temperature-dependent viscosity effect was applied to the double-diffusive binary fluid, and the Galerkin method was used to determine the critical Rayleigh numbers for the free-free, rigid-free, and rigid-rigid representing the lower-upper boundaries. The lower and upper boundary was set to be either conducting or insulating to temperature. The purpose of this study is to study the stability of Rayleigh-Benard convection with different temperature conditions in a binary fluid saturated by an anisotropic porous layer. The obtained eigenvalue is numerically solved with respect to various temperatures and velocities using the single-term Galerkin technique. The results, presented graphically, indicate that the rigid-rigid boundaries are more stabilize compared to rigid-free and free-free boundaries. It is also shown that an increase of temperature-dependent viscosity tends to destabilize the onset of double-diffusive convection.