The role of shock induced trailing-edge separation in limit cycle oscillations

Author:: Cunningham, Atlee M., Jr.
Published:: Feb 1, 1989.
Physical Description:: 1 electronic document

Online Version

hdl.handle.net , Connect to this object online.

Availability

Finding items...

Restrictions on Access:

Unclassified, Unlimited, Publicly available.
Free-to-read Unrestricted online access

Summary:

The potential role of shock induced trailing edge separation (SITES) in limit cycle oscillations (LCO) was established. It was shown that the flip-flop characteristics of transition to and from SITES as well as its hysteresis could couple with wing modes with torsional motion and low damping. This connection led to the formulation of a very simple nonlinear math model using the linear equations of motion with a nonlinear step forcing function with hysteresis. A finite difference solution with time was developed and calculations were made for the F-111 TACT were used to determine the step forcing function due to SITES transition. Since no data were available for the hysteresis, a parameter study was conducted allowing the hysteresis effect to vary. Very small hysteresis effects, which were within expected bounds, were required to obtain reasonable response levels that essentially agreed with flight test results. Also in agreement with wind tunnel tests, LCO calculations for the 1/6 scale F-111 model showed that the model should have not experienced LCO.

Other Subject(s):

AERODYNAMICS

Collection:

NASA Technical Reports Server (NTRS) Collection.

Note:

Document ID: 19890009885.
Accession ID: 89N19256.
NASA, Langley Research Center, Transonic Unsteady Aerodynamics and Aeroelasticity 1987, Part 2; p 449-462.

Terms of Use and Reproduction:

No Copyright.

View MARC record | catkey: 15691554