Chapter 4 — Blood Flow and Rheology Workflows

Figure 7.1 — Non-Newtonian Fluids and Blood Rheology

CFDrs supports a focused subset of physiologically relevant geometries — vascular bifurcations, venturi / stenosis regions, microfluidic screens, and TPMS (triply-periodic minimal-surface) scaffolds. Each of these geometries couples a cfd-schematics CSG primitive to a low-dimensional CFD solve (1-D, 2-D, or 3-D), with non-Newtonian rheology for blood.

The Vascular Bifurcation

For CSG composition of vascular domains and non-Newtonian blood rheology modeling, see Vascular Bifurcations and Stenosis.

Microfluidic Mixing Screens

Microfluidic screens are serpentine or bifurcation arrays designed for mixing, separation, or hemolysis screening. CFDrs handles them as a chain of bifurcations:

use cfd_schematics::serpentine::SerpentineBuilder;

let chip = SerpentineBuilder::new()
    .section_count(20)
    .channel_radius(0.25)
    .turning_radius(2.5)
    .build();

Each section is solved with [cfd-3d] time-stepping, then stitched together for the chip-scale perfusion metric.

FDA Shear-Limit Screening

CFDrs exposes a shear-limited screening API that walks a serpentine / bifurcation chain and reports branches with shear stress above an FDA-style threshold. The API is intentionally minimal so that custom geometries can plug in:

let report = cfd_1d::screening::shear_violations(&state, &geometries)?;
for branch in report.violations {
    eprintln!("branch {}: peak shear {} Pa (limit 9.0)", branch.id, branch.peak);
}

TPMS Scaffolds

Tissue scaffolds modeled as TPMS (Schwarz P, Gyroid, …) are CSG-built and tiled for cfd-3d FEM assembly. Boundary conditions are velocity-driven at the inlet and outflow at the outlet.

Examples Referenced by This Chapter

Part IV covers six example chapters:

• blood_flow_1d_validation — 1-D reduced model, validated against a reference phantom.
• bifurcation_2d_blood_validation — 2-D Frauhofer-Keller bifurcation with non-Newtonian blood.
• blood_rheology_models — three rheology models compared on the same patient-specific geometry.
• venturi_blood_flow_validation — venturi stenosis under Newtonian and Carreau rheology.
• serpentine_mixing_comprehensive — serpentine mixer design space, 1-D reduced to chip-scale.
• cross_fidelity_branching — concurrently run a 1-D, 2-D, and 3-D branch of a vascular bifurcation and compare outputs.

Further Reading

• cfd-schematics source
• cfd-1d source
• Turbulence and Multiphase Flow for cavitation modelling relevant to stenosed regions.