BHARADWAJ, P. Výpočtová a experimentální analýza cyklu peristaltického čerpadla využívaného v klinických aplikacích [online]. Brno: Vysoké učení technické v Brně. Fakulta strojního inženýrství. 2025.

Posudek vedoucího

Jagoš, Jiří

At the beginning of this review, it must be mentioned that the last objective of the thesis – Validation of the results from CFD simulations of the peristaltic pump on the experimental circuit available at the faculty – was not fulfilled. However, this was due to the fact that, during the course of the work, it became evident that it was more important to dedicate time to studying two different approaches to modelling the pump flow and to include a comparison of both methodologies in the final thesis. Given the complexity of these methods, it can be stated that this extension has effectively replaced the originally defined objective of experimental validation. Major revisions: The introduction is somewhat broader than required, and therefore the section leaves no space for a proper review on hemolysis evaluation in peristaltic pumps by means of numerical methods (i.e., goal one). Nevertheless, it still provides a suitable background, which is typically expected at the Faculty of Mechanical Engineering, especially for such interdisciplinary work). The literature review of CFD studies on numerical modelling of peristaltic pumps is included only in Chapter 6, but it remains weak. Although it is true that averaged boundary conditions are sufficient for the simulation, it is not correct to state that they reduce computational demands. Using different ramping functions (linear for the analytical method and cosine-based for the overset approach) may substantially affect the results, particularly during the compression and release phases. This can also be observed in Figures 7-7 and the following ones. However, the student did not address this issue in any part of the text. From Figure 7-9 it can be observed that the gap model does not work properly and does not fully close the clearance. Flow in the gap is indeed reduced, but still too high to represent complete closure. The comparison of flow through the narrow clearance is further complicated by inconsistent scales of the velocity maps, making it impossible to conclude whether consistency between methods has been achieved. The discussion of wall shear stress in relation to Figure 7-11 is entirely incorrect and wrongly attributed to the gap model. At this point, some analytical estimations of expected wall shear stress would have been appropriate. The large discrepancies in the averaged wall shear stress values between the deformed and non-deformed walls are highly suspicious and undermine the credibility of the results. It would also be beneficial to present the shear stress distribution along the tube length at specific time steps, as averaging conceals many errors and provides limited insight. Moreover, the very poor quality of Figures 7-12 to 7-17, where only a rather pronounced discrepancy between the methods can be seen, further decreases the credibility of the simulations. Minor revisions: There is also inconsistency in the titles of the supervisor (once Prof., once Ing.). The thesis randomly alternates between British and American spelling (e.g., haemoglobin vs. hemoglobin), often even within a single paragraph. The description of the pump cycle in Figure 5-2 does not correspond to the actual figure. The citation and referencing format is unsatisfactory, and the resolution of the figures is generally very poor. In summary, the thesis demonstrates considerable effort, but the overall quality of the work remains very low. The literature review is weak, the numerical methodology contains a number of shortcomings, and the presentation of results is at times confusing and inconsistent. Despite these limitations, the student has managed to address the main theme of the thesis to a degree that can be considered sufficient. Therefore, I propose that the student be allowed to defend the work.

Posudek oponenta

Hájek, Petr

The submitted thesis is well-balanced and most chapters are written in a comprehensible manner. The research study summarizes the function and purpose of peristaltic pumps used in healthcare, although the connection to the practical part of the thesis is lacking in some places. In the practical part, two computational models of a developed pump are created. In the first model, the occlusion of the pump is controlled by deformation of the wall, with mesh deformation ensured by the diffusion method or remeshing. The second model uses overset meshes, where the roller runs directly over the background fluid mesh. The work has some shortcomings in terms of the calculation settings: (1) it is not entirely clear whether full occlusion or only partial occlusion should occur, (2) the kinematics and velocities of the pump rollers are explained in a confusing manner, (3) the difference in roller velocities in the calculation and in the experiment is insufficiently discussed, (4) the volume flow rate would deserve formulas with and without a minus sign, and (5) in Figures 7-12 to 7-17, a zoom-in on the areas of interest would be useful. I am moving the other shortcomings to the questions section. On the other hand, I positively evaluate the use of statistics to assess the stability of the transient analysis and the detailed description of the differences between the methods, including their settings.  The entire work lacks citations, or they are misplaced, and the citation style does not meet our standards. I would avoid using copyrighted images. The biggest shortcoming is the failure to fulfill the last point of the assignment, because the results of the calculations are not compared with the experiment. However, since the student has demonstrated the ability to create advanced computational models and analyze their results, I recommend the work for defense.

eVSKP id 162400