Cartesian Cut-cell Methods for High Reynolds Number Flows

Speaker: Alex Kleb, Analytical Mechanics Associates, NASA Ames Research Center
February 5, 2026

Presentation

Abstract

Computational fluid dynamics is essential for designing aircraft, turbines, and other engineering systems. However, generating suitable computational meshes for complex geometries remains the primary bottleneck in analysis workflows, often requiring days of manual effort. Traditional boundary-conforming meshes excel at capturing near-wall physics in viscous flows but demand specialized expertise and extensive preprocessing time. Cartesian cut-cell methods provide automatic mesh generation for complex geometries in minutes, yet they struggle with high Reynolds number viscous flows where boundary layers exhibit rapid velocity changes that require prohibitively fine resolution for isotropic elements. The challenge is accurately modeling boundary layer physics on Cartesian cut-cell meshes without sacrificing the automatic mesh that makes such methods attractive.

In this work, I show that an ordinary differential equation (ODE) wall function incorporating pressure-momentum balance enables accurate high Reynolds number viscous flow predictions on coarse Cartesian cut-cell meshes with the RANS equations. The ODE solves a one-dimensional boundary value problem at each wall boundary face that accounts for the transition from the viscous dominated near-wall region to the inviscid wake region, allowing forcing points to operate effectively at y+ >600. The ODE can achieve correct skin friction predictions on meshes more than four times coarser than analytical wall functions require. These results demonstrate that automatic high-fidelity viscous flow analysis is achievable without manual mesh generation expertise.

Biography

Alex Kleb holds a Ph.D. in Aerospace Engineering and Scientific computing from the University of Michigan, Ann Arbor. He is a researcher in the Cart3D group at NASA Ames Research Center, where his work focuses on the extension of viscous Cartesian methods to three dimensions.

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