Swim-cap surface texture and the sphere drag crisis: force histories, flow fields, surface samples, and meshes from fixed-time-step URANS simulations

Simulation data for the manuscript "Surface texture, boundary-layer transition, and drag on a swimmer's head: a computational study across the sphere drag crisis." A smooth sphere (geometry 1) and a simplified crown-textured swim-cap model (geometry 2), both 0.2 m in diameter, were simulated in water at 1.6, 1.8, 2.0, and 2.2 m/s (Reynolds numbers 3.2–4.4 × 10⁵) using pimpleFoam (OpenFOAM v2512) and the Langtry–Menter transition model. Both bodies were meshed with identical parameters and advanced with the same fixed time step, 1.5 × 10⁻³ s, to t = 80 s. geom1_fields.tar, geom2_fields.tar: main runs of the two geometries at the four velocities. time_step_fields.tar: geometry 1 with time steps of 3.0 × 10⁻³ s (four velocities) and 7.5 × 10⁻⁴ s (1.6 m/s). grid_fields.tar, verification_fields.tar: final flow fields of the grid study (coarse and fine meshes) and the free-stream turbulence study (cases S1–S3), both on geometry 1 at 1.8 m/s. meshes.tar: the four meshes. analysis.tar: analysis and figure scripts, derived data (statistics, force histories, and surface samples), the dictionaries and force histories of the grid and turbulence studies, geometries, and meshing logs. Each run folder in the first three archives contains the initial and final (t = 80 s) fields, the solver dictionaries, the force histories and surface samples, and the solver log; the folder names give the geometry, time step, and velocity. To rerun a case, copy the matching mesh from meshes.tar to constant/polyMesh. Version 2.0.0 replaces the runs of version 1.0.0, in which the time step differed between the two geometries. The version 1.0.0 geometry 1 runs are included, continued to t = 80 s, in time_step_fields.tar.