For various sinonasal conditions, including chronic rhinosinusitis, saline irrigation is an accepted standard-of-care treatment. This study was aimed at determining the effect of increased irrigation volumes and greater squeeze force on mucosal irrigation. A sinonasal cavity computational model was reconstructed from high-resolution CT scans of a healthy, unoperated 25-year old female. Seven combinations of irrigation volumes (70, 150, 200, and 400 mL) and squeeze forces (ramp time 0.1, 0.5, and 1.0 s) at a fixed head tilt of 0 degrees to the horizontal (Frankfort position) were performed. Velocity, pressure, and wall shear stress, together with mapping of surface coverage and residual volumes at specific locations and time were demonstrated. Higher volume irrigation (400 mL) and greater squeeze force (ramp time 0.1 s) improved irrigation coverage on the ipsilateral and contralateral sinonasal surfaces and increased shear force (approximately 140 Pa). An increase in irrigation volume from 70 to 150 mL approximately doubled sinus surface coverage and from 70 to 200 mL tripled sinus surface coverage. A faster squeeze also contributed to increased sinus surface coverage but its effect was less influential. We infer that the greater irrigation volume and squeeze force improve therapeutic benefit in terms of lavage and distribution of topical medications.

Eductors are multi-functional devices that can be used for pumping, mixing, and heat transfer, and hence for commercially available eductors, optimum operational point for one function is not clearly defined. This paper computationally studies two-phase flow and mass transfer in a water jet eductor, involving liquid water as primary fluid and water vapor as secondary fluid. It has been prepared with the objective of study of thermal-fluid behavior within eductor and shares the detailed computational process for other similar applications. This work focuses on the performance of eductor as condenser along with identification of critical operational variables. This research studies eductor as a combined vacuum pump and condenser for thermal desalination, where water vapor is produced using a low-temperature heat source (below 95 °C). The Eulerian approach with thermal phase change model was used to predict direct contact condensation (DCC) with ANSYS-Fluent. The results demonstrated enhanced flow entrainment due to secondary fluid condensation which also causes unstable flow. In general, it was observed that the increase in back pressure decreased the flow entrainment, but this also helped maintain complete condensation within the eductor which helps reduce pressure shocks in the system. The computational model used demonstrated that it can be an effective solution to industrial problems of phase change, especially for comparative optimization processes.

Indoor air quality and its effect on respiratory health are reliant on understanding the level of inhalation exposure, particle inhalability, and particle deposition in the respiratory airway. In the indoor environment, controlling airflow through different ventilation systems can reduce inhalation exposure. This produces a wide variety of complex flow phenomena, such as recirculation, coanda flow, separation, and reattachment. Airborne particles drifting through the air, that move within the breathing region become inhaled into nasal cavity the nostrils. Studies have developed the aspiration efficiency to assist in predicting the fraction of inhaled particles. Inside the nasal cavity, micron and submicron particle deposition occurs in very different ways (inertial impaction, sedimentation, diffusion) and different locations. In addition, fibrous particles such as asbestos are influenced by tumbling effects and its deposition mechanism can include interception. Indoor fluid-particle dynamics related to inhalation exposure and eventual deposition in the respiratory airway is presented. This study involves multi-disciplinary fields involving building science, fluid dynamics, computer science, and medical imaging disciplines. In the future, an integrated approach can lead to digital/in-silico representations of the human respiratory airway able to predict the inhaled particle exposure and its toxicology effect.

Particle intake by human breathing is important for developing relevant estimates of exposure in the indoor environments; however, relatively few studies are devoted to the influence from human activities. This study evaluates the nasal inhalability of micron particles for a manikin in motion by transient computational fluid dynamics (CFD) simulations. The model was built using a full-scale manikin with key facial features at the nose and mouth. The manikin was moving at a speed of 0.8 m/s through stagnant air in an indoor environment achieved by dynamic mesh. Three nasal inhalation rates of 15, 27, and 40 LPM (litres per minute) and four particle sizes (7, 22, 52, and 82 μm) were considered. The particle intake fraction was calculated to quantify the nasal inhalability of particles over different conditions. Fluid flow field of the motion-induced wake flow and particle trajectories were visualized to reveal the principles of the particle inhalability for a body in motion. This study quantifying the particle intake for a moving manikin will help to characterize a more holistic scenario for respiration modellings and developing estimates of exposure affected by human activities.

Understanding the particle exposure characteristics in human respiratory airways plays important roles in assessing the therapeutic or toxic effects of inhaled particles. In this study, numerical modelling approach was used to investigate micron-sized particle deposition in an anatomically realistic human nasal cavity. Flow rate of 15 L/min representing typical normal breathing rate for an adult was adopted, and particles were passively released from the ambient air adjacent to the nostrils. Through introducing a surface mapping technique, the 3D nasal cavity was "unwrapped" into a 2D planar domain, which allows a complete visual coverage of the spatial particle deposition in the intricate nasal cavity. Furthermore, deposition enhancement factor was applied to extract regional deposition concentration intensity relative to background intensity of the whole nasal passage. Results show that micron particle exposure in the nasal cavity is closely associated with nasal anatomical shape, airflow dynamics, and particle inertia. Specifically, the main passage of the nasal cavity received high particle deposition dosage, especially for larger micron-sized particles due to increased particle inertia. The nasal vestibule exhibited limited particle filtration effect and most deposited particles in this region concentrated posteriorly.

Heat transfer modelling in indoor environments requires an accurate prediction of the convective heat transfer phenomenon. Because of the lower computational cost and numerical stability, eddy viscosity turbulence models are often used. These models allow modification to turbulent Prandtl number, and near wall correction which influences stagnation points, entrainment, and velocity and time scales. A modified v²-f model was made to correct the entrainment behaviour in the near wall and at the stagnation point. This new model was evaluated on six cases involving free and forced convection and room airflow scenarios and compared with the standard k-ε, and k-ω-SST models. The results showed that the modification to the v²-f model provided better predictions of the buoyant heat transfer flows while the standard k-ε failed to reproduce and underestimate the convective heat transfer. The k-ω-SST model was able to predict the flow field well only for a 2D square cavity room, and 3D partitioned room case, while it was poor for the other four cases.