Passive control of bluff body using stepped-nose obstacle

The effectiveness of the stepped-nose obstacle in the prevention of flow separation over the surface of a bluff body to achieve drag reduction has been examined. Two nondimensional step lengths, small step configuration (SSC) and large step configuration (LSC), were employed to investigate their effectiveness over the baseline configuration (BC). In the baseline configuration, the flow separated at the leading-edge corners and separation bubbles were observed within the shear layers, resulting in a large wake. It was observed that in the SSC case, the separated flow at the leading corners reattaches to either side of the main body, indicating a reduced wake width compared with the BC case. Meanwhile, in the LSC case, the flow smoothly reattaches to the lateral sides of the body, leading to an effective reduction in wake width as compared with BC case. Consequently, the vortex shedding process was confirmed to a very narrow path as compared with BC and SSC cases.