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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "E: Electric Vehicles".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 59210

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Prof. Dr. Janusz Piechna

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Faculty of Power and Aeronautical Engineering, Warsaw University of Technology, 00-665 Warszawa, Poland
Interests: fluid mechanics; gas dynamics; unsteady flows; car aerodynamics; aerodynamics of animals; numerical simulations
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Dear Colleagues,

Currently, car powertrains are undergoing significant changes. The amount of heat generated as well as the dynamics and nature of heat sources in cars are different from previously. Cars must be cooled in a different way. Vehicle weight remains the same or is slightly higher. Weight distribution in a vehicle is different. Automation and electronic linking of vehicles leads to the formation of clusters consisting of several cars. Car aerodynamics is currently focused mainly on lowering the aerodynamic drag of cars with large dimensions and often bizarre but fashionable shapes. However, new aspects of vehicle motion are emerging. It has been noticed that the aerodynamics of cars change when cornering.

Often, cars have fixed or movable aerodynamic elements to compensate for dangerous changes in their dynamic characteristics at higher driving speeds, caused by unfavorable body shapes optimized for low aerodynamic resistance. Movable body parts usually generate forces that press the car body to the road, but at the cost of increasing the aerodynamic drag. Therefore, they should be activated for short periods when their operation improves performance or increases safety. Movable aerodynamic parts take time to generate aerodynamic forces. Responses to changing road conditions are usually delayed. In the current era of intense development of electric and autonomous cars and the development of the 5G network, information on road configuration, traffic of other vehicles, weather, and wind conditions is available well in advance.

This makes it possible to activate movable aerodynamic elements earlier and fully deploy their capabilities when their operation is needed. This in turn makes it possible to predict the need to use movable aerodynamic elements to improve the dynamics, fluidity, and safety of the movement. Techniques to simulate the dynamics of vehicles with variable geometry and variable aerodynamic properties as well as techniques for coupling information obtained from sensors placed on cars with the operation of movable elements are the basic subjects of papers to be submitted.

Prof. Dr. Janusz Piechna
Guest Editor

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Keywords

FSI
turbulence modeling
adaptive aerodynamics
vehicle–vehicle interaction
noise reduction
drag reduction
instantaneous aerodynamic downforce generation
competitive car aerodynamics
aerodynamic–dynamic interaction
trucks aerodynamics
urban car aerodynamics
predictive aerodynamics (information from other vehicles/sensors built-in in the road infrastructure)

Published Papers (13 papers)

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Research

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19 pages, 4775 KiB

Open AccessArticle

Numerical Study of the Sports Car Aerodynamic Enhancements

by Krzysztof Kurec

Energies 2022, 15(18), 6668; https://0-doi-org.brum.beds.ac.uk/10.3390/en15186668 - 13 Sep 2022

Viewed by 5291

Abstract

This study was prepared to demonstrate how the aerodynamics of a sports car can be enhanced, emphasizing aerodynamic improvements, and utilizing small movable elements. All the presented results were obtained using the numerical simulations performed in ANSYS Fluent in steady-state conditions. It was investigated how the performance of a car equipped with the splitter and the rear wing could be improved. The benefits of a top-mounted wing configuration were presented compared to a bottom-mounted setup. A change to the top-mounting configuration enabled undisturbed flow around the suction side of the wing and a more favorable placement of the wing to the car body. In the given case, an 80% increase of downforce was achieved in the performance mode of the car setup and a 16% increase of drag in the air braking mode. A method of the front splitter active steering was presented, which enabled a change of the generated downforce using only a small element that enabled an instant change of 30% without the necessity of moving the whole splitter plate. The described modifications of the sports car not only improved its aerodynamic properties but also enabled the means to accommodate it with an active aerodynamic system that would allow a quick adaptation to the current driving conditions. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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24 pages, 11811 KiB

Open AccessArticle

CFD Study of High-Speed Train in Crosswinds for Large Yaw Angles with RANS-Based Turbulence Models including GEKO Tuning Approach

by Maciej Szudarek, Adam Piechna, Piotr Prusiński and Leszek Rudniak

Energies 2022, 15(18), 6549; https://0-doi-org.brum.beds.ac.uk/10.3390/en15186549 - 07 Sep 2022

Cited by 7 | Viewed by 2699

Abstract

Crosswind action on a train poses a risk of vehicle overturning or derailment. To assess if new train designs fulfill the safety requirements, computational fluid dynamics is commonly used. This article presents a comprehensive wind flow analysis on an example of a TGV high-speed train. Large yaw angle range is studied with the application of widely used Reynolds-averaged Navier–Stokes (RANS) turbulence models. The predictive performance of popular RANS-based models in that regime has not been reported extensively before. The context of simulations is a study of crosswind stability using methodology presented in norm EN 14067-6:2018. It is shown that for yaw angles up to 45 degrees, aerodynamic forces predicted by all the studied RANS-based models are consistent with experimental data. At larger yaw angles, flow structure becomes complicated, separation lines are no longer defined by geometry, and significant discrepancies between turbulence models appear, with relative differences between models up to 30%. A detailed study was performed to investigate differences between turbulence models for specific angles of 40, 60, and 80 degrees, which correspond to distinctive ranges of moment characteristics. Finally, a successful attempt was made to tune a GEKO turbulence model to fit the experimental data. This allowed us to reduce the maximum relative error in comparison to the experiment in the full yaw angles range down to 12.7%, which is in line with the norm requirements. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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27 pages, 100958 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Comprehensive CFD Aerodynamic Simulation of a Sport Motorcycle

by Krzysztof Wiński and Adam Piechna

Energies 2022, 15(16), 5920; https://0-doi-org.brum.beds.ac.uk/10.3390/en15165920 - 15 Aug 2022

Cited by 3 | Viewed by 8005

Abstract

Nowadays, aerodynamics is a key focal point in the vehicle design process. Beyond its direct impact on the performance of a vehicle, it also has significant effects on economics and safety. In the last decade numerical methods, mainly Computational Fluid Dynamics (CFD), have established themselves as a reliable tool that assists in the design process and complements classical tunnel tests. However, questions remain about the possible obtained accuracy, best practices and applied turbulence models. In this paper, we present a comprehensive study of motorcycle aerodynamics using CFD methods which, compared to the most common car aerodynamics analysis, has many specific features. The motorcycle, along with its rider, constitutes a shape with very complex aerodynamic properties. A detailed insight into the flow features is presented with detailed commentary. The front fairing, the front wheel and its suspension were identified as the main contributors to the aerodynamic drag of the motorcycle and its rider. The influence of rider position was also studied and identified as one of the most important elements when considering motorcycle aerodynamics. An extensive turbulence models study was performed to evaluate the accuracy of the most common Reynolds-averaged Navier–Stokes models and novel hybrid models, such as the Scale Adaptive Simulation and the Delayed Detached Eddy Simulation. Similar values of drag coefficients were obtained for different turbulence models with noticeable differences found for

k - ϵ

models. It was also observed that near-wall treatment affects the flow behaviour near the wheels and windshield but has no impact on the global aerodynamic parameters. In the summary, a discussion about the obtained results was set forth and a number of questions related to specifics of motorcycle CFD simulations were addressed. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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27 pages, 16568 KiB

Open AccessArticle

Feasibility Study of a Fan-Driven Device Generating Downforce for Road Cars

by Maciej Szudarek, Adam Piechna and Janusz Piechna

Energies 2022, 15(15), 5549; https://0-doi-org.brum.beds.ac.uk/10.3390/en15155549 - 30 Jul 2022

Cited by 1 | Viewed by 2752

Abstract

This paper, submitted to the special issue of Energies “Future of Road Vehicle Aerodynamics”, proposes and justifies the use of an old idea of generating downforce by actively drawing air from under the car body and exhausting it to the outside. Instead of traditional moving mechanical-curtain elements, a new method for sealing the clearance under the body with an air curtain is proposed. Basic information on the geometry and flow characteristics of such a solution suitable for use in automobiles is presented. The performance of such a fan-driven device generating downforce is studied over a wide range of driving speeds. The device allows for significantly improved vehicle acceleration, shorter braking distances, and extension of the range of safe cornering speeds. The paper shows the successive stages of development of the idea, from the 2D model to the 3D model, and an attempt to implement the device on a sports car. The distributions of pressure, velocity, pathlines and values of aerodynamic forces obtained at assumed fan compressions for different driving speeds are presented. The advantages and disadvantages of the analyzed device are discussed, and further optimization directions are outlined. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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28 pages, 15937 KiB

Open AccessArticle

Towards Balanced Aerodynamic Axle Loading of a Car with Covered Wheels—Inflatable Splitter

by Maciej Szudarek, Konrad Kamieniecki, Sylwester Tudruj and Janusz Piechna

Energies 2022, 15(15), 5543; https://0-doi-org.brum.beds.ac.uk/10.3390/en15155543 - 30 Jul 2022

Cited by 4 | Viewed by 2388

Abstract

Generating aerodynamic downforce for the wheels on the front axle of a car is a much more difficult task than for the rear axle. This paper, submitted to the special issue of Energies “Future of Road Vehicle Aerodynamics”, presents an unusual solution to increase the aerodynamic downforce of the front axle for cars with covered wheels, with the use of an elastic splitter. The effect of the inflatable splitter on the aerodynamic forces and moments was studied in a DrivAer passenger car and a fast sports car, Arrinera Hussarya. Providing that the ground clearance was low enough, the proposed solution was successful in increasing the front axle downforce without a significant increase in drag force. The possibility of emergency application of such a splitter in the configuration of the body rotated by up to 2 degrees with the front end raised was also analyzed. An elastic, deformed splitter remained effective for the nonzero pitch case. The results of the calculations are presented in the form of numerical data of aerodynamic forces, pressure and velocity distributions, and their comparisons. The benefits of the elastic splitter are documented, and the noted disadvantages are discussed. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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16 pages, 12490 KiB

Open AccessArticle

Flow and Thermal Analysis of a Racing Car Braking System

by Carlo Cravero and Davide Marsano

Energies 2022, 15(8), 2934; https://0-doi-org.brum.beds.ac.uk/10.3390/en15082934 - 16 Apr 2022

Cited by 7 | Viewed by 4199

Abstract

The braking system of a racing car is one of the main design challenges. The flow around and inside the wheel of an F1 car with all braking system components is analyzed in order to evaluate the heat transfer after a braking event. Very few studies have been published on this topic, mainly due to the high confidentiality level in the racing car sector. In the present work, using an actual geometry of an early 2000s F1 car, the braking system is simulated using a CFD approach. The boundary conditions for the wheel and brake system are taken from the simulation of a vehicle model with a front wing. Different heat transfer phenomena are progressively added to the model in order to understand their effects, including thermal convection only, radiation and conjugate heat transfer. Two different vehicle velocities are simulated to quantify and compare the heat removal after a braking event. The different heat transfer mechanisms have dramatic effects on the prediction of the brake cooling results, and these are quantified in order to understand the limitations of the simplified approaches. Finally, the influence of the ambient pressure at two different altitudes on the heat transfer from a braking event is studied. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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16 pages, 5040 KiB

Open AccessArticle

Fluid-Structure Interaction Analysis of a Competitive Car during Brake-in-Turn Manoeuvre

by Jakub Broniszewski and Janusz Ryszard Piechna

Energies 2022, 15(8), 2917; https://0-doi-org.brum.beds.ac.uk/10.3390/en15082917 - 15 Apr 2022

Cited by 12 | Viewed by 2372

Abstract

The relationship between the presented work and energy conservation is direct and indirect. Most of the literature related to energy-saving focuses on reducing the aerodynamic drag of cars, which typically leads to the appearance of vehicle motion instabilities at high speeds. Typically, this instability is compensated for by moving aerodynamic body components activated above a certain speed and left in that position until the vehicle speed drops. This change in vehicle configuration results in a significant increase in drag at high velocities. The presented study shows a fully coupled approach to fluid–structure interaction analyses of a car during a high-speed braking-in-turn manoeuvre. The results show how the aerodynamic configuration of a vehicle affects its dynamic behaviour. In this work, we used a novel approach, combining Computational Fluid Dynamics (CFD) analysis with the Multibody Dynamic System. The utilisation of an overset technique allows for car movement in the computational domain. Adding Moving Reference Frame (MRF) to this motion removes all restrictions regarding car trajectory and allows for velocity changes over time. We performed a comparative analysis for two aerodynamic configurations. In the first one, a stationary rear airfoil was in a base position parallel to a trunk generating low drag. No action of the driver was assumed. In the second scenario, brake activation initiates the rotation of the rear airfoil reaching in 0.1 s final position corresponding to maximum aerodynamic downforce generation. Also, no action of the driver was assumed. In the second scenario, the airfoil was moving from the base position up to the point when the whole system approached its maximum downforce. To determine this position, we ran a separated quasi-steady analysis in which the airfoil was rotating slowly to avoid transient effects. The obtained results show the importance of the downforce and load balance on car stability during break-in-turn manoeuvres. They also confirm that the proposed methodology of combining two independent solvers to analyse fluid–structure phenomena is efficient and robust. We captured the aerodynamic details caused by the car’s unsteady movement. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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28 pages, 15133 KiB

Open AccessArticle

Influence of the Car Movable Aerodynamic Elements on Fast Road Car Cornering

by Janusz Ryszard Piechna, Krzysztof Kurec, Jakub Broniszewski, Michał Remer, Adam Piechna, Konrad Kamieniecki and Przemysław Bibik

Energies 2022, 15(3), 689; https://0-doi-org.brum.beds.ac.uk/10.3390/en15030689 - 18 Jan 2022

Cited by 10 | Viewed by 5880

Abstract

In the case of road cars, road safety is the primary factor. The geometry of high-speed road cars has no regulatory restrictions. In addition to the high engine power and effective shape, they can use various types of additional movable aerodynamic elements to adjust their aerodynamic characteristics to the road conditions. Based on the geometry of a two-seater prototype of such a vehicle, a numerical analysis of the influence of a number of additional movable aerodynamic elements on its aerodynamic characteristics was performed. Several of them were installed on the prototype. An electronic system recording a number of motion parameters of the entire car body and some of its movable elements installed on the body was designed and built. The system has been adapted to program the motion of additional aerodynamic elements according to the set algorithms of their activation, temporarily changing the aerodynamic characteristics of the car. An experimental study of the effect of changes in the aerodynamic characteristics of the prototype on its dynamic properties during a drive through a test road section was carried out. It was shown to what extent an average driver can increase the safe speed of the curve of the road using the possibilities of moving aerodynamic elements installed on it. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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17 pages, 10863 KiB

Open AccessArticle

Influence of Different Plates Arrangements on the Car Body

by Krzysztof Kurec, Konrad Kamieniecki and Janusz Piechna

Energies 2022, 15(2), 619; https://0-doi-org.brum.beds.ac.uk/10.3390/en15020619 - 16 Jan 2022

Cited by 3 | Viewed by 1961

Abstract

The purpose of this study was to investigate whether small plates covering the roof and the hood of the DrivAer estate vehicle can be used as airbrakes and increase its drag as well as the downforce. The presented results were obtained with the use of the commercial computational fluid dynamics software ANSYS^® Fluent. The main findings of the article are that the aerodynamic devices such as flaps covering surfaces of the vehicle can have a significant impact on drag increase and can be used not only to make the design of the car more striking but also beneficial when utilized as a part of an active aerodynamic setup. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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29 pages, 21693 KiB

Open AccessArticle

CFD Analysis of the Influence of the Front Wing Setup on a Time Attack Sports Car’s Aerodynamics

by Maciej Szudarek and Janusz Piechna

Energies 2021, 14(23), 7907; https://0-doi-org.brum.beds.ac.uk/10.3390/en14237907 - 25 Nov 2021

Cited by 9 | Viewed by 6129

Abstract

In time attack races, aerodynamics plays a vital role in achieving short track times. These races are characterized by frequent braking and acceleration supported by aerodynamic downforce. Usually, typical cars are modified for these races by amateurs. Adjusting the aerodynamic solutions to work with bodies developed for other flow conditions is difficult. This paper presents the results of a numerical analysis of the effects of installing a straight wing in front of or above the body on the modified vehicle system’s aerodynamic characteristics, particularly on the front wheels’ aerodynamic downforce values. The paper presents the methodology and results of calculations of the aerodynamic characteristics of a car with an additional wing placed in various positions in relation to the body. The numerical results are presented (C_d, C_l, C_m, C_lf, C_lr), as well as exemplary pressure distributions, pathlines, and visualizations of vortex structures. Strong interactions between the wing operation and body streamline structure are shown. An interesting and unexpected result of the analysis is that the possibility of obtaining aerodynamic downforce of the front wheels is identified, without an increase in aerodynamic drag, by means of a wing placed in a proper position in front of the body. A successful attempt to balance the additional downforce coming from the front wing on the front axle is made using a larger spoiler. However, for large angles of attack, periodically unsteady flow is captured with frequency oscillations of ca. 6–12 Hz at a car speed of 40 m/s, which may interfere with the sports car’s natural suspension frequency. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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33 pages, 14165 KiB

Open AccessArticle

Low Pressure Tube Transport—An Alternative to Ground Road Transport—Aerodynamic and Other Problems and Possible Solutions

by Janusz Piechna

Energies 2021, 14(13), 3766; https://0-doi-org.brum.beds.ac.uk/10.3390/en14133766 - 23 Jun 2021

Cited by 6 | Viewed by 3133

Abstract

This paper presents the concept of one possible but unconventional implementation of a Low Pressure Tube Transport (LPTT) system for a network with station-to-station distances of 300 km, based on the use of circular tunnels in which modular vehicles consisting of three interconnected functional segments move on wheels with airless tires. The physical limitations associated with high-speed vehicle travel in tunnels are presented. The reasons for the expected inconvenience in the travel system, compensated by short travel times, are justified. Assumptions for the use of locomotion, safety, and passenger segments in the construction of a vacuum modular vehicle are presented, as well as systems to ensure the efficient conversion of serial traffic in tunnels to parallel traffic in station areas. Schemes of station construction and traffic organization in the station area are presented, as well as assumptions for a number of systems increasing the safety of vehicle traffic used in emergency situations. Visualizations of some solutions are presented. Details of the construction of a locomotive segment based on a multi-wheel system of airless wheels with the use of a system of linear motors for acceleration and an inertial drive system between them to reduce its weight are presented. Some conclusions from tests conducted on built simulators, mechanical and virtual, of the passenger segment of a vacuum vehicle are discussed. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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20 pages, 5812 KiB

Open AccessArticle

Fluid-Dynamic Force Measurement of Ahmed Model in Steady-State Cornering

by Takuji Nakashima, Hidemi Mutsuda, Taiga Kanehira and Makoto Tsubokura

Energies 2020, 13(24), 6592; https://0-doi-org.brum.beds.ac.uk/10.3390/en13246592 - 14 Dec 2020

Cited by 4 | Viewed by 3003

Abstract

The effects of on-road disturbances on the aerodynamic drag are attracting attention in order to accurately evaluate the fuel efficiency of an automobile on a road. The present study investigated the effects of cornering motion on automobile aerodynamics, especially focusing on the aerodynamic drag. Using a towing tank facility, measurements of the fluid-dynamic force acting on Ahmed models during steady-state cornering were conducted in water. The investigation included Ahmed models with slant angles θ = 25° and 35°, reproducing the wake structures of two different types of automobiles. The drag increase due to steady-state cornering motion was experimentally measured, and showed good agreement with previous numerical research, with the measurements conducted at a Reynolds number of 6 × 10⁵, based on the model length. The Ahmed model with θ = 35° showed a greater drag increase due to the steady-state cornering motion than that with θ = 25°, and it reached 15% of the total drag at a corner with a radius that was 10 times the vehicle length. The results indicated that the effect of the cornering motion on the automobile aerodynamics would be more important, depending on the type of automobile and its wake characteristics. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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Review

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31 pages, 103415 KiB

Open AccessReview

A Review of Active Aerodynamic Systems for Road Vehicles

by Janusz Piechna

Energies 2021, 14(23), 7887; https://0-doi-org.brum.beds.ac.uk/10.3390/en14237887 - 24 Nov 2021

Cited by 11 | Viewed by 6253

Abstract

Comfort, safety, high travel speeds, and low fuel consumption are expected characteristics of modern cars. Some of these are in conflict with one other. A solution to this conflict may be time-varying body geometry realized by moving aerodynamic elements and appropriate systems for controlling their motion. This paper presents a review of existing technical solutions and the results of published research on the effects of active flow control around a vehicle on its dynamic properties. Active aerodynamic systems typically adjust certain aerodynamic characteristics based on the vehicle speed, but systems using other information such as acceleration, yaw rate, steering angle, and brake pressure, as well as fully automatic systems, are also considered. This review provides information on historical and current methods, models, and their effectiveness in designing vehicle bodies and the movable aerodynamic elements mounted on them. Technical solutions in which the driver is an element of the control system, automatic systems, their models, models of movable aerodynamic elements, and coupled dynamic-aerodynamic models are presented. A number of types of moving aerodynamic element solutions used for different purposes are considered in this paper and conclusions are presented. Full article

(This article belongs to the Special Issue Future of Road Vehicle Aerodynamics)

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