Numerical Simulation of Flow in Karst Conduits

Karst conduits exhibit strong geometric irregularities that control flow resistance and transport but are often represented by smooth-pipe models. High-fidelity simulations with Nek5000 show that such irregularities act as effective roughness elements, increasing drag, promoting early transition, and producing coexisting laminar, transitional, and turbulent regions. A centreline-based framework is introduced to define hydraulic diameter and roughness, providing global descriptors suitable for simplified network-scale models of karst aquifers.