Ruelle-Takens-Newhouse and degenerate period-doubling routes to chaos in a wavy-channel flow under mixed convection

Wavy channels are widely used to enhance heat transfer in various applications, but their nonlinear dynamics under mixed convection remain poorly understood. Our numerical study reveals that mixed convection fundamentally alters the routes to chaos in wavy-channel flows: symmetric channels show both the Ruelle-Takens-Newhouse and degenerate period-doubling routes, asymmetric channels show only the latter route, and semi-wavy channels show no routes to chaos. The Pomeau-Manneville intermittency route, previously observed in isothermal conditions, is notably absent. These insights into the nonlinear dynamics of wavy-channel flows provide crucial guidance for optimizing heat transfer devices.