CFD Investigation Of Internal Flow And Particle Deposition In Human Upper Respiratory Tract

The inhaled particles are the culprit for aggravating fog and haze pollution.They damage the atmospheric visibility and climate,and simultaneously seriously jeopardize the human health.The investigation for airflow patterns and deposition characteristics of inhalable particles in the human upper airway(HUA)not only helps explain the pathogenesis of respiratory disease,but also provides the theoretical guidance for the design of spray in treating the respiratory disease.Thus,it is of great theoretical significance and practical value.In this thesis,the 3-D anatomically accurate HUA model was reconstructed from CT-scan images of a Chinese male patient(38 years,BMI 25.7).The computational fluid dynamics(CFD)with the large eddy simulation(LES)method was applied to simulate the airflow dynamics within the HUA model under three different respiratory intensities(Q = 16.8 L/min,30 L/min,60 L/min)in both inspiration and expiration processes.The motion and deposition of five different particle sizes(d = 1 μm,2.5 μm,5 μm,7.5 μm,10 μm)are calculated via unsteady tracking under condition of unsteady respiration,and the deposition fraction of particles are counted in different region of HUA.For airflow field,the instantaneous velocity contours,velocity and pressure distribution of feature points under three different respiration intensities have been presented.The results show that the jet flow that resulted from contraction of pharyngeal structure is the main reason for flow separation and back-flow.Meanwhile,the contraction of pharyngeal also leads to large pressure differences appearing before and after a flow constriction.It is found that the turbulence is more obvious with the increase of respiration.For particles field,the distribution and histogram of five different size particles are analyzed to explain the effect of the respiration and particle size on particle deposition characteristics.The results reveals that the particles prefer to depositing in throat at any particles size.With the increasing of respiratory intensity,the particledeposition rate of each size gradually grows,and the particle deposition rate also increases as the increasing of particle size.In addition,it is found that the inertia is the main influence factor to the particles deposition.With the increasing of the respiratory intensity,the inertia effects on particles deposition significantly reduces.