Showing papers in "Journal of Aircraft in 2014"

Multipoint High-Fidelity Aerostructural Optimization of a Transport Aircraft Configuration

Abstract: This paper presents multipoint high-fidelity aerostructural optimizations of a long-range wide-body transonic transport aircraft configuration. The aerostructural analysis employs Euler computational fluid dynamics with a 2-million-cell mesh and a structural finite-element model with 300,000 degrees of freedom. The coupled adjoint sensitivity method is used to efficiently compute gradients, enabling the use of gradient-based optimization with respect to hundreds of aerodynamic shape and structural sizing variables. The NASA Common Research Model is used as the baseline configuration, together with a wing box structure that was designed for this study. Two design optimization problems are solved: one where takeoff gross weight is minimized, and another where fuel burn is minimized. Each optimization uses a multipoint formulation with five cruise conditions and two maneuver conditions. Each of the optimization problems have 476 design variables, including wing planform, airfoil shape, and structural thickne...

Aerodynamic Design Optimization Studies of a Blended-Wing-Body Aircraft

Abstract: The blended wing body is an aircraft configuration that has the potential to be more efficient than conventional large transport aircraft configurations with the same capability. However, the design of the blended wing is challenging due to the tight coupling between aerodynamic performance, trim, and stability. Other design challenges include the nature and number of the design variables involved, and the transonic flow conditions. To address these issues, a series of aerodynamic shape optimization studies using Reynolds-averaged Navier–Stokes computational fluid dynamics with a Spalart–Allmaras turbulence model is performed. A gradient-based optimization algorithm is used in conjunction with a discrete adjoint method that computes the derivatives of the aerodynamic forces. A total of 273 design variables—twist, airfoil shape, sweep, chord, and span—are considered. The drag coefficient at the cruise condition is minimized subject to lift, trim, static margin, and center plane bending moment constraints. ...

Experimental Investigation of the NASA Common Research Model

Abstract: An experimental aerodynamic investigation of the NASA Common Research Model has been conducted in the NASA NTF (National Transonic Facility). Data have been obtained at chord Reynolds numbers of 5, 19.8 and 30 million for the WB and WBT0 configurations. Data have also been obtained at a chord Reynolds number of 5 million for the WBNP, WBT+2 and WBT-2 configurations. Force and moment, surface pressure and surface flow visualization data were obtained but only the force and moment data are presented herein. Model deformation measurements, aeroelastic, nacelle/pylon Reynolds number and tail effects have been assessed. The model deformation measurements showed more twist as you go out the wing span, with a break in the high q(sub infinity) data close to CL = 0.6 which is consistent with separation near the tip. Increases in dynamic pressure give an increase in pitching moment and drag and a decrease in lift for the WB and WBT0 configuration at Mach = 0.7, 0.85 and 0.87. The addition of a nacelle/pylon gave an increase in drag, decrease in lift and a less nose down pitching moment around the design lift condition of 0.5. Increases in chord Reynolds number have been found to follow the normal Reynolds number trends except at the 19.8 million low q(sub infinity) cases. The abnormality of the 19.8 million low q(sub infinity) cases is being investigated. The tail effects also follow the expected trends. All of the data shown fall within the 2-sigma limits for repeatability.

Summary of Data from the Fifth Computational Fluid Dynamics Drag Prediction Workshop

Abstract: Results from the Fifth AIAA Computational Fluid Dynamics Drag Prediction Workshop are presented. As with past workshops, numerical calculations are performed using industry-relevant geometry, methodology, and test cases. This workshop focused on force/moment predictions for the NASA Common Research Model wing-body configuration, including a grid refinement study and an optional buffet study. The grid refinement study used a common grid sequence derived from a multiblock topology structured grid. Six levels of refinement were created, resulting in grids ranging from 0.64×106 to 138×106 hexahedra, a much larger range than is typically seen. The grids were then transformed into structured overset and hexahedral, prismatic, tetrahedral, and hybrid unstructured formats all using the same basic cloud of points. This unique collection of grids was designed to isolate the effects of grid type and solution algorithm by using identical point distributions. This study showed reduced scatter and standard deviation fr...

Development of Variable Camber Morphing Airfoil Using Corrugated Structure

Abstract: This paper describes the development and the wind tunnel test of a variable geometry morphing airfoil using corrugated structures. Proof-of-concept study of a morphing wing with corrugated flexible seamless flap-like structure is verified by finite element analysis, and a prototype is manufactured using carbon fiber reinforced plastics. For the actuation system, two servomotors are installed inside the prototype wing to control the airfoil shape by the chordwise tension of the connected wires. Successful actuation of the prototype wing is demonstrated under the air speed up to 30 m/s in the wind tunnel test. Basic aerodynamic properties are also evaluated in comparison to traditional airfoil with a hinged control surface. Lift increase of variable corrugated wing is recognized compared to the traditional wing when the aileron angle increases.

Reexamined Structural Design Procedures for Very Flexible Aircraft

Abstract: This paper reviews the applicability of some conventional structural design practices to the analysis and design of very flexible aircraft. The effect of large structural deformations and the coupling between aeroelasticity and flight dynamics is investigated in different aspects of the aircraft structural design process, including aeroelastic stability, loads, and flight dynamics and control. This is illustrated with a numerical example of the static and dynamic responses of a representative high-altitude long-endurance vehicle. Suggestions are presented for the development of appropriate frameworks to design and analyze very flexible aircraft.

Summary of the Fourth AIAA Computational Fluid Dynamics Drag Prediction Workshop

Abstract: Results from the Fourth AIAA Drag Prediction Workshop are summarized. The workshop focused on the prediction of both absolute and differential drag levels for wing–body and wing–body/horizontal-tail configurations of the NASA Common Research Model, which is representative of transonic transport aircraft. Numerical calculations are performed using industry-relevant test cases that include lift-specific flight conditions, trimmed drag polars, downwash variations, drag rises, and Reynolds-number effects. Drag, lift, and pitching moment predictions from numerous Reynolds-averaged Navier–Stokes computational fluid dynamics methods are presented. Solutions are performed on structured, unstructured, and hybrid grid systems. The structured-grid sets include point-matched multiblock meshes and overset grid systems. The unstructured and hybrid grid sets comprise tetrahedral, pyramid, prismatic, and hexahedral elements. Effort is made to provide a high-quality and parametrically consistent family of grids for each g...

Helicopter Rotor Design Using a Time-Spectral and Adjoint-Based Method

Abstract: A time-spectral and adjoint-based optimization method was developed and applied to helicopter rotor design for unsteady level flight. The time-spectral method is a fast and accurate computational fluid dynamics algorithm for computing unsteady flows. It transforms the flow-governing equations into a periodic steady state by using a Fourier spectral derivative operator. An accompanying steady-state adjoint formulation was implemented in the time-spectral form of the governing equations to enable design optimization for unsteady flows. The time-spectral analysis was validated against conventional time-accurate computational fluid dynamics computation and flight test data of a UH-60A helicopter rotor during high-speed forward flight. A multidisciplinary analysis of blade structural dynamics was carried out through a comprehensive analysis coupling procedure that accounted for aeroelasticity and enforced vehicle trim. The adjoint-based design method was applied to optimize the blade shape of the UH-60A rotor....

Aircraft Design with Active Load Alleviation and Natural Laminar Flow

Abstract: Maneuver load alleviation, gust load alleviation, and natural laminar flow are integrated into aircraft conceptual design. The concurrent design of the aircraft and its active load alleviation systems can yield significant gains. The simultaneous application of maneuver load alleviation and gust load alleviation to a short-haul aircraft leads to an 11% reduction in fuel burn and 7% reduction in direct operating cost. These savings are diminished if maneuver load alleviation and gust load alleviation are applied independently. The synergy between active load control and natural laminar flow is also explored. It is possible to invest some of the weight savings from load alleviation to achieve extensive laminar flow. The combination of load alleviation and natural laminar flow increases the fuel and cost savings to upwards of 18 and 11%, respectively. It is concluded that load alleviation can shift the transonic transport optimum toward low-sweep, natural laminar flow wings. Sensitivity studies finally demon...

Sonic Boom Mitigation Through Aircraft Design and Adjoint Methodology

Abstract: This paper presents a novel approach to design of the supersonic aircraft outer mold line (OML) by optimizing the A-weighted loudness of sonic boom signature predicted on the ground. The optimization process uses the sensitivity information obtained by coupling the discrete adjoint formulations for the augmented Burgers Equation and Computational Fluid Dynamics (CFD) equations. This coupled formulation links the loudness of the ground boom signature to the aircraft geometry thus allowing efficient shape optimization for the purpose of minimizing the impact of loudness. The accuracy of the adjoint-based sensitivities is verified against sensitivities obtained using an independent complex-variable approach. The adjoint based optimization methodology is applied to a configuration previously optimized using alternative state of the art optimization methods and produces additional loudness reduction. The results of the optimizations are reported and discussed.

Computational and Experimental Analysis of a High-Performance Airfoil Under Low-Reynolds-Number Flow Condition

Abstract: A high-performance Ishii airfoil was analyzed using both a wind-tunnel and large-eddy simulations at a low-Reynolds-number condition (Re=23,000). The design guidelines for an airfoil shape with a high lift-to-drag ratio under the aforementioned condition are described by analyses of flowfields and aerodynamic characteristics of the Ishii airfoil. Compared with conventional airfoils, such as the NACA 0012 and NACA 0002, the shape characteristic effects of the Ishii airfoil on its flowfield and aerodynamic characteristics are discussed. The shape on the suction side of the Ishii airfoil can cause delays in the flow separation at low angle of attacks. The separated flow reattaches, and a separation bubble forms even when trailing-edge separation changes to leading-edge separation. The separation bubble contributes to an increase in lift coefficient. In addition, the Ishii airfoil can gain a high positive pressure on the pressure side as compared with the other two symmetric airfoils due to the camber near th...

Comparisons of Theoretical Methods for Predicting Airfoil Aerodynamic Characteristics

Abstract: A number of airfoils have been tested in the Pennsylvania State University low-speed low-turbulence wind tunnel, and the results of these tests are compared with those predicted using several well-known theoretical methods. The theoretical methods used are the potential-flow/integral boundary-layer methods XFOIL 6.96 and PROFIL07 and the Reynolds-averaged Navier–Stokes solver OVERFLOW 2.2e. This version of the OVERFLOW solver contains an implementation of the transitional shear-stress transport turbulence model developed by Langtry and Menter (“Correlation-Based Transition Modeling for Unstructured Parallelized Computational Fluid Dynamics Codes,” AIAA Journal, Vol. 47, No. 12, 2009, pp. 2894–2906). This model is capable of capturing the influence of transition on the flowfield through a local-correlation method. The airfoils considered for this study are the E 387, S805, PSU 94-097, HTR1555, S903, and S824. Although none of the theoretical methods considered were consistently the best overall, all codes ...

Numerical Study of Helicopter Rotors in a Ship Airwake

Abstract: Operating helicopters in a naval environment is challenging because it imposes a pilot workload significantly higher than that during land-based operations. The aerodynamic interaction between the aircraft and the ship wake is known to play an important role in increasing the pilot workload, hence reducing the aircraft capability as a result of maintaining safety. As a further step toward numerical prediction of ship/helicopter operational limitations, computational-fluid-dynamics simulations are conducted for the Canadian Patrol Frigate. The effect of the rotor is included in the simulation, first using an actuator-disc method together with steady calculations, then using rotor blades and the unsteady Reynolds-averaged Navier–Stokes equations. Results using the actuator-disc method demonstrate the importance of coupling effects on the wake and rotor inflow when the rotor is operating close to the ship and therefore the invalidity of superposition methods. The case of a Sea King helicopter main rotor hove...

Aeroelastic Topology Optimization of Blade-Stiffened Panels

Abstract: Metallic blade-stiffened panels are optimized for various eigenvalue metrics of interest to the aerospace community. This is done via solid isotropic material with penalization-based topology optimization: the stiffeners are discretized into finite elements, and each element is assigned a design variable, which may vary from 0 (void) to 1 (solid). A known issue with eigenvalue-based optimization is discontinuities due to mode switching, which may be avoided through a series of eigenvalue separation constraints, or (more challenging, but less restrictive) a bound method with mode tracking. Both methods are demonstrated to obtain optimal stiffener topologies for panel buckling, but only the former is used for aeroelastic panel-flutter problems. Satisfactory flutter optimal results are obtained, but the work concludes with a discussion of the challenges associated with the use of a bound method for aeroelastic problems, with specific complications posed by the advent of hump modes.

Summary of the 2008 NASA Fundamental Aeronautics Program Sonic Boom Prediction Workshop

Abstract: The Supersonics Project of the NASA Fundamental Aeronautics Program organized an internal sonic boom workshop to evaluate near-field sonic-boom prediction capability at the Fundamental Aeronautics Annual Meeting in Atlanta, Georgia, on 8 October 2008. Workshop participants computed sonic-boom signatures for three nonlifting bodies and two lifting configurations. Cone–cylinder, parabolic, and quartic bodies of revolution comprised the nonlifting cases. The lifting configurations were a simple 69 deg delta-wing–body and a complete low-boom transport configuration designed during the High Speed Research Project in the 1990s with wing, body, tail, nacelle, and boundary-layer diverter components. The AIRPLANE, Cart3D, FUN3D, and USM3D flow solvers were employed with the ANET signature propagation tool, output-based adaptation, and a priori adaptation based on freestream Mach number and angle of attack. Results were presented orally at the workshop. This article documents the workshop and results and provides c...

Uncertainty Propagation in Hypersonic Aerothermoelastic Analysis

Abstract: This study sets the framework for uncertainty propagation in hypersonic aeroelastic and aerothermoelastic stability analyses. First, the aeroelastic stability of typical hypersonic control surface section is considered. Variability in the uncoupled natural frequencies of the system are modeled using beta probability distributions. Uncertainty is propagated to the

Quasi-Three-Dimensional Aerodynamic Solver for Multidisciplinary Design Optimization of Lifting Surfaces

Abstract: This paper presents the development of a quasi-three-dimensional aerodynamic solver, which provides accurate results for wing drag comparable to the higher-fidelity aerodynamic solvers at significantly lower computational costs. The proposed solver calculates the viscous wing drag using the combination of a two-dimensional airfoil analysis tool with a vortex lattice code. Validation results show that the results of the quasi-three-dimensional solver are in good agreement with higher-fidelity computational fluid dynamics solvers. The quasi-three-dimensional solver is used for a wing shape multidisciplinary design optimization. A multidisciplinary design optimization problem is formulated to design the wing shape of a typical passenger aircraft. The aircraft maximum takeoff weight is considered as the objective function. Two optimization algorithms, a local and a global optimum finder, are implemented in the multidisciplinary design optimization system. The optimization results indicate that the global opti...

Design and Analysis of a Droop Nose for Coanda Flap Applications

Abstract: The present study describes the fundamentals of droop nose design for improving the aerodynamics of airfoils with active high-lift using an internally blown Coanda-type flap. The main objectives are to increase the stall angle of attack and reduce the power required by the high-lift system. A two-dimensional sensitivity analysis explores the effects of varying airfoil camber and thickness in the first 20% of the chord. The resulting droop nose configuration improves the maximum lift coefficient by about 20% and increases the stall angle of attack by around 10–15 deg. A target lift coefficient of about 4.7 is reached with 28% less jet momentum coefficient, compared to the clean nose. As the modified leading-edge geometry presents different stall mechanisms, the aerodynamic response to variations of jet momentum is also different. In particular, for a jet momentum coefficient above 0.035, the stall angle of attack increases with jet momentum, in contrast with the behavior observed with the clean nose.

Real-Time Flight Simulation of Highly Maneuverable Unmanned Aerial Vehicles

Abstract: This paper focuses on full six degree-of-freedom aerodynamic modeling of small unmanned aerial vehicles at high angles of attack and high sideslip in maneuvers performed using large control surfaces at large deflections for aircraft with high thrust-to-weight ratios. Configurations, such as this, include many of the currently available propeller-driven radio-controlled model airplanes that have control surfaces as large as 50% chord, deflections as high as 50 deg, and thrust-to-weight ratios near 2∶1. Airplanes with these capabilities are extremely maneuverable and aerobatic, and modeling their aerodynamic behavior requires new thinking because using traditional stability-derivative methods is not practical with highly nonlinear aerodynamic behavior and coupling in the presence of high prop-wash effects. The method described outlines a component-based approach capable of modeling these extremely maneuverable small unmanned aerial vehicles in a full six degree-of-freedom real-time environment over the full...

Reduced-Order Modeling of Unsteady Aerodynamics Across Multiple Mach Regimes

Abstract: A reduced-order model for unsteady aerodynamic calculations across a range of Mach regimes based on linear convolution and a nonlinear correction factor is developed. Separate investigations are conducted for the sub-, trans-, and supersonic Mach regimes, and overall good results are seen when reduced-order model results are compared with full-order computational-fluid-dynamics solutions, though the reduced-order model errors tend to decrease as the Mach number increases. To assist reduced-order model construction, the method-of-segments simplified model has been created and tested throughout these same Mach regimes. Finally, a practical example of the reduced-order model’s applicability is presented by following a single test case from subsonic up through supersonic flight.

CFL3D, FUN3d, and NSU3D Contributions to the Fifth Drag Prediction Workshop

Abstract: Results presented at the Fifth Drag Prediction Workshop using CFL3D, FUN3D, and NSU3D are described These are calculations on the workshop-provided grids and drag-adapted grids The NSU3D results have been updated to reflect an improvement to skin-friction calculation on skewed grids FUN3D results generated after the workshop are included for custom participant-generated grids, as well as a grid from a previous workshop Uniform grid refinement at the design condition shows a tight grouping in calculated drag, where the variation in the pressure component of drag is larger than the skin-friction component At this design condition, a fine-grid drag value was predicted with a smaller drag adjoint adapted grid via tetrahedral adaption to a metric and mixed-element subdivision The buffet study produced a larger variation than the design case, which is attributed to large differences in the predicted side-of-body separation extent Various modeling and discretization approaches had a strong impact on predi

Aircraft Robust Trajectory Optimization Using Nonintrusive Polynomial Chaos

Abstract: The development of algorithms for aircraft robust dynamic optimization considering uncertainties (for example, trajectory optimization) is relatively limited compared to aircraft robust static optimization (for example, configuration shape optimization). In this paper, an approach for dynamic optimization considering uncertainties is developed and applied to robust aircraft trajectory optimization. In the present approach, the nonintrusive polynomial chaos expansion scheme is employed to convert a robust trajectory optimization problem with stochastic ordinary differential equations into an equivalent deterministic trajectory optimization problem with deterministic ordinary differential equations. Two computational strategies for trajectory optimization considering uncertainties are compared. The performance of the developed method is studied by considering a classical deterministic trajectory optimization problem of supersonic aircraft short-time climb with uncertainties in the aerodynamic data. Detailed...

Inverse Design of Low-Boom Supersonic Concepts Using Reversed Equivalent-Area Targets

Abstract: A promising path for developing a low-boom configuration is a multifidelity approach that (1) starts from a low-fidelity low-boom design, (2) refines the low-fidelity design with computational fluid dynamics (CFD) equivalent-area (Ae) analysis, and (3) improves the design with sonic-boom analysis by using CFD off-body pressure distributions. The focus of this paper is on the third step of this approach, in which the design is improved with sonic-boom analysis through the use of CFD calculations. A new inverse design process for off-body pressure tailoring is formulated and demonstrated with a low-boom supersonic configuration that was developed by using the mixed-fidelity design method with CFD Ae analysis. The new inverse design process uses the reverse propagation of the pressure distribution (dp/p) from a mid-field location to a near-field location, converts the near-field dp/p into an equivalent-area distribution, generates a low-boom target for the reversed equivalent area (Ae,r) of the configuration, and modifies the configuration to minimize the differences between the configuration s Ae,r and the low-boom target. The new inverse design process is used to modify a supersonic demonstrator concept for a cruise Mach number of 1.6 and a cruise weight of 30,000 lb. The modified configuration has a fully shaped ground signature that has a perceived loudness (PLdB) value of 78.5, while the original configuration has a partially shaped aft signature with a PLdB of 82.3.

Investigation of Aeroelastic Effects on the NASA Common Research Model

Abstract: Static fluid-structure coupled simulations were performed on NASA’s Common Research Model to assess the influence of aeroelastic effects on the numerical prediction of the overall aerodynamic coefficients and wing static pressure distributions. The numerical results of both rigid steady-state computational fluid dynamics and static aeroelastic coupled simulations were compared to the experimental data from wind tunnel test campaigns at NASA’s National Transonic Facility and the NASA Ames Research Center’s 11-Foot Transonic Wind Tunnel Facility. Coupled analyses were performed using an in-house simulation procedure built around the German Aerospace Research Center’s flow solver TAU and the commercial finite element analysis code NASTRAN®. The results show a considerable reduction of deviations between the computational results obtained during the fourth and fifth AIAA Computational Fluid Dynamics Drag Prediction Workshops and the measured data when aeroelastic wing deformations are taken into account.

DLR Results from the Third AIAA Computational Fluid Dynamics Drag Prediction Workshop

Abstract: A summary about the DLR, German Aerospace Center results from the fourth AIAA Computational Fluid Dynamics Drag Prediction Workshop is presented. Compared to the investigations in the previous three workshops, the latest workshop had a stronger focus on drag and trim drag predictions as well as pitching moment calculations. Therefore, the new Common Research Model developed by NASA’s Subsonic Fixed Wing Aerodynamics Technical Working Group and tested in NASA wind tunnels is used. It represents a state-of-the-art transonic transport aircraft configuration, and in contrast to the configurations previously taken, it includes an optional horizontal tailplane with three different tail settings. DLR has defined three objectives for its activities in the fourth drag prediction workshop. At first, investigations should identify solution accuracy and grid convergence behavior using prismatic element dominant grids for boundary-layer resolution in comparison to hexahedral element dominant grids. Second, the influen...

Aircraft Route Optimization for Formation Flight

Abstract: We quantify the fuel and cost benefits of applying extended formation flight to commercial airline operations. Central to this study is the development of a bi-level, mixed-integer real formation flight optimization framework. The framework has two main components: 1) a continuous-domain aircraft mission performance optimization and 2) an integer optimization component that selects the best combination of optimized missions to form a formation flight schedule. The mission performance reflects the effects of rolled-up wakes, formation heterogeneity, and formation-induced compressibility. The results show that an airline can use formation flight to reduce fuel burn by 5.8% or direct operating cost by 2.0% in a long-haul international schedule. The savings increase to 7.7% in fuel or 2.6% in cost for a large-scale, transatlantic airline alliance schedule. These results include the effects of a conservative fuel reserve for formation flight. Sensitivity studies show that a modest reduction in the cruise Mach ...

Numerical Study of Aerodynamics of a Wing-in-Ground-Effect Craft

Abstract: The flow around a wing-in-ground-effect craft flying at α=3 deg and α=9 deg over flat and wavy ground is simulated and investigated by using ANSYS FLUENT, employing the compressible Reynolds-averaged Navier–Stokes equations and the Spalart–Allmaras turbulence model. The sliding mesh technology is used to simulate the relative motion between the wing-in-ground-effect craft and wavy ground. The effects of the wavy ground, flight height, and angle of attack on the aerodynamic characteristics and flowfield are analyzed in detail. The aerodynamic forces are found to be periodic when the wing-in-ground-effect craft flies over wavy ground. The aerodynamic forces over both flat and wavy ground vary with flight height in the same pattern. As the flight height reduces, the lift, drag, and nose-down pitching moment all increase at both angles of attack (α=3 deg and α=9 deg); however, the lift-to-drag ratio increases for all flight heights at α=3 deg, while it first increases and then decreases at α=9 deg. Redu...

Receptance-Based Active Aeroelastic Control Using Multiple Control Surfaces

Abstract: Design of next generation aircraft/sensorcraft for improved performance, such as gust load alleviation towards aircraft stability and flutter suppression during its flight operation, may necessitate wing technology that can be controlled and manipulated by active means. Moreover, in recent years the efforts are underway to realize “Fly by Feel” concepts, which are aimed in utilizing on-board sensors (embedded) and actuators (control surfaces) of the aircraft towards the design of active control system for desired performance. This paper presents active control strategies for wings having multiple control surfaces, which are purely based upon in-flight receptance (measured) data. The proposed receptance based control approach has several advantages over the traditional state-space based control because it circumvents approximation errors in reduced order modeling; it captures the true interaction between structure and aerodynamic loads; and it requires modest size of matrices (depending upon the available number of sensors and actuators) for control gain computations. In this study, multi-input state and output feedback control strategies for active aeroelastic control using the method of receptances is developed. The control gains are computed for the extension of flutter boundaries via pole placement. At first, by using numerical receptances obtained from the aeroelastic model of a flexible wing having multiple control surfaces, the proposed methodology is demonstrated. In order to test and demonstrate the receptance method for more complex aircraft geometries, configurations and aerodynamic loading conditions, numerical receptances from Finite Element models of aircraft wings with multiple control surfaces were extracted for the proposed control design. Presented studies and control approach may become the basis for optimal placement and sizing of control surfaces in a given wing section for active aeroelactic control and enhanced flight performance.

Aerodynamic Installation Effects of an Over-the-Wing Propeller on a High-Lift Configuration

Abstract: Preliminary design studies indicate that a cruise-efficient short takeoff and landing aircraft has enhanced takeoff performance at competitive direct operating costs when using high-speed propellers in combination with internally blown flaps. The original tractor configuration is compared to an over-the-wing propeller, which allows for noise shielding. An additional geometry with partially embedded rotor similar to a channel wing is considered to increase the beneficial interaction. This paper shows the aerodynamic integration effects with a focus on climb performance and provides an assessment of the three aforementioned configurations for a simplified wing segment at takeoff conditions. Steady Reynolds-averaged Navier–Stokes simulations have been conducted using an actuator disk model and were evaluated based on the overall design. Interacting with the blown flap, the conventional tractor propeller induces large lift and drag increments due to the vectored sliptream. Although this effect is much smaller...

Minimum-Fuel Ascent of a Hypersonic Vehicle Using Surrogate Optimization

Abstract: A general strategy is identified to compute the minimum fuel required for the ascent of a generic hypersonic vehicle that is propelled by a dual-mode ramjet–scramjet engine with hydrogen fuel. The study addresses the ascent of an accelerator vehicle rather than a high-speed cruiser. Two general types of ascent trajectories are considered: acceleration within scramjet mode, and acceleration across the ramjet–scramjet transition boundary maximum acceleration and maximum dynamic pressure (lowest allowed altitude) were shown to be near optimum for scramjet-mode trajectories, but optimized trajectories were found to be more complex when both modes are considered. The first-principles model used in this paper computes the combustion efficiency using finite-rate chemistry and a fuel–air mixing model. It also computes the inlet efficiency with a shock wave interaction code, and thus avoids empirical formulas for efficiency that were used in previous models.