Off-rotor induced flow by a finite-state wake model

1996 ◽  
Author(s):  
David Peters ◽  
Wenming Gao
Keyword(s):  
Finite State ◽  
Induced Flow ◽  
Wake Model

scholarly journals A Numerical Study of a Rotor Induced Flow Based on a Finite-State Dynamic Wake Model.

2021 ◽  
Vol 22 (2) ◽  
pp. 307-324
Author(s):  
L. G. A. Ferreira ◽  
C. C. Pagani Júnior ◽  
E. M. Gennaro ◽  
C. De Marqui Junior
Keyword(s):  
Numerical Study ◽  
Mathematical Formulation ◽  
Problem Formulation ◽  
Flow Induced Vibration ◽  
Finite State ◽  
Practical Engineering ◽  
Rotor Disk ◽  
Induced Flow ◽  
Wake Model ◽  
Rotary Wings

A Helicopter rotor undergoes unsteady aerodynamic loads ruled by the aeroelastic coupling between the elastic blades and the dynamic wake induced by rotary wings. Modeling the dynamic interaction between the structural and aerodynamic fields is a key point to understand aeroelastic phenomena associated with rotor stability, flow induced vibration and noise generation, among others. In this study, we address the Generalized Dynamic Wake Model, which describes the inflow velocity field at the rotor disk as a superposition  of a finite number of induced flow states. It is a mature model that has been validated based on experimental data and numerically investigated from an eigenvalue problem formulation, whose eigenvalues and eigenvectors provide a deeper insight on the dynamic wake behavior. The paper extends the results presented in the literature to date in order to support physical interpretation of inflow states drawn from the finite-state wake model for flight conditions varying from hover to edgewise flight. The discussion of the wake model mathematical formulation is also oriented towards practical engineering applications to fill a gap in the literature.

Finite state induced flow models. II - Three-dimensional rotor disk

1995 ◽  
Vol 32 (2) ◽  
pp. 323-333 ◽  
Author(s):  
David A. Peters ◽  
Cheng Jian He
Keyword(s):  
Three Dimensional ◽  
Flow Models ◽  
Finite State ◽  
Rotor Disk ◽  
Induced Flow

Finite‐State Induced‐Flow Model for Rotors in Hover and Forward Flight

1989 ◽  
Vol 34 (4) ◽  
pp. 5-17 ◽  
Author(s):  
David A. Peters ◽  
David Doug Boyd ◽  
Cheng Jian He
Keyword(s):  
Flow Model ◽  
Forward Flight ◽  
Finite State ◽  
Induced Flow

Technical Note: Finite State Induced Flow Model in Vortex Ring State

2000 ◽  
Vol 45 (4) ◽  
pp. 318-320 ◽  
Author(s):  
Chengjian He ◽  
C. S. Lee ◽  
Weibin Chen
Keyword(s):  
Vortex Ring ◽  
Flow Model ◽  
Technical Note ◽  
Finite State ◽  
Induced Flow ◽  
Vortex Ring State

Finite state induced flow models. I - Two-dimensional thin airfoil

1995 ◽  
Vol 32 (2) ◽  
pp. 313-322 ◽  
Author(s):  
David A. Peters ◽  
Swaminathan Karunamoorthy ◽  
Wen-Ming Cao
Keyword(s):  
Two Dimensional ◽  
Flow Models ◽  
Thin Airfoil ◽  
Finite State ◽  
Induced Flow

Correlation of Measured Induced Velocities with a Finite‐State Wake Model

1991 ◽  
Vol 36 (3) ◽  
pp. 59-70 ◽  
Author(s):  
David A. Peters ◽  
Cheng Jian He
Keyword(s):  
Finite State ◽  
Wake Model

Coupling of a State-Space Inflow to Nonlinear Blade Equations and Extraction of Generalized Aerodynamic Force Mode Shapes

1993 ◽  
Vol 46 (11S) ◽  
pp. S295-S304 ◽  
Author(s):  
Donizeti de Andrade ◽  
David A. Peters
Keyword(s):  
Aerodynamic Force ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Mode Shapes ◽  
State Equations ◽  
Force Mode ◽  
Rotor Disk ◽  
Induced Flow ◽  
Wake Model

The aeroelastic stability of helicopter rotors in hovering flight has been investigated by a set of generalized dynamic wake equations and hybrid equations of motion for an elastic blade cantilevered in bending and having a torsional root spring to model pitch-link flexibility. The generalized dynamic wake model employed is based on an induced flow distribution expanded in a set of harmonic and radial shape functions, including undetermined time dependent coefficients as aerodynamic states. The flow is described by a system of first-order, ordinary differential equations in time, for which the pressure distribution at the rotor disk is expressed as a summation of the discrete loadings on each blade, accounting simultaneously for a finite number of blades and overall rotor effects. The present methodology leads to a standard eigenanalysis for the associated dynamics, for which the partitioned coefficient matrices depend on the numerical solution of the blade equilibrium and inflow steady-state equations. Numerical results for a two-bladed, stiff-inplane hingeless rotor with torsionally soft blades show the importance of unsteady, three-dimensional aerodynamics in predicting associated generalized aerodynamic force mode shapes.

An Approximate Finite State Dynamic Wake Model for Predictions of Inflow below the Rotor

2021 ◽  
Author(s):  
Feyyaz Guner ◽  
J. V. R. Prasad ◽  
David A. Peters
Keyword(s):  
Velocity Potential ◽  
Dynamic Pressure ◽  
Frequency Control ◽  
Flight Simulation ◽  
Low Frequencies ◽  
Simulation Fidelity ◽  
State Dynamic ◽  
Finite State ◽  
Time Marching ◽  
Wake Model

The velocity potential based finite state dynamic inflow model can predict inflow anywhere in the flow field once velocity potential states and costates are known. However, solution to costate equations requires backward time marching, making it incompatible for integration into real-time flight simulation. This paper explores two types of quasi-steady approximations to the costate equations, both of which eliminate the need for backward time marching. The fidelities of the resulting inflow models are assessed through comparisons of off-disk inflow predictions for an isolated rotor. Further, the implication of the inflow model approximations on the flight simulation fidelity is assessed using the coupled body/rotor/inflow dynamics model of a generic helicopter model. It is shown that, in both cases, the quasi-steady approximations to the inflow model retain simulation model fidelity at low frequencies, a typical frequency range of pilot control inputs. Notable fidelity loss is seen at high-frequency control inputs, specifically for cases where horizontal tail is operating at a higher dynamic pressure within the rotor wake.

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