Author: E. Carson Yates (Jr.)
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 74
Book Description
The flutter characteristics of several wings with an aspect-ratio of 4.0, a taper ratio of 0.2, and a quarter-chord sweepback of 45 deg. have been investigated analytically for Mach numbers up to 2.0. The calculations were based on the modified-strip-analysis method, the subsonic-kernel-function method, piston theory, and quasi-steady second-order theory. Results of t h e analysis and comparisons with experiment indicated that: (1) Flutter speeds were accurately predicted by the modified strip analysis, although accuracy at t h e highest Mach numbers required the use of nonlinear aerodynamic theory (which accounts for effects of wing thickness) for the calculation of the aerodynamic parameters. (2) An abrupt increase of flutter-speed coefficient with increasing Mach number, observed experimentally in the transonic range, was also indicated by the modified strip analysis. (3) In the low supersonic range for some densities, a discontinuous variation of flutter frequency with Mach number was indicated by the modified strip analysis. An abrupt change of frequency appeared experimentally in the transonic range. (4) Differences in flutter-speed-coefficient levels obtained from tests at low supersonic Mach numbers in two wind tunnels were also predicted by the modified strip analysis and were shown to be caused primarily by differences in mass ratio. (5) Flutter speeds calculated by the subsonic-kernel-function method were in good agreement with experiment and with the results of the modified strip analysis. (6) Flutter speed obtained from piston theory and from quasi-steady second-order theory were higher than experimental values by at least 38 percent.
Subsonic and Supersonic Flutter Analysis of a Highly Tapered Swept-wing Planform, Including Effects of Density Variation and Finite Wing Thickness, and Comparison with Experiments
Author: E. Carson Yates (Jr.)
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 74
Book Description
The flutter characteristics of several wings with an aspect-ratio of 4.0, a taper ratio of 0.2, and a quarter-chord sweepback of 45 deg. have been investigated analytically for Mach numbers up to 2.0. The calculations were based on the modified-strip-analysis method, the subsonic-kernel-function method, piston theory, and quasi-steady second-order theory. Results of t h e analysis and comparisons with experiment indicated that: (1) Flutter speeds were accurately predicted by the modified strip analysis, although accuracy at t h e highest Mach numbers required the use of nonlinear aerodynamic theory (which accounts for effects of wing thickness) for the calculation of the aerodynamic parameters. (2) An abrupt increase of flutter-speed coefficient with increasing Mach number, observed experimentally in the transonic range, was also indicated by the modified strip analysis. (3) In the low supersonic range for some densities, a discontinuous variation of flutter frequency with Mach number was indicated by the modified strip analysis. An abrupt change of frequency appeared experimentally in the transonic range. (4) Differences in flutter-speed-coefficient levels obtained from tests at low supersonic Mach numbers in two wind tunnels were also predicted by the modified strip analysis and were shown to be caused primarily by differences in mass ratio. (5) Flutter speeds calculated by the subsonic-kernel-function method were in good agreement with experiment and with the results of the modified strip analysis. (6) Flutter speed obtained from piston theory and from quasi-steady second-order theory were higher than experimental values by at least 38 percent.
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 74
Book Description
The flutter characteristics of several wings with an aspect-ratio of 4.0, a taper ratio of 0.2, and a quarter-chord sweepback of 45 deg. have been investigated analytically for Mach numbers up to 2.0. The calculations were based on the modified-strip-analysis method, the subsonic-kernel-function method, piston theory, and quasi-steady second-order theory. Results of t h e analysis and comparisons with experiment indicated that: (1) Flutter speeds were accurately predicted by the modified strip analysis, although accuracy at t h e highest Mach numbers required the use of nonlinear aerodynamic theory (which accounts for effects of wing thickness) for the calculation of the aerodynamic parameters. (2) An abrupt increase of flutter-speed coefficient with increasing Mach number, observed experimentally in the transonic range, was also indicated by the modified strip analysis. (3) In the low supersonic range for some densities, a discontinuous variation of flutter frequency with Mach number was indicated by the modified strip analysis. An abrupt change of frequency appeared experimentally in the transonic range. (4) Differences in flutter-speed-coefficient levels obtained from tests at low supersonic Mach numbers in two wind tunnels were also predicted by the modified strip analysis and were shown to be caused primarily by differences in mass ratio. (5) Flutter speeds calculated by the subsonic-kernel-function method were in good agreement with experiment and with the results of the modified strip analysis. (6) Flutter speed obtained from piston theory and from quasi-steady second-order theory were higher than experimental values by at least 38 percent.
NASA Technical Note
Experimental and Analytical Investigation of the Flutter of Flat Built-up Panels Under Streamwise Inplane Load
Author: Robert W. Hess
Publisher:
ISBN:
Category : Damping (Mechanics)
Languages : en
Pages : 98
Book Description
The flutter of 13 panels subject to streamwise inplane load at Mach numbers of 1.57 and 1.96 has been investigated. Panel length-width ratios ranged from 1 to 4.2. The experimental flutter boundary was compared with an analytical flutter boundary for six of the panels. Damping, both aerodynamic and structural, was found to have a pronounced effect on the analytical flutter boundary. The agreement between analysis and experiment was dependent upon how structural damping was introduced in the formulation of the problem.
Publisher:
ISBN:
Category : Damping (Mechanics)
Languages : en
Pages : 98
Book Description
The flutter of 13 panels subject to streamwise inplane load at Mach numbers of 1.57 and 1.96 has been investigated. Panel length-width ratios ranged from 1 to 4.2. The experimental flutter boundary was compared with an analytical flutter boundary for six of the panels. Damping, both aerodynamic and structural, was found to have a pronounced effect on the analytical flutter boundary. The agreement between analysis and experiment was dependent upon how structural damping was introduced in the formulation of the problem.
Flutter Studies to Determine Nacelle Aerodynamic Effects on a Fan-jet Transport Model for Two Mount Systems and Two Wind Tunnels
Author: Moses G. Farmer
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 44
Book Description
Low-speed flutter studies of a dynamically and elastically scaled model of a large multijet transport airplane have been conducted primarily to determine the nacelle aerodynamic effects for high-bypass-ratio fan-jet engines. Data were obtained on a vertical rod mount in two wind tunnels and on a two-cable mount in one of the tunnels. The flutter response of the model was found to be dependent on nacelle aerodynamics, engine-pylon stiffness, mount-system-wind-tunnel configuration, and mass ratio.
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 44
Book Description
Low-speed flutter studies of a dynamically and elastically scaled model of a large multijet transport airplane have been conducted primarily to determine the nacelle aerodynamic effects for high-bypass-ratio fan-jet engines. Data were obtained on a vertical rod mount in two wind tunnels and on a two-cable mount in one of the tunnels. The flutter response of the model was found to be dependent on nacelle aerodynamics, engine-pylon stiffness, mount-system-wind-tunnel configuration, and mass ratio.
Comparative Evaluation of Methods for Predicting Flutter and Divergence of Unswept Wings of Finite Span
Author: Edward Carson Yates
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 62
Book Description
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 62
Book Description
Scientific and Technical Aerospace Reports
NASA Technical Memorandum
A Selected Listing of NASA Scientific and Technical Reports for ...
Monthly Catalog of United States Government Publications
Author: United States. Superintendent of Documents
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages :
Book Description
February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages :
Book Description
February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index