A research team led by Jong Ji Song, a researcher at the Faculty of Mechanical Science and Technology, has suggested a method of modeling the output boundary conditions of a cardiovascular system, which is very important to properly simulate blood flow in a cardiovascular system.
Modeling of output boundary conditions of a cardiovascular system is, in essence, that of one of the several parts not reflected in a three-dimensional modeling for simulation analysis, that is, reflecting the change in the characteristic quantities in several parts omitted in the three-dimensional model as boundary conditions.
Blood vessels not reflected in the three dimensional model of a cardiovascular system are modeled by parameters such as resistance (R), elasticity (E) and compliance (C) to form an electrical circuit analogous model. From this model, output pressure waveforms are formed.
They modeled the output of the artery in a series connection of proximal resistance Rp to the parallel connection of compliance C and distal resistance Rd to reflect the transient of blood flow and the elasticity of a blood vessel. They modeled the coronary output in the combination of resistance of coronary artery Ra, coronary compliance Ca, microcirculation resistance Ram, myocardial compliance Cim, coronary vein resistance Rv and ventricular pressure Pim(t).
Then, from the model mentioned above, he obtained blood pressure waveforms at the artery output and coronary output of the model whose heart rate is 80 beats/min, cardiac output 120mL, diastolic and systolic pressures 80mmHg and 130mmHg respectively, split ratio of coronary and system circulation 0.04 and that of left and right coronary artery 7/3.
Setting these blood pressure waveforms as output boundary conditions, they performed analysis by ANSYS Fluent 19.2 during two heart rate cycles.
They applied the boundary conditions to five persons who were to have heart operations and compared them with the clinical data.
The comparison showed the error of systolic pressure, diastolic pressure and one cycle cardiac output were -1.07~0.86%, -1.1~0.88% and -0.89~1.87% respectively, which means this method of modeling output boundary conditions is very effective.
The suggested method can be applied to a cardiac operation simulating system for the simulation and analysis of the preoperative and postoperative state of blood flow in the cardiovascular system. In addition, it can predict the effectiveness of planned operations and relapse after operations, and provide clinical simulation results for postoperative healing programs.
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