A coupled free-wake/panel method for rotor/fuselage/empennage aerodynamic interaction and helicopter trims

Abstract

A coupled free-wake/panel method to predict the rotor downwash aerodynamic interaction and helicopter trims is presented. Free-wake method was developed to analyze aerodynamics interference of rotor wake, based on lifting-surface theory and vortex method, which relates the core radius, span station, and circulation of initial tip vortex with the blade-bound circulation distribution, and eliminates the empirical parameters during rotor free wake analysis. Helicopter fuselage with empennage was discretized into source panels. The vortex line mirror method was adopted to account for wake acceleration phenomenon that resulted from the close interaction between rotor wake and fuselage surface. The rotor wake geometry and downwash simulations were investigated including comparisons with the available measured data. Combined with the helicopter flight dynamics model and embedded in the trim procedure, the free-wake/panel coupled method was applied to calculate the rotor wake and its interference on other components of a full-scale UH-60A rotorcraft in level flight. Comparisons among predictions, referenced results, and experimental results are made for rotor wake geometries, blade-bound vortex, blade tip vortex, rotor downwash velocity, and control stick positions, and encouraging results were obtained. To validate the present method, this paper discusses the fundamental formulation, the numerical algorithms, and the simulation results.

Review of vortex methods for rotor aerodynamics and wake dynamics

“…Continuum Dynamics, Inc. [35,95] developed this comprehensive analysis model by combining several extended versions of their previous models; they later employed CHARM to analyze various rotorcraft phenomena such as rotor/airframe flow interaction [35], vibration [96], and noise propagation [97]. Other noteworthy combinations of VLM and the panel method for comprehensive analysis of rotorcraft can be found in Jang et al [41] and Cao et al [45], which investigate pressure fluctuation on fuselage surfaces and aerodynamic interaction among rotorcraft components, respectively. For more on coupled VLM and panel analysis, we encourage you to read the NASA Ames report by Wayne Johnson [98] on developing a comprehensive analysis.…”

“…Researchers have used different vortex methods to tackle these challenges. The main topics in rotor aerodynamics are the influences of interactions among components [41,[45][46][47] and with nearby infrastructure (e.g., brownout and shipboard operation) [48,49], on rotorcraft performance, stability, control, and safety. There have also been several investigations on the design of rotorcraft configuration to improve aerodynamic performance [50][51][52].…”

A simple and conservative unstructured sliding-mesh approach for rotor–fuselage aerodynamic interaction simulation

“…9,10 Recently, Cao et al. 11 developed a coupled free-wake/panel method for rotor/fuselage/empennage aerodynamic interaction. For more accurate prediction, the rotor was modeled as a momentum source 12 or an actuator disk, 13,14 and the Euler or Navier–Stokes equations were used to simulate the rotor–fuselage problems.…”

A Cost Effective Approach for Subsonic Aeroelastic Stability Analysis of Turbomachinery 3D Blade Cascade. A Reduced Order Aeroelastic Model Numerical Approach

“…However, modified PM can be used for the separated flow case [11]. These methods are compre-95 hensively adopted for aerodynamics/aeroelastic modeling of wind turbines [12,13,14], helicopter rotors [15,16], ship propeller [17] and aircraft aeroelasticity [18]. A ROM approach for wind turbine aeroelasticity is adopted by Rezaei et al [19] More details about the-100 oretical and numerical implementation of PM can be found in Katz [20].…”