Simulation Study on the Mass Transport Based on the Ciliated Dynamic System of the Respiratory Tract

Abstract

To study the mass transport of mucociliary clearance of the human upper respiratory tract, a two-dimensional mass transport model based on the ciliated movement was established by using the immersed boundary-lattice Boltzmann method (IB-LBM). In this model, different characteristics of the mucus layer (ML) and the periciliary liquid (PCL) were taken into account. A virtual elastic membrane was introduced to divide the two layers dynamically. All moving boundaries that were involved in the present simulation were modeled with the immersed boundary. The Newtonian fluid was used to model the flow in PCL, and the viscoelastic fluid based on the Oldroyd-B model was used for the flow in ML; the two types of flow were both solved by the LBM framework. Based on the model, the ML thickness, the cilia density, and the phase difference of adjacent cilia were regulated, respectively, to study the transport velocity of the ML. In addition, the motion law of solid particles in PCL was also studied. According to the results, four primary conclusions were drawn. (1) At a given beating pattern, the increase of the ML thickness will decrease its transport velocity. (2) Increasing the cilia density can promote the mean transport velocity of the ML. (3) By raising the phase difference of adjacent cilia to a certain scope, the transport of ML can be accelerated. (4) In PCL, particles initially located on the upper part of the cilia tend to migrate upward and then get close to the ML. The above study can provide some reasonable explanations for the mechanism of the mucociliary clearance system, which is also helpful to the further understanding of the mass transport principle of the human upper respiratory tract.

Effects of continuous and discrete boundary conditions on the movement of upper-convected maxwell and Newtonian mucus layers in coughing and sneezing

“…Therefore, the inertia terms could be neglected and Stokes equations solved for the mucus flow. For numerical simulations, the ASL layer was modeled as a single-layer [12,14,[51][52][53] or a two-layer [11,17,[54][55][56] models based on hypotonic-defensin and modern hypotheses, respectively. The cilia movement was also replaced with continuous oscillating functions (sine or cosine) at the lower boundary of the periciliary layer.…”

“…The cilia movement was also replaced with continuous oscillating functions (sine or cosine) at the lower boundary of the periciliary layer. However, the real boundary condition is not a continuous oscillating function and also should be applied at the interface of the mucus-periciliary layer [1,7,14,56]. Due to the low dynamic viscosity of air, free slip condition was always used at the mucus-air interface [8,10,13,16,17,57].…”

Engineered modular microphysiological models of the human airway clearance phenomena

“…Yet, the fabrication method adopted, in this study, to produce MAC is limited to the microscale, while nanofabrication has still to be developed. The integration of dimensional analysis may be another strategy to achieve dynamic similarity between the proposed in vitro model and the human airway system, by taking advantage of numerical analyses that have already been proposed to model ciliary dynamics (Vanaki et al, 2019) and MCC phenomena in both physiological and pathological states (Chatelin & Poncet, 2016; Chatelin et al, 2017; Sedaghat et al, 2016; Vanaki et al, 2020; Zhu et al, 2019). The proposed MCC model can, in turn, support numerical approaches in investigating how different ciliary features and configurations, as well as the composition and viscoelastic behavior of both PCL and mucus affect MCC and thus closely reproduce in silico airway human dynamics.…”

From Static to Dynamic: A Review on the Role of Mucus Heterogeneity in Particle and Microbial Transport

“…Besides the models summarized in these reviews, Zhu et al 243 developed a two-dimensional mass transport model to simulate a mucociliary clearance system, which was responsible for preventing bacteria, viruses, and harmful particles from invading the airway. This computational model is based on ciliated movement using the immersed boundary-lattice Boltzmann method and divides the mucociliary clearance system into two units: McL as a viscoelastic fluid and the periciliary liquid as a Newtonian fluid.…”