Reproducible Equal-Width Geometric Design Framework for Hydrodynamic-Cavitation Venturi Devices: Reuleaux Cross Section and Controlled Axial Twist

Hydrodynamic cavitation in Venturi devices is strongly influenced by geometry and is increasingly considered as a non-thermal route for process intensification in continuous-flow applications, including water-treatment contexts. However, Venturi design practice still relies largely on incremental modifications of circular throats and on loosely formalized heuristics, which limits reproducibility and systematic comparison. This work presents a reproducible geometry-driven framework for the design of an equal-width Venturi throat under a fixed transverse envelope constraint. Two parameterized configurations are considered: a constant-width Reuleaux-triangle cross section (VRA) and a controlled axial-twist variant (VRAt). A minimal set of geometric design indicators is formulated in terms of throat flow area, wetted perimeter, hydraulic diameter, and geometric near-wall coverage within a prescribed thickness; for VRAt, a dimensionless kinematic factor is additionally introduced to quantify the path-length increase associated with the imposed twist. Under equal-width conditions, the Reuleaux section preserves the wetted perimeter of the circular reference while reducing flow area, whereas the twisted variant preserves the same transverse throat metrics and isolates twist as an explicit geometric design variable. The contribution is methodological: it provides a reproducible framework for early-stage geometric design and comparison of Venturi configurations relevant to hydrodynamic cavitation. It does not, by itself, report experiments, validation, or hydraulic, cavitation, or water-treatment performance predictions.