General Rotorcraft Aeromechanical Stability Program Grasp
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General Rotorcraft Aeromechanical Stability Program Grasp Theory Manual
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Author :
language : en
Publisher:
Release Date : 1990
General Rotorcraft Aeromechanical Stability Program Grasp Theory Manual written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with Aeroelasticity categories.
General Rotorcraft Aeromechanical Stability Program Grasp Version 1 03 User S Manual
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Author : A. Stewart Hopkins
language : en
Publisher:
Release Date : 1988
General Rotorcraft Aeromechanical Stability Program Grasp Version 1 03 User S Manual written by A. Stewart Hopkins and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1988 with categories.
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.
Introduction To Grasp General Rotorcraft Aeromechanical Stability Program A Modern Approach To Rotorcraft Modeling
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Author : Dewey H. Hodges
language : en
Publisher:
Release Date : 1986
Introduction To Grasp General Rotorcraft Aeromechanical Stability Program A Modern Approach To Rotorcraft Modeling written by Dewey H. Hodges and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1986 with categories.
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.
General Rotorcraft Aeromechanical Stability Program Grasp Version 1 03
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Author : National Aeronautics and Space Administration (NASA)
language : en
Publisher: Createspace Independent Publishing Platform
Release Date : 2018-07-07
General Rotorcraft Aeromechanical Stability Program Grasp Version 1 03 written by National Aeronautics and Space Administration (NASA) and has been published by Createspace Independent Publishing Platform this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-07-07 with categories.
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...
General Rotorcraft Aeromechanical Stability Program Grasp Theory Manual
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Author : National Aeronautics and Space Adm Nasa
language : en
Publisher: Independently Published
Release Date : 2018-11-18
General Rotorcraft Aeromechanical Stability Program Grasp Theory Manual written by National Aeronautics and Space Adm Nasa and has been published by Independently Published this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-11-18 with Science categories.
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...
Application Of Grasp General Rotorcraft Aeromechanical Stability Program To Nonlinear Analysis Of A Cantilever Beam
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Author : Howard E. Hinnant
language : en
Publisher:
Release Date : 1987
Application Of Grasp General Rotorcraft Aeromechanical Stability Program To Nonlinear Analysis Of A Cantilever Beam written by Howard E. Hinnant and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with categories.
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.
Correlation Of Analytical Calculations From Grasp General Rotorcraft Aeromechanical Stability Program With Torsionally Soft Rotor Data
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Author : Donald L. Kunz
language : en
Publisher:
Release Date : 1987
Correlation Of Analytical Calculations From Grasp General Rotorcraft Aeromechanical Stability Program With Torsionally Soft Rotor Data written by Donald L. Kunz and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with categories.
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.
Analysis Of Structures With Rotating Flexible Substructures Applied To Rotorcraft Aeroelasticity In Grasp General Rotorcraft Aeromechanical Stability Program
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Author : Dewey H. Hodges
language : en
Publisher:
Release Date : 1987
Analysis Of Structures With Rotating Flexible Substructures Applied To Rotorcraft Aeroelasticity In Grasp General Rotorcraft Aeromechanical Stability Program written by Dewey H. Hodges and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with categories.
The initial version of the General Rotorcraft Aeromechanical Stability Program (GRASP) was developed for analysis of rotorcraft in steady, axial flight and ground contact conditions. In these flight regimes, the material continua of the rotorcraft may experience deformations which are independent of time. GRASP can obtain this steady-state solution and can solve the eigenproblem associated with perturbations about such a steady-state solution. GRASP is the first program implementing a new method for dynamic analysis of structures, parts of which may be experiencing discrete motion relative to other parts. Application of this new method to GRASP, including substructuring, frames of reference, nodes, finite elements and constraints, is described in the paper. The library of finite elements includes a powerful nonlinear beam element that incorporates aeroelastic effects based on a simple nonlinear, aerodynamic theory with unsteady induced inflow.
Analytical Modeling Of Helicopter Static And Dynamic Induced Velocity In Grasp
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Author :
language : en
Publisher:
Release Date : 1987
Analytical Modeling Of Helicopter Static And Dynamic Induced Velocity In Grasp written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with categories.
This paper describes the methodology used by the General Rotorcraft Aeromechanical Stability Program (GRASP) to model the characteristics of the flow through a helicopter rotor in hovering or axial flight. Since the induced flow plays a significant role in determining the aeroelastic properties of rotorcraft, the computation of the induced flow is an important aspect of the program. Because of the combined finite-element/multibody methodology used as the basis for GRASP, the implementation of induced velocity calculations presented an unusual challenge to the developers. To preserve the modeling flexibility and generality of the code, it was necessary to depart from the traditional methods of computing the induced velocity. This is accomplished by calculating the actuator disc contributions to the rotor loads in a separate element called the air mass element, and then performing the calculations of the aerodynamic forces on individual blade elements within the aeroelastic beam element. Keywords: Rotor flow fields; Rotary wings.
Rotorcraft Aeromechanics
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Author : Wayne Johnson
language : en
Publisher: Cambridge University Press
Release Date : 2013-04-29
Rotorcraft Aeromechanics written by Wayne Johnson and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-04-29 with Mathematics categories.
A rotorcraft is a class of aircraft that uses large-diameter rotating wings to accomplish efficient vertical take-off and landing. The class encompasses helicopters of numerous configurations (single main rotor and tail rotor, tandem rotors, coaxial rotors), tilting proprotor aircraft, compound helicopters, and many other innovative configuration concepts. Aeromechanics covers much of what the rotorcraft engineer needs: performance, loads, vibration, stability, flight dynamics, and noise. These topics include many of the key performance attributes and the often-encountered problems in rotorcraft designs. This comprehensive book presents, in depth, what engineers need to know about modelling rotorcraft aeromechanics. The focus is on analysis, and calculated results are presented to illustrate analysis characteristics and rotor behaviour. The first third of the book is an introduction to rotorcraft aerodynamics, blade motion, and performance. The remainder of the book covers advanced topics in rotary wing aerodynamics and dynamics.