Author:
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ISBN:
Category : Aeroelasticity
Languages : en
Pages : 156

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Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
ISBN: 9781731363589
Category : Science
Languages : en
Pages : 158

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Book Description
The general rotorcraft aeromechanical stability program (GRASP) was developed to calculate aeroelastic stability for rotorcraft in hovering flight, vertical flight, and ground contact conditions. GRASP is described in terms of its capabilities and its philosophy of modeling. The equations of motion that govern the physical system are described, as well as the analytical approximations used to derive them. The equations include the kinematical equation, the element equations, and the constraint equations. In addition, the solution procedures used by GRASP are described. GRASP is capable of treating the nonlinear static and linearized dynamic behavior of structures represented by arbitrary collections of rigid-body and beam elements. These elements may be connected in an arbitrary fashion, and are permitted to have large relative motions. The main limitation of this analysis is that periodic coefficient effects are not treated, restricting rotorcraft flight conditions to hover, axial flight, and ground contact. Instead of following the methods employed in other rotorcraft programs. GRASP is designed to be a hybrid of the finite-element method and the multibody methods used in spacecraft analysis. GRASP differs from traditional finite-element programs by allowing multiple levels of substructure in which the substructures can move and/or rotate relative to others with no small-angle approximations. This capability facilitates the modeling of rotorcraft structures, including the rotating/nonrotating interface and the details of the blade/root kinematics for various types. GRASP differs from traditional multibody programs by considering aeroelastic effects, including inflow dynamics (simple unsteady aerodynamics) and nonlinear aerodynamic coefficients. Hodges, Dewey H. and Hopkins, A. Stewart and Kunz, Donald L. and Hinnant, Howard E. Ames Research Center AERODYNAMIC STABILITY; AEROELASTICITY; DYNAMIC STRUCTURAL ANALYSIS; FINITE ELEMENT METHOD; HOVERING; ROTARY WING AIRCR...

Author: A. Stewart Hopkins
Publisher:
ISBN:
Category :
Languages : en
Pages : 70

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The Rotorcraft Dynamics Division, Aeroflightdynamics Directorate, U.S. Army Aviation Research and Technology Activity has developed the General Rotorcraft Aeromechanical Stability Program (GRASP) to perform calculations that will assess the stability of rotorcraft in hovering flight and ground contact conditions. This computer program is designed to be a state-of-the-art, hybrid, finite-element/multibody code that can be applied to all existing and future helicopter configurations. While GRASP was specifically designed to solve rotorcraft stability problems, its innovative structure and formulation allow for applications to a wide range of structures. This manual describes the preparation of the input file required by Version 1.03 of GRASP, the procedures used to invoke GRASP on the NASA Ames Research Center Cray X-MP 48 computer, and the interpretation of the output produced by GRASP. The parameters used by the input file are defined, and summaries of the input file and the job control language are included. Keywords: Aeroelasticity; Rotary wings.

Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722416171
Category :
Languages : en
Pages : 64

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Book Description
The Rotorcraft Dynamics Division, Aeroflightdynamics Directorate, U.S. Army Aviation Research and Technology Activity has developed the General Rotorcraft Aeromechanical Stability Program (GRASP) to perform calculations that will assess the stability of rotorcraft in hovering flight and ground contact conditions. The program is designed to be state-of-the-art, hybrid, finite-element/multibody code that can be applied to all existing and future helicopter configurations. While GRASP was specifically designed to solve rotorcraft stability problems, its innovative structure and formulation allow for application to a wide range of structures. This manual describes the preparation of the input file required by Version 1.03 of GRASP, the procedures used to invoke GRASP on the NASA Ames Research Center CRAY X-MP 48 computer, and the interpretation of the output produced by GRASP. The parameters used by the input file are defined, and summaries of the input file and the job control language are included. Hopkins, A. Stewart and Kunz, Donald L. Ames Research Center...

Author: Dewey H. Hodges
Publisher:
ISBN:
Category :
Languages : en
Pages : 18

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Book Description
The General Rotorcraft Aeromechanical Stability Program (GRASP) is described in terms of its capabilities and development philosophy. The program is capable of treating the nonlinear static and linearized dynamic behavior of structures represented by arbitrary collections of rigid-body and beam elements that may be connected in an arbitrary fashion and are permitted to have large relative motions. The main limitation is that periodic coefficient effects are not treated, restricting the solutions to rotorcraft in axial flight and ground contact conditions. Rather than following in the footsteps of other rotorcraft programs, GRASP is more of a hybrid between finite element programs and spacecraft-oriented multibody programs. GRASP differs from standard finite-element programs by allowing multiple levels of substructures in which the substructures can move and/or rotate relative to others with no small-angle approximations. This capability facilitates the modeling of rotorcraft structures, including the rotating/nonrotating interface and details of the blade/root kinematics for various rotor types.

Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 520

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Author: Howard E. Hinnant
Publisher:
ISBN:
Category :
Languages : en
Pages : 11

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The General Rotorcraft Aeromechanical Stability Program (GRASP) was developed to analyse the steady-state and linearized dynamic behavior of rotorcraft in hovering and axial flight conditions. Because of the nature of problems GRASP was created to solve, the geometrically nonlinear behavior of beams is one area in which the program must perform well in order to be of any value. Numerical results obtained from GRASP are compared to both static and dynamic experimental data obtained for a cantilever beam undergoing large displacements and rotations caused by deformations. The correlation is excellent in all cases.

Author: Michael J. McNulty
Publisher:
ISBN:
Category :
Languages : en
Pages : 396

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Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 746

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Author: Donald L. Kunz
Publisher:
ISBN:
Category :
Languages : en
Pages : 18

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As a part of the continuing effort to develop and validate the General Rotorcraft Aeromechanical Stability Program (GRASP), a correlation study is presented to compare the frequency, moment, and stability data for a model-scale, torsionally-soft, helicoptor rotor with GRASP numerical calculations. The hierarchical representation of the model rotor is discussed along with the calculations of the vacuum frequencies, the steady-state blade moments in air, and the aeroelastic stability. Correlation is generally quite good. The GRASP predictions of the first vacuum flap frequencies are outstanding and the first vacuum lag and torsion frequencies correlate reasonably well with the experimental data. Consistently outstanding results are obtained for all of the steady blade moments. The calculations of stability data are in general as good as those made by other programs, but are not quite as good as anticipated.