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Future tactical aircraft will likely remove the vertical tail to leverage the benefits to efficiency and weight. Many species of birds control their flight without a vertical surface by rotating their tails. This work details an a...
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Future tactical aircraft will likely remove the vertical tail to leverage the benefits to efficiency and weight. Many species of birds control their flight without a vertical surface by rotating their tails. This work details an analysis on a bio-inspired rotating empennage (BIRE) control system that operates similarly to a bird's tail. An aerodynamic model is presented for the baseline fighter aircraft and a variant of the aircraft employing the BIRE control system. To analyze the trade-off between longitudinal and lateral control in static trim, we analyzed two trim scenarios for each aircraft: the steady, coordinated turn and steady-heading sideslip. These trim conditions were analyzed at several flight conditions that were identified to be important in a fighter aircraft flight envelope. Our analysis shows that the BIRE control system is able to replicate the trim capabilities of the baseline aircraft, though sharp changes in control surface deflections were required to trim the aircraft with the center of gravity at its nominal position. This could prove to be significant when designing a control system to provide stability to the BIRE variant through active damping. The BIRE was shown to have a chance of tail strike in certain landing scenarios when landing in steady-heading sideslip. An analysis of the dynamic behavior and control of the BIRE variant will be required before final conclusions on the possibility of tail strike can be drawn.
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This work explores the effects of a Bio-Inspired Rotating Empennage (BIRE) on the static and dynamic stability and handling qualities of a fighter aircraft. The BIRE-modified aircraft does not have a vertical tail, and is instead ...
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This work explores the effects of a Bio-Inspired Rotating Empennage (BIRE) on the static and dynamic stability and handling qualities of a fighter aircraft. The BIRE-modified aircraft does not have a vertical tail, and is instead capable of rotating the horizontal tail about the body x-axis for maneuvering. The dynamic characteristics of the BIRE-modified aircraft are compared to a baseline unmodified aircraft, similar to the F16, with a traditional vertical tail in the linear aerodynamic range below stall. Linearized aerodynamic models for each aircraft, based on previous work, are used alongside a set of coupled dynamic equations of motion for asymmetric aircraft, derived in this work, to estimate the dynamic response of each aircraft to disturbances from steady level and banked trim conditions. The static stability analysis suggests that modifying the baseline with a BIRE decreases the aircraft's static pitch, roll and yaw stability. The dynamic stability analysis suggests that modifying the baseline aircraft with a BIRE; 1) slightly decreases the aircraft's short period damping and slightly increases the aircraft's short period frequency, 2) decreases the aircraft's phugoid damping and slightly increases the aircraft's phugoid frequency, 3) slightly increases the aircraft's roll damping, 4) decreases the aircraft's spiral damping for steady level flight and increases the aircraft's spiral damping sensitivity to center of gravity location when banked, and 5) produces a non-traditional dutch roll mode. The handling quality analysis suggests that modifying the baseline aircraft with a BIRE has a negligible effect on the aircraft's short period, phugoid, roll, and spiral handling quality levels, but decreases the aircraft's dutch roll handling quality levels.
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Some aspects of the development of a modern, unstructured, subsonic-supersonic panel method are presented. Linear panel methods have been successfully applied to supersonic flow in the past. However, renewed interest in low-order ...
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Some aspects of the development of a modern, unstructured, subsonic-supersonic panel method are presented. Linear panel methods have been successfully applied to supersonic flow in the past. However, renewed interest in low-order methods calls for revisiting supersonic panel methods and assessing how they may take advantage of modern computing power and algorithms. Various methods for distributing surface singularities, calculating influence coefficients, and enforcing boundary conditions are explored and derived. A novel method for recursively determining domains of dependence in linearized supersonic flow is also presented. As part of the current research effort, a pilot code, called TriPan, is being developed which implements multiple formulations for incompressible flow using linear doublets and constant sources. Certain details of TriPan, such as wake modeling and pressure calculation, are shared. Results from TriPan compared to experimental and analytic results are also shared.
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摘要 :
Some aspects of the development of a modern, unstructured, subsonic-supersonic panel method are presented. Linear panel methods have been successfully applied to supersonic flow in the past. However, renewed interest in low-order ...
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Some aspects of the development of a modern, unstructured, subsonic-supersonic panel method are presented. Linear panel methods have been successfully applied to supersonic flow in the past. However, renewed interest in low-order methods calls for revisiting supersonic panel methods and assessing how they may take advantage of modern computing power and algorithms. Various methods for distributing surface singularities, calculating influence coefficients, and enforcing boundary conditions are explored and derived. A novel method for recursively determining domains of dependence in linearized supersonic flow is also presented. As part of the current research effort, a pilot code, called TriPan, is being developed which implements multiple formulations for incompressible flow using linear doublets and constant sources. Certain details of TriPan, such as wake modeling and pressure calculation, are shared. Results from TriPan compared to experimental and analytic results are also shared.
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Aircraft mass and inertial properties are required for predicting the dynamics and handling qualities of aircraft. However, such properties can be difficult to estimate since these depend on the external shape and internal structu...
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Aircraft mass and inertial properties are required for predicting the dynamics and handling qualities of aircraft. However, such properties can be difficult to estimate since these depend on the external shape and internal structure, systems, and mass distributions within the airframe. Mass and inertial properties of aircraft are often predicted using computer-aided design software, or measured using various experimental techniques. The present paper presents a method for quickly predicting the mass and inertial properties of complete aircraft consisting of components of constant density. Although the assumption of constant density may appear limiting, the method presented in this paper can be used to approximate mass properties of complex internal structures. Inertial estimates for rectangular cuboids, cylinders, spheres, wing segments, and rotors are presented here. The influence of geometric properties of wing segments such as sweep, taper, airfoil geometry, and dihedral are included. The utility of the method is presented and the accuracy is evaluated with various test cases.
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To meet the growing need for fast and accurate supersonic flow solutions, we present the implementation of a subsonic-supersonic, unstructured panel method. Novel results of this work include a source-free, Dirichlet boundary cond...
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To meet the growing need for fast and accurate supersonic flow solutions, we present the implementation of a subsonic-supersonic, unstructured panel method. Novel results of this work include a source-free, Dirichlet boundary condition formulation, a streamlined approach to domain of dependence calculation on unstructured meshes, and some aspects of automatic supersonic wake modeling. We also present a complete method for calculating subsonic and supersonic influence coefficients. We examine the numerical behavior of the method and find it robust with respect to control point placement, mesh refinement, and mesh regularity. We also show the method is highly accurate for small-perturbation flows when compared to analytic results.
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Active wing shaping, or morphing, of an aircraft wing has the potential to substantially improve aircraft efficiency. In recent years, several studies have sought to quantify the efficiency improvements possible through active win...
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Active wing shaping, or morphing, of an aircraft wing has the potential to substantially improve aircraft efficiency. In recent years, several studies have sought to quantify the efficiency improvements possible through active wing shaping, but relatively few have considered how it may affect the optimum flight-path trajectory. In this paper, we seek to characterize the fuel savings from active wing shaping over an approximate optimum flight trajectory. To accomplish this, we present a simple direct trajectory optimization framework that can be used to rapidly perform a large number of trajectory optimizations to explore the design space of aircraft employing active wing shaping controls and identify how wing shaping may affect the total aircraft fuel consumption. Example solutions are presented for the approximate optimal flight-path trajectory and fuel consumption of the NASA Ikhana high-endurance UAV configuration and the NASA Common Research Model configuration. Results indicate that the use of active wing-shaping controls for load alleviation can result in up to around 8% fuel savings over an optimized baseline design operating along the optimized trajectory. It is also shown that active wing shaping tends to favor optimal trajectories with lower velocity, higher lift coefficient, and higher lift-to-drag ratio than the baseline design.
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The elliptic lift distribution produces the minimum induced drag for a given wingspan and desired lift outside of ground effect. This distribution can be generated on any wing by using geometric and/or aerodynamic twist. However, ...
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The elliptic lift distribution produces the minimum induced drag for a given wingspan and desired lift outside of ground effect. This distribution can be generated on any wing by using geometric and/or aerodynamic twist. However, in ground effect, the elliptic lift distribution is not necessarily that which minimizes induced drag. The present work uses a modern numerical lifting-line algorithm to evaluate how the optimum lift distribution varies as a function of height above ground for a rectangular wing. The results of this work can be used to reduce takeoff distances on morphing wings or wings that can actively change twist or camber during flight. It was found that ground effect alters the lift and induced drag distribution on a rectangular wing. In ground effect, the lift is shifted inboard while the induced drag is shifted outboard. Optimally twisting the wing in ground effect significantly reduces the induced drag compared to the untwisted wing. However, the twist distribution found to achieve this minimum induced drag was nearly identical to the twist distribution needed to achieve an elliptic lift distribution for a rectangular wing, except when the wing is extremely close to the ground.
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Parabolic flaps exhibit promising aerodynamic improvements over traditional flaps and are being considered on modern morphing aircraft. While the ideal aerodynamics of parabolic flaps has been studied in the past, this work examin...
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Parabolic flaps exhibit promising aerodynamic improvements over traditional flaps and are being considered on modern morphing aircraft. While the ideal aerodynamics of parabolic flaps has been studied in the past, this work examines the viscous phenomena associated with the parabolic flap deflection, including trailing edge separation and drag. Experimental tests using load cell and particle image velocimetry (PIV) along with numerical analysis using CFD RANS and XFOIL performed on a NACA 0015 airfoil with parabolic flaps are presented with a discussion on the flowfield physics. Proper Orthogonal Decomposition (POD) analyses are performed on the various test models to compare the dominant flow structures in each case. Aerodynamic coefficient results are compared to those of traditional articulated flaps and a means of condensing and smoothing the aerodynamic coefficient data is presented.
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摘要 :
Parabolic flaps exhibit promising aerodynamic improvements over traditional flaps and are being considered on modern morphing aircraft. While the ideal aerodynamics of parabolic flaps has been studied in the past, this work examin...
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Parabolic flaps exhibit promising aerodynamic improvements over traditional flaps and are being considered on modern morphing aircraft. While the ideal aerodynamics of parabolic flaps has been studied in the past, this work examines the viscous phenomena associated with the parabolic flap deflection, including trailing edge separation and drag. Experimental tests using load cell and particle image velocimetry (PIV) along with numerical analysis using CFD RANS and XFOIL performed on a NACA 0015 airfoil with parabolic flaps are presented with a discussion on the flowfield physics. Proper Orthogonal Decomposition (POD) analyses are performed on the various test models to compare the dominant flow structures in each case. Aerodynamic coefficient results are compared to those of traditional articulated flaps and a means of condensing and smoothing the aerodynamic coefficient data is presented.
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