Unsteady actuating blade model for CFD/CSD analysis of a tiltrotor

The paper presents an effective method to evaluate the unsteady flow field around a rotor through a Computational Fluid Dynamics model based on the actuator blade approach. The actuator blade extends the classical actuator disk model without the necessity to perform time or azimuth averaging operations. In this way, a time accurate investigation of the influence of the rotor wake on the rotor itself and on other non-rotating parts (fuselage, wings) can be performed. The method exploits the overset grid technique to allow an easy identification of the location of the sources distributed in the flow field to enforce the correct blade loads. The kinematics and the dynamics of the rotating parts is computed thought the coupling with a multibody solver and transmitted to the CFD as movement of the independent surface grids associated with each actuator blade. This allows to keep into account both rigid and elastic movements, including those related to movable surfaces. A comparison with experimental results obtained for a four blade tiltrotor are shown to verify the quality of the prediction of the flow field. Additionally, a comparison with the results obtained through a classical actuator disk allows to quantify the effects of the employment of the time-accurate approach with respect to the time-averaged results of the actuator disk model.

[1]  Massimo Biava,et al.  Wing-Rotor Aerodynamic Interaction in Tiltrotor Aircraft , 2012 .

[2]  Giuseppe Gibertini,et al.  Experimental investigation of a trailing edge L-shaped tab on a pitching airfoil in deep dynamic stall conditions , 2014 .

[3]  A. Jameson,et al.  Three-dimensional Euler equation simulation of propeller-wing interaction in transonic flow , 1983 .

[4]  Giovanni Droandi,et al.  Experimental investigation of the rotor-wing aerodynamic interaction in a tiltwing aircraft in hover , 2015 .

[5]  Marilyn J. Smith,et al.  Analysis of Rotor-Fuselage Interactions Using Various Rotor Models , 2005 .

[6]  P. Roe.  Approximate Riemann Solvers, Parameter Vectors, and Difference Schemes , 1997 .

[7]  Frédéric Le Chuiton,et al.  Actuator Disc Modelling for Helicopter Rotors , 2004 .

[8]  Giuseppe Gibertini,et al.  Aerodynamic blade design with multi-objective optimization for a tiltrotor aircraft , 2015 .

[9]  N. J. Yu,et al.  Flow prediction for propfan configurations using Euler equations , 1984 .

[10]  Pietro Alli.  Erica: The European Tiltrotor. Design and Critical Technology Projects , 2003 .

[11]  V. Venkatakrishnan.  On the accuracy of limiters and convergence to steady state solutions , 1993 .

[12]  W. Henshaw,et al.  Composite overlapping meshes for the solution of partial differential equations , 1990 .

[13]  A. Strauß.  Theory Of Wing Sections Including A Summary Of Airfoil Data , 2016 .

[14]  A. Jameson.  Time dependent calculations using multigrid, with applications to unsteady flows past airfoils and wings , 1991 .

[15]  Giuseppe Quaranta,et al.  Soft-Inplane Tiltrotor Aeromechanics Investigation Using Two Comprehensive Multibody Solvers , 2008 .

[16]  Marco Morandini,et al.  An Efficient Formulation for General-Purpose Multibody/Multiphysics Analysis , 2014 .

[17]  Eli Turkel,et al.  Assessment of Preconditioning Methods for Multidimensional Aerodynamics , 1997 .

[18]  David A. Peters,et al.  Theoretical prediction of dynamic inflow derivatives , 1980 .

[19]  Politecnico di Milano,et al.  Experimental Investigation on a 1/4 Scaled Model of an High-Performance Tiltwing Aircraft in Hover , 2014 .

[20]  Marilyn J. Smith,et al.  An efficient actuating blade model for unsteady rotating system wake simulations , 2014 .

[21]  David Michael O'Brien,et al.  Analysis Of Computational Modeling Techniques For Complete Rotorcraft Configurations , 2006 .

[22]  John D. Berry,et al.  Helicopter Fuselage Aerodynamics Under a Rotor by Navier-Stokes Simulation , 1997 .