Računalna simulacija strujanja krvi u arteriji s premosnicom

undergraduate thesis

• Title (english): Numerical simulation of blood flow in an artery with a bypass graft
• Author: Blaž Petric
• Mentor: Ivo Džijan (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2022-09-29, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Process Energy Engineering

Abstract

Razvojem računala i numeričkih metoda pojavili su se uvjeti za numeričko modeliranje složenih strujanja kao što je strujanje krvi u arterijskom krvotoku. Cilj ovog rada je provesti numeričku simulaciju strujanja krvi kroz arterijsku premosnicu. U radu je definiran matematički model nestlačivog, izotermnog, laminarnog, 3D pulsirajućeg strujanja unutar krvne žile s krutom stijenkom. Izrađena su i analizirana dva geometrijski različita modela spajanja premosnice na zdravi dio krvne žile: spoj u obliku koljena i spoj u obliku račve. Pulsirajuće strujanje krvi ostvareno je propisivanjem vremenskog profila volumenskog protoka krvi na ulazu u domenu i ugradnjom Windkessel modela s 3 elementa kao rubnog uvjeta na izlazu iz domene. Uloga Windkessel modela je uzimanje u obzir podatljivosti krvne žile, perifernog otpora mikrocirkulacije i ulazne impedancije aortnog zaliska. Intenzitet oscilatornosti smičnih naprezanja uzet je u obzir umnoškom 𝑂𝑆𝐼 ∙ 𝜏𝑤, u kojem faktor 𝑂𝑆𝐼 iskazuje stupanj promjene smjera smičnog naprezanja, a 𝜏𝑤 predstavlja srednju vrijednost smičnog naprezanja na stijenci krvne žile. Iznos tog umnoška se koristi kao kriterij za procjenu uvjeta za stvaranje hiperplazije (zadebljanje stijenke krvne žile). Simulacija je provedena u programskom paketu OpenFOAM dok je analiza rezultata napravljena u programu ParaView i gnuplot. Rezultati simulacije pokazuju da su zbog nagle promjene smjera strujanja krvi i postojanja oštrih rubova vrijednosti smičnog naprezanja veće u slučaju spoja premosnice i krvne žile u obliku račve u usporedbi sa spojem u obliku koljena. Također su u slučaju spoja u obliku račve i vrijednosti umnoška 𝑂𝑆𝐼 ∙ 𝜏𝑤 nekoliko puta veće u području gdje se u stvarnim uvjetima očekuje nastanak hiperplazije.

Abstract (english)

With the development of computers and numerical methods, the conditions for numerical modeling of complex flows such as blood flow in the arterial blood stream appeared. The aim of this work is to run a numerical simulation of blood flow through an arterial bypass. In this thesis is defined mathematical model of incompressible, isothermal, laminar, 3D pulsating flow inside a blood vessel with a rigid wall. Two geometrically different models of joining the bypass to a healthy part of the blood vessel were created and analyzed: a joint in the form of a knee and a joint in the form of a fork. The pulsatile blood flow was achieved by prescribing the time profile of the volume blood flow at the entrance to the domain and incorporating the Windkessel model with 3 elements as a boundary condition at the exit from the domain. The role of the Windkessel model is to consider the compliance of the blood vessel, the peripheral resistance of the microcirculation and the input impedance of the aortic valve. The intensity of oscillatory shear stress is considered by the product 𝑂𝑆𝐼 ∙ 𝜏𝑤, in which the OSI factor expresses the degree of change in the direction of wall shear stress, and 𝜏𝑤 represents the mean value of wall shear stress on the blood vessel wall. The amount of this product is used as a criterion for evaluating the conditions for the formation of hyperplasia (thickening of the blood vessel wall). The simulation was carried out in the OpenFOAM software package, while the results were analyzed in the ParaView and gnuplot. The simulation results show that due to the sudden change in blood flow direction and the existence of sharp edges, the wall shear stress values are higher in the case of the junction of the bypass and blood vessel in the form of a fork compared to the junction in the form of a knee. Also, in the case of joint in the form of a fork, values of the product 𝑂𝑆𝐼 ∙ 𝜏𝑤 are several times higher in the area where the occurrence of hyperplasia is expected in real conditions.

• Keywords: računalne simulacije; hemodinamika; premosnica; Windkessel model; smično naprezanje
• Keywords (english): computer simulations; hemodynamics; bypass; Windkessel model; wall shear stress
• Language: croatian
• URN:NBN: urn:nbn:hr:235:250030
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka strojarstva (sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2022-09-22 09:21:19