Fast-time Wake Vortex Model Predictions Compared with Observations Behind Landing Aircraft Near the Ground (Invited)

Abstract

NASA has recently collected a large dataset of wake vortex and weather observations at Memphis International Airport. The wake data consists primarily of vortices generated between one and two wingspans above the ground. Most of the landings in the dataset include field observations of all the required environmental and aircraft data needed for input into fast-time wake vortex prediction models; including vertical profiles of wind speed, air temperature and eddy dissipation rate, as well as the aircraft weights. Prior to the collection of this data set there was only a small amount of data that could be used in the evaluation of the skill of fast-time wake vortex prediction models when the vortices were generated within a couple wingspans of the ground surface. This new data set significantly increases the amount of data available for the assessment of the models in this important region. Comparison of three fast-time model predictions with the new Memphis data indicates there are several areas where the models can be improved in the in ground effect region; specifically better parameterization of the effect of turbulence, and inclusion of the effect of headwind. Nomenclature APA = AVOSS Prediction Algorithm (a fast-time wake vortex model) AVOSS = Aircraft VOrtex Spacing System b = vortex separation distance, m b o = initial vortex separation distance, m EDR, ε = eddy dissipation rate, m 2 /s 3 EDR* = nondimensional eddy dissipation rate, = (ε b o ) 1/3 / v o g = acceleration due to gravity, m 2 /s IGE = In-Ground Effect region HW = Headwind, m/s LMCT = Lockheed Martin Coherent Technologies NGE = Near-Ground Effect region OGE = Out-of-Ground Effect region RoI = Region of Interest, used by Lockheed Martin Offline Wake Processing algorithm SNR = Signal to Noise Ratio, dB AIAA Aviation 2 T = time, seconds T* = nondimensional time, where T * = T / (b o / v o ) TDAWP = TASS Driven Algorithms for Wake Prediction (a fast-time wake vortex model) u = crosswind velocity, m/s U a = airspeed, m/s v o = initial vortex descent rate, m/s W = aircraft weight, kg Y = vortex lateral position, m Z = vortex altitude, m Z* = nondimensional vortex height, = Z/b o Γ ο = initial vortex circulation intensity, = gW/(2πρU a b o ), m 2 /s Γ* = nondimensional circulation intensity, = Γ/Γ o ρ= air density, kg/m 3 ϴ = potential temperature, K φ = glide slope, degrees