Acceleration-Based In Situ Eddy Dissipation Rate Estimation with Flight Data

Abstract

Inducing civil aviation aircraft to bumpiness, atmospheric turbulence is a typical risk that seriously threatens flight safety. The Eddy Dissipation Rate (EDR) value, as an aircraft-independent turbulence severity indicator, is estimated by a vertical wind-based or aircraft vertical acceleration-based algorithm. Based on the flight data of civil aviation aircraft, the vertical turbulence component is obtained as the input of both algorithms. A new method of computing vertical acceleration response in turbulence is put forward through the Unsteady Vortex Lattice Method (UVLM). The lifting surface of the target aircraft is assumed to be a combination of wing and horizontal tail in a turbulent flight scenario. Vortex rings are assigned on the mean camber surface, forming a non-planar UVLM, to further improve the accuracy. Moreover, the neighboring vortex lattices are placed as close as possible to the structural edge of control surfaces. Thereby, a complete algorithm for estimating vertical acceleration and in situ EDR value from Quick Access Recorder (QAR) flight data is proposed. Experiments show that the aerodynamic performance is computed accurately by non-planar UVLM. The acceleration response by non-planar UVLM is able to track the recorded acceleration data with higher accuracy than that of the linear model. Different acceleration responses at different locations are also obtained. Furthermore, because the adverse effects of aircraft maneuvers are separated from turbulence-induced aircraft bumpiness, the new acceleration-based EDR algorithm shows better accuracy and stability.

The Optimization of Aircraft Acceleration Response and EDR Estimation Based on Linear Turbulence Field Approximation

“…Instead of a polynomial fitting function and linear transfer function, the UVLM was used for acceleration estimation in this study; thus, the performance of the UVLM was tested as a basis for further acceleration response analysis. The refined aerodynamic performance can be obtained with a certain number of vortex lattices on the lifting panel [6]. Therefore, under the premise of ensuring the computing accuracy, an appropriate grid resolution to improve the computing efficiency was studied at first.…”

“…Since the objective EDR estimation requires the acceleration response only induced by turbulence, the adverse effects of aircraft maneuvers must be eliminated in computing the acceleration response by cruciform assembly. Both the acceleration-based and wind-based EDR estimation in [6] were cited in this study.…”

“…Instead, aircraft-based measurement becomes an effective way of turbulence severity estimation. In addition to pilot subjective reports [4], several objective indicators of turbulence severity have been proposed, including the root mean square of vertical acceleration (RMS-g) [5], the eddy dissipation rate (EDR) [6], and the derived vertical equivalent gust (DEVG) [7].…”

Flight Data-Based Wind Disturbance and Air Data Estimation

“…In addition, the spectrum function of the von Karman model has a roll-off rate of −5/3 in the high-frequency section. However, as an approximation of the von Karman model, the roll-off rate of the Dryden model is −2 [23,30]. The temporal spectra of three turbulence components in the von Karman model are…”

“…Φ 1 , Φ 2 and Φ 3 represent the temporal spectra of longitudinal, lateral, and vertical turbulence, respectively. According to the von Karman model, the length scales are selected as L 1 = L 2 = L 3 = 669 m for above 762 m of flight altitude, while the turbulence intensity variates [23]. The turbulence components are generated by exciting the forming filters with unit-intensity white noise.…”