Browse Topic: Scale models
This study presents a data-driven approach for strengthening aviation safety by integrating human factors assessment with modern predictive modeling techniques. The work focuses on understanding how human performance, operational conditions, and system-level interactions collectively influence safety risk, and how these interactions can be quantified to support improved design and decision-making. Unlike previous studies that address human factors or predictive modeling in isolation, this research offers a unified framework that links causal human factors indicators with statistical modeling, feature extraction, and machine learning based risk estimation. The novelty of this work lies in the structured pipeline that transforms raw categorical and narrative human factors information into measurable predictors that can be analyzed using structural modeling and machine learning. The methodology includes data preparation, dimensionality reduction, latent pattern discovery, dependence
With the growing trend of electric vehicles (EVs) incorporating regenerative braking systems, many compact SUVs, including hybrids and EVs, still utilize drum brakes on the rear wheels to strike a balance between cost, performance, and durability. Drum brake squeal remains a complex and persistent challenge in the field of vehicle noise, vibration, and harshness (NVH). This issue stems from dynamic instability caused by time–dependent friction forces. Traditional linear modal analysis has been used to study the mechanisms behind drum brake squeal, focusing on harmonic vibrations in large–scale models. However, these methods often fail to accurately correlate with real world behavior due to the presence of extra, non-physical modes. To address this, time–domain analysis approaches have been explored, incorporating detailed friction models and contact mechanics. These methods consider different root causes for high and low–frequency squeal and have shown promising results in accurately
This paper presents the design of a cost-effective fuel injector driver designed for accelerated testing of injectors. The driver simulates injection patterns across a wide range of vehicle operating conditions and can be programmed with injection maps for different engines, test cycles based on drawing specifications, pre-defined engine running profiles, and manual control, where the user defines PWM frequency and duty cycle. It also enables remote operation through a Wi Fi access point. An injector driver-based test setup was developed to study wear and evaluate leakage tendency in an injector design. To simulate extended field usage in a short timeframe, an accelerated operating cycle was derived using telematics data. Injector samples were tested with periodic leak rate measurements. Conducting such tests at vehicle level or on engine test bench would involve significant time and cost. This setup is an effective tool for rapid comparative analysis across supplier design, enabling
Endoscopic imaging system development requires coordination between various engineering disciplines, especially for optical illumination and imaging engines, particularly when adding fluorescence imaging capabilities. The optical illumination and imaging engines set the foundation for building intuitive and effective imaging products around and become even more critical when adding fluorescence imaging (FI) capabilities to user needs.
Thermal or infrared signature management simulations of hybrid electric ground vehicles require modeling complex heat sources not present in traditional vehicles. Fast-running multi-physics simulations are necessary for efficiently and accurately capturing the contribution of these electrical drivetrain components to vehicle thermal signature. The infrared signature and heat transfer simulation tool, “Multi-Service Electro-optic Signature” (MuSES), is being updated to address these challenges by expanding its thermal-electrical simulation capabilities, provide a coupling interface to system zero- and one-dimensional modeling tools, and model three-dimensional air flow and its convection effects. These simulation capabilities are used to compare the infrared signatures of a tactical ground vehicle with a traditional powertrain to a hybrid electric version of the same vehicle and demonstrate a reduction in contrast while operating under electrically powered conditions of silent watch and
Hybrid additive manufacturing (AM) and subtractive manufacturing (SM) processes utilize the combination of AM (e.g., LPBF and DED) and SM (e.g., milling and turning operations) to produce the final part. Due to the poor surface roughness resulting from the uneven melting of powders in AM, the subtractive process is a necessary finishing operation to improve the surface roughness of the AM part. The hybrid AM/SM technology combines the benefits of AM and SM processes to create complex geometry while introducing good surface finish and compressive stress to prevent crack initiation. However, the relationship between large process parameter space and the residual stress/distortion in the part is not well understood, which impedes the adoption of hybrid AM/SM to minimize the residual stress in the final product. To expedite the process optimization, we establish a pipeline for the sequential modeling of additive manufacturing (AM) and subtractive manufacturing (SM) processes. Key
This paper discusses the development of a quantitatively-accurate non-linear hybrid flight dynamics model of a hover-capable Air-Launched Tailsitter Unmanned Aerial System (ALUAS) in order to 1) understand its dynamics during complicated maneuvers, and 2) provide a high-fidelity framework to develop novel control laws. Wind tunnel tests were conducted on a 1:1 scale model of the full aircraft to measure the airloads, which were used in the simulation as a lookup table. Flight tests of the ALUAS were performed in hover, transition, and cruise to collect a large amount of unique state measurements by providing large excitations to induce highly transient motion. The flight dynamics predictions using Rotorcraft Comprehensive Analysis System (RCAS) software were then compared with experimental flight test data. To correct any discrepancies in the RCAS physics-based predictions, a correction was learned from the experimental measurements, making use of the large amount of collected flight
This paper explores a significant step forward, regarding the further detailed understanding of the Fenestron®. Since its patent in 1968 – for the Gazelle helicopter –, the shrouded tail rotor has been resized, inclined, modulated, etc. and has thus been continuously enhanced on different rotorcraft. Half a century after its invention, Airbus is once again exploring in more detail the magic of the Fenestron®, with the objective of optimizing it even further, for future helicopter applications. To grasp and observe properly some specific phenomena, a model (scaled to one third) capable of both unprecedented functions and modularities, was developed. The present paper will describe in detail the novel model and the related challenges and solutions. This model is capable of high rotor speed and dynamic pitch inputs, delivering power levels high enough to reach stall effects, while allowing the measurement of propulsive efficiency and to differentiate rotor vs fairing thrust. Furthermore
This paper presents an overview of the comprehensive aerodynamic framework developed at ERC for the analysis and simulation of electric vertical takeoff and landing (eVTOL) aircraft. Addressing the challenges inherent to distributed propulsion architectures and the complex transition between hover and forward flight, the methodology integrates multi-fidelity simulation tools ranging from analytical models and low-fidelity simulation to fully-resolved transient CFD. The framework addresses all phases of aircraft design and validation, and includes dedicated insight into aeroacoustics, aeroelasticity, and interactional aerodynamics problems. A modular approach is adopted, where individual phenomena are first studied in isolation before being synthesized into an aircraft model. Experimental validation through wind tunnel testing, full-scale static thrust test stand measurements, and scaled model flight tests is essential to ensuring model accuracy and validity. The paper concludes with an
Current paper summarizes a correlation study of two flow solvers (CREATETE-AV Helios and Simcenter STAR-CCM+), routinely used at Sikorsky, with multiple model-scale wind-tunnel tests. The Helios modeling approach was aiming for a high-fidelity accurate simulation, whereas the STAR-CCM+ modeling approach was aiming for a fast turn-around time with reasonable solution accuracy with a relatively coarse mesh and simplifications. The two solvers generally agreed well with the test data within reasonable accuracy and captured the airloads and flowfield trends. The calculations presented herein show the impact of the turbulence model on component loads, the aerodynamic interactions among components, and the effect of transition modeling on rotor performance. The Reynolds-Averaged Navier-Stokes CFD model generally delayed separation and resulted in lower drag. By modeling the airframe supporting structure in CFD simulations, an improvement on correlation for inflow on the propeller plane was
Aeroelastic stability prediction is critical to the successful design, development and flight testing of rotorcraft. As configurations reach higher speeds, new challenges in high Mach number unsteady aerodynamic modeling need to be addressed, especially for higher frequency aeroelastic modes with significant coupling. In this paper, Linear Unsteady aerodynamics and Leishman-Beddoes attached flow models are applied and compared to 2D CFD (airfoil) and 3D CFD/CSD (rotor) analysis for operating conditions of interest. The Leishman-Beddoes model demonstrates improved agreement with CFD data. In the 2D assessment, RCAS is used to model a representative airfoil undergoing prescribed pitch and heave oscillations. CFD results are presented to compare each model (Linear Unsteady and Leishman-Beddoes). In the 3D assessment, a full rotor CFD/CSD test case is evaluated for aeroelastic stability and compared to RCAS standalone analysis. The RCAS rotor structural model is coupled with the HELIOS CFD
Electrification in the automotive industry has been steadily rising in popularity for many years, and with any technology there is always a desire to reduce development cost by efficiently iterating designs using accurate simulation models. In the case of rotating machinery and other devices that produce vibrations, an important physical behavior to simulate is Noise Vibration and Harshness (NVH). Efficient workflow to account for NVH was established at Schaeffler for eMotor design. Quantitative prediction is difficult to achieve and is occasionally intended only for faster iterations and trend prediction. A good validated qualitative simulation model would help achieve early NVH risk assessment based on the specified requirement and provide design direction and feasibility guidance across the design process to mitigate NVH concerns. This paper seeks to provide a general approach to validate the simulation model. The correlation methods used in this paper consist of a combination of
This study investigates the flow characteristics in the test section of a model-scale, three-quarters open-jet, closed-loop return wind tunnel equipped with a novel device featuring three subsystems to generate transient yaw, gusts, and turbulence. The effect of each subsystem on the resulting turbulent and unsteady flows is evaluated individually and simultaneously. It is demonstrated that this new turbulence generation system can generate yaw distributions with standard deviations ranging from 2.1° to 8.0°. This replicates a wide range of on-road yaw behavior. Additionally, the subsystems can activate transient yaw events and unsteady gusts. Frequency sweeping was demonstrated to fill a wide range of low-frequency spectra, which helps recreate the on-road flow spectra in wind tunnels. Unsteady gusts of more than 15% of the mean flow velocity were achieved. The active turbulence subsystem generates turbulence levels from a few percent, passively, to over 20% intensity levels actively
Effective thermal management is crucial for vehicles, impacting both passenger comfort and safety, as well as overall energy efficiency. Electric vehicles (EVs) are particularly sensitive to thermal considerations, as customers often experience range anxiety. Improving efficiency not only benefits customers by extending vehicle range and reducing operational costs but also provides manufacturers with a competitive edge and potential revenue growth. Additionally, efficient thermal management contributes to minimizing the environmental impact of the vehicle throughout its lifespan. Digital twins have gained prominence across various industries due to their ability to accelerate development while minimizing testing costs. Some applications have transitioned to comprehensive three-dimensional models, while others employ model reduction techniques or hybrid approaches that combine different modeling methods. The discovery of unknown working mechanisms, more efficient and effective control
A two-phase wind tunnel test was conducted to evaluate aerodynamic performance on a 1/5th scale model of the Sikorsky/Boeing X2™ technology representative aircraft for Future Vertical Lift (FVL). The test program provided valuable aerodynamic data for two important elements of the design: the faired coaxial hub system and the main inlet flow leading to the engine interface. Studies from previous X2™ technology aircraft have shown that hubs, pylons and sail fairings have strong interactions, and if well integrated can lead to low drag aircraft designs. Rotorcraft main inlets generally have aggressive turns; therefore, this inlet design was investigated for distortion and total pressure loss. Accuracy of modeling these aerodynamic interactions using Computational Fluid Dynamics (CFD) and other forms of computational aerodynamic assessment requires supporting empirical testing for validation. The two wind tunnel facilities used in Phase 1 and 2 offered different and unique advantages
Researchers at the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) have conducted a series of structural component and seat level tests to improve finite element model (FEM) characterization of a representative vertical take-off and landing (eVTOL) test article developed by NASA. A full-scale dynamic test was conducted on the representative eVTOL test article in November of 2022. The test article represented a high wing, six passenger eVTOL design concept and is referred to as the lift plus cruise (LPC) test article. The full-scale test identified limitations in the analytical models used to predict aircraft structural response, in particular the composite material models did not effectively capture brittle failure of the structure which were measured during dynamic loading. To better understand the mechanism behind the composite material failure mechanisms observed and to improve the FEM, intact sample specimens of the composite airframe structure
The constant, undisturbed rotor hub rotational speed is a commonly applied boundary condition and simplification in computational analyses of helicopter rotors. Revoking this simplification and considering rotor-drivetrain interactions in the hub's rotational degree of freedom can - but doesn't necessarily - improve the predictions of structural blade loads, especially in the lead-lag direction. To estimate the drivetrain's potential to influence the lead-lag loads, this paper proposes the systematic evaluation of the modified collective lead-lag modes. These eigenmodes, as well as the resulting modification of lead-lag loads in the aeromechanic simulation, are presented and compared for the rotordrivetrain configurations of the Eurocopter Bo105 and the Sikorsky UH-60A. The study focuses on understanding the drivetrain's influence rather than on making high fidelity predictions. In the Bo105 case, the drivetrain impact on the lead-lag moments is significantly more pronounced than for
The CH-53K® King Stallion™ is the most advanced heavy lift helicopter developed by Sikorsky, a Lockheed Martin Company, to address the requirements of the United States Marine Corps. The aircraft was designed to support missions with a maximum design gross weight of 88,000 lbs and can carry external loads up to 36,000 lb. Performance flight tests for the CH-53K® have been completed as part of its System Design and Development (SDD) phase. Tethered hover and level forward flight performance measurements have been acquired that are used as a basis for Naval Air Training and Operating Procedures Standardization (NATOPS) flight manual performance charts. They were also used in the Key Performance Parameter (KPP) verification analysis, demonstrating that the CH-53K® exceeds its KPP for mission effectiveness. In addition to overview descriptions of the performance flight test program, the test results are herein compared with predictions from aircraft performance modeling tools that were
This paper investigates optimal wing arrangements for electric Vertical Take-Off and Landing (eVTOL) aircraft, leveraging on their design flexibility with electric propulsion system. The study employs a multidisciplinary approach with the objective of integrating aerodynamic analysis, static and dynamic stability assessments, and pilot feedback to evaluate various wing configurations. Analytical techniques were adopted to evaluate aerodynamic performance and static stability, while experimental flight testing on scale models was conducted to validate these findings. Additionally, the Cooper-Harper rating system was introduced to capture pilot perceptions of aircraft handling qualities. Results inform eVTOL designers on wing arrangements that offer enhanced aerodynamic efficiency, stability, and handling qualities, ultimately expanding the operational scope and applications of eVTOL aircraft. The study concludes the versatility of the high aspect ratio conventional wing on eVTOL
Multirotor UAS spanning Groups 3 and 4 have received increased attention as candidates for tactical resupply missions due to their VTOL capability and payload capacity. The objective of this work is to better understand how the parameters of multicopter UAS flight dynamics models scale with size in support of expanding the Army's unmanned aerial reconnaissance capability. A family of coaxial multirotor UAS spanning Groups 2 and 3 have been flight tested to gather data for flight dynamics modeling and validation. These UAS consist of the TRV-80, TRV-150, and the subscale Eagle platform. A series of test points including static stability, trim shot, frequency sweeps, doublets, and maximum climb rate maneuvers were collected. Wind data was simultaneously collected using a 3-axis ultrasonic anemometer to characterize wind conditions and characteristics during testing. Flight data were collected in varying payload configurations ranging from 0-120 pounds and at flight conditions ranging
Rotorcrafts frequently operate in environments with severe atmospheric turbulence, for instance transferring people offshore to and from oil rigs as well as operating from and around ships. The presence of high turbulence can deteriorate performance, stability, and controllability of the rotorcraft. Additionally, such challenging conditions also generate loads that both airframe and rotor components must withstand. Following this, it is crucial to consider the impact of these operational atmospheric conditions during rotorcrafts design and development. In this context, numerical models are a fundamental tool to provide an easier and quicker way to explore the operative envelopes of the helicopter compared to performing experimental activities. This paper presents a rotor loads correlation activity between an experimental test designed and carried out by Leonardo Helicopters in which an AW189 helicopter was placed in the wake of a C-27J Spartan aircraft and a multibody structural model
Electric Vertical Takeoff Landing (eVTOL) aircraft feature heavy electric motors, battery packs, and rigid fixed-pitch rotors supported on flexible arms. Under substantial time-varying aerodynamic loads associated with variable rotor speeds and, with low intrinsic damping, such lightweight arms respond in bending and torsion at relatively high levels. In this paper, two methods of reducing vibration response in the operating frequency range are explored, one based on damping, the other on stiffness. A tailored particle impact damper system was evaluated experimentally to address near-periodic vibration over a range of frequencies. A forced torsional response test showed consistent 50% vibration reduction, with a 5% mass penalty. To stiffen the system, a cross-braced strut approach linked two arms such that the natural frequencies of their torsion modes would be increased beyond the rotor operating frequency range. A finite element model was developed and validated for a representative
This article presents aeroelastic analysis of the ERATO blade with double-swept design and an homogenised structure, using both computationally intensive and rapid aerodynamics solvers coupled with a projection-based reduced-order model (ROM) for the structure. The study focuses on investigating the impact of blade flexibility on aerodynamic performance during hover flight, and comparing with experimental data. In terms of modelling, the ROM allows for efficient computation of structural displacements, while capturing the non-linear physics and the complex structural response induced by the double-swept configuration. The aerodynamic analysis incorporates different solvers including among others Computational Fluid Dynamics (CFD) with elsA, Vortex Particle Method (VPM) and Blade Element Momentum Theory (BEMT). This multi-solver approach is employed to assess the capability of fast aerodynamic methods to reproduce the desired flow, coupling properties and flight performance. The
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