ABSTRACT
As demo nstrated in p revious c hapters, t he he art is a co mplex organ that pumps oxygenated blood throughout the body via a closed loop called t he circulatory system. is chapter discusses the mechanics of the heart and circulatory system that requires a non-steady-state-compliant alg orithm. A mo deling met hod is introduced to account for the staged time-dependent boundary conditions, in o rder to solve for the uid dynamics characteristics. Since the heart is much too complex to analyze in its entirety, it is modeled in this chapter as a two-cycle, four-cylinder engine. e purpose of representing the heart as a mec hanical system is not only to simplify it, but to calculate the total work of the heart as well. is four-cylinder engine is represented in two halves: the arterial c hambers a nd t he co ronary c hambers. e tw o a rterial chambers (i .e., v entricles) a re r epresented ma thematically b y a pump, while the two venous chambers (i.e., atria) are represented as a reservoir. e reasoning behind this is that the arterial chambers push b lood forward and t herefore can b e represented as a force acting on a uid (i.e., a pump), while the venous chambers “draw” blood into it and ac t as a p ressure di erence where one pressure limit is t heoretically zero (i .e., a r eservoir). e engine analogy is to combine these two systems into one to allow for the total work of the system to b e considered. e rest of the cardiovascular system (i.e., the arteries, coronaries, and veins) is represented by a thin-walled tube with a constant diameter taken from the average of the diameters of the major arteries and the major veins. is syst em has a nite len gth wi th no “b ranching” o r
breaks. e “tube” has the compliance and wall friction characteristics of an actual artery.
