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STRUCTURAL ANALYSIS OF AN EQUIVALENT BOX-WING REPRESENTATION OF SENSORCRAFT JOINED-WING CONFIGURATION FOR HIGH-ALTITUDE, LONG-ENDURANCE (HALE) AIRCRAFT

MARISARLA, SOUJANYA
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1116215297

Abstract Details

2005, MS, University of Cincinnati, Engineering : Mechanical Engineering.
The current research focuses on studying the modal response of a joined wing aircraft based on the Sensorcraft configuration. Sensorcraft, a class of High-Altitude, Long-Endurance (HALE) aircraft, is an Unmanned Air Vehicle (UAV), and is being studied by the AFRL for applications involving telecommunication relay, environmental sensing and military reconnaissance. The Sensorcraft is designed to operate at high altitudes (60,000 ft) with low speed and for long durations of time (60 to 80 hours). At these operating conditions, the density, and hence, the Reynolds number, is low. These conditions require the Sensorcraft to operate with high lift and low drag with high-aspect ratio wings. Moreover, the vehicle must be lightweight and strong, and offer high aerodynamic performance and efficiency. The AFRL has identified a diamond shape joined wing configuration for Sensorcraft due to the primary structural advantage of strength as each wing braces the other against lift loads.The University of Cincinnati (UC), along with its partners, AFRL and Ohio State University are working together to study the complete nonlinear aeroelastic behavior of the joined-wing model. At UC, four different structural modeling approaches were adopted for analysis. The current research focuses on the analysis of an in-house Sensorcraft joined wing model developed by the AFRL. This model is an equivalent representation of the actual 3-D joined wing model. The wing is idealized as a box structure consisting of shells, rods, beams, shear panels and concentrated masses. This box wing structure has the advantage of being computationally inexpensive over the full 3-D model, and has been optimized to minimize the deflections of the antennae equipment in the control surface of the wing. The fluid loads applied on the box-wing structure are obtained from a concurrent aerodynamic analysis for different mach numbers and angles of attack performed at UC.A modal representation is obtained for different operating boundary conditions as the first step in the overall aeroelastic analysis of the joined wing. AFRL has obtained the modal representation for the Sensorcraft model using NASTRAN, and as part of the DAGSI project requirement, the structural analyses at UC are performed using ANSYS. The results are compared with those from NASTRAN and the correctness of the methodology is verified. Prior to the NASTRAN box-wing model translation into ANSYS, a number of validation tests are performed to test the consistency between the functionalities of the ANSYS elements and NASTRAN elements. Once the results of the validation test cases are found to be satisfactory, the actual analysis of the joined wing is performed for clamped, rigid and symmetry boundary conditions at the wing roots. The frequencies were found to be different between the two codes for each of these boundary conditions. In order to trace the issue causing the differences in the results, a number of simpler joined wing models are analyzed. Finally, the problem is traced down to differences in the formulation between the constraint equations in ANSYS and RBE1 elements in NASTRAN.Due to the assumption of small deflections, linear static analysis is performed and considered sufficient for predicting the displacement response. However, a nonlinear analysis is also performed to validate the assumptions of linearity that have been used in the modeling of the wing. The tip deflection from linear is estimated to be 5.3 % of the span of the wing. For higher angles of attack, the pressure difference between the upper and lower surfaces of the wing is higher, and consequently the lift forces are greater in magnitude. This could cause larger deformation in the main wing that could potentially lead to buckling of the aft wing. Hence, an eigenvalue buckling analysis is performed which show that the wing is stable and not prone to buckling for the loads employed for the linear static analysis. A procedure is also established to determine the structural response under time varying aerodynamic loads from the CFD analysis. This analysis serves as a starting point for future complete aeroelastic analysis of the joined wing.
Dr. Urmila Ghia (Advisor)
154 p.
Engineering, Mechanical
Finite Element Analysis; Structural Analysis; Modal Analysis; Box-Wing; Joined-Wing

Recommended Citations

Citations

  • MARISARLA, S. (2005). STRUCTURAL ANALYSIS OF AN EQUIVALENT BOX-WING REPRESENTATION OF SENSORCRAFT JOINED-WING CONFIGURATION FOR HIGH-ALTITUDE, LONG-ENDURANCE (HALE) AIRCRAFT [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1116215297

    APA Style (7th edition)

  • MARISARLA, SOUJANYA. STRUCTURAL ANALYSIS OF AN EQUIVALENT BOX-WING REPRESENTATION OF SENSORCRAFT JOINED-WING CONFIGURATION FOR HIGH-ALTITUDE, LONG-ENDURANCE (HALE) AIRCRAFT. 2005. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1116215297.

    MLA Style (8th edition)

  • MARISARLA, SOUJANYA. "STRUCTURAL ANALYSIS OF AN EQUIVALENT BOX-WING REPRESENTATION OF SENSORCRAFT JOINED-WING CONFIGURATION FOR HIGH-ALTITUDE, LONG-ENDURANCE (HALE) AIRCRAFT." Master's thesis, University of Cincinnati, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1116215297

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Cincinnati and OhioLINK.