Mesh Sensitivity Analysis for Quantitative Shear Stress Assessment in Blood Pumps Using Computational Fluid Dynamics

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Computational Science

Background:

• Blood recirculating devices aim to reduce blood trauma by minimizing nonphysiologic shear stresses.
• Computational fluid dynamics (CFD) is increasingly used for hydraulic and hemocompatibility assessments, but direct hemolysis predictions remain limited.
• Near-wall mesh resolution significantly impacts shear stress quantification in complex flow regions, affecting blood damage prediction accuracy.

Purpose of the Study:

• To investigate the required mesh refinement for accurate shear stress quantification in critical areas of a rotary centrifugal blood pump.
• To determine the influence of mesh resolution on numerical hemolysis prediction accuracy.
• To establish a reliable mesh quality criterion (y+) for CFD simulations of blood pumps.

Main Methods:

• Performed three-dimensional CFD simulations of a generic centrifugal blood pump using varying mesh sizes (3x10^6 to 30x10^6 elements).
• Quantified shear stress at meshing-sensitive hotspots (blade leading edge, tip clearance gap) using the nondimensional mesh characteristic number (y+).
• Calculated hemolysis using an Eulerian scalar transport model to evaluate mesh-related errors.

Main Results:

• The nondimensional mesh characteristic number (y+) underestimated maximum wall shear stress by 60% on average with a recommended value of 1, but was accurate below 0.1.
• Mesh insensitivity for hemolysis prediction was achieved with a maximum y+ below 0.2, requiring approximately 18x10^6 mesh elements.
• Coarser meshes resulted in meshing-related errors of up to 25% in hemolysis predictions.

Conclusions:

• Precise shear stress quantification and accurate hemolysis prediction in blood pumps necessitate stringent mesh refinement, particularly in regions with complex flow.
• A maximum y+ value below 0.2 is identified as a critical threshold for reliable CFD-based hemocompatibility assessment.
• Future research should focus on the transferability of these findings to different geometries and the adaptation of blood damage models for improved quantitative predictions.