Control of flow over a backward facing step

• Main Author: Woolman, Scott G.
• Other Authors: Healey, J. Val
• Published: Monterey, California: Naval Postgraduate School 2013
• Online Access: http://hdl.handle.net/10945/34960

Approved for public release; distribution unlimited. === The poor aerodynamic design of the superstructures of today's Navy ships create a highly turbulent airwake that can make shipboard helicopter operations quite hazardous. This study is part of a longer-term project to tailor airflow over a ship's helicopter deck in order to improve the poor quality of the airflow. This airflow is thought to be largely responsible for several costly blade strike mishaps involving H-46 helicopters during start-up and shut down. Numerous computer simulations were conducted using the Phoenics Computational Fluid Dynamics code to simulate airflow over a backward-facing- step. The latter represents a simple 2-d model of flow behind a typical hangar flight deck combination. In each run a deflector of different size, orientation or porosity was placed in a specific location in an attempt to reduce the size of the recirculation zone, the velocities and the turbulence levels. Of the studies involved, a vertical deflector offset downstream with its lower edge at the top of the step produced the best overall results.