Ground Effect on Wings and its Control in High Sea States
Abstract
APPROVED FOR PUBLIC RELEASEWith over 70% of the Earth s surface covered by water, air vehicles that can safely operate in ground effect (GE) over water would significantly amplify the reach and capability of the Navy, while simultaneously exploiting the aerodynamic benefits of GE for enhanced vehicle efficiency. The greatest challenge for GE aircraft comes from the requirement that they be capable of operating in close proximity to the water surface in high sea-states, characterized by large amplitude three-dimensional (3D) wave surface topologies and gusty wind conditions. These high sea-state conditions generate complex aerodynamic effects on the wings in ground effect (WIG), leading to concomitant rapid changes in aerodynamic forces and moments, resulting in severe stability and control problems for these aircraft. Thus, understanding the flow physics and scaling of these complex aerodynamic phenomena with key dimensionless parameters and devising effective flow-control approaches that can rapidly mitigate aerodynamic instability for these WIG are the critical next step in the development of these vehicles, and this provides the motivation for the current project. The technical objectives are to (i) understand WIG aerodynamics in high sea states and identify relevant dimensionless parameters andkey mechanisms that cause large changes in dynamic forces/moments and adversely impact aircraft flight control, (ii) assess and quantify the effect of each parameter and their scaling on aerodynamics and control, (iii) devise and optimize effective flow control approaches tailored to forecast and reject appropriately-modeled and estimated disturbances, and (iv) assess the impact of the flow-control approaches on an aircraft operating in GE in high sea states. To address these objectives, the team proposes five key innovations. First, we introduce a robust flow-physics-based characterization scheme specifically tailored for WIGs in high sea states, rooted in fundamental aerodynamic principles. Secondly, we implement the characterization via a first-principles-based "Force Partitioning Method" (FPM), enabling precise quantification of various inviscid and viscous physical mechanisms and associated scaling laws derived from simulation and experimental data. Third, these methodologies are integrated with a comprehensive suite of experimental, computational, and theoretical approaches aimed at unraveling the intricate flow physics of both 2D and 3D WIG configurations. This integration involves extensive exploration of the vast parameter space through numerous experiments conducted in specialized facilities such as a water-wave tow tank, a wind-wave tank, and a wind tunnel equipped with a traveling wave generator, alongside numericalsimulations utilizing time-accurate simulations capable of simulating chord Reynolds numbers up to 500,000. Measurements range fromaerodynamic coefficient time histories to detailed flow measurements of select cases using tomographic particle image velocimetry and 3D particle tracking velocimetry, enabling analysis via the FPM. Fourth, we develop disturbance models to capture the influence of deterministic waves and stochastic wind gusts on aerodynamic coefficients, along with innovative passive, tunable, and active flow-control solutions potentially capable of mitigating dynamic destabilizing loads and moments inherent in high sea states. The efficacy of the various flow-control methods is rigorously evaluated in experiments and simulations. Finally, we integrate the effective flow-control subsystem components and refined disturbance models into a vehicle-level model to assess flight control characteristics comprehensively. Collectively, these contributions promise significant insights, enhancements, and advancements in WIG vehicle technology relevant to the Navy.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 09, 2024
- Source ID
- N000142412516
Entities
People
- Louis N Cattafesta
Organizations
- Illinois Institute of Technology
- Office of Naval Research
- United States Navy