Aerospace Engineering N. C. State University Air Terminal Wake Vortex Simulation D. Scott McRae, Hassan A. Hassan N.C. State University 4 September 2003

Aerospace Engineering N. C. State University Outline Objective Present TASS Features Proposed new capabilities Turbulence simulation Adaptive mesh algorithms Discussion

Aerospace Engineering N. C. State University Objective A detailed simulation of the interaction of aircraft trailing vortices with the local terminal area conditions. Enhance TASS (Terminal Area Simulation System) to include: –Dynamic adaptive resolution of the vortices –A new physically based turbulence model –A new embedded domain boundary interface algorithm

Aerospace Engineering N. C. State University Present TASS Features 3-D Compressible nonlinear non- hydrostatic LES model –Modified Smagorinsky subgrid turbulence model –Periodic boundary conditions –Numerous microphysics models –Fixed grid resolution

Aerospace Engineering N. C. State University Proposed TASS Enhancements Configure TASS to execute as an embedded module in standard Met models –Predictive use with actual local conditions and aircraft trailing vortex characteristics data base.

Aerospace Engineering N. C. State University An AVOSS Tool Continuously executing Met model, updated by local observations Upon aircraft operation, insert trailing vortices from data base into embedded dynamically resolved LES terminal area module. Boundary interface conditions to and from Met model. Graphical/visual display of vortex position, extent and strength versus time. Operation interval based on actual conditions.

Aerospace Engineering N. C. State University New Capabilities –Governing equations transformed to a dynamically moving mesh. –r- refinement solution adaptive mesh algorithm to improve resolution and thereby accuracy of vortex and LES simulation. –Grid spacing continuously variable, with no fixed ratio with the boundary grid. –Arbitrarily non-continuous grid and two-way, conservative information transfer at boundary with surrounding meteorological model

Aerospace Engineering N. C. State University New Capabilities (2) NCSU’s hybrid large eddy simulation/Reynolds averaged Navier- Stokes model (LES/RANS) –The LES/RANS model is based on the exact equations that govern: The variance of velocity, i.e. the kinetic energy of fluctuations, k. The variance of vorticity ( enstrophy ). This equation provides the velocity length scale. The variance of temperature,. The dissipation rate of temperature variance- provides the temperature length scale.

Aerospace Engineering N. C. State University New Capabilities (3) The LES/RANS model: –Employs a one- equation model for the eddy viscosity –Has a flow dependent blending function which shifts the model from the RANS component near the surface to LES away from the surface.

Aerospace Engineering N. C. State University Examples of Prior Applications Regional Air Quality Modeling Grid adapted to GIS terrain data Aerospace flows Simulation of atmospheric turbulence Animations

Aerospace Engineering N. C. State University Mesh adapted to SAMI data 0700, June 7, 1995 (GIT)

Aerospace Engineering N. C. State University Plume structure as resolved by adaptive grid, 1700 June 7, 1995 (GIT)

Aerospace Engineering N. C. State University Surface elevation contours for the Island of Hawaii (left) and a grid adapted to these contours (right) (GIT)

Aerospace Engineering N. C. State University Embedded Adaptive Module in MM5

Aerospace Engineering N. C. State University Detail of Adaptation to Vorticity

Aerospace Engineering N. C. State University Adaptive algorithm examples: –T. Odman, GIT

Aerospace Engineering N. C. State University 3-D Supersonic Inlet Unstart

Aerospace Engineering N. C. State University Summary Enhance TASS to provide: –Dynamic solution resolution –Physically based turbulence modeling –Improved boundary conditions Include as embedded module in Met models Type/weight dependent vortex insertion Visual/graphical display

Aerospace Engineering N. C. State University Adaptive Mesh Algorithm –Three stage process. –Split equations into a stationary mesh and mesh movement set. Solve stationary mesh equations on the mesh adapted to the preceding time step. Adapt the mesh to the solution obtained on the stationary mesh. Solve the moving mesh portion of the set,

Aerospace Engineering N. C. State University NCSU interface algorithm: –The opposing mesh is “tiled” into the adjacent domain. –Information is then transferred to the “tiled” cells from the surroundings.

Aerospace Engineering N. C. State University NCSU interface algorithm: –An example of the discontinuous meshes that share an interface: