2000 Wake vortex transport and decay in ground effect vortex linking with the ground.pdf

AIAA 2000-0757 Wake Vortex Transport and Decay in Ground Effect: Vortex Linking with the Ground Fred H. Proctor and David W. Hamilton NASA Langley Research Center Hampton, VA Jongil Han North Carolina State University Raleigh, NC 38th Aerospace Sciences Meeting Exhibit January 10-13, 2000 / Reno, NV For permission to copy or republish, contact the American Institute of Aeronautics and Astronautics 1801 Alexander Bell Drive, Suite 500, Reston, Virginia 20191-4344 x z American Institute of Aeronautics and Astronautics 1 Wake Vortex Transport and Decay in Ground Effect: Vortex Linking with the Ground Fred H. Proctor* and David W. Hamilton ? NASA Langley Research Center Hampton, Virginia Jongil Han ? North Carolina State University Raleigh, NC Abstract Numerical simulations are carried out with a three- dimensional Large-Eddy Simulation (LES) model to explore the sensitivity of vortex decay and transport in ground effect (IGE). The vortex decay rates are found to be strongly enhanced following maximum descent into ground effect. The nondimensional decay rate is found to be insensitive to the initial values of circulation, height, and vortex separation. The information gained from these simulations is used to construct a simple decay relationship. This relationship compares well with observed data from an IGE case study. Similarly, a relationship for lateral drift due to ground effect is constructed from the LES data. In the second part of this paper, vortex linking with the ground is investigated. Our numerical simulations of wake vortices for IGE show that a vortex may link with its image beneath the ground, if the intensity of the ambient turbulence is moderate to high. This linking with the ground (which is observed in real cases) gives the appearance of a vortex tube that bends to *Research Scientist, Airborne Systems Competency, AIAA member ? Research Scientist, Airborne Systems Competency ? Research