Drag Reduction on the 25-deg Ahmed Model Using Fluidic Oscillators

Transportation of goods and people involves moving objects through air, which leads to a force opposing motion. This drag force can account for more than 60% of power consumed by a ground vehicle, such as a car or truck, at highway speeds. This paper studies drag reduction on the 25-deg Ahmed generic vehicle model with quasi-steady blowing at the roof-slant interface using a spanwise array of fluidic oscillators. A fluidic oscillator is a simple device that converts a steady pressure input into a spatially oscillating jet. Drag reduction near 7% was attributed to separation control on the rear slant surface. Particle image velocimetry (PIV) and pressure taps were used to characterize the flow structure changes behind the model. Oil flow visualization was used to understand the mechanism behind oscillator effectiveness. An energy analysis suggests that this method may be viable from a flow energy perspective.