Motion Effects on Leading-Edge Vortex Behavior Over Delta Wings and Generalized Modeling

Effects of static attitude and three different motions on vortex behavior and its breakdown over delta wings have been investigated. These motions include 1) harmonic oscillation or ramp-and-hold motion in roll at constant resultant angle of attack, 2) harmonic oscillation or ramp-and-hold in pitch and 3) coning at constant resultant angle of attack A basic 65° delta wing configuration was tested in two wind tunnels as well as in a water tunnel. A roll rig, pitch rig and coning rig (OPLEC) were employed for the investigation. Quite different flow characteristics have been found within the spiral vortex breakdown region even under steady conditions. The point where vortex breaks down into large scale turbulence has a very long response time to perturbations and is the major cause for the dramatic time dependence observed in the airloads. In addition, bi-stable vortex breakdown locations are observed in the case of slender delta wings when breakdown is located close to the trailing edge. Under dynamic conditions, the behavior of the vortex and its breakdown region have been found to be highly dependent on motion waveform and reduced angular rates An analytical model based on the Nonlinear Indicial Response Method and a formulation suggested by Tobak et al, and capable of reflecting the above effects is proposed to predict breakdown location under dynamic conditions. SYMBOLS b wing span c0 wing root chord D vortex core diameter s local semi-span U∞ freestream velocity XVB chordwise vortex breakdown location xVB non-dimensional vortex breakdown location c XVB = α angle of attack α non-dimensional pitch rate ∞ ω = U c β sideslip angle δ deviation Paper presented at the RTO AVT Symposium on “Advanced Flow Management: Part A – Vortex Flows and High Angle of Attack for Military Vehicles”, held in Loen, Norway, 7-11 May 2001, and published in RTO-MP-069(I). Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 00 MAR 2003 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Motion Effects on Leading-Edge Vortex Behavior Over Delta Wings and Generalized Modeling 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) NATO, Research and Technology Organisation, BP 25, 7 rue Ancelle, F-92201 Neuilly-Sur-Seine Cedex, France 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release, distribution unlimited 13. SUPPLEMENTARY NOTES Also see: ADM001490, The original document contains color images. 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 22 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18