Numerical simulations of aerosol delivery to the human lung with an idealized laryngeal model, image-based airway model, and automatic meshing algorithm

Abstract

The authors proposed a new method to automatically mesh computed tomography (CT)-based three-dimensional human airway geometry for computational fluid dynamics (CFD)-based simulations of pulmonary gas-flow and aerosol delivery. Traditional methods to construct and mesh realistic geometry were time-consuming, because they were done manually using image-processing and mesh-generating programs. Furthermore, most of CT thoracic image data sets do not include the upper airway structures. To overcome these issues, the proposed method consists of CFD grid-size distribution, an automatic meshing algorithm, and the addition of a laryngeal model along with turbulent velocity inflow boundary condition attached to the proximal end of the trachea. The method is based on our previously developed geometric model with irregular centerlines and cross-sections fitted to CT segmented airway surfaces, dubbed the “fitted-surface model.” The new method utilizes anatomical information obtained from the one-dimensional tree, e.g., skeleton connectivity and branch diameters, to efficiently generate optimal CFD mesh, automatically impose boundary conditions, and systematically reduce simulation results. The aerosol deposition predicted by the proposed method agreed well with the prediction by a traditional CT-based model, and the laryngeal model generated a realistic level of turbulence in the trachea. Furthermore, the computational time was reduced by factor of two without losing accuracy by using the proposed grid-size distribution. The new method is well suited for branch-by-branch analyses of gas-flow and aerosol distribution in multiple subjects due to embedded anatomical information.

A Feasible Computational Fluid Dynamics Study for Relationships of Structural and Functional Alterations with Particle Depositions in Severe Asthmatic Lungs

“…The resulting model captured subject-specific airway features such as Cr and D h . At this step, we created a synthetic turbulence [ 29 ] right above the glottal constricted regions, because the SARP study [ 24 ] did not gather oropharynx scans. The turbulent intensity and largest eddy size were set to 0.29 and 8 mm, respectively, to mimic the turbulent flows found in the CFD simulations with oropharynx [ 30 ].…”

Contributions of Kinetic Energy and Viscous Dissipation to Airway Resistance in Pulmonary Inspiratory and Expiratory Airflows in Successive Symmetric Airway Models With Various Bifurcation Angles

“…1(b)). Diameter ratios of the glottis and the cross section above the glottis to the trachea were empirically imposed as 0.677 and 1.24, respectively [27]. The following h values were used to examine the effect of the bifurcation angle on the airway resistance: 15 deg, 25 deg, 35 deg, 45 deg, and 55 deg (Table 1, Fig.…”

“…To create triangular surface and tetrahedral volume meshes for branch-by-branch domains, we employed the software GMSH [28]. The grid size of each subdomain was determined from the branch diameter and flow rate for creating similar wall units [27]. As for the mesh size, the average distance from the wall to the first grid for the case with Q trachea ¼ 20 L/min was 4.7 in wall units (y þ ), which was smaller than the viscous sublayer thickness (y þ ¼ 5).…”

“…A more specific description for mesh generation can be found in Ref. [27]. This mesh size was validated in the previous lung airflows simulation [29].…”

Respiratory simulator for robotic respiratory tract treatments

“…Other studies have used CT images and automatic meshing to compute the fluid dynamics of pulmonary gas flow [12], have concentrated on oscillatory flow in the laryngeal channel [16] or have studied power loss mechanisms in pathological tracheas [1]. On the other hand, physical apparatus that simulate the human respiratory system have been developed to characterise particle delivery within lungs [11] and to simulate specific lung pathologies [10].…”