Novel assisted cough system based on simulating cough airflow dynamics

Cough is a defensive behavior that protects the respiratory system from infection and clears airway secretions.Cough airflow dynamics have been analyzed by a variety of mathematical and experimental tools.In this paper,the cough airflow dynamics of 42 subjects were obtained and analyzed.An identification model based on piecewise Gauss function for cough airflow dynamics is proposed through the dimensionless method,which could achieve over 90%identification accuracy.Meanwhile,an assisted cough system based on pneumatic flow servo system is presented.The vacuum situation and feedback control are used to increase the simulated peak cough flow rate,which are important for airway secretion clearance and to avoid airway collapse,respectively.The simulated cough peak flow could reach 5 L/s without the external assistance such as manual pressing,patient cooperation and other means.Finally,the backstepping control is developed to generate a simulated cough airflow that closely mimics the natural cough airflow of humans.The assisted cough system opens up wide opportunities of practical application in airway secretion clearance for critically ill patients with COVID 2019 and other pulmonary diseases.

A review on numerical studies of airflow dynamics and particle deposition in human respiratory system Author links open overlay panel

Accurate assessment and prediction of airflow dynamics and particle deposition in the human respiratory tract are essential for human health,involving inhaled drugs for treating various diseases and toxic particles that can cause illnesses.This intricate process involves complex multiphase flow with distinct respiratory characteristics.Computational fluid dynamics(CFD)acts as a bridge,overcoming the limitations of in vivo and in vitro experiments and providing a means to fully comprehend and reveal the fundamental mechanisms of respiratory flow and particle behavior on a microscopic scale.This paper provides a comprehensive overview and concise summary of recent advancements in the numerical simulation of airflow and particle deposition in the human respiratory tract.Particularly,it summarizes the transition of respiratory tract models from segmented models to emerging physiological characteristic models and whole-lung airway models,and the latest developments on the effects of key factors such as geometric variations,respiratory patterns,and particle physical/chemical properties on respiratory flow and particle deposition.A notable focus of this review is on emerging physiological characteristics models and their associated complex airflow and particle dynamics inside it.The paper concludes with recommendations for future research to further advance the development of this field.

Characteristics and comfort evaluation of sinusoidal airflows by regulating motor rotating frequency of a floor fan

Increasing air movement by utilizing electric fans is among the common approaches for comfort and energy savings in buildings in summer;however,the use of electric fans is usually the forced constant airflow.This study reformed the one-chip computer program of a floor fan motor and simulated dynamic airflow through controlling the rotating frequency only.The flow field characteristics of constant,oscillated,sinusoidal airflows with periods of 10 s,30 s,60 s,100 s were measured.The comfort performance was evaluated by chamber experiments,with 20 subjects exposed to six airflow patterns under 30℃,70%RH.The results showed that the simulated sinusoidal airflows had relatively higher turbulence intensity(32%–37%)andβvalues(>0.4).While subjects’thermal sensations were not statistically significant among six airflows,their reported discomfort symptoms during 60 min exposure were reduced under sinusoidal airflows.The calculated convective heat transfer shared similar variations to instantaneous air velocity and skin temperature.A large fluctuation of 10–50 W/m^(2)and higher total convective heat loss(3000–3500 W/m^(2))were found for sinusoidal period 30 s.This study develops a new method to simulate varying air velocities through conveniently controlling the fan motor amplitude and frequency,and verifies the comfortable feelings to dynamic sinusoidal airflows.The work benefits to improve the performance of the current electric fans with lower costs and promote the applications of personal ventilation devices in buildings,thus optimizing human thermal comfort,reducing dependences on air conditionings and achieving building energy efficiency.

Effective improvement of a local thermal environment using multi-vent module-based adaptive ventilation

Indoor thermal comfort is essential as it improves living standards.Activity scenarios of personnel are in the process of a dynamic change.In most interior spaces with fixed working stations,people directly blown by cold air have a poor thermal experience.Therefore,to meet the differentiated environmental demands,one challenge is to explore novel ventilation strategies to satisfy the changing environmental needs.An adaptive strategy,multi-vent module-based adaptive ventilation(MAV),was designed to increase the adjustability of air distribution and better adapt to variable demands.A classroom was chosen as a representative model with multiple scenarios during its use.Simulations were conducted to verify the three-level control effect of MAV on improving the thermal environment.The results revealed that different vent solutions create different airflow patterns and thermal environments,which can be matched to the scenarios.The scale for ventilation efficiency No.4,which measured the influence scope of supply air,was used to evaluate the zoning division control in MAV.The space under the charge of a concerned MAV module showed a higher SVE4 than that at other zones.This implied that the zoning division can be effectively implemented.Thermal comfort measured using the air diffusion performance index,predicted mean vote,and draught rate showed that the application of MAV is better than that of the fixed MV mode,and the discomfort experienced when exposed to cold air can be avoided.It is believed that these results will help extend the research of adaptive ventilation strategies.