11. Bioengineering and Bio-thermal Fluid Dynamics

Investigation of micron-sized particles suspended in a fluid is still crucial and ongoing in many industrial applications. An important biomedical application is the transport and deposition of fibrous particles in the respiratory tract (e.g., usage for medical inhalation, health risk of toxic asbestos fibers inspiration). Due to obvious ethical barriers in obtaining data about the transport and deposition of fibers in the lungs in vivo, validated numerical simulations are an irreplaceable tool in bringing valuable insights. The conventional method of Lagrangian particle tracking using drag coefficients models neglects the particle rotations. Recently, Tian et al. deployed the Euler-Lagrange Euler-Rotation (ELER) technique where the fibrous particles were approximated by ellipsoids. This enables an efficient solution of the rotational movement in solving the Euler rotational equations. As was shown in many studies later, the rotation of the particles has a significant impact on deposition characteristics and it could not be neglected. Nevertheless, a detailed comparison of the numerical simulations of fibrous motion with experimental results is rare in the literature. This paper presents a comparison of the ELER method in a pipe flow based on measured experimental data. First, the validation of the Euler-Lagrange Euler-Rotation method implemented into the OpenLB open-source solver based on the Lattice Boltzmann Method (LBM) is conducted. As a next step, the method is verified with the benchmark case: transport of a micrometre-sized ellipsoidal particle suspended in a laminar pipe flow, numerical results presented by Tian et al. A good agreement between the reference data and our results is observed, however, no comparison with experimental data was evaluated there. In the final simulation, the inhouse experimental setup performed was reproduced numerically. We studied the particle orientation at the end of the glass tube and in the bifurcation using high-speed camera measurements revealing two prevalent orientations of the fibers to the streamlines – parallel and perpendicular. Comparison between the numerical results and the experimental data showed discrepancies – the majority of particles in the simulation are aligned parallel and rotational movements of the particles were not observed in the experiments. Although the straightforward numerical method of ELER for the transport and deposition of fibers is used for many applications, the experimental reality in the replica of the respiratory tract yields slight differences which need to be considered and further investigated to deploy the method properly.

Miroslav Jícha

Prof.