Dominant Flow Structures In The Wake of A Cyclist

Abstract

In this wind tunnel investigation the time-averaged wake structure is analyzed for a full scale cyclist mannequin over a complete crank cycle. At typical elite level road cycling speeds, detailed velocity field measurements were performed by traversing a four-hole dynamic pressure probe in planes behind the mannequin for 15° increments in crank position. They highlight the complexity of flows associated with cyclist geometries and show that variations in drag with leg position are primarily attributed to changes in the flow regime and not frontal surface area. The wake is shown to be highly three-dimensional with the primary flow structures consisting of multiple streamwise vortices. The formation strength and interaction of these structures about the center plane of the mannequin depend on whether each leg is in an up or down position around the crank cycle. This dependence on the position of each leg results in an asymmetrical wake configuration for the majority of crank positions tested. This is further highlighted in a series of flow visualization studies showing the origin and asymmetry in the formation of these structures over the upper body with crank position. This work highlights the importance of considering multiple flow regimes when investigating the aerodynamic performance of cyclists.