CFD Analysis of Indoor Ventilation for Airborne Virus Infection Indoor airflow patterns and air residence times significantly influence the spread of airborne infectious viruses, such as COVID-19. These factors can be quantified using computational fluid dynamics (CFD). In this study, CFD was utilized to assess the indoor airflow patterns and calculate air residence times in a typical restroom with high personnel flow and low ventilation efficiency. The results identified regions with high air residence times, indicating potential risk areas for airborne virus retention. Furthermore, the effects of different ventilation strategies on these high-risk areas were analyzed. Despite meeting air change standards, certain regions were found to potentially pose a higher risk due to prolonged air residence times. Based on these findings, recommendations for improving ventilation systems to reduce the risk of airborne virus infection were proposed. This study highlights the necessity of a more nuanced approach to indoor air assessment than simply calculating air changes per hour. It was concluded that (1) different ventilation strategies can greatly affect the air residence time in the room and (2) the variance of air residence time in the air circulation area are large in some locations, even with simple ventilation adjustments.

Cardiovascular disease (CVD) is one major cause of morbidity caused by the progress of atherosclerosis without any symptoms and has a high risk of Transient Ischemic Stroke (TIS). The carotid bifurcation and bulb are the region where the blood flow is irregular, which may lead to the progression of the plague. The flow disruption due to stenosis in idealised carotid artery has been extensively investigated using Fluid Structure interaction (FSI). However, the haemodynamic of patient specific carotid artery has been intensively studied. In this study, a comparison of blood flow in healthy and stenosed (80% blockage in the carotid bulb region) was carried out using Two- way FSI analysis considering non-Newtonian blood viscosity and isotropic property for vessel wall. Haemodynamic parameters such as velocity streamline, pressure, vorticity, helicity, Time-Averaged Wall shear stress (TAWSS) and Oscillatory Shear Index (OSI) were analysed along with structural parameters such as wall displacement and von Mises stress. The comparison between healthy and stenosed arteries reveals that stenosis significantly increases the velocity magnitude due to the reduced flow area caused by plaque buildup. This narrowing also results in elevated pressure upstream of the stenosis. In both healthy and stenosed arteries, maximum deformation occurs near the bifurcation at the left and right lateral sections, with the highest von Mises Stress located near the internal wall of the flow divider. In stenosed arteries, the stress magnitude is six times higher than in healthy arteries, illustrating the profound effect stenosis has on haemodynamic. Overall, the analysis emphasizes how stenosis disrupts normal blood flow and alters bio-fluid dynamics in the carotid artery

An airway is likely to be contacted with virus. When the virus is adhered to the airway by breath, some humans maybe get infected. Therefore, the infection risk is important to predict by evaluating quantitatively the adhesion area and the amount of virus. The airway consists of the nasal cavity (such as the maxillary sinus, ethmoid sinus, frontal sinus, and sphenoidal sinus), pharynx, larynx, trachea, bronchi, and lungs. In this study, CFD analysis of transport process of virus concentration in the airway was conducted by considering adhesion and breathing waveform, and the infection risk at sinuses were predicted. The 3D geometry of the nasal cavity can be constructed from 2D-CT (Computed Tomography) image data utilizing ITK-SNAP. The flow within the nasal cavity is assumed to an incompressible, unsteady (pulsatile flow), and turbulent. The continuity equation and the Navier-Stokes equations are used in computational fluid dynamics (CFD) analysis. In CFD analysis, the boundary condition at the inlet is defined that the pressure is zero, and the concentration is dependent on inlet mass flow. The boundary condition at outlet is defined that the velocity is the simulated breathing waveform, and the gradient of concentration is free. The wall boundary condition of concentration is adhesion. It has been determined that the Ethmoid Sinus exhibits a heightened propensity for viral adhesion within the nasal cavity, based on the evaluation of the amount of adhesion. In addition, it was found that the flow is complexed by considering the breathing waveforms. It was found that the concentration diffusion in Maxillary Sinus (Region 1) and Ethmoid Sinus (Region 2) was increased by the generated vortexes. Besides, it was found that the amount of adhesion increases more than twice by considering the adhesion.