Patients who receive mechanical heart valve (MHV) implants require mandatory anticoagulation medication after MHV implantation due to the thrombogenic potential of the devise. Optimization of MHV designs may facilitate in reducing the flow induced thrombogenic potential. To accomplish this goal highly resolved 3D geometries of different bileaflet mechanical heart valves were examined to study the contribution of distinct flow phases to platelet damage. Both turbulent and direct numerical simulations (DNS) were conducted and compared. A multiphase approach was formulated, in which the blood interacts with a large number of particles injected in the fluid domain, representing the platelets passing through the MHV. Loading histories experienced by the platelets were calculated by computing the combined effect of stress and exposure time. Platelet stress accumulation during randomized repetitive passages past the valves were calculated using a damage accumulation model. The results from the simulations were used as an input to our hemodynamic shearing device (HSD) which emulated the numerical loading waveforms, and platelet activity measured in order to quantify the thrombogenic potential of different MHVs.