ENGR 298 – Seminar Chaderjian

ENGR 298 – Seminar in Fluid Mechanics Fall Quarter 2014-­‐15 There and Back Again – An Unexpected Journey in Rotorcraft CFD Dr. Neal Chaderjian NASA Ames Research Center Tuesday, October 21, 2014. 4:15-­‐5:15 pm Building 300, Room 300 Rotorcraft perform many useful civil and military functions by virtue of their ability to take off and land vertically. This ability is primarily accomplished by rotors, which produce complex vortical flows that are challenging to accurately predict with computational fluid dynamics (CFD). Unlike fixed-­‐wing applications, a rotor blade can encounter the tip vortices of preceding blades. This interaction can strongly affect the vehicle performance, acoustics, and vibrations. The situation is further complicated by rotor blade flexibility, requiring a computational structural dynamics (CSD) analysis. Rotorcraft simulations are therefore inherently unsteady and multidisciplinary, combining CFD, CSD, and a steady flight trim algorithm that determines the blade motions. Recent advances in accurately predicting the figure of merit (FM), the chief performance parameter for rotorcraft hover, will be discussed. A detailed analysis will be presented, showing the effects of grid refinement, spatial order-­‐of-­‐accuracy, and turbulence model to obtain the FM for the first time within experimental error. Moreover, an adaptive mesh refinement (AMR) capability in the Navier-­‐Stokes OVERFLOW code will be demonstrated for rotors in hover and forward flight. These high-­‐resolution wakes, together with detached eddy simulation (DES), will reveal complex turbulent interactions and vortical worm structures that were previously unknown. The source and plausibility of these vortical worms will be discussed. Refreshments available at 4pm. Seminar begins at 4:15 pm. Questions: jjalonso@stanford.edu, x3-­‐9954 Subscribe/unsubscribe to list: https://mailman.stanford.edu/mailman/listinfo/fmseminar Seminar series website: http://adl.stanford.edu/e298