First Application of an Eddy-Scale Hemolysis Model to the Food and Drug Administration Nozzle Using Computational Fluid Dynamics

Computational fluid dynamics (CFD) is increasingly important in biomedical engineering; however, its use in medical device design remains constrained by regulatory requirements for model validation and verification. To address this, the Food and Drug Administration (FDA) proposed a benchmark nozzle geometry for standardized validation. This study employs a turbulence-based hemolysis model-the Ozturk-Papavassiliou-O'Rear (OPO) model-to investigate the FDA nozzle and identify red blood cell (RBC) damage caused by eddy structures similar in size to RBCs. Flow simulations were conducted for sudden contraction (SC) and gradual cone (GC) nozzle configurations at inlet velocities of 0.46 and 0.6 m/s (throat Reynolds of 3,500 and 6,500). Regions where eddies fall within the damaging Kolmogorov length scale were identified and analyzed. Hemolysis predictions were made using the eddy surface area distribution and validated against experimental hemolysis index (HI) data. For SC, a qualitative indicator, the cumulative eddy surface area of 6-20 μm, was provided; a numerical HI was postponed until a recalibration specific to SC and independent verification. For GC, the OPO model reproduced experimental trends in hemolysis risk localization but underpredicted absolute HI. These findings suggest that the OPO model offers a viable approach to predicting turbulence-resolved hemolysis in medical device design.