Wing-body Configuration Research Articles

Turbulent boundary layer separation control using plasma actuator at Reynolds number 2000000

An experimental investigation was conducted to evaluate the effect of symmetrical plasma actuators on turbulent boundary layer separation control at high Reynolds number. Compared with the traditional control method of plasma actuator, the whole test model was made of aluminum and acted as a covered electrode of the symmetrical plasma actuator. The experimental study of plasma actuators’ effect on surrounding air, a canonical zero-pressure gradient turbulent boundary, was carried out using particle image velocimetry (PIV) and laser Doppler velocimetry (LDV) in the 0.75m×0.75m low speed wind tunnel to reveal the symmetrical plasma actuator characterization in an external flow. A half model of wing-body configuration was experimentally investigated in the ∅ 3.2m low speed wind tunnel with a six-component strain gauge balance and PIV. The results show that the turbulent boundary layer separation of wing can be obviously suppressed and the maximum lift coefficient is improved at high Reynolds number with the symmetrical plasma actuator. It turns out that the maximum lift coefficient increased by approximately 8.98% and the stall angle of attack was delayed by approximately 2° at Reynolds number 2×106. The effective mechanism for the turbulent separation control by the symmetrical plasma actuators is to induce the vortex near the wing surface which could create the relatively large-scale disturbance and promote momentum mixing between low speed flow and main flow regions.

Experimental Investigation on Limit Cycle Wing Rock Effect on Wing Body Configuration Induced by Forebody Vortices

The purpose of this paper is to present the aerodynamic and flow characteristics of a slender body with a 30° swept wing configuration undergoing a limit cycle oscillation using a synchronous measurement and control technique of wing rock/particle image velocimetry/dynamic pressure associated with the time history of the wing rock motion. The experimental investigation was concentrated on 3 main areas: motion characteristics, static and dynamic surface pressures and static and dynamic particle image velocimetry. The tests’ results revealed that the lag in asymmetric twin vortices over the forebody switching from the left vortice pattern to the right one exhibits a hysteresis evolvement during the wing rock motion; the asymmetric triple vortices over the forebody interacted with the flowfield over wings appeared to induce the instability and damping moments. The main flow phenomena responsible for wing rock of wing body configuration were completely determined by the forebody vortices. These exhibit apparent dynamic hysteresis in vertical position, which further influences the wing flows, and the dynamic hysteresis of flows yields the damping moments sustaining the oscillations.

Numerical Study on Transitional Flows Using a Correlation-Based Transition Model

A correlation-based transition model is assessed against distinct test cases. The configurations include a zero-pressure-gradient flat plate, a single-element aeronautical airfoil, a multielement high-lift airfoil and a wing–body configuration. These test cases are selected in order to cover different transition mechanisms in increasingly complex scenarios. The simulations are performed considering the compressible preconditioned Reynolds-averaged Navier–Stokes equations, which are one of the options offered by the CFD++ finite volume solver. Turbulence closure is achieved with the shear-stress transport model. This turbulence model is augmented by a transition model based on two additional transport equations: one for the intermittency, and another for the momentum-thickness Reynolds number. Flow parameters, such as freestream turbulence intensity and turbulence length scale, or the eddy viscosity ratio, have important effects on transition onset and extension of the transition region. Mesh refinement and dependence are numerical parameters investigated in this work. The dimensionless wall distance has a significant impact in the computational results. The transition model is also very sensitive to the inflow boundary conditions for the turbulence variables, namely, the freestream turbulence intensity and the eddy viscosity ratio. Good agreement with the experimental data is observed.

Experimental study of transonic buffet phenomenon on a 3D swept wing

The objective of this paper is to analyze the 3D buffet phenomenon which appears on a swept wing at a high Mach number and/or high angle of attack. This aerodynamic instability induces strong wall pressure fluctuations and as such limits aircraft envelope. Consequently, it is interesting to understand this phenomenon in order to not only improve aircraft performance but also to provide more flexibility during the design phase. Results from two wind tunnel tests on a 3D half wing-body configuration are presented for several freestream Mach numbers (0.78–0.86) and Reynolds numbers (2.83 × 106–8.49 × 106, based on the aerodynamic mean chord). The buffet phenomenon is characterized using steady and unsteady wall pressure measurements. By opposition to the 2D buffet which exhibits rather a well marked peak in the pressure spectra, the 3D buffet is characterized by a broadband bump at a much higher Strouhal number (between 4 and 7 times higher). It is also observed that two different instabilities coexist on the suction side of the wing: the 3D buffet phenomenon (with Strouhal numbers ranging between 0.2 and 0.6) and the Kelvin-Helmholtz instability (with Strouhal numbers ranging between 1 and 4). Each phenomenon has a different Strouhal number but also different convection velocities and propagation directions.

Multidisciplinary Approach to Assessing Actuation Power of a Hybrid Wing–Body

Hybrid wing–body configurations, such as the N2A-EXTE, have the potential to meet NASA Environmentally Responsible Aviation goals. These configurations have redundant elevons typically spanning the entire trailing edge of the wing, for which the large areas result in the generation of large hinge moments. To ensure aircraft stability with a reduced static margin, high control surface deflection rates may also be required. The combination of large actuation loads and rates results in significant actuation power requirements, which affect both fuel burn and the sizing of the actuation subsystem. In the early design phases, there is significant uncertainty regarding the magnitude of the actuation power, which may depend on the vehicle’s static margin, the design and designated roles of the redundant control surfaces, actuator design parameters, and the intensity of encountered atmospheric turbulence. The objective of this paper is to present a methodical approach for assessing this uncertainty and relating it to aspects of the vehicle and actuation system design. Doing so will facilitate decision-making in early vehicle design. Following the sizing and optimization of electric actuators to meet the actuation requirements of the N2A-EXTE hybrid wing–body configuration’s control surfaces, the power consumption of these actuators was evaluated in cruise conditions under the following scenarios: 1) varying atmospheric turbulence, 2) varying vehicle center of gravity, 3) varying control surface utilization, and 4) varying actuator design parameters.

DLR natural and hybrid transonic laminar wing design incorporating new methodologies

AbstractIn the present work natural laminar flow (NLF) and hybrid laminar flow (HLF) wing designs are presented which were obtained by combining new methodologies with experience and knowledge obtained with traditional laminar wing design methods. The NLF wing design is performed for wing-body configurations with backward swept wing (BSW) and forward swept wing (FSW). Initial aerofoil sections were obtained by using a new sectional conical wing method which allows the design of transonic wing sections, taking into account the effects of sweep and taper for the computational cost of a 2D method. Except for flow regions with strong 3D influence, wings constructed with these aerofoils showed an acceptably large region with laminar boundary layer and small shocks at design and specified off-design conditions. For regions close to the body and the tip a 3D inverse design method was further required. For the BSW case, due to cross flow a premature transition occurred. Therefore, a HLF panel was required to obtain a larger laminar region. A suction distribution was obtained using the suction distribution module of the automated target pressure generator (ATPG). This generator optimises the pressure distributions in terms of minimising drag while keeping certain boundary conditions constant, e.g. lift and momentum. Using the ATPG, the laminar extent of the BSW NLF design could be further improved for the inboard wing. With the new methodologies design work was reduced. They lead to a design with reserves that allow for acceptable off-design performance qualities by keeping the wing laminar over a wide range of flight conditions.

Efficient Multiobjective Optimization of Amphibious Aircraft Fuselage Steps with Decoupled Hydrodynamic and Aerodynamic Analysis Models

AbstractThis paper proposes an efficient framework for multiobjective optimization of the fuselage step on a large amphibious aircraft using a combination of computational aerodynamic and hydrodynamic methods. Both cruise drag and water take-off resistance and distance are calculated to evaluate the effects of the two key parameters, the longitudinal location and the depth of the step. A Reynolds-averaged Navier-Stokes (RANS) model was used for the calculation of cruise drag of the wing body configuration. Water take-off resistance and distance required for the baseline configuration were calculated using a volume of fluid method for hydrodynamic calculation and RANS method for aerodynamic calculation, respectively. A drag breakdown method was adopted to improve the efficiency of the hydraulic calculations. The method can achieve an accuracy of less than 5% difference compared to fully viscous calculations with only half of the computational time. The optimization is achieved using a combination of design...

Aerodynamic Shape Optimization of Common Research Model Wing–Body–Tail Configuration

Wing shape is one of the main drivers of aircraft aerodynamic performance, so most aerodynamic shape optimization efforts have focused solely on the wing. However, the performance of the full aircraft configuration must account for the fact that the aircraft needs to be trimmed. Thus, to realize the full benefit of aerodynamic shape optimization, one should optimize the wing shape while including the full configuration and a trim constraint. To evaluate the benefit of this approach, we perform the aerodynamic shape optimization of the Common Research Model wing–body–tail configuration using gradient-based optimization with a Reynolds-averaged Navier–Stokes model that includes a discrete adjoint implementation. We investigate the aerodynamic shape optimization of the wing with a trim constraint that is satisfied by rotating the horizontal tail. We then optimize the same wing–body configuration without the tail but with an added trim drag penalty based on a surrogate model we created before the optimization. The drag coefficient is minimized subject to lift and trim constraints. We found that considering the trim during optimization is a better approach than using a fixed-wing moment constraint. We also show that the trim drag surrogate model we created yields a minimum drag coefficient that is within 1.2 counts of the minimum drag coefficient obtained by rotating the tail to satisfy the trim constraint. However, we recommend rotating the tail within the optimization process to obtain the best possible performance.

Optimal trajectory and heat load analysis of different shape lifting reentry vehicles for medium range application

Abstract The objective of the paper is to compute the optimal burn-out conditions and control requirements that would result in maximum down-range/cross-range performance of a waverider type hypersonic boost-glide (HBG) vehicle within the medium and intermediate ranges, and compare its performance with the performances of wing-body and lifting-body vehicles vis-a-vis the g-load and the integrated heat load experienced by vehicles for the medium-sized launch vehicle under study. Trajectory optimization studies were carried out by considering the heat rate and dynamic pressure constraints. The trajectory optimization problem is modeled as a nonlinear, multiphase, constraint optimal control problem and is solved using a hp-adaptive pseudospectral method. Detail modeling aspects of mass, aerodynamics and aerothermodynamics for the launch and glide vehicles have been discussed. It was found that the optimal burn-out angles for waverider and wing-body configurations are approximately 5° and 14.8°, respectively, for maximum down-range performance under the constraint heat rate environment. The down-range and cross-range performance of HBG waverider configuration is nearly 1.3 and 2 times that of wing-body configuration respectively. The integrated heat load experienced by the HBG waverider was found to be approximately an order of magnitude higher than that of a lifting-body configuration and 5 times that of a wing-body configuration. The footprints and corresponding heat loads and control requirements for the three types of glide vehicles are discussed for the medium range launch vehicle under consideration.

Performance Assessment of a Transonic Wing–Body Configuration with Riblets Installed

The effectiveness of the riblets, one of the most interesting drag-reduction device, is discussed in this paper. Numerical simulations by the Reynolds-averaged Navier–Stokes equations with the riblets properly taken into account are presented. Riblets are modeled as a singular roughness problem by modifying the classical Wilcox boundary condition for rough walls. The boundary condition is able to predict the flow features in the low roughness range (transitional roughness) where riblets operate. A brief discussion of the simulations performed to validate the model is first presented. Then, a complex wing–body configuration is analyzed, and the overall effect of riblets on the aerodynamic coefficients is evaluated. Calculations of a complete aircraft configuration at transonic conditions show how a proper optimized choice of the riblet height can significantly improve the drag reduction.

Numerical Analysis of Flow Over the NASA Common Research Model Using the Academic Computational Fluid Dynamics Code Galatea

A recently developed academic computational fluid dynamics (CFD) code, named Galatea, is used for the computational study of fully turbulent flow over the NASA common research model (CRM) in a wing-body configuration with and without horizontal tail. A brief description of code's methodology is included, while attention is mainly directed toward the accurate and efficient prediction of pressure distribution on wings' surfaces as well as of computation of lift and drag forces against different angles of attack, using an h-refinement approach and a parallel agglomeration multigrid scheme. The obtained numerical results compare close with both the experimental wind tunnel data and those of reference solvers.

Exergy-Based Performance Assessment of a Blended Wing–Body with Boundary-Layer Ingestion

Aircraft have evolved into extremely complex systems that require adapted methodologies and tools for efficient design processes. A theoretical formulation based on exergy management is proposed for assessing the aerothermopropulsive performance of future aircraft configurations. The theoretical formulation has been numerically implemented in a FORTRAN code to postprocess Reynolds-averaged Navier–Stokes flow solutions. First, the exergy formulation is presented, and then the approach is applied to assess the performance of a simplified (two-dimensional) blended wing–body configuration with boundary-layer ingestion. The challenge of applying conventional drag/thrust bookkeeping is discussed, and the pertinence of the formulation is thereby reinforced. It is shown that this architecture wastes very little exergy in its wake/jet by exhibiting an exergy-waste coefficient lower than 3% in steady flight. Finally, heat transfer upstream of the propulsion system is found to yield an approximate 1.5% fuel saving. Overall, the benefit of the single-currency aspect of the exergy analysis is highlighted.

Method for Evaluating Electrically Actuated Hybrid Wing–Body Control Surface Layouts

Hybrid wing–body configurations are currently an active field of research as potential candidates to meet NASA Environmentally Responsible Aviation goals. One characteristic of these configurations is the presence of a large number of redundant flight control surfaces. However, the design process and decision rationale for a given control surface layout is rarely discussed in the open literature. This work investigated tradeoffs between drag, control authority, actuator weight, and actuation power requirements as a function of the number and spacing of elevons. The actuators were sized based on hinge moments computed during nominal and failed control flight conditions. These effects were propagated upward to estimate changes to fuel burn, a system-level metric important to the Environmentally Responsible Aviation program, via the Breguet range equation. A model of the NASA N2A-EXTE hybrid wing–body configuration concept was used to demonstrate these tradeoffs. The study concluded that adjacent elevons could be combined to achieve reductions in weight, power usage, and fuel burn. This resulted in a reduced number of elevons from the baseline and unequal span fractions.

Efficient aero-structural design optimization: Coupling based on reverse iteration of structural model

Traditional coupled multi-disciplinary design optimization based on computational fluid dynamics/computational structure dynamics (CFD/CSD) aims to optimize the jig shape of aircraft, and general multi-disciplinary design optimization methodology is adopted. No special consideration is given to the aircraft itself during the optimization. The main drawback of these methodologies is the huge expanse and the low efficiency. To solve this problem, we put forward to optimize the cruise shape directly based on the fact that the cruise shape can be transformed into jig shape, and a methodology named reverse iteration of structural model (RISM) is proposed to get the aero-structural performance of cruise shape. The main advantage of RISM is that the efficiency can be improved by at least four times compared with loosely-coupled aeroelastic analysis and it maintains almost the same fidelity of loosely-coupled aeroelastic analysis. An optimization framework based on RISM is proposed. The aerodynamic and structural performances can be optimized simultaneously in this framework, so it may lead to the true optimal solution. The aerodynamic performance was predicted by N-S solver in this paper. Test shows that RISM predicts the aerodynamic and structural performances very well. A wing-body configuration was optimized by the proposed optimization framework. The drag and weight of the aircraft are decreased after optimization, which shows the effectiveness of the proposed framework.

Auralization of Hybrid Wing–Body Aircraft Flyover Noise from System Noise Predictions

System noise assessments of a state-of-the-art reference aircraft (similar to a Boeing 777-200ER with GE90-like turbofan engines) and several hybrid wing–body aircraft configurations were recently performed using NASA engine and aircraft system analysis tools. The hybrid wing–body aircraft were sized to an equivalent mission as the reference aircraft and assessments were performed using measurements of airframe shielding from a series of propulsion airframe aeroacoustic experiments. The focus of this work is to auralize flyover noise from the reference aircraft and the best hybrid wing–body configuration using source noise predictions and shielding data based largely on the earlier assessments. Here, auralization refers to the process by which numerical predictions are converted into audible pressure time histories. It entails synthesis of the source noise and propagation of that noise to a receiver on the ground. For each aircraft, three flyover conditions are auralized. These correspond to approach, sideline, and cutback operating states, but flown in straight and level flight trajectories. The auralizations are performed using synthesis and simulation tools developed at NASA. Audio and visual presentations are provided to allow the reader to experience the flyover from the perspective of a listener in the simulated environment.

Airframe integration for an LH2 hybrid-electric propulsion system

Purpose – The purpose of this paper is to explore some of the challenges associated with the integration of an LH2-fuelled advanced hybrid-electric distributed propulsion system with the airframe. The airframe chosen as a case study is an ultra-high-capacity blended wing body configuration. It is designed to represent an A-380 class vehicle but in the 2025-2030 timeframe. The distributed propulsion system is a hybrid-electric concept that utilizes high-temperature superconducting technologies. The focus of the study is the application of LH2 as a fuel, with comment being given to kerosene and LCH4. Design/methodology/approach – The study consists of a conceptual design developed through the preliminary design phase and part way into the detailed design phase. Findings – The relationship between passenger capacity and fuel capacity is developed. Some remaining challenges are identified. Practical implications – The study supports further conceptual design studies and more detailed system studies. Social im...

Enriched Basis Functions for Handling Wake–Body Intersections in Dirichlet Panel Methods

The theory and an implementation of enriched basis functions in Dirichlet (source-doublet) panel methods to simplify the geometric constraints of wake–body intersections is presented. In the approach, a discontinuous basis function is introduced to represent the jump in surface scalar velocity potential at the intersection of a wake sheet and a network of body panels. By introducing this set of enriched basis functions to represent discontinuous potentials, the method can easily handle intrapanel discontinuities while maintaining a scalar-potential-only Dirichlet formulation. As a result, discretized geometries from CAD and computational-fluid-dynamics tools may be used in the resulting enriched basis Dirichlet panel method without modification. A simple spherical geometry, a well-documented wing–body configuration as well as a generic wing–body configuration are presented.

Analysis of the Common Research Model Using Structured and Unstructured Meshes

Two general-purpose Reynolds-averaged Navier–Stokes flow solvers, OVERFLOW and BCFD, are used to analyze the NASA Common Research Model in a wing–body configuration. The codes are run on structured and unstructured common-grid families built specifically for the Fifth AIAA CFD Drag Prediction Workshop, allowing for a meaningful comparison of data. The results from a grid-convergence study are evaluated for each solver and grid type with focus on isolating individual effects of turbulence model and differencing scheme on computed forces, moments, and wing pressures. A medium mesh consisting of 5.1 million cells is used for a buffet-onset study to better understand variations in high-speed wing-separation prediction driven by the strengthening shock and by corner-flow physics at the wing–body juncture. Numerical simulation of side-of-body separation continues to be a challenge for Reynolds-averaged Navier–Stokes methods, in which solutions are sensitive to grid density and turbulence model, among other variables. However, a newly developed quadratic constitutive relation is employed with favorable results. Two additional studies are conducted to 1) investigate how well common-grid solutions compare with those on a grid built using best practices for a given flow solver, and 2) quantify the effects of transition and wing twist to provide insight on how the comparisons of computational fluid dynamics results with experimental data may be influenced.

Turbulence Model Study for the Flow Around the NASA Common Research Model

A turbulence model study was performed for the wing–body configuration of NASA’s common research model on common hybrid grids provided by the Fifth Drag Prediction Workshop Committee and on an in-house-generated hybrid grid. Here, eddy-viscosity models with and without quadratic constitution relation extension, which accounts for the anisotropy of normal turbulent stresses, and a differential Reynolds stress model were applied. In this paper, first, the influence of turbulence models on the prediction of side-of-body separation in the wing–body region and on the overall aerodynamic force and moment coefficients is discussed, and later, the influence of grid refinement on the predictions is presented. Finally, the effect of the quadratic constitution relation extension on the predictions of eddy-viscosity models is demonstrated and performance of different turbulence models is discussed by comparing numerical predictions with the experimental data from NASA’s National Transonic Facility.

Aerodynamic design optimization by using a continuous adjoint method

This paper presents the fundamentals of a continuous adjoint method and the applications of this method to the aerodynamic design optimization of both external and internal flows. General formulation of the continuous adjoint equations and the corresponding boundary conditions are derived. With the adjoint method, the complete gradient information needed in the design optimization can be obtained by solving the governing flow equations and the corresponding adjoint equations only once for each cost function, regardless of the number of design parameters. An inverse design of airfoil is firstly performed to study the accuracy of the adjoint gradient and the effectiveness of the adjoint method as an inverse design method. Then the method is used to perform a series of single and multiple point design optimization problems involving the drag reduction of airfoil, wing, and wing-body configuration, and the aerodynamic performance improvement of turbine and compressor blade rows. The results demonstrate that the continuous adjoint method can efficiently and significantly improve the aerodynamic performance of the design in a shape optimization problem.