Browse Topic: Fairings
The payload fairing of a launch vehicle is subjected to extremely high acoustic loads, with peak levels occurring during lift-off and transonic aerodynamic regimes. The external acoustic field penetrates the fairing, producing intense internal sound pressure levels that can challenge the integrity of spacecraft components. Accurate characterization of the vibroacoustic behavior of the payload fairing and its enclosed cavity is therefore essential to ensure spacecraft survivability. The internal acoustic field is governed by the coupled dynamics of the fairing structure and the spacecraft configuration, making it critical to quantify the acoustic environment for different payload arrangements. This study presents a detailed vibroacoustic analysis of a payload fairing with multiple spacecraft configurations to evaluate the resulting internal sound pressure distribution. Vibroacoustic finite element analysis is employed in the low frequency range, while statistical energy analysis is utilized for mid and high frequency ranges. Representative models are developed, and the predicted structural and acoustic responses are validated against experimental acoustic test measurements. The validated models are subsequently extended to other spacecraft configurations to perform sensitivity studies. The influence of various parameters on the internal sound pressure levels is assessed, and the resulting perturbations across frequency bands are quantified. The outcome of this study provides a comprehensive understanding of the internal acoustic environment within payload fairing, aiding in the specification of qualification acoustic test level for spacecraft.
The paper presents the successful drag reduction of the Racer demonstrator's rotor head through its innovative full fairing, based on a robust de-risking methodology leveraging 2D Robust Design Optimization (RDO) for airfoils, 3D CFD analysis with multiple fidelity levels, and experiments. We provide a unique end-to-end comparison across the full development cycle, correlating simulation predictions with both experimental and flight-test data. The fully faired architecture achieves a significant 42% reduction in rotor-hub form drag. At the full-vehicle level, flight tests confirm a 10% net drag reduction, including complex interactions with the airframe. This real-world measurement correlates highly with dynamic URANS predictions (11-12%), while effectively contextualizing the more optimistic 16% gains observed during static wind-tunnel and steady RANS evaluations. These findings provide a comprehensive validation of the low-drag fairing concept, offering valuable insights for the aerodynamic design of future high-speed rotorcraft.
This study investigates the use of the Overset mesh method for propeller simulations in OpenFOAM and compares it with the Arbitrary Mesh Interface (AMI) approach. While AMI is well validated for rotor aeroacoustics, it is limited in handling large relative motions and complex component interactions. In contrast, the Overset method enables flexible simulation of transition kinematics using overlapping grids, though its aeroacoustic capability in OpenFOAM has not been well established. A comparative analysis was conducted on a Joby-scale five-bladed propeller at an 80° tilt angle without a fairing, representing a transition-flight condition. Aerodynamic and acoustic predictions were obtained using hybrid DDES coupled with the Ffowcs Williams–Hawkings method. Results show that the Overset method provides improved agreement with experimental thrust and torque and captures stronger leading-edge vortices than AMI. Both methods resolve blade-vortex and blade-wake interactions. However, the Overset approach produces higher broadband noise due to stronger vortices and interpolation effects, while AMI yields smoother pressure fields and clearer tonal content. In the far field, AMI better matches experimental SPL trends. Overset shows larger first-BPF SPL errors (up to 22.5 dB vs. 5.7 dB for AMI), though OASPL differences remain small. Overall, Overset is less reliable for noise prediction and more computationally expensive.
This study presents computational analyses of coaxial rotor hub flows and validation against experimental data obtained from the fifth Rotor Hub Flow Prediction Workshop. Experiments were conducted in a 12-inch diameter water tunnel at Pennsylvania State Applied Research Laboratory, employing tomographic particle-image velocimetry (Tomo-PIV) and precise hub drag measurements. Three CFD codes (UMD Mercury, CREATETM-AV Helios, and OVERFLOW) utilizing hybrid Reynolds-Averaged Navier-Stokes (RANS) / Large Eddy Simulation (LES) modeling based on Spalart–Allmaras turbulence model, were applied to replicate and analyze hub flows. Counter-rotating coaxial rotor hubs under free-air condition was simulated as the simplest case and the hub drags are compared between the three CFD codes. The full water tunnel configuration, consisting of two hubs, a fairing, and shafts, was also simulated and compared to experimental results, with a focus on hub drag, wake velocity fields, and turbulence quantities. Results demonstrated that the computational frameworks effectively captured key flow physics, although some discrepancies in drag harmonics, wake velocity and turbulence intensity magnitudes were observed. Additionally, the study highlighted the impact of rotor hub geometry and installation of sail-fairing on drag and wake structures. These findings contribute to improve computational predictions, essential for designing high-speed rotor hub configurations.
A computational study is conducted on a coaxial rotor hub and sail fairing configuration to analyze hub surface forces and the characteristics of its downstream wake. The flow conditions and grids are based on experimental tests performed at the Penn State Applied Research Lab (ARL) Water Tunnel at a baseline Reynolds number. Grid development for the rotor hubs and sail fairing is done using Pointwise v18.04R1 and Chimera Grid Tools (version 2.2). Simulations are performed using NASA's OVERFLOW2.4b Reynolds Averaged Navier-Stokes solver. The drag forces on the rotor hubs are computed and compared to standalone drag data to analyze the effects of interactional aerodynamics. Flow features, frequency content and Reynolds stresses of the wake are analyzed. Frequency content and Reynolds stresses show clear spatial bias. The anisotropy of the Reynolds stresses is computed and used to determine the character of the wake turbulence.
The commercial vehicle development process needs to consider the vehicle aerodynamics not only in ideal flow conditions, but also in the turbulent real world environment. The turbulent real world environment includes not only atmospheric turbulence, but also the vehicle to vehicle interactions that happen when driving around other vehicles or into and out of the wake of in/on coming vehicles. A vehicle driving into the wake of an oncoming vehicle not only experiences an increase in the total aerodynamic forces, it also experiences unsteady transient loads over the vehicle components such as windshield, mirror, sunvisor, door and side fairing. To properly design specific components, designers need to understand the magnitude of unsteady forces on various vehicle components, otherwise these components may fail which imposes warranty and safety risks. In this paper, we attempt to understand the various forces acting on the primary vehicle during a passing maneuver. The main purpose is to understand the incremental unsteady forces acting on the major components such as windshield, side door, sunvisor and mirror. Result from this study shows, very large swings in side-force magnitude, which could lead to vehicle stability issues for empty trailers that are subjected to large forces acting on little inertial mass. Local forces on isolated components show very high frequency unsteady load that could lead to component fatigue and failure if these loading conditions are not incorporated as part of the vehicle component design.
Conventional high-lift systems allow transport aircraft to safely operate at low speeds for landing and takeoff. These high-lift devices, such as Fowler flaps, are complex, heavy, and have high part counts. Fowler flap mechanisms also protrude externally under the wings, requiring external fairings, which increase cruise drag. Simple-hinged flaps are less complex, and an ideal choice for low-drag cruise efficiency. However, simple-hinged flaps require high flap deflections to achieve lift comparable to Fowler flaps. These flap deflections cause severe adverse pressure gradients, which generate flow separation that is difficult to control. In response to these challenges, NASA developed the High Efficiency Low Power (HELP) active flow control (AFC) system.
A computational investigation of aerodynamic drag of coaxial rotor hubs is performed and compared with test data from a prior experiment. The counter-rotating coaxial hub model considered is based on a rotor design developed by AVX Aircraft Company. Component-level contributions to overall hub drag are quantified by building up the rotor from a bare shaft to complete hubs and control systems and measuring the drag as components are added. Fifteen total configurations are considered with CFD and compared to the experimental drag measurements of ten configurations from prior wind tunnel test data. The drag of each hub configuration is presented relative to a baseline configuration featuring the complete coaxial rotor hub and control system without the blade fairings. The CFD results and experimental data verify that the total hub drag is reduced by 25%-29% by incorporating the blade fairings. Nearly half of the remaining drag is from the mast and pitch links, while the blade grip contributes another 25% of the overall drag. The CFD results also show high level of interference drag (9.95%) which includes aerodynamic interference between mast/split plate, upper/lower swash plates, and swash plate/split plate.
The challenge of increasing range and speed of a rotorcraft is encountered in the scope of the European CleanSky2 "Fast Rotorcraft" project by Airbus Helicopters with the compound helicopter design RACER (RapidAndCostEfficientRotorcraft) for which the box wing and the tail parts designs are respectively protected by patent. This paper presents the DLR contributions to the RACER development. This includes the aerodynamic design of the wing and tail section as well as an overall assessment of performance and noise. In a first step the aerodynamic properties of the configuration are evaluated both isolated and with consideration of the main rotor and lateral rotor interferences by the use of actuator discs. In the second step, the investigated possibilities to improve the configurations performance are described. These include airfoil design for improved high lift performance of the wing and tail section, an optimization of the box wing circulation distribution on the upper and lower wing. Additionally, the intersection fairings were improved and the efficiency of the trim flaps was evaluated. In this regard, it could be determined for which cases an isolated approach is appropriate and when the rotor interference should be considered. At the end the evaluation of the aero acoustics of the configuration is conducted. The applied configuration shows good aerodynamic characteristics with some further cruise and off design optimization potential.
Fabrication and assembly of the majority of control surfaces for Boeing’s 777X airplane is completed at the Boeing Defense, Space and Security (BDS) site in St. Louis, Missouri. The former 777 airplane has been revamped to compete with affordability goals and contentious markets requiring cost-effective production technologies with high maturity and reliability. With tens of thousands of fasteners per shipset, the tasks of drilling, countersinking, hole inspection, and temporary fastener installation are automated. Additionally and wherever possible, blueprint fasteners are automatically installed. Initial production is supported by four (4) Electroimpact robotic systems embedded into a pulse-line production system requiring strategic processing and safeguarding solutions to manage several key layout, build and product flow constraints. Commonality amongst the robots was desired to allow each to effectively address any of the commodities which range from small fairings to very large empennage and leading edge assemblies that required the automation to work its way around from the upper to lower surface. Multi-function end effectors enable processes to be completed in one pass from initial hole preparation to installed fastener. Advanced safety systems are utilized which include programmable laser scanners on the robots and tooling that are automatically configured based on the present tooling. Operator access and part flow through the cell are paramount, driving the design of a flush floor rail system and the ability to operate robots in dual zones, further driving the requirement for flexible cell processing and safeguarding techniques.
NASA's Langley Research Center has designed a Multifunctional Boost Protective Cover (MBPC) for a Launch Abort System (LAS). In the event of a crewed launch, the innovation provides a redundant means of saving the crew, and for an unmanned launch, it provides the means for recovering a very expensive, sensitive, and/or dangerous payload. In addition, costs are reduced by minimizing insurance premiums and costly delays to fabricate new, complex satellite systems in the event of a failed launch. NASA is seeking development partners and potential licensees.
The effects of passive, active, and combined flow control on the aerodynamic performance of an unpowered, bladeless 1/5th scale model of the X2 Technology™ Demonstrator have been assessed through a variety of surface and off-body measurements in a low-speed wind tunnel test, Re = 88x10³ [1/ft] and M∞ = 0.13. The baseline model employs a state-of-the-art low-drag coaxial hub design. Further drag reduction was investigated through minor design alterations, endplates, vortex generators, steady blowing and suction, and oscillatory blowing. Each drag mitigation control approach was individually assessed. Flow control technologies that produced the most promising test results were combined for further augmented performance. Six-component external balance loads, independent hub and tail loads, and surface and wake flow and pressure measurements were used to determine aerodynamic performance and the detailed physics of the flow control attributes. The wind tunnel test showed that the addition of endplates provided vehicle drag reduction of 4%. Steady blowing from the rotor shaft fairing reduced drag 4% and the combination of endplates and blowing decreased drag 6-8%.
Many modern aircraft, including rotorcraft, require conformal antennas and fairings to reduce wind drag, ice accretion, lightning strikes, and impact damage. An innovative composite wing configuration with a structural Ultra High Frequency (UHF) antenna window "aperture" has been developed. The wing is based on variants of lightweight X-Cor® sandwich core technology for durability and damage tolerance, with tailored electromagnetic properties in the aperture region of the wing. This paper presents a brief introduction to helicopter wings, a summary of recent research at Boeing and Army leading to this design, and the development approach used for this project. Structural and electromagnetic analyses are provided, and measurement results of an early prototype are summarized. The emphasis of this paper is on the wing configuration details surrounding the antenna aperture. The approach can be replicated on almost any current or future aircraft or rotorcraft.
A sequence of scale model wind tunnel tests have been conducted to help design the S-97 RAIDER™ aircraft and better understand the aerodynamics of X2 Technology™ rotorcraft incorporating coaxial rigid lift offset rotors, low drag airframes, and a pusher propeller. The tests provided inputs to aerodynamics and flight dynamics simulations, validation data for CFD, and aerodynamic loads for design. The first test obtained high Reynolds number aerodynamic coefficients for airfoil families planned for the main rotor blades. A particular focus was on forward and reverse flow data for a thick single ended airfoil and a double-ended airfoil. A 1/10 scale unpowered airframe was then tested in the UTRC Pilot Wind Tunnel to obtain basic aerodynamic loads, plus flow interaction diagnostics on the fuselage, tail, and at the propeller plane. A hub and sail fairing drag test was conducted to obtain quantitative drag measurements on multiple fairing geometries, and to get insight into the effect of rotation, gaps, and the presence of blade stubs. A diagnostic test using a 1/5 scale model of the X2 Technology™ demonstrator investigated the aerodynamic interaction between the airframe and the propeller, and helped better understand the flight test data. The final tests were of a Mach-scale powered main rotor and fuselage in the National Full Scale Aerodynamics Facility 40x80' test section. The two entries included airframe-only, airframe plus upper rotor, and airframe plus coaxial rotor. The powered model results discussed in this paper will concentrate on the interactions between the main rotor, fuselage, and empennage.
Vehicle performance is highly dependent on the design and material used. Fairing of a Human Powered Vehicle (HPV) is responsible for the reduction in the aerodynamic drag force and its material determines the overall weight and the top speed of the vehicle. Selection of material for fairings depends on various physical, mechanical and manufacturing properties along with practical considerations like availability of material. Today, an ever-increasing variety of composite materials and polymers are available, each of them possessing their own characteristics, applications, advantages and limitations. Many automotive composites are used for manufacturing fairings. Materials like Carbon fiber, Glass fiber (E glass, S glass), Aramid fiber (Kevlar 29, Kevlar 49) are some of the viable options that have been used in the past for manufacturing fairing of HPVs. The problem of material selection arises because of conflicting attributes of different alternative materials with respect to the application. The selection of an optimal material for an engineering design from among two or more alternatives is a Multi-Attribute Decision Making (MADM) problem. In this paper, MADM methods like fuzzy Analytical Hierarchy Process (AHP) have been applied to investigate the problem of material selection for the vehicle. The proposed approach will be a valuable resource for decision making that includes qualitative factors as well as subjective way of assigning relative importance among various attributes.
Many modern aircraft, including rotorcraft, require conformal antennas and fairings to reduce wind drag, ice accretion, lightning strikes, and impact damage. An innovative approach to embedding Very High Frequency (VHF) antenna elements in the leading and trailing edges of a helicopter empennage has been developed. A prototype has been fabricated and tested on a mockup of a helicopter empennage, consisting of the vertical stabilizer (tail), horizontal stabilator, and gearbox. Testing has shown that the design can meet typical communications range requirements. A history of helicopter empennage antennas, the development approach, design features and key innovations, and measured results are presented and discussed. The approach can be replicated on almost any current or future aircraft or rotorcraft.
ABSTRACT This paper discusses mathematical modeling of helicopters towing loads that are submerged in water. Special attention is paid to the role of cable hydrodynamics and effects of curvature. Analytical predictions for a four-bladed conventional utility helicopter towing a representative load with fins for passive stabilization and depth control are shown for steady and level forward and turning flight conditions. As the lengths of the cable increase, the total drag from the tow cable is comparable to that on the submerged load and cannot be ignored. The role of hydrodynamic fairings is critical for reducing rotor power requirements. In turning flight, drag on the cable causes the towed body to turn with a radius that is smaller than the helicopter, and asymptotes to the center of the turn with increasing turn rate. Engine power may be limited by straight-line tow speeds, and not the peak turn rate.
Sandwich structures are ideal structures for very light weight and stiff components for applications in aerospace vehicles. In common transport aircraft sandwich structures are often used for secondary parts like flaps, fairings, and interior equipment. In helicopter industry, also primary structural components are made from sandwich material. When designing sandwich structures, special attention has to be paid to special sandwich failure modes. Due to the very light and relatively weak sandwich core, local and global instability phenomena become very important. Common light weight sandwich structures loaded in compression or bending fail in the compression loaded facing locally due to face sheet wrinkling or the whole sandwich fails more or less globally by sandwich shear crimping. Both failure modes are addressed in this paper. Comparisons of coupon test results with analytical approaches are done and some recommendations for designing sandwich structures are given.
A roof fairing is a commonly used add-on for trucks or tractor-trailers, where a significant difference in height exists between the cabin and the container. A roof fairing reduces the aerodynamic drag on the vehicle by directing the onward wind flow smoothly onto the container and thus reducing flow separation in front of the container. Since standard containers are available in two different heights and there are cases when vehicles ply without load i.e. without a container, it is necessary to adjust the height of the fairing accordingly to maintain an optimum aerodynamic configuration. While adjustable fairings have been in use in the commercial vehicle industry, these fairings are usually shaped as flat plates, often with open sides for ease of folding. A highly curved and bulbous fairing helps in reducing drag better, especially in presence of side winds, although it makes adjustability difficult. The current paper presents the benefits of installing an adjustable roof fairing on a truck. It has been observed that a well profiled roof fairing gives 4.03% reduction in coefficient of drag over a bent plate fairing and the adjustable roof fairing provides 6.35% improvement in fuel savings compared to fixed roof fairing for the truck with tall container.
The OVERFLOW chimera grid Navier Stokes code was used to analyze a wide variety of airplane configurations. The code performed reliably and was found to have comparable accuracy to the structured grid code TLNS3D. It is easier to develop overlapping grid blocks to represent a complex configuration than it is to develop grid blocks that must abut one another. The process is inherently modular. One can add or subtract components like tip-lights, compound winglets, struts, nacelles, tails and fairings at will. The gain in grid simplicity is offset by the complication in specifying block connectivity, however. The overset blocks are typically of better quality, but there is a drawback in that it is not always possible to guarantee flux conservation. The recent development of software for automatic connectivity holds promise for the routine use of OVERFLOW by design engineers.
Progress on two programs to evaluate composite structural components in flight service on commercial helicopters is described. Thirty-six ship sets of composite components that include the litter door, baggage door, forward fairing, and vertical fin have been installed on Bell Model 206L helicopters that are operating in widely different climatic areas. Four horizontal stabilizers and ten tail rotor spars that are production components on the S-76 helicopter will be tested after prescribed periods of service to determie the effects of the operating environment on their performance. Concurrent with the flight evaluation, specimens from materials used to fabricate the components are being exposed in ground racks and tested at specified intervals to determine the effects of outdoor environments. Results achieved from 14,000 hours of accumulated service on the 206L components, tests on a S-76 horizontal stabilizer after 1600 hours of service, tests on a S-76 tail rotor spar after 2300 hours service, and two years of ground based exposure of material coupons are reported.
The results of a wind tunnel study and a computer simulation are used to determine the effects of aerodynamics on the lateral-directional stability and crosswind response of passenger car/utility trailer combinations. Single and tandem axle utility trailer configurations, with and without drag reducing add-on aerodynamic fairings, were considered with both sedan and station wagon tow cars. Results showed that including aerodynamic terms in the six degree of freedom model reduces the trailer tow angle stability and damping by a few percent. More importantly, the random crosswind response, expressed in terms of tow car yaw velocity, was amplified about 20 to 30 percent when a drag reducing device was added to the trailer.
Items per page:
50
1 – 50 of 51