Browse Topic: Drag

Items (4,511)
In order to manage the serious global environmental problems, the automobile industry is rapidly shifting to electric vehicles (EVs) which have a heavier weight and a more rearward weight distribution. To secure the handling and stability of such vehicles, understanding of the fundamental principles of vehicle dynamics is inevitable for designing their performance. Although vehicle dynamics primarily concerns planar motion, the accompanying roll motion also influences this planar motion as well as the driver's subjective evaluation. This roll motion has long been discussed through various parameter studies, and so on. However, there is very few research that treats vehicle sprung mass behavior as “vibration modes”, and this perspective has long been an unexplored area of vehicle dynamics. In this report, we propose a method to analytically extract the vibration modes of the sprung mass by applying modal analysis techniques to the governing equations of vehicle handling and stability
Kusaka, KaoruYuhara, Takahiro
This paper introduces a new approach for measuring changes in drag force across different vehicle configurations using an on-road testing technique. The method involves fixing the vehicle’s power across configurations and then measuring the resulting speed differences. A detailed formulation is provided on how these speed variations can be used to calculate the change in drag force for each configuration. The OBD II port is used to access and record additional data necessary for the calculations. The method is applied to both a passenger car and a commercial van to evaluate drag changes for different vehicle add-ons. A roof sign was installed at various positions along the roof of the vehicles to assess drag increases, while novel rear appendages were fitted to both vehicles to evaluate the resulting drag reductions. Detailed CFD simulations were performed on the road-tested configurations to compare the simulated drag changes with those measured on the road. Excellent agreement was
Connolly, Michael GerardIvankovic, AlojzO'Rourke, Malachy J.
An energy-use analysis is presented to examine the potential energy-savings and range-extension benefits of aerodynamic improvements to tractors and trailers used in commercial transportation. The impetus for the study was the observation of aerodynamically-redesigned/optimized tractor shapes of emerging zero-emission commercial vehicles that have the potential for significant drag reduction over conventional aerodynamic tractors. Using wind-tunnel test results, a series of aerodynamic performance models were developed representing a range of tractor and trailer combinations. From modern day-cab and sleeper-cab tractors to aerodynamically-optimized zero-emission cab concepts, paired with standard dry-van trailers or low-drag trailer concepts, the study examines the energy use, and potential savings thereof, from implementing various fleet configurations for different operational duty cycles. An energy-use analysis was implemented to estimate the energy-rate contributions associated
McAuliffe, BrianGhorbanishohrat, Faegheh
A new method for bearing preload measurement has shown potential for both high accuracy and fast cycle time using the frequency response characteristics of the power transmission system. One open problem is the design of the production controller, which relies on a detailed sensitivity study of the system frequency response to changes in the bearing and system design parameters. Recently, an analytical model was developed for multi-row tapered roller bearings that includes all appropriate bearing and power transmission system design parameters. During the assembly process, some of the parameters related to the roller positions cannot be controlled. These parameters include the actual position of the first roller compared to the vertical axis, the relative position of the rollers between the bearing rows, and others. This work presents a sensitivity analysis of the effects of those uncontrollable parameters on the analytical model. The sensitivity study determines the percentage change
Gruzwalski, DavidMynderse, James
With better performance and usage of clean and renewable energy, electric vehicles have ushered in more and more consumers’ favor nowadays. However, insufficient driving range especially in hot and cold ambient conditions still greatly restricts the extensive application of electric vehicles. This paper presents a methodology of establishing multi-discipline coupled full vehicle model in AMESim to investigate the energy consumption and driving range of an electric vehicle in normal and hot ambient conditions. Full vehicle energy consumption test was carried out in the climate chamber to check the accuracy of simulation results. Firstly, basic framework of the full vehicle model established in AMESim was introduced. Next, modeling details of sub-systems including vehicle dynamic system, electrical system, coolant circuit system, air-conditioning system and control strategy were illustrated. Then, full vehicle energy consumption tests were carried out in 23°C and 38°C ambient conditions
Zhou, ShuaiLiu, HuaijuYu, HuiliYan, XuYan, Junjie
Roller bearings are used in many rotating power transmission systems in the automotive industry. During the assembly process of the power transmission system, some types of roller bearings (e.g., tapered roller bearings) require a compressive preload force. Those bearings' rolling resistance and lifespan strongly depend on the preload set during the installation process. Therefore, accurate preload setting can improve bearing efficiency, increase bearing lifespan, and reduce maintenance costs over the life of the vehicle. A new method for bearing preload measurement has shown potential for high accuracy and fast cycle time using the frequency response characteristics of the power transmission system. One open problem is the design of the production controller, which relies on a detailed sensitivity study of the system frequency response to changes in the bearing and system design parameters. Recently, an analytical model was developed for multi-row tapered roller bearings that includes
Gruzwalski, DavidMynderse, James
Experimental studies of wind tunnel blockage for road vehicles have usually been conducted in model wind tunnels. Models have been made in a range of scales and tested in a working section of fixed size. More recently CFD studies of blockage have been undertaken, which allow a fixed vehicle size and the blockage is varied by changing the cross section of the flow domain. This has some inherent advantages. A very recent database of CFD derived drag and lift coefficients for different road vehicle shapes and simple bodies tested in a closed wall tunnel with a wide range of blockage ratios has become available and provides some additional insight into the blockage phenomenon. In this paper a process is developed to derive the parameters influencing wind tunnel blockage corrections from CFD data. These are shown to be reasonably effective for correcting the measured drag and lift coefficients at blockage ratios up to 10%.
Howell, JeffButcher, DanielGleason, Mark
Novel experimental and analytical methods were developed with the objective of improving the reliability and repeatability of coast-down test results. The methods were applied to coast-down tests of a SUV and a tractor-trailer combination, for which aerodynamic wind-tunnel data were available for comparison. The rationale was to minimize the number of unknowns in the equation of motion by measuring rolling and mechanical resistances and wheel-axle moments of inertia, which was achieved using novel experimental techniques and conventional rotating-drum tests. This led to new modelling functions for the rolling and mechanical resistances in the equation of motion, which was solved by regression analysis. The resulting aerodynamic drag coefficient was closer to its wind-tunnel counterpart, and the predicted low-speed road load was closer to direct measurements, than the results obtained using conventional methods. It is anticipated that applying the novel techniques to characterize the
Tanguay, Bernardde Souza, Fenella
The vehicle wake region is of high importance when analyzing the aerodynamic performance of a vehicle. It is characterized by turbulent separated flow and large low-pressure regions that contribute significantly to drag. In some cases, the wake region can oscillate between different modes which can pose an engineering challenge during vehicle development. Vehicles that exhibit bimodal wake behavior need to have their drag values recorded over a sufficient time period to take into account the low frequency shift in drag signal, therefore, simulating such vehicle configurations in CFD could consume substantial CPU hours resulting in an expensive and inefficient vehicle design iterations process. As an alternative approach to running simulations for long periods of time, the impact of adding artificial turbulence to the inlet on wake behavior and its potential impact on reduced runtime for design process is investigated in this study. By adding turbulence to the upstream flow, the wake
DeMeo, MichaelParenti, GuidoMartinez Navarro, AlejandroShock, RichardFougere, NicolasRazi, PooyanOliveira, DaniloLindsey, CraigYu, ChenxingBreglia Sales, Flavio
The natural wind experienced on public roads can increase the yaw angle and therefore drag coefficient (CD), which may contribute to the discrepancy between catalog fuel economy and actual fuel economy. The impact of yaw characteristics alone on fuel economy during actual driving has not been verified or proven as it is difficult to obtain actual driving data under uniform conditions. For this reason, shape optimization is normally performed at zero-yaw through the aerodynamic development phases. In this paper, two vehicles with different yaw sensitivity characteristics are driven simultaneously, and fuel economy measurements are performed simultaneously with ambient airflow, environment, and vehicle conditions. The results where the conditions of the two vehicles match are extracted to clarify the impact of the differences of yaw characteristics on fuel economy. The obtained results matched the values predicted by theoretical calculations for the impact of yaw angle on fuel economy
Onishi, YasuyukiNichols, LarryMetka, Mattmasumitsu, YasutakaInoue, Taisuke
Emerging zero-emission-powertrain concepts are providing opportunities to re-shape heavy trucks for improved aerodynamic performance. To investigate the potential for energy savings through aerodynamic improvements, with a goal to inform operators and regulators of such benefits, a multi-phase project was initiated to design and evaluate aerodynamic improvements for Class 8 tractor-trailer combinations. While the focus was battery-electric and hydrogen-fuel-cell powered trucks, improvements for internal-combustion powered trucks were also examined. Previously-reported activities included a scaled-model wind-tunnel test that demonstrated the potential for up to 9% drag reduction from simple shape adaptations, with a follow-up CFD study providing guidance towards further optimization. This paper presents wind-tunnel-test results using a high-fidelity 30%-scale model of a new aerodynamic tractor concept, with comparison to a conventional North American Class 8 tractor with a modern
Ghorbanishohrat, FaeghehMcAuliffe, BrianO'Reilly, Harrison
Reducing aerodynamic drag through Vehicle-Following is one of the energy reduction methods for connected and automated vehicles with advanced perception systems. This paper presents the results of an investigation aimed at assessing energy reduction in light-duty vehicles through on-road tests of reducing the aerodynamic drag by Vehicle-Following. This study provides insights into the effects of lateral positioning in addition to intervehicle distance and vehicle speed, and the profile of the lead vehicle. A series of tests were conducted to analyze the impact of these factors, conducted under realistic driving conditions. The research encompasses various light-duty vehicle models and configurations, with advanced instrumentation and data collection techniques employed to quantify energy-saving potential. The study featured two sets of L4 capable light duty vehicles, including the Stellantis Pacifica PHEV minivan and Stellantis RAM Truck, examined in various lead and following vehicle
Poovalappil, AmanRobare, AndrewSchexnaydre, LoganSanthosh, PruthwirajBahramgiri, MojtabaBos, Jeremy P.Chen, BoNaber, JeffreyRobinette, Darrell
With the increasing prevalence of electric vehicles (EVs), decreasing vehicle drag is of upmost importance, as range is a primary consideration for customers and has a direct bearing on the cost of the vehicle. While the relationship between drag and range is well understood, there exists a discrepancy between the label range and the real-world range experienced by customers. One of the factors influencing the difference is the ambient wind condition that modifies the resultant air speed and yaw angle, which is typically minimized during SAE coast-down testing. The following study implements a singular wind-averaged drag (WAD) coefficient which is derived from a 3-point yaw curve to show the impact of yaw as compared to the zero-yaw condition. This leads to an interesting dilemma for the vehicle aerodynamicist: whether to optimize the vehicle's exterior shape for low wind (zero yaw) conditions or for real-world conditions where the ambient wind generally produces a few degrees of yaw
Kaminski, MeghanD'Hooge, AndrewBorton, Zackery
This paper is a continuation of a previous effort to evaluate the post-impact motion of vehicles with high rotational velocity within various vehicle dynamic simulation softwares. To complete this goal, this paper utilizes a design of experiments (DOE) method. The previous papers analyzed four vehicle dynamic simulation software programs; HVE (SIMON and EDSMAC4), PC-Crash and VCRware, and applied the DOE to determine the most sensitive factors present in each simulation software. This paper will include Virtual Crash into this methodology to better understand the significant variables present within this simulation model. This paper will follow a similar DOE to that which was conducted in the previous paper. A total of 32 trials were conducted which analyzed ten factors. Aerodynamics, a factor included in the previous DOE, was not included within this DOE because it does not exist within Virtual Crash. The same three response variables from the previous DOE were measured to determine
Roberts, JuliusCivitanova, NicholasStegemann, JacobBuzdygon, DavidThobe, Keith
As global warming and environmental problems are becoming more serious, tires are required to achieve a high level of performance trade-offs, such as low rolling resistance, wet braking performance, driving stability, and ride comfort, while minimizing wear, noise, and weight. However, predicting tire wear life, which is influenced by both vehicle and tire characteristics, is technically challenging so practical prediction method has long been awaited. Therefore, we propose an experimental-based tire wear life prediction method using measured tire characteristics and the wear volume formula of polymer materials. This method achieves practical accuracy for use in the early stages of vehicle development without the need for time-consuming and costly real vehicle tests. However, the need for improved quietness and compliance with dust regulations due to vehicle electrification requires more accuracy, leading to an increase in cases requiring judgment through real vehicle tests. To address
Ando, Takashi
Vehicle handling is significantly influenced by aerodynamic forces, which alter the normal load distribution across all four wheels, affecting vehicle stability. These forces, including lift, drag, and side forces, cause complex weight transfers and vary non-linearly with vehicle apparent velocity and orientation relative to wind direction. In this study, we simulate the vehicle traveling on a circular path with constant steering input, calculate the normal load on each tire using a weight transfer formula, calculate the effect of lift force on the vehicle on the front and rear, and calculate the vehicle dynamic relation at steady state because the frequency of change due to aerodynamic load is significantly less than that of the yaw rate response. The wind velocity vector is constant while the vehicle drives in a circle, so the apparent wind velocity relative to the car is cyclical. Our approach focuses on the interaction between two fundamental non-linearity’s: the nonlinear
Patil, HarshvardhanWilliams, Daniel
The increased importance of aerodynamics to help with overall vehicle efficiency necessitates a desire to improve the accuracy of the measuring methods. To help with that goal, this paper will provide a method for correcting belt-whip and wheel ventilation drag on single and 3-belt wind tunnels. This is primarily done through a method of analyzing rolling-road only speed sweeps but also physically implementing a barrier. When understanding the aerodynamic forces applied to a vehicle in a wind tunnel, the goal is to isolate only those forces that it would see in the real-world. This primarily means removing the weight of the vehicle from the vertical force and the rolling resistance of the tires and bearings from the longitudinal force. This is traditionally done by subtracting the no-wind forces from the wind at testing velocity forces. The first issue with the traditional method is that a boundary layer builds up on the belt(s), which can then influence a force onto the vehicle’s
Borton, Zackery
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
Chaligné, SébastienGaylard, Adrian PhilipSimmonds, NicholasTurner, Ross
This paper summarizes work on the application of a new and fully parallelized native GPU-based finite-volume solver on the DrivAER Notchback configuration using a wall-function LES approach. A series of meshes generated using a Rapid-Octree strategy have been investigated, and results for drag, surface pressure coefficient and velocity profile are compared with available experimental data.
Menter, FlorianDalvi, AshwiniFlad, DavidSharkey, Patrick
In this work, a modified Ahmed body with both upsweep and downsweep was used to create a complex wake. The time-averaged streamline topology revealed that the wake was composed primarily of a torus past the vertical base and two pairs of streamwise-oriented vortices on the upper and lower slant edges. Several vortex identification methods including three-dimensional (3D) (Q−, λ2−, Ω−criteria, and Liutex method) and two-dimensional (2D) (Γ1−criterion) methods were compared to determine the effectiveness in identifying complex wake structures. Of the 3D methods analyzed, none produced wholly satisfactory results. The Q− and λ2−criteria were plagued by well noted issues; failing to separate shear from rotation and threshold sensitivity which led to inconsistently identifying the weaker torus. The Ω−criterion addressed all of these concerns, especially identifying the torus consistently. However, the identified torus structure did not reflect the physical structure observed using the
Aultman, MatthewDuan, Lian
As the first pure electric flagship sedan under the Geely Galaxy brand, a challenging aerodynamic target was set at the early stage of Geely Galaxy E8 for reducing electric power consumption and improving vehicle range. In response, the aerodynamic team formulated a detailed development plan and an overall drag reduction strategy. After conducting numerous loops of simulations and wind tunnel tests, along with continuous cross-disciplinary communication and collaboration, a product with outstanding aerodynamic performance was successfully developed. During the aerodynamic development of the E8, the primarily utilized steady-state simulations sometimes revealed significant discrepancies when compared to wind tunnel test results, particularly in schemes such as the air curtain, aerodynamic rims, and rear light feature optimizations. Some trends were even contradictory. Further investigations demonstrated that unsteady simulation methods captured different flow field information
Li, QiangLiu, HuanYang, TianjunLiang, ChangqiuZhu, ZhenyingLiao, Huihong
The research presented in this paper proposes an effective numerical approach based on computational fluid dynamics (CFD) to analyze the flow structure around the Formula 1 rear wing. The study investigates the influence of endplates on the flow behavior and aerodynamic attributes of the wing. Additionally, it examines the implementation of louvers and cutouts to manipulate the interaction of multiple vortices, thereby mitigating the strength of primary wingtip vortices and the consequent induced drag. Three-dimensional steady-state computations were conducted using the ANSYS® commercial suite. The FLUENT™ solver, employing Reynolds-averaged Navier–Stokes (RANS) equations modeled with a two-equation shear stress transport (SST) k-ω turbulence model, was utilized for the analysis. Post-processing and visualization of the flow field in the near wake region downstream of the rear wing were performed using Tecplot®. Validation of the turbulence model was achieved through the quasi-3D NACA
Kalsi, Mandeep SinghJoshi, Upendra Kumar
The paper present numerical effects of supercritical airfoil SC (2) 0414 having circular cavities at three different chord wise locations from leading to trailing edge. Here passive control method is widely applied by altering the \baseline airfoil surface coordinates to ascertain the aerodynamic behavior of the cavity at 40 %, 50 % and 60 % of the chord length respectively. The cavity shapes were deformed using Bezier curve to observe vortex pattern in the cavity region. Structured meshing was employed. The analysis was performed on SC 2 (0) 414 two-dimensional airfoil using commercial CFD ANSYS Fluent software where Spalart- Allmaras turbulence model technique is chosen to solve boundary layer problems on adverse pressure gradient and tested at extended range of angle of attack (-150 to 150) at Mach number 0.85. The study highlights the aerodynamic characteristics of lifting coefficient, drag coefficient and lift to drag ratio. It was observed that the cavity in suction surface
Pushparaj, Catherine VictoriaP, Booma DeviD, PiriadarshaniGanesan, BalajiGanesan, Santhosh KumarRaja, Vijayanandh
Current work details the preliminary CFD analysis performed on custom-built race car by Team Sakthi Racing team as part of Formula SAE competition using OpenFOAM. The body of the race car is designed in compliance with FSAE regulations, OpenFOAM utilities and solvers are used to generate volumetric mesh and perform CFD analysis. Formula student tracks are typically designed with numerous sharp turns and a few long straights to maintain low speeds for safety. In order to enhance the cars’ performance in sharp turns, the race car should be equipped with aerodynamic devices like nose cone and wings on both the rear and front ends within the confines of the formula student racing rules. Thus, efficient aerodynamic design is highly critical to maximizing tire grip by ensuring consistent contact with the track, reducing the risk of skidding, and maintaining control, especially during high-speed maneuvers. In this work, the performance and behavior of the race car, both with and without the
Rangarajan, KishorePushpananthan, BlesscinAnumolu, LakshmanSelvakumar, KumareshJayakumar, Shyam Sundar
From biology, to genetics, and paleontology, these fields share the DNA as a common and time-proven tool. In science, pressure may be such a tool, shared by thermodynamics, material science, and astrophysics, but not by aerodynamics. Pressure is a shorthand for a force acting perpendicular to a surface. When this surface is reduced to zero, so should the pressure. The wing area of an aircraft acts as a reference area to calculate its parasite drag coefficient. In this scenario, the parasite drag acts as a force over the wing area. If the wing area is reduced to zero, its parasite drag does not, as the fuselage is still generating parasite drag. The ratio of the parasite drag and wing area is an example of a pressure construct that uses a physically irrelevant reference area and has no absolute zero. Pressure constructs, more frequently used than pressures in aerodynamics, are a math-based parameter that preserve dimensional propriety according to the Buckingham Pi theorem but lacks a
Burgers, Phillip
The aerodynamic force produced by external flows over two-dimensional bodies is typically decomposed into two components: lift and drag. In race cars, the lift is known as downforce and it is responsible for increasing tire grip, thereby enhancing traction and cornering ability. Drag acts in the direction opposite to the car’s motion, reducing its acceleration and top speed. The primary challenge for aerodynamicists is to design a vehicle capable of producing high downforce with low drag. This study aims to optimize the shape of a multi-element rear wing profile of a Formula 1 car, achieving an optimal configuration under specific prescribed conditions. The scope of this work was limited to a 2-D model of a rear wing composed of two 4-digit NACA airfoils. Ten control parameters were used in the optimization process: three to describe each isolated profile, two to describe their relative position, and two to describe the angles of attack of each profile. An optimization cycle by finite
Souza Dourado, GuilhermeHayashi, Marcelo Tanaka
Road loads, encompassing aerodynamic drag, rolling resistance, and gravitational effects, significantly impact vehicle design and performance by influencing factors such as fuel efficiency, handling, and overall driving experience. While traditional coastdown tests are commonly used to measure road loads, they can be influenced by environmental variations and are costly. Consequently, numerical simulations play a pivotal role in predicting and optimizing vehicle performance in a cost-effective manner. This article aims to conduct a literature review on road loads and their effects on vehicle performance, leveraging experimental data from past studies from other researchers to establish correlations between measured road loads and existing mathematical models. By validating these correlations using real-world measurements, this study contributes to refining predictive models used in automotive design and analysis. The simulations in this study, utilizing five distinct empirical
Pereira, Leonardo PedreiraBraga, Sérgio Leal
The fuel economy performance of road vehicles is one of the most important factors for a successful project in the current automotive industry due to greenhouse effect gases reduction goals. Aerodynamics and vehicle dynamics play key roles on leading the automaker fulfill those factors. The drag coefficient and frontal area of the vehicle are affected by several conditions, where the ground height and pitch angle are very relevant, especially for pickup trucks. In this work, we present a combined study of suspension trim heights and aerodynamics performance of a production pickup truck, where three different loading conditions are considered. The three weight configurations are evaluated both in terms of ground height and pitch angle change considering the suspension and tires deflection and these changes are evaluated in terms of drag coefficient performance, using a Lattice-Boltzmann transient solver. Results are compared with the baseline vehicle at road speed condition, where both
Buscariolo, Filipe FabianTerra, Rafael Tedim
This document specifies dimensional, functional and visual requirements for Automotive grade coaxial cable. This material will be designated AG for general-purpose automotive applications or AG LL for low loss applications. It is the responsibility of the user of this cable to verify the suitability of the selected product (based on dimensional, mechanical, electrical and environmental requirements) for its intended application. It is the responsibility of the supplier to retain and maintain records as evidence of compliance to the requirements detailed in this standard.
USCAR
Aerodynamic analysis is a primary requirement in the development of electric scooters to predict the impact of air flow around the vehicle on critical performance parameters including the overall range, vehicle stability due to wind loads, air cooling of electric motor and battery. Any new design of vehicle requires an aerodynamic evaluation to estimate the variations in drag forces with speed. It is prohibitively expensive and time consuming to perform full-scale model wind tunnel tests on each variant of the vehicle configuration for wide range of driving scenarios. Physics-based 3D simulation is the preferred approach in the present context and the use of Computational Fluid Dynamics (CFD) for such cases has been well understood and established. Although only the external shape changes make a difference to external aerodynamics, sometimes even a small variation in shape could trigger unwanted flow behavior leading to large drag forces, or enhance the vehicle performance by reducing
Balachandran, KarthikDas, AlokShinde, Pranav
Since the inception of battery driven electric vehicles in the automotive world, there has been a constant challenge in maximizing the range of an electric vehicles through various means including battery technology, vehicle weight optimization, low drag coefficients etc. The tires being a viscoelastic composite material have now become a vital to the range performance of an EV. The rolling resistance of a tire is now become a hotter topic than ever. The rolling resistance coefficient (RRC) is the measure of energy loss during rolling due to viscoelastic dissipation in the tire. The viscous dissipation in tire arises due to hysteresis in the various components of a tire including tread, sidewall, inner liner, apex etc rubber compounds. The internal friction between layers of body ply, steel belts and tread crown ply also contribute to the internal heat generation. Therefore, the development of ultra-low RRC tires is a serious challenge for tire engineers. Nevertheless, the recent
Mishra, NitishSingh, Ram Krishnan
The SAE J2923 procedure is a recommended practice that applies to on-road vehicles with a GVWR below 4540 kg equipped with disc brakes.
Brake Dynamometer Standards Committee
This paper investigates the drag reduction matching of modular flying cars based on a nested configuration. To address the high aerodynamic drag issue of traditional modular flying car configurations, a nested design scheme is proposed. In this scheme, the cabin is extracted from a low-drag car and combined with the flying module using a nested approach, achieving aerodynamic matching between the cabin, driving module, and flying module. First, the conceptual design of the new modular flying car and the parameters of each module, including the driving module, cabin module, and flying module, are introduced. Then, computational fluid dynamics (CFD) methods are utilized to numerically simulate the aerodynamic characteristics of the new flying car, and the results are compared with the existing typical modular flying car, AIRBUS. The research results show that the nested modular flying car exhibits superior aerodynamic performance in both driving and flying modes. Compared to the typical
Li, YanlongYe, ShengfeiZhou, Hua
The objective of the paper is to enhance the aerodynamic performance of an aircraft wing using the injection–suction method. This method utilizes simulation techniques based on the Reynolds-averaged Navier–Stokes (RANS) equations with a k-epsilon turbulence model solver. The results of the simulations demonstrate a significant improvement in the wing’s performance, with a 33% increase in the stalling angle and a 10% enhancement in the lift coefficient compared to the baseline airfoil. The drag value is decreasing up to 40% depending on the angle of attack. The novelty of this proposed method was in the strategic placement of injection and suction. Injection is applied over the top airfoil at the separation point, while suction is applied at the midsection of the bottom airfoil. This configuration optimizes the aerodynamic flow over the wing, leading to improved performance metrics of lift coefficient and stall angle. This concept has potential applications in subsonic fixed-wing
Rameshbhai, Patel AnkitkumarPatidar, Vijay KumarBalaji, K.
The objective of this study is to develop a new aerofoil shape to enhance aerodynamic efficiency in turbo machinery applications. Numerical and experimental analyses were conducted by solving the RANS equations using the k-omega SST and standard k-epsilon models. A wind tunnel was employed to measure the lift and drag coefficients of the aerofoil, and these results were compared with those of existing turbo machinery designs. The results indicate a 38% increase in the peak lift coefficient and a 25% improvement in stall characteristics. Additionally, a 20% reduction in overall drag was observed across both methods. The novelty of this work lies in creating a more curved aerofoil using the Bézier curve method and the subsequent assessment of its aerodynamic performance through numerical and experimental approaches. The proposed method can be applied to various aerofoil types to enhance the aerodynamic performance of low-speed turbo machinery.
R Vala, JigneshPatel, D. K.Umathe, ManishaBalaji, K.
Over the past twenty years, the automotive sector has increasingly prioritized lightweight and eco-friendly products. Specifically, in the realm of tyres, achieving reduced weight and lower rolling resistance is crucial for improving fuel efficiency. However, these goals introduce significant challenges in managing Noise, Vibration, and Harshness (NVH), particularly regarding mid-frequency noise inside the vehicle. This study focuses on analyzing the interior noise of a passenger car within the 250 to 500 Hz frequency range. It examines how tyre tread stiffness and carcass stiffness affect this noise through structural borne noise test on a rough road drum and modal analysis, employing both experimental and computational approaches. Findings reveal that mid-frequency interior noise is significantly affected by factors such as the tension in the cap ply, the stiffness of the belt, and the properties of the tyre sidewall.
Subbian, JaiganeshM, Saravanan
This research study investigates the influence of undercover design on three critical aspects of vehicle performance: water entering into air intake filter, Aerodynamic performance, thermal performance on vehicle engine room components (Condenser, Radiator and Air Intake System). Undercover serves the purpose of protecting Engine, underhood components and also improves aerodynamics of the vehicle. Through CFD simulations, various undercover design configurations: Full Undercover, no undercover and half undercover cases are evaluated to assess their effectiveness in mitigating the water ingress into the air intake system. Additionally, we explore the implications of these design alterations on the thermal performance and aerodynamic drag. By systematically exploring these interactions, results provided valuable insights on the effect of three undercover configurations related to vehicle performance which can help automotive engineers to develop the undercovers that strike a balance
Padakandla, Kishore KumarNagendra, K. YallaBisoyi, Ram Prasad
There are examples in aerodynamics that take advantage of electric-to-aerodynamic analogies, like the law of Biot–Savart, which is used in aerodynamic theory to calculate the velocity induced by a vortex line. This article introduces an electric-to-aerodynamic analogy that models the lift, drag, and thrust of an airplane, a helicopter, a propeller, and a flapping bird. This model is intended to complement the recently published aerodynamic equation of state for lift, drag, and thrust of an engineered or a biological flyer by means of an analogy between this equation and Ohm’s law. This model, as well as the aerodynamic equation of state, are both intended to include the familiar and time-proven parameters of pressure, work, and energy, analytical tools that are ubiquitous in all fields of science but absent in an aerodynamicists’ day-to-day tasks. Illustrated by various examples, this modeling approach, as treated in this article, is limited to subsonic flight.
Burgers, Phillip
The Kenworth booth at the 2024 Advanced Clean Transportation (ACT) Expo in Las Vegas garnered much interest thanks to the reveal of its futuristic-looking SuperTruck 2. Developed over a six-year period as part of the DOE's SuperTruck program, the demonstrator vehicle improved freight efficiency by up to 136% compared to the 2009 T660 model. The team improved fuel efficiency up to 12.8 mpg and reduced the combination weight by about 7,100 lb (3,220 kg) - 4,150 lb (1,880 kg) from the tractor and 2,950 lb (1,340 kg) from the trailer. The design led to a 48% reduction in drag compared to Kenworth's baseline vehicle. A Paccar MX-11 diesel engine, rated at 455 hp (339 kW), is paired with a Paccar TX-12 automated transmission and a 48-volt electric generator, creating a mild hybrid system to operate accessories and provide engine-off “hoteling.” The 48V generator also powers the exhaust heater in an in-house-developed close coupled aftertreatment system that demonstrated CARB 2027 ultra-low
Gehm, Ryan
Homologation is an important process in vehicle development and aerodynamics a main data contributor. The process is heavily interconnected: Production planning defines the available assemblies. Construction defines their parts and features. Sales defines the assemblies offered in different markets, where Legislation defines the rules applicable to homologation. Control engineers define the behavior of active, aerodynamically relevant components. Wind tunnels are the main test tool for the homologation, accompanied by surface-area measurement systems. Mechanics support these test operations. The prototype management provides test vehicles, while parts come from various production and prototyping sources and are stored and commissioned by logistics. Several phases of this complex process share the same context: Production timelines for assemblies and parts for each chassis-engine package define which drag coefficients or drag coefficient contributions shall be determined. Absolute and
Jacob, Jan D.
The problem of transport-related greenhouse gas (GHG) emissions is common knowledge. In recent years, the electrification of cars is being prompted by many as the best solution to this issue. However, due to their rather big battery packs, the embedded ecological footprint of electric cars has been shown to be still quite high. Therefore, depending on the size of the vehicle, tens -if not hundreds- of thousands of kilometres are needed to offset this burden. Human-powered vehicles (HPVs), thanks to their smaller size, are inherently much cleaner means of transportation, yet their limited speed impedes widespread adoption for mid-range and long-range trips, favouring cars, especially in rural areas. This paper addresses the challenge of HPVs speed, limited by their low input power and non-optimal distribution of the resistive forces. The article analyses dissipation sources from rolling resistance, aerodynamics, inertia, and more for various vehicles, emphasizing the fundamental role of
Di Gesù, AlessandroGastaldi, ChiaraDelprete, Cristiana
The present study discusses the determination of the Seal drag force in the application where an elastomeric seal is used with a metallic interface in the presence of different fluids. An analytical model was constructed to predict the seal drag force and an experimental test was performed to check the fidelity of the analytical model. A Design of Experiment (DoE) was utilized to perform an experimental test considering different factors affecting the Seal drag force. Statistical tools such as the Test for Equal Variances and One Way Analysis of Variance (ANOVA) were used to draw inferences for the population based on samples tested in the DoE test. It was observed that Glycol fluids lead to lubricant wash-off resulting in increased seal drag force. Additionally, non-lubricated seals tend to show higher seal drag force as compared to lubricated seals.
Yarolkar, MakrandTelore, MilindPatil, Sandip
Dimensional optimization has always been a time-consuming process, especially for aerodynamic bodies, requiring much tuning of dimensions and testing for each sample. Aerodynamic auxiliaries, especially wings, are design dependent on the primary model attached, as they influence the amount of lift or reduction in drag which is beneficial to the model. This study aims to reduce the time period taken to finalize the design parameter for the same. For a wing, the angle of attack is essential in creating proper splits to incoming winds, even under high velocities with larger distances from the separation point. In the case of a group of wings, each wing is then mentioned as a wing element, and each wing is strategically positioned behind the previous wing in terms of its vertical height and its self-angle of attack to create maximum lift. At the same time, its drag remains variable to its shape ultimately maximizing the CL/CD ratio. A high value of CL indicates a significant component of
Hujare, Pravin PHujare, Deepak PChoudhary, PrateekSakat, AbhishekKaranjkar, Rushil
The design of aerospace applications necessities precise predictions of aerodynamic properties, often obtained through resource-intensive numerical simulations. These simulations, though they are accurate, but are unsuitable for iterative design processes due to their computational complexity and time-consuming nature. To address this challenge, machine learning, with its data-driven approach and advanced algorithms, offers a novel and cost-effective solution for predicting airfoil characteristics with exceptional precision and speed. This study explores the application of the Back-Propagation Neural Network (BPNN), a machine learning model, to forecast critical aerodynamic coefficients such as lift and drag for airfoils. The BPNN model is fed with input parameters including the airfoils name, flow Reynolds number, and angle of attack in relation to incoming flows. Training the BPNN model is accomplished using a dataset derived from CFD simulations employing the Spalart–Allmaras
M N, LochanN, RakshithaPrasad, B K SwathiSivasubramanian, Jayahar
Severe problem of aerodynamic heating and drag force are inherent with any hypersonic space vehicle like space shuttle, missiles etc. For proper design of vehicle, the drag force measurement become very crucial. Ground based test facilities are employed for these estimates along with any suitable force balance as well as sensors. There are many sensors (Accelerometer, Strain gauge and Piezofilm) reported in the literature that is used for evaluating the actual aerodynamic forces over test model in high speed flow. As per previous study, the piezofilm also become an alternative sensor over the strain gauges due to its simple instrumentation. For current investigation, the piezofilm and strain gauge sensors have mounted on same stress force balance to evaluate the response time as well as accuracy of predicted force at the same instant. However, these force balance need to be calibrated for inverse prediction of the force from recorded responses. A reliable multi point calibration
Kamal, AbhishekDeka, SushmitaSahoo, NiranjanKulkarni, Vinayak
The study of aerodynamic forces in hypersonic environments is important to ensure the safety and proper functioning of aerospace vehicles. These forces vary with the angle of attack (AOA) and there exists an optimum AOA where the lift to drag force ratio is maximum. In this paper, computational analysis has been performed on a blunt cone model to study the aerodynamic characteristics when hypersonic flow is allowed to pass through the model. The flow has a Mach number of 8.44 and the AOA is varied from 0° to 20°. The commercial CFD solver ANSYS FLUENT is used for the computational analysis and the mesh is generated using the ICEM CFD module of ANSYS. Air is selected as the working fluid. The simulation is carried out for a time duration of 1.2 ms where it reaches a steady state and the lift and drag forces and coefficients are estimated. The pressure, temperature, and velocity contours at different angles of attack are also observed. It is found that the lift-to-drag ratio increases
Deka, SushmitaKamal, AbhishekPatra, SanjuktaSahoo, Niranjan
Defense Innovation Unit Washington D.C. info@DIU.mil
This paper presents a mechanical energy control volume analysis for incompressible flow around road vehicles using results from Detached Eddy Simulation Computational Fluid Dynamics calculations. The control volume approach equates the rate of work done by surface forces of the vehicle to (i) the rate of work and kinetic energy flux at the control volume boundaries (particularly in the vehicle wake) and (ii) the rate of energy loss in the domain. At the downstream control volume boundary, the wake terms can be divided into lift-induced and profile drag terms. The rate of energy loss in the domain can be used as a volumetric analog for drag (drag counts/m3, when normalized). This allows for a quantitative break down of the contributions of different flow features/regions to the overall drag force. The formulation presented here includes terms for common features in automotive CFD simulations including shaft power (also known as ventilation drag) from rotating wheels, static ground
Norman, PaulHoward, Kevin
Planning for charging in transport missions is vital when commercial long-haul vehicles are to be electrified. In this planning, accurate range prediction is essential so the trucks reach their destinations as planned. The rolling resistance significantly influences truck energy consumption, often considered a simple constant or a function of vehicle speed only. This is, however, a gross simplification, especially as the tire temperature has a significant impact. At 80 km/h, a cold tire can have three times higher rolling resistance than a warm tire. A temperature-dependent rolling resistance model is proposed. The model is based on thermal networks for the temperature at four places around the tire. The model is tuned and validated using rolling resistance, tire shoulder, and tire apex temperature measurements with a truck in a climate wind tunnel with ambient temperatures ranging from -30 to 25 °C at an 80 km/h constant speed. Dynamic tire simulations were conducted using a heat
Lind Jonsson, OskarEriksson, LarsHolmbom, Robin
The increasing importance of minimizing drag and the absence of an exhaust system result in battery electric vehicles (BEVs) commonly having a very streamlined underbody. Although this shape of underbody is typically characterized by a low acoustic interference potential, significant flow resonance can be observed for certain vehicle configurations and frequencies below 30 Hz. Since the interior of the vehicle can be excited as a Helmholtz resonator, these low-frequency fluctuations result in reduced comfort for the passengers. As preliminary studies have shown, the flow around the front wheel spoilers significantly influences this flow phenomenon. Flow separation occurs at the front-wheel spoilers and at the front wheels. This leads to the generation of vortices which are growing significantly while being transported downstream with the flow. Even small geometric changes to add-on components on the underbody significantly influence both aerodynamics and aeroacoustics. Thus, the goal
Breitenbücher, LauraWagner, AndreasWiegand, ThomasBrink, Maarten
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