MASOOD, U. Numerické simulace transportu a depozice vláken v zjednodušeném modelu dýchacích cest [online]. Brno: Vysoké učení technické v Brně. Fakulta strojního inženýrství. 2023.

Posudek vedoucího

Elcner, Jakub

Despite strong warnings, Mr. Usman Masood chose to work on a topic in the area of fibrous aerosols and numerical simulations with which he had no previous experience. He thus accepted the challenge of having to study a vast amount of material and learn to use rather complicated and sophisticated software. The thesis consists of three objectives. All these objectives were fulfilled in the sense of the assignment, however, in the case of the first objective I expected a more detailed description of the possibilities offered by the Discrete Elements Method (DEM) within fibrous aerosols research. Due to the computational complexity and limitations of the DEM, the modification of the drag coefficient on a spherical particle in the Lagrangian method, based on the Tran Cong approach, was finally chosen as the optimal approach. The literary research was carried out by the student himself based on a large number of supplied sources. Fulfilling the goals of the thesis required studying a lot of materials and tutorials to understand the use of Star-CCM+ solver to set up the numerical simulations. Then he consulted the work regularly and actively during the practical part and applied most of my recommendations and comments. I rate the thesis with grade D in terms of student´s approach and his poor time management. He devoted insufficient amount of time to the topic regarding its complexity, where a slow start caused a time overrun in the final stage, which has reflected in the final quality of the thesis.

Posudek oponenta

Bělka, Miloslav

This master thesis deals with numerical simulation of fiber transport through the model of respiratory airways. The first few chapters consists of general information about fibers, modeling approaches and a review of experimental and numerical studies regarding fiber deposition in human respiratory airways. The next chapters contain results of Discrete Element Modeling simulation of fiber transport in idealized model and Euler-Lagrange simulation of fiber deposition results in realistic airway model. The thesis contains many grammatical errors or typing errors, such as in the word Stroke number. There are sentences with one subject and several verbs. The texts in the figures is not legible in many cases. There are many citation mistakes, some claims are not supported by citations, some citations do not contain any information about the statement they are connected to. Student also copied entire paragraphs from the impacted paper without using quote marks. The theoretical part comprises of many false statements, such as that aerosol is a rigid particle. It is not, aerosol is a mixture of particles, both liquid or solid, suspended in the gas. The description of methods used for fiber modeling is rather short, very vague and lacks proper insight. A comparison of methods that would show advantages and disadvantages of specific approaches is also missing. The student mixed up equations for drag coefficient given by Haider and Levenspiel and Tran-Cong et al. The equations for specific properties, such as shape factor, sphericity, and circularity are also wrong. One of the goals of the thesis was to perform DEM simulations of fiber transport. This goal was not reached because of long computational time with a short commentary. I would assume there would be more complex analysis of the reasons for such a long computational time, e.g. an analysis of the used particle-particle contact model. As a substitute goal, the particle deposition simulation in a realistic airway model using modified drug coefficient was carried out. The simulation description lacks boundary condition description, sensitivity study from the point of computational mesh or number of parcels. The results discussion is full of wrong statements, the student mixed up segments, for example segment 3 is the outlet to left lower lobe, not the first bifurcation. Moreover, the realistic airway model consists of respiratory airways from mouth to the 7th generation of tracheobronchial branching. The student describes it as oropharyngeal-laryngeal region. The increasing number of particles penetrating the model and reaching the lobes means that the deposition in the model is decreasing, the student interprets it the other way around. Generally, the student did not understand the topic at all which resulted in many mistakes throughout the thesis. The quality of the thesis is not sufficient and the student failed to complete the planned goals.  

eVSKP id 149610