Browse Topic: Concept vehicles
This paper presents an efficient numerical framework for prediction of broadband noise scattering through time-domain synthesis and propagation. For efficient scattering of broadband noise sources, a time-domain boundary element method is applied to propagate all frequencies together in a single computation. To obtain a time-resolved incident field without high-fidelity aerodynamic simulation, a stochastic broadband noise synthesis method is developed based on a semi-analytical airfoil broadband noise modeling approach. The framework is validated for airfoil trailing edge noise prediction, and the correspondence of the time-domain broadband noise synthesis method to existing semi-analytical broadband noise models is demonstrated. The framework is then applied to predict fuselage scattering of rotor tonal and broadband noise for a full-size urban air mobility concept vehicle. Significant differences are observed between the scattering effects in the tonal and broadband contributions.
The DarkSky One is a concept of a concept car. It doesn't physically exist, but a lot of thought went into the design, which was intended to create the first car with nighttime driving front-of-mind. SAE Media spoke with Ruskin Hartley, CEO and executive director of DarkSky International, the group behind the car, at the 2026 Detroit Auto Show, where the DS One was introduced.
NASA is conducting investigations in Advanced Air Mobility (AAM) aircraft and operations, including the development of Urban Air Mobility (UAM) aircraft designs that can be used to focus and guide research activities in support of AAM. This report is an investigation of the impact of technology and mission variations on several of the NASA AAM concept aircraft: quadrotor, quiet single main rotor, side-by-side, and tiltrotor configurations, with turboshaft and electric propulsion variants for each. First, the mission and aircraft models of the baseline designs were reassessed and updated, including rotor geometry optimization, update of the rotor performance models, and disk loading optimization. For these eight designs, technology and mission excursions were performed. Relative to the calibration cases that can be considered examples of good design practice, the impact of the weight technology factors is significant. For the electric aircraft, there is a very large impact of battery specific energy (Wh/kg), and correspondingly a very large impact of mission range. The vision of Advanced Air Mobility is driven by missions that will enable new transportation capabilities. Hence it is appropriate to compare Concept Vehicles of different lift and propulsive architectures, all designed to accomplish the same UAM mission. It is also useful however to consider specific missions that can take advantage of the strengths of individual aircraft configurations. So alternate designs were also developed for the concept vehicles: for turboshaft aircraft, longer unrefueled range, including faster cruise speed for the tiltrotor; for electric aircraft, shorter range and more realistic battery weight.
Durability validation of full vehicle structures is crucial to ensure long-term performance and structural integrity under real-world loading conditions. Physical test strain and finite element (FE) strain correlation is vital for accurate fatigue damage predictions. During torture track testing of the prototype vehicle, wheel center loads were measured using wheel force transducers (WFTs). In same prototype strain time histories were recorded at critical structural locations using strain gauges. Preliminary FE analysis was carried out to find out critical stress locations, which provided the basis for placement of strain gauges. Measured loads at wheel centers were then used in Multi Body Dynamics (MBD) simulations to calculate the loads at all suspension mount points on BIW. Using the loads at hard points transient analyses were performed to find out structural stress response. Strain outputs from the FE model were compared with physical measurements. Insights gained from these comparisons were used to update the model to achieve better correlation with test data. The findings of this paper establish a robust methodology for improving vehicle durability assessments by enhancing confidence in fatigue life predictions and structural performance. By integrating physical testing and FE simulations, this approach ensures accurate strain correlation and effective validation of long-term performance. It also provides a scalable framework for validating structural changes, supporting lightweight material integration, and enabling Value Analysis/Value Engineering (VAVE) initiatives to optimize cost-effectiveness and performance. This methodology strengthens simulation-driven durability development, offering valuable insights for future vehicle programs.
The present work demonstrates a transient Fluid-Structure-Interaction (FSI) based numerical methodology for estimation of aerodynamic-induced flutter of the rear bumper of a Sports Utility Vehicle (SUV). Finite Volume Method (FVM) based High-fidelity transient full vehicle aerodynamic simulations were conducted for the estimation of the transient aerodynamic load. Subsequently, by mapping this transient aero load onto the surface of the rear bumper, Finite Element Method (FEM) based dynamic structural simulations were performed to predict its response. The results obtained through simulations were then compared against experimental wind tunnel test data of a prototype car with modified bumper for the specific test-case. The pressure and the time series data of rear bumper deflection were captured at multiple probe locations from wind tunnel experiments at 140 and 200 kmph. The distribution of pressure on the rear surfaces of the car was well captured by the aerodynamic simulation at both speeds. The deflection amplitude and patterns across multiple probe locations and across the two speeds were reproduced with reasonable accuracy by the methodology.
In recent decades, vehicles have evolved from mere means of individual transportation to something much more meaningful. They are no longer mere metal bodies housing combustion engines, but now play a complex role in people’s lives, encompassing emotional, aesthetic, and symbolic aspects. These factors influence consumers’ choice of a model, brand, or version. Based on a literature review of the global automotive sector, including brand literature, scientific articles, and current automotive news, this study aims to analyze the main design and positioning trends adopted by large multinationals in the market. Using the Jeep Renegade as a case study, three design proposals for the model are illustrated and presented as follows: a “facelift,” a “new generation,” and a “concept vehicle.” Next, these design trends are conceptualized, initially illustrating the respective sketches and drafts, which take into account market positioning and the different options for the models presented in each situation described. Furthermore, knowledge that considers biomimetics is used to obtain new solutions and automotive design proposals. Inventor software is used to develop and model the “concept vehicle,” and FlashPrint is used to 3D print the parts, thus enabling the modification of a 1/24 scale Jeep model. Therefore, this study, related to automotive design trends, presents proposals for the conceptual development of automotive models, as well as integrating rapid processes related to perspective drawings and sketches, modeling and robustness features, aerodynamic profile, engineering, and 3D prototyping. Finally, the results allow for conclusions and highlight the different configurations, variables, lines, and new lines that prevail in proposing a different idea and a new design.
The calibration of automotive electronic control units is a critical and resource-intensive task in modern powertrain development. Optimizing parameters such as transmission shift schedules for minimum fuel consumption traditionally requires extensive prototype testing by expert calibrators. This process is costly, time-consuming, and subject to variability in environmental conditions and human judgment. In this paper, an artificial calibrator is introduced – a software agent that autonomously tunes transmission shift maps using reinforcement learning (RL) in a Software-in-the-Loop (SiL) simulation environment. The RL-based calibrator explores shift schedule parameters and learns from fuel consumption feedback, thereby achieving objective and reproducible optimizations within the controlled SiL environment. Applied to a 7-speed dual-clutch transmission (DCT) model of a Mild Hybrid Electric Vehicle (MHEV), the approach yielded significant fuel efficiency improvements. In a case study on a 4.7 km Worldwide harmonized Light-Duty vehicles Test Cycle (WLTC) driving segment, the RL-optimized shift strategy reduced fuel consumption from a baseline of 0.46 L to 0.37 L. Furthermore, when starting from an already optimized shift map representative of a series production vehicle’s calibration, the artificial calibrator further enhanced fuel efficiency, achieving approximately a 0.6 % reduction in fuel consumption for the 4.7 km segment and nearly a 5 % reduction for the full WLTC. The artificial calibrator thus demonstrates a promising methodology to frontload calibration tasks in simulation, thereby offering the potential to reduce reliance on resource-intensive physical testing and to significantly accelerate the development of fuel-efficient powertrain control software.. The direct compatibility of parameter files with real vehicle Electronic Control Unit (ECUs) and the validated SiL behavior suggest high transferability of learned strategies, offering the potential for minimal fine-tuning on physical vehicles post-simulation.
In support of research and development for Urban Air Mobility (UAM) operations, the National Aeronautics and Space Administration (NASA) is developing a fleet of Vertical Takeoff and Landing (VTOL) concept vehicles. These vehicles aim to identify key areas for technological growth and provide reference data to the UAM community. A six-passenger Tiltwing concept recently added to the fleet offers new opportunities to explore the UAM design space through trade studies of the power and propulsion systems. In this paper, a turboelectric powertrain is designed and analyzed using the Numerical Propulsion System Simulation (NPSS) tool, the NPSS Power System Library, and a motor drivetrain optimization tool. Direct and geared motor drivetrains are designed and compared across a UAM design mission. Sensitivity of the Tiltwing maximum takeoff weight to motor drivetrain weights and efficiencies is estimated and used to inform optimal motor and gearbox selection. Results indicate that direct-drive and geared-drive configurations are comparable for this vehicle, with slight advantages to direct-drive when the radius of the drivetrain is unconstrained. When the drivetrain radius is constrained, a geared-drive system becomes more optimal.
A follow-on study to the 2024 paper by Kottapalli, Silva, and Boyd is presented with improved acoustics tools to examine whether the Vertical Aviation International (VAI) Fly Neighborly operational recommendations that are designed for single main rotor/tail rotor configurations will hold for non-conventional UAM rotorcraft with multiple rotors. The 6-occupant quadrotor concept vehicle designed under the NASA Revolutionary Vertical Lift Technology (RVLT) Project is studied. The tip speed is 550 ft/sec, with three blades per rotor. Predictions are made for three steady maneuvers: level turns, descending turns, and climbing turns. The RVLT Toolchain is exercised using CAMRAD II, pyaaron/AARON/ANOPP2 and AMAT (ANOPP2 Mission Analysis Tool). Quadrotor noise trends are analyzed using Sound Exposure Level (SEL) ground maps because it is anticipated that the upcoming updated Fly Neighborly recommendations will involve SEL maps. Importantly, unlike conventional helicopters with a single main rotor, quadrotor noise can increase in a direction opposite to the turn direction; this finding may need to be taken into consideration in formulating the upcoming updated Fly Neighborly recommendations. The recommendation Level turns are quieter than descending turns is followed by this quadrotor under the flight conditions examined. Turning away from the advancing blade … is quieter than turning into the advancing blade is not relevant for symmetric aircraft such as the quadrotor. Straight flight is quieter than turning flight is not predicted to be best for this quadrotor under the flight conditions examined – turning flight is quieter than straight flight for the quadrotor in this study.
This paper demonstrates methods of aircraft sizing, flight dynamics modeling, and performance analysis using a lift+cruise concept vehicle with an electric powertrain and variable-speed rotors. The central focus is the development of methods to relate the aircraft design sizing constraints to achievable maneuverability and predicted handling qualities. A toolchain is demonstrated that performs aircraft sizing, mass moment of inertia estimation, powertrain modeling, trim optimization, dynamics linearization, handling qualities prediction, and quantification of achievable maneuverability under both nominal conditions and control effector failures. A convex optimization problem framework is introduced to compute agility bound estimates without requiring control system design or control allocation, potentially supporting rapid design iteration as well as early detection of deficiencies and undesirable operating conditions. This analysis is supplemented with more conventional methods of analysis to provide additional perspective and observations. Overall, the results suggest that each modeling and analysis element in the demonstrated toolchain adds significant value, with the combined approach supporting a more efficient and comprehensive exploration of trade-offs within the design space.
A novel multirotor concept is proposed for airlifting the emergency medical personnel without the use of a rescue helicopter (designed for patient transport) during the first line emergency services. Based on this concept, two configurations are designed and introduced, comprising a common quadrotor system with single and dual pusher propellers, respectively. An initial flight performance assessment is conducted for the introduced configurations by means of trim calculations in two distinctive flight modes across the entire designated flight speed range, initially without rotor-rotor interactions, and subsequently, with their inclusion. For this purpose, an existing mid-fidelity rotor-rotor interaction method is extended to capture the interactions in all three directions between the rotors that are arbitrarily positioned and oriented to each other. The trim calculations including rotor-rotor interactions show a 10% increase in the vehicle power at the maximum flight speed. The interactions between the pusher propellers and the lifting rotor wakes result in sudden increases up to 100% in the induced inflow of the propellers at low-speed regimes. The paper presents the two conceptual configurations along with their model syntheses and the results of the trim calculations. The influences of the rotor-rotor interactions on the trim results are discussed both at the rotor and the vehicle level.
The integrated bracket is a plastic part that packages functional components such as the ADAS (Advanced Driver Assistance System) camera, rain light sensor, and the mounting provisions of the auto-dimming IRVM (Inner Rear View Mirror). This part is fixed on the windshield of an automobile using double-sided adhesive tapes and glue. ADAS, rain light sensors, and auto-dimming IRVM play an important part in the safety of the driver and everyone present in the automobile. This makes proper functioning of the integrated bracket very integral to occupant safety. Prior to this work, the following literature; Integrated Bracket for Rain Light Sensor/ADAS/Auto-Dimming IRVM with provision of mounting for Aesthetic Cover [1] outlines the design considerations and advantages of mounting several components on the same bracket. It follows the theme where the authors first define the components packaged on the integrated bracket and then the advantages of packaging multiple components on a single bracket. However, it fails to showcase the development phase of the part. In this paper, the authors take the readers through a set of issues faced in the development phase of integrated bracket. The development phase is the phase when tooled-up parts arrive at the manufacturing plant and get assembled on the vehicle. During this phase, issues at the part level and assembly level are addressed by respective engineering teams. The issue resolution comprises three main parts: root cause analysis, immediate corrective action, and permanent corrective action. Root cause analysis is where the cause is identified. Immediate corrective action is a temporary solution to the problem that can be implemented on day one without any lead time. Permanent corrective action is the final stage of issue resolution where the improved parts start arriving at the manufacturing plant after tool modification.
The current Range Rover is the fifth generation of this luxury SUV. With a drag coefficient of 0.30 at launch, it was the most aerodynamically efficient luxury SUV in the world. This aerodynamic efficiency was achieved by applying the latest science. Rear wake control was realised with a large roof spoiler, rear pillar and bodyside shaping, along with an under-floor designed to reduce losses over a wide range of vehicle configurations. This enabled manipulation of the wake structure to reduce drag spread, optimising emissions measured under the WLTP regulations. Along with its low drag coefficient, in an industry first, it was developed explicitly to achieve reduced rear surface contamination with reductions achieved of 70% on the rear screen and 60% over the tailgate when compared against the outgoing product. This supports both perceptions of luxury along with sensor system performance, demonstrating that vehicles can be developed concurrently for low drag and reduced rear soiling. This paper describes the development journey of the car, from initial phases extensively exploiting simulation through to testing pre-production prototype vehicles in both FKFS Aeroacoustic and Thermal Wind Tunnels.
Some challenges, such as reworking airbags to meet all seating scenarios, will be solved by the OEM as the final system integrator. Rearward-facing front seats have generally been limited to concept cars that explore a far-away world in which SAE Level 5 autonomous driving has been perfected. Magna has rewritten that playbook, winning a contract with a Chinese OEM for a reconfigurable seating system that includes fully rotating front seats on long rails, creating an unusually flexible cabin. Currently configured for vehicles with two rows of seating, the system features power-swivel seats along rails or tracks nearly two meters (6.6 ft) long. The front passenger and driver seats can rotate 270 degrees.
This research aims to develop an inverse controller to track target vibration signals for the application to car subsystem evaluations. In recent times, perceptive assessments of car vibration have been technically significant, particularly parts interacting with passengers in the car such as steering wheels and seats. Conventional vibration test methods make it hard to track the target vibration signals in an accurate manner without compensating for the influence of the transfer function. Hence, this paper researched the vibration tracking system based on inverse system identification and digital signal processing technologies. Specifically, the controller employed a semi-active algorithm referring to both the offline modeling of the inverse system and the adaptive control. The semi-active controller could reconstruct the target vibration signal in a more efficient and safer way. The proposed methodology was first confirmed through computation simulations using Simulink. The simulation results verified that the semi-active controller could outperform the conventional active controller with respect to converging speed and stability. Following the simulation studies, actual vibration tests validated the suggested method in a steering wheel. A weight disturbance of about 0.24 kg was attached to the steering wheel to realize the possible change in the system characteristics. The semi-active controller could successfully track target vibration, such as a single or a dual harmonic signal, at the target spot of the steering wheel within the control error of about 1.6 dB regardless of the variation of the system transfer function. The proposed semi-active controller will provide an accurate, efficient tracking of vibrations in the evaluation of car subsystems.
Advanced Rotorcraft Technology (ART) and the NASA Ames Aeromechanics branch have jointly developed FLIGHTLAB® simulation models for Advanced Air Mobility (AAM) VTOL concept vehicles. The overarching purpose of the simulation model development is to establish a set of well defined reference vehicles for FLIGHTLAB users and the rotorcraft community. The ongoing research effort and enhancement of these AAM simulation models to fulfill the role of quality reference vehicles is this paper's focus. The content of this paper expands on the established characteristics of these AAM models in three primary areas. First, enhancement of the lift+cruise and tiltwing models with elastic airframe properties is discussed. The process of setting up the elastic airframe model in FLIGHTLAB, as well as the impacts on flight characteristics are explained. The introduction of the elastic airframe modeling allows these models to be used in flight dynamics, loads, and vibration analysis of the configuration designs. Next, linear model generation from the enhanced simulation model is covered. Confirming the validity of the linearized models is of importance, as these linear models are utilized for flight control design and tuning for these experimental configurations. For the final focus, the progress towards implementation of these models into the NASA Ames Vertical Motion Simulator (VMS) is described. This task seeks to demonstrate the procedures of integrating a FLIGHTLAB flight simulation in the VMS environment, test fully integrated simulation with communication between flight dynamics, control, and propulsion models, and explore the essential aspects of simulation model integration in a full flight simulator environment. This includes I/O definition, initialization, trim, flying, etc. By expanding the capabilities of the AAM simulation models, they continue to develop as valuable and approachable modeling references.
Kia's entry into the light commercial vehicle market, launched at CES in Las Vegas, provided an overview of the potential range, from last-mile delivery vehicles to medium cargo vans. Kia's Platform Beyond Vehicles (PBVs) will enter production with the PV5 in 2025 at a new PBV-dedicated plant in Hwaseong, Korea. The larger PV7 will follow between 2027 and 2032. PV5, similar in size to the Ford Transit Connect, was always going to be the first of the range to enter production, according to executive vice president and head of Kia Global Design, Karim Habib. Design plans include a van, a high-roof van and a robot taxi. “The primary purpose was a business-to-business vehicle,” says Habib.” The business-to-customer side was definitely not very high on the list at the beginning. It came in more and more as the product took shape and as we saw the potential for it, but the business-to-business side was definitely the most important, whether it's ride-hailing or delivery logistics.
In the early stages of vehicle development, it is critical to establish performance goals for the major systems. The fundamental modes of body and chassis frames are typically assessed using FE models that are discretized using shell elements. However, the use of the shell-based FE method is problematic in terms of fast analysis and quick decision-making, especially during the concept phase of a vehicle design because it takes much time and effort for detailed modeling. To overcome this weakness, a one-dimensional (1D) method based on beam elements has been extensively studied over several decades, but it was not successful because of low accuracy for thin-walled beam structures. This investigation proposes a 1D method based on thin-walled beam theory with comparable accuracy to shell models. Most body pillars and chassis frame members are composed of thin-walled beam structures because of the high stiffness-to-mass ratio of thin-walled cross sections. However, thin-walled cross-sections are also vulnerable to sectional deformations in out-of-plane and in-plane directions, called warping and distortion, respectively. The proposed higher-order beam elements employ these sectional deformations as additional degrees of freedom. The validity of the proposed method is verified by solving the frame and body structures of a vehicle, whose results are compared with those of shell models. Furthermore, we develop a pre/post-processing program for higher-order beam analysis. Through this program, we can save significant time and effort in not only building higher-order beam models but also conducting sensitivity analysis for various variations.
When it displayed its Concept CLA Class for the first time in North America at CES 2024, Mercedes-Benz focused on the car's merging of novel user-experience, new all-encompassing operating system and a radical sound-system concept - all as examples of the company's intent to own its software-defined destiny. But the Concept CLA Class is more than a software story: it also is the showcase for the upcoming Mercedes-Benz Modular Architecture (MMA) that underpins the company's imminent new generation of compact, entry-level EVs. In a roundtable interview with media during CES, Christoph Starzynski, vice-president - development, Mercedes-Benz Cars, said several of the hardware innovations in the Concept CLA Class are central to improving EV performance across many segments, not just entry-level models. The concept car, he said, previews next-generation hardware that will be available when the production CLA models begin later in 2024 to replace the current-generation CLA, which has been in the market for some six years.
This paper describes a building-block approach for high-fidelity computational fluid dynamic simulations of NASA's Lift+Cruise (L+C) Vertical Take-off and Landing (VTOL) concept vehicle. The Reynolds-Averaged Navier-Stokes (RANS) equations are solved on overset structured grids using OVERFLOW. For these analyses, overset meshes are generated using recently developed automated meshing tools. A baseline study is initially performed on the vehicle fuselage with wings and tails. Vehicle components such as pylons and gears are then added individually and together to study incremental component aerodynamic effects. The results from this study are also used to demonstrate the capabilities of the automatic meshing tools for performing rapid computational analyses.
This initial study examines whether the Helicopter Association International (HAI) Fly Neighborly operational recommendations that are based on single main rotor/tail rotor configurations will hold for non-conventional UAM rotorcraft with multiple rotors. The 6-occupant quadrotor concept vehicle designed under the NASA Revolutionary Vertical Lift Technology (RVLT) Project is studied. The tip speed is 550 ft/sec, with three blades per rotor ("550/3"). Predictions are made for three steady maneuvers: level turns, descending turns, and climbing turns. The RVLT Toolchain is exercised using CAMRAD II, pyaaron/AARON/ANOPP2 and a beta version of AMAT (ANOPP2 Mission Analysis Tool). AMAT provides functionality to acoustically model the curved flight paths associated with maneuvers. In addition to quadrotor trim and performance, this study includes analysis of azimuthal variations of the vertical blade loading and its derivative in the form of contour plots on a rotor plane and line plots at one radial location (r/R=0.765). Quadrotor noise trends are analyzed using maximum Overall Sound Pressure Level (OASPL) and Effective Perceived Noise Level (EPNL). The Fly Neighborly guideline that addresses descents ("Level turns are quieter than descending turns") is predicted to hold for the RVLT Quadrotor as well.
GM Defense announced in July 2022 that the U.S. Army selected it to provide a battery-electric vehicle for analysis and demonstration. As a subsidiary of General Motors, that vehicle could be based on none other than the GMC Hummer EV pickup (www.sae.org/news/2022/06/hummer-ev-drive), production of which had just begun months before. Less than a year after that announcement, GM Defense in June 2023 revealed at the Modern Day Marine Expo in Washington, D.C. its Electric Military Concept Vehicle (eMCV). Featuring GM's Ultium Platform, the EV propulsion architecture satisfied the U.S. Army's requirement for a light- to heavy-duty BEV that helps to reduce fossil-fuel reliance in operational and garrison environments.
Elektrobit CEO discusses the landscape of automotive software development and explains why a lot of software doesn't have to be all that transformational. The phrase “software-defined vehicle” has embedded in the vehicle-development lexicon as the catchall for a new era of digitally driven products. But there is persistent disagreement about even the phrase's definition, much less the engineering scope required to transition from the industry's hardware-intensive history to a software-driven environment.
With funding from the US Departments of Transportation, Energy, Defense, and others, Airborne LiDAR Pipeline Inspection Sensor (ALPIS®) has evolved from a simple proof of concept model to a fully capable and successful commercial airborne pipeline inspection system. The ALPIS® system has undergone a long development period.
Asahi Kasei's concept electric shuttle is a rolling showcase of the supplier's materials and electronics innovations, with a strong focus on sustainability. Dubbed the AKXY2, it is “a complete vehicle design - exterior and interior,” Michael Franchy, director of North American Mobility at Asahi Kasei America, told SAE Media in Detroit. The AKXY2 showcases 18 technologies, including two collaborations with startup companies identified by Asahi Kasei's corporate venture-capital arm. Fifteen of the Asahi Kasei technologies either are in production or production-ready. “Everything visible, touchable and interactable is made from Asahi Kasei original or collaborative technology,” Franchy said. The concept emphasizes three overlapping themes: sustainability, satisfaction and society.
The technology below the smooth skin of BMW's i Vision Dee concept car, unveiled at CES 2023, marks a major step forward in the company's electric-vehicle competitiveness. Models based on the automaker's Neue Klasse EV architecture will ditch today's rectangular prismatic batteries for the type of large, cylindrical-form-factor cells that Tesla is pioneering with its “4680” cells, so named for their 46 mm × 80 mm dimensions. For its sixth-generation EV batteries, BMW and its battery partners - including China's CATL and EVE Energy - will adopt even-larger cells of “4595” and “46120” sizes. At a pre-CES media backgrounder held in Munich in December 2022, Martin Schuster, BMW Group VP for high-voltage batteries, said the new cells pack at least 10% more active battery material relative to their metal cases and are 20% more energy-dense.
The present numerical study investigates the design and analysis of a concept model Le Mans Grand Touring Prototype (LMGTP) car. Through analysis, aerodynamic pitch sensitivity and related factors are found to be detrimental to the straight-line stability of these high-speed race cars. Simulations are carried out on a commercial Computational Fluid Dynamics (CFD) tool for varying pitch angles of the car from −1° to +2.5°. For each pitch angle, steady-state pressure contours, velocity contours, and streamlines are presented. Additionally, coefficients and force values of lift and drag are calculated with the k-omega turbulence model implemented. Obtained numerical results are validated via Ahmed Body studies reported in the literature, and an average error deviation of 1.013% is exhibited. It is observed that lift force at the front axle increases with increasing pitch angles, leading to reduced pitch stability. At a peak of 2.5° pitch angle, the destabilizing lift force peaks at 1872 N, with the trend showing potential for front axle liftoff. The obtained results are validated with the aerodynamic stability derivative using MATLAB Simulink. A strong correlation is observed for CFD results with respect to theoretical aerodynamic pitch stability derivative calculations with peak nose-up conditions (+2.5°) indicating the highest levels of instability.
The NVH optimization of new vehicle models can in principle only be carried out in a relatively late stage of the development process, when the geometrical data (CAD) are available and can be used to generate detailed Finite Element (FE) models of the car body. Unfortunately, in this stage of the development process most of the geometrical data are already fixed and countermeasures are limited and expensive. In order to be able to evaluate design concepts in an earlier conceptual stage of the development process existing models of similar predecessor vehicles must be used leading to techniques such as “mesh-morphing” or “concept modelling” (see for instance [1, 2]). Here, a different approach is investigated based on a substructuring technique. In principle the coupling of the component-structures coming from different models would require post-processing in order to obtain compatible interface degrees-of-freedom (DOFs), an operation which in most cases must be carried out manually and is very time consuming. This paper presents a novel substructuring approach that tackles a continuous interface by only considering a small set of coupling DoFs. This approach employs the discretisation of interfaces between structural parts or structural-acoustic domains in terms of pivotal points and patches. In this manner, the requirement of spatial continuity between the models of the separate substructures is no longer needed and subsystems with incompatible interfaces can be coupled. Thus, an efficient vibro-acoustic design optimisation procedure for components shared by different vehicle models, such as the car floor, is enabled. It will be shown that a single car floor model can be successfully coupled with different upper-body structures, even when they have a different location of coupling DoFs.
A code-to-code comparison has been performed for high-fidelity simulations of NASA's six-passenger quadrotor air taxi concept vehicle. The multidisciplinary simulations combine comprehensive rotorcraft dynamics with high-fidelity fluid dynamics obtained from an unsteady Navier-Stokes computational fluid dynamics code. An internal overset-grid assembler, Yoga, developed at the NASA Langley Research Center, is employed to efficiently handle the communications between component grids particularly for the present large-scale, unstructured-grid systems. The simulation results are then compared with those in the literature. A quantitative comparison of converged trim angles has been performed and normal force, chord force, and pitchingmoment coefficients are presented for qualitative comparison. Workflow changes to meet the unique demands of multirotor vehicle analysis are also discussed.
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