Numerical calculations of three‐dimensional turbulent vortex breakdown

Numerical solutions to the three‐dimensional, unsteady, incompressible Reynolds‐averaged Navier‐Stokes equations have been obtained for bubble‐type vortex breakdown. Two different turbulence models were employed: (1) standard K‐ε and (2) an explicit, regularized algebraic Reynolds stress model. Results are computed at a Reynolds number of 10,000. The algebraic Reynolds stress model produced a breakdown bubble with a larger length‐to‐diameter ratio than did the K‐ε model. Breakdown also occurred at lower levels of adverse pressure gradient for the algebraic stress model than for the K‐ε model. In each case single‐cell breakdown structures resulted. This is contrasted with numerical calculations for laminar breakdown which reveal the existence of complex multicell bubble breakdown structures.