# Bladeless Heart Pump Design: Modeling and Numerical Analysis
## 4 Results and Discussion
A comparison between the blackeless heart pump presented in this study and HeartMate II  
Figure 4:0 The scalar shear stress (SSS) (Pa) for computational domain: (**a**) a disk plane, \(z=0\) mm; (**b**) the offset plane, \(z=0.05\) mm; (**c**) the offset plane, \(z=0.2\) mm; (**d**) a central plane, \(z=0.5\) mm (central between disks). (Thoratec Corporation) is conducted numerically. The HeartMate II showed acceptable hemocompatibility and overall good quality during many years of implantation [36; 37; 38]. The pumps are numerically compared at operating point \(\Delta p=65\) mmHg and angular velocity \(\omega=6000\) rpm. The HeartMate II flow is \(Q=5\) L/min while the blackeless heart pump flow is \(Q=5.43\) L/min. The HeartMate II pump has a WSS in the range of 0 to 1025 Pa and a SSS in the range of 0.0632 to 3302 Pa. The blackeless heart pump has a WSS in the range of 0 to 308 Pa and an SSS in the range of 0 to 667 Pa. The developed blackeless heart pump has no recirculation zones or stagnation zones, which is very beneficial from the hemocompatibility viewpoint. In addition, WSS and SSS parameters of the blackeless pump are lower than the HeartMate II, which positively affects the hemocompatibility performance of the pump. In further research, more attention will be focused on the recognized limitations in this study. The numerical analysis is derived for operating point (\(\Delta p=65\) mmHg and \(\omega=6000\) rpm). Therefore, further analysis on different operating points is advisable. The results of the present study show that the shear stress and exposure times in blackless heart pump are relatively low and acceptable; however, due to assumption of ideal flow separator, the effects of the gap between flow separator and disk are not taken into consideration. The pump is considered as five separate computational domains (five spaces between disks). A numerical CFD simulation, covering a complete computation domain with small gaps, is required to explore effects of gaps on shear stress, which can be subject to future studies. Furthermore, a distance between the two rotating disks is relatively small so the effects of a flow in narrow channels should be considered [32; 39]. Another limitation of this study is that the blood is assumed as an incompressible single-phase Newtonian fluid. Blood is a multiphase non-Newtonian fluid. In further research, more attention will be focused on a more realistic blood model. In the numerical analysis, the inlet speed is constant although there is a pulsation due to a heartbeat. Therefore, the model with the pulsatile inlet velocity profile is advised for future studies. Moreover, the time dependent non-Newtonian model of blood should be considered. Separation of blood particles and plasma occurs in the boundary layer of the disk, which has a negative impact on the blood. Blood and disks rotate mostly as a rigid body and the amount of relative velocity between the disk and the blood is small Equation (7). The smaller impact on separation is expected. In further research, it is necessary  
Figure 4:1 \(\Delta p\)-\(Q\) characteristic curves. to investigate the effect of the separation and its influence on the hemocompatibility of this pump. The results of numerical analysis presented in this paper require experimental validation. From a technological viewpoint, the pump is easy to manufacture, allowing for easy prototyping. The experimental study of the bladeless heart pump prototype, in an 'open-loop' mock circulatory system, would provide valuable results and enable the validation of the numerical results.