Vehicle Drag Research Articles

Structural and CFD Analysis of Unmanned Aerial Vehicle by using COMSOL Multiphysics

The purpose of this article is to reduce the structural weight and drag of an unmanned aerial vehicle (UAV) or drone while increasing its endurance. To achieve a high strength to weight ratio, Finite Element Analysis is used to study the structural strength characteristics of UAV frames. A computational fluid dynamic analysis (CFD) is performed for different angles of attack and vehicle speeds to estimate the drag coefficient using the k-e turbulence model. The analysis results show that the designed UAV vehicle has excellent performance characteristics and stability at 5° AoA and 3 m/sec. This article outlines the overall design of the unmanned aerial vehicle, which was created using the CATIA V6 platform. COMSOL 5.6 software is used for structural and CFD analysis.

Reduction of Aerodynamic Drag of Heavy Vehicles using CFD

Abstract: Aerodynamic drag is the force that opposes an object’s motion. When a vehicle no matter the size, is designed to allow air to move fluidly over its body, aerodynamic drag will have less of an impact on its performance and fuel economy. Heavy trucks burn a significant amount of fuel as to overcome the air resistance. More than 50% of an 18-wheeler’s fuel is spent reducing aerodynamic drag on the highways. Keywords: Aerodynamics, Heavy vehicles, ANSYS, Aerodynamic Drag, Fuel efficiency.

Fluid–Structure Interaction of Symmetrical and Cambered Spring-Mounted Wings Using Various Spring Preloads and Pivot Point Locations

The fluid–structure interaction of a pivoting rigid wing connected to a spring and subjected to freestream airflow in a wind tunnel is presented. Fluid–structure interactions can, on the one hand, lead to undesirable aerodynamic behaviour or, in extreme cases, to structural failure. On the other hand, improved aerodynamic performance can be achieved if a controlled application within certain limitations is provided. One application is the reduction of drag of road vehicles at higher speeds on a straight, while maintaining downforce at lower speeds during cornering. Conversely, another application concerns increased downforce at higher windspeeds, enhancing vehicle stability. In our wind tunnel experiments, the angle of incidence of the spring-mounted wing is either increased or decreased depending on the pivot point location and spring torque. Starting from a specified initial angle, the aerodynamic forces overcome a pre-set spring preload at incrementally increased freestream velocity. Reynolds numbers at a range of Re = 3 × 104 up to Re = 1.37 × 105 are considered. The application of a symmetrical NACA 0012 and a cambered NACA 6412 airfoil are tested in the wind tunnel and compared. For both airfoils mounted ahead of the aerodynamic centre, stable results were achieved for angles above 15 and below 12 degrees for the symmetrical airfoil, and above 25 and between 10 and −2 degrees for the cambered airfoil. Unsteady motions were observed around the stall region for both airfoils with all spring torque settings and also below −2 degrees for the cambered airfoil. Stable results were also found outside of the stall region when both airfoils were mounted behind the aerodynamic centre, although the velocity ranges were much smaller and highly dependent on the pivot point location. An analysis is reported concerning how changing the spring torque settings at each pivot point location effects performance. The differences in performance between the symmetrical and cambered profiles are then presented. Finally, an evaluation of the systems’ effects was conducted with conclusions, future improvements, and potential applications.

On the drag reduction of road vehicles with trailing edge-integrated lobed mixers

Trailing edge-integrated lobed-mixing geometries are proposed as a viable method for road vehicle aerodynamic drag reduction. Experiments are conducted on a 1/24th-scale model, representative of a Heavy Goods Vehicle, at a width-based Reynolds number of 2.8 × 105. A broad range of pitches and penetration angle values is examined, with detailed comparisons also made to high-aspect-ratio rear tapering. Changes to mean drag coefficients and wake velocities are evaluated and assessed from both the time-independent and time-dependent perspectives. Results show significant drag reductions for lower pitches at higher penetration angles, where the performance of regular tapering is found substantially degraded. The mechanisms responsible for drag reduction are identified to be reductions in the wake size and a shift in the vertical wake balance. The former is shown to be a result of the enhancement in inboard momentum close to the trailing edges through the generation of pairs of counter-rotating streamwise vortices, with the latter attributed to the downstream evolution of the vortices. Overall, these results identify such geometries to be suitable for improving vehicle drag while minimising the losses in internal space.

Multi-objective optimization study on the power cooling performance and the cooling drag of a full-scale vehicle

Multi-objective optimization study on the power cooling performance and the cooling drag of a full-scale vehicle

Design and Analysis of Foreward Step Automotive

Nowadays with increase in competition in automobile sector, vehicle aerodynamics plays an important role. Aerodynamics affect the performance of vehicle due to change in parameters such as lift and drag force which plays a significant role at high speeds. With improvement in computer technology, manufacturers are looking toward computational fluid dynamics instead of wind tunnel testing to reduce the testing time and keeps the cost of R&D low. In this paper, lift and drag of production vehicle are determined by the analysis of flow of air around it using Ansys 18.0. After that, analysis was done on the car with different engine hood angles. Based on Cl and Cd values, optimal model was selected. To validate steady state results, transient state analysis was done on this optimal model. By introducing this considerably reduce the drag and increase lift hence improves the performance of vehicle.

Control of Sunroof Buffeting Noise by Optimizing the Flow Field Characteristics of a Commercial Vehicle

When a commercial vehicle is driving with the sunroof open, it is easy for the problem of sunroof buffeting noise to occur. This paper establishes the basis for the design of a commercial vehicle model that solves the problem of sunroof buffeting noise, which is based on computational fluid dynamics (CFD) numerical simulation technology. The large eddy simulation (LES) method was used to analyze the characteristics of the buffeting noise with different speed conditions while the sunroof was open. The simulation results showed that the small vortex generated in the cab forehead merges into a large vortex during the backward movement, and the turbulent vortex causes a resonance response in the cab cavity as the turbulent vortex moves above the sunroof and falls into the cab. Improving the flow field characteristics above the cab can reduce the sunroof buffeting noise. Focusing on the buffeting noise of commercial vehicles, it is proposed that the existing accessories, including sun visors and roof domes, are optimized to deal with the problem of sunroof buffeting noise. The sound pressure level of the sunroof buffeting noise was reduced by 6.7 dB after optimization. At the same time, the local pressure drag of the commercial vehicle was reduced, and the wind resistance coefficient was reduced by 1.55% compared to the original commercial vehicle. These results can be considered as relevant, with high potential applicability, within this field of research.

Study on vehicle drag reduction simulation based on Suzen–Huang model

In the past numerical simulation of plasma and fluid coupling, the usually used Suzen numerical simulation model has the defect that the error increases with the increase in excitation voltage. The static test of the ionic wind is used to modify the parameters of the Suzen simulation model, and it applied the modified Suzen model to the flow control of the automobile external flow field, which shows good consistency with the wind tunnel test results. Results show that the Suzen model modified by the static test results of the ionic wind is suitable for different excitation voltage conditions. The corrected body force and charge density distribution conform to the change trend of plasma discharge, and the error between the maximum ionic wind velocity obtained by simulation and the test result is within 4%; the modified Suzen model is successfully applied to the plasma flow control of automobile aerodynamic drag reduction. The results show that the exciter suppresses the generation of periodic separation vortices in the tail of the model, which makes the vorticity in the wake significantly decrease, thereby reducing the energy dissipation and the aerodynamic drag of the model. Through the research in this paper, the modified Suzen model reduces the simulation error. Plasma flow control technology is applied to the field of automobile aerodynamic drag reduction, which has accumulated important experience methods and data foundation for the engineering application of this technology. It also provides new methods for improving vehicle aerodynamic performance and fuel economy.

Numerical and Experimental Analysis of Subsonic and Transonic Base Pressure

Base drag of space vehicles with large, truncated base usually forms a considerable component of overall drag. The base drag is usually difficult to be accurately predicted due to the intrinsic complexity of base flow. The subsonic and transonic base pressure characteristics were studied by large scale wind tunnel test and Reynolds-Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) hybrid numerical simulation. The test results show that interferences of both tail sting and ventral blade varies evidently with Mach numbers. The RANS/LES hybrid method was proved to be effective as the calculated time-average base pressure and base drag agree well with wind tunnel test, and detailed flow structures were successfully captured. The base flow pattern is complicated in sub- and transonic regime that either single support scheme is not sufficient to obtain an accurate measurement of base drag. Various support schemes and high precision numerical method are recommended in similar studies.

An Ultra-Efficient Lightweight Electric Vehicle—Power Demand Analysis to Enable Lightweight Construction

A detailed analysis of the power demand of an ultraefficient lightweight-battery electric vehicle is performed. The aim is to overcome the problem of lightweight electric vehicles that may have a relatively bad environmental impact if their power demand is not extremely reduced. In particular, electric vehicles have a higher environmental impact during the production phase, which should be balanced by a lower impact during the service life by means of a lightweight design. As an example of an ultraefficient electric vehicle, a prototype for the Shell Eco-marathon competition is considered. A “tank-to-wheel” multiphysics model (thermo-electro-mechanical) of the vehicle was developed in “Matlab-Simscape”. The model includes the battery, the DC motors, the motor controller and the vehicle drag forces. A preliminary model validation was performed by considering experimental data acquisitions completed during the 2019 Shell Eco-marathon European competition at the Brooklands Circuit (UK). Numerical simulations are employed to assess the sharing of the energy consumption among the main dissipation sources. From the analysis, we found that the main sources of mechanical dissipation (i.e., rolling resistance, gravitational/inertial force and aerodynamic drag) have the same role in the defining the power consumption of such kind of vehicles. Moreover, the effect of the main vehicle parameters (i.e., mass, aerodynamic coefficient and tire rolling resistance coefficient) on the energy consumption was analyzed through a sensitivity analysis. Results showed a linear correlation between the variation of the parameters and the power demand, with mass exhibiting the highest influence. The results of this study provide fundamental information to address critical decisions for designing new and more efficient lightweight vehicles, as they allow the designer to clearly identify which are the main parameters to keep under control during the design phase and which are the most promising areas of action.

A study on practical method to estimate drag of super-cavitating underwater vehicles

In this paper, a simple practical method to estimate the drag of Super-Cavitating Underwater Vehicles (SCUV) is proposed that can obtain the drag with only principal dimensions in an initial design stage. SCUV is divided into cavitator, forebody, afterbody, base, and control fin and the drag of each part is estimated. The formulas for the drag coefficient are proposed for the disk and cone type cavitators and wedges used as control fins. The formulas are a function of cavitation number, cone or wedge angle, and Reynolds number. This method can confirm the drag characteristics of SCUV that the drag hump appears according to the coverage of the body by the cavity and the cavitator drag remains only when the entire body is covered by cavity. Applying this method to SCUV of various shapes, it is confirmed that the effects of cavitating and non-cavitating conditions, cavitator and body shape, and speed could be found.

Drag reduction of 3D bluff body using SDBD plasma actuators

In the current research, a series of different combinations of plasma SDBD actuators mounted on a simplified road vehicle have been experimentally studied to find the optimum position of the actuators for controlling the flow separation and reducing the vehicle form drag. Separation point of the flow over the rear ramp, large trailing vortices of the standard model, and laminar separation bubble (LSB) of the rear ramp leading edge are among the most significant factors to be controlled. The experiments were conducted at Reynolds numbers ranging from 0.55 × 106 to 1.11 × 106 in a subsonic wind tunnel while the pressure distribution over the model and its streamwise force balance were accurately measured. Significant drag reduction due to the use of DBD actuators was observed. As such, for the range of tested Reynolds numbers, a maximum of 25.1% of drag reduction in the vehicle drag coefficient could be achieved. The optimum combinations of activation voltages (6, 9, and 12 kV) and wave frequencies (6, 10, and 14 kHz) for plasma actuators were also found. Furthermore, it was observed that SDBD actuators mounted on the rear ramp of the model had a deeper impact on the vehicle drag coefficient compared to the other actuators.

Center Floor Undercover Air Guide Development to Improve Aerodynamic Drag for a Passenger Car

Cooling airflow is essential to the vehicle air conditioning system and engine cooling module. The cooling airflow in the engine room flows out through the front subframe, front wheelhouse, roll-rod, etc. and mixes with the upstream external flow in the underbody of the vehicle so that it affects the aerodynamic drag on the rear part of the vehicle. An air guide is developed to reduce the aerodynamic drag. It is attached on the center floor undercover and induces cooling airflow exited from the engine room to flow to the rear section of the underbody of a vehicle. It can reduce up to 2.3 % of the aerodynamic drag of baseline vehicle. Numerical flow simulations are performed at the velocity of 140 km/h vehicle driving condition.

Prediction and Aerodynamic Analysis of Interior Noise and Wind Drag Generated by the Outside Rear-View Mirror for Commercial Vehicles

The outside rear-view mirror (OSRVM) is installed on the vehicle’s surface, which causes unwanted aerodynamic noise and wind drag during driving. It is important to use simulation methods to predict the performance of aerodynamic noise and wind drag of commercial vehicles due to the OSRVM. Considering the wind drag of the OSRVM, a combinational simulation strategy is employed to calculate external flow and interior acoustic fields of commercial vehicles, respectively. The flow field is computed a priori with an incompressible flow solver. The acoustic field was then computed based on the information extracted from the CFD solver. To obtain the interior noise level at the driver’s ears, a vibroacoustic model is used to calculate the response of the window glass structure and interior cavities, where the unsteady aerodynamic pressure loading on the two side windows’ surface is treated as the acoustic source field. The paper provides flow field and acoustic simulations for three OSRVM configuration models. The results are compared to data obtained in road sliding test measurement on the commercial vehicle. The accuracy of the hybrid simulation method is proved, and the comparative analyses verify that the OSRVM B model dramatically reduces the interior noise and wind drag of commercial vehicles.

Spike root oblique jet effect on drag and heat load reduction performance for hypersonic vehicles

How to effectively reduce aeroheating load and drag is an important issue in the engineering application of the hypersonic vehicles. In this paper, a novel combined aerodisk-spike root oblique jet strategy has been proposed for drag and heat reduction. The Reynolds-averaged Navier Stokes equations are solved based on the finite volume method, and the shear stress transport turbulence model is used. The reliability of the developed in-house codes has been verified systematically. The results demonstrate that the introduction of aerodisk and oblique jet makes the flow field change obviously, and this novel strategy gets an excellent effect on drag and heat reduction. Then the laws of pressure and Stanton number distributions have been studied in deep. Furthermore, the influences of spike length, oblique jet pressure ratio, and aerodisk diameter on the flow field, drag and heat reduction performance are investigated. Increasing the spike length-to-diameter and jet pressure ratio can enhance the performance of drag and heat reduction. The drag coefficient decreases by about 26% when the spike length-to-diameter increases from 0.5 to 3.0, and the total heat load can be decreased by 38.6% as the jet pressure ratio increases from 0.4 to 0.7. The larger aerodisk diameter can also get a better heat reduction performance. However, the increasing of aerodisk diameter makes the total drag rise sharply. The total drag coefficient increases by about 43% as the aerodisk diameter ratio varies from 0.18 to 0.48.

Assessment on jet direction effect on drag and heat reduction efficiency for hypersonic vehicles

Introducing jet for drag reduction and thermal protection in hypersonic flows has attained worldwide attentions due to its giant potential, and this paper focused on the drag and heat reduction efficiency of unit mass flow rate for different jet directions in hypersonic flows. The developed code employed conjugate heat transfer approach to solve unsteady Reynolds-averaged Navier-Stokes equations and Fourier's heat conduction equation simultaneously, and then it was thoroughly validated by two classical experiments. Based on that, the flow field characteristics induced by different jet directions under the constant mass flow rate of jet were numerically investigated. Besides, two parameters were introduced to quantitatively evaluate the drag and heat reduction efficiency of different jet directions. The obtained results show that though the total mass flow rate of jet is constant, jet direction still has a decisive influence in manipulating the flow structures, and the rear jet would result in more complicated shock waves due to the interaction between the rear jet flow and spike. The force produced by the jet is the key role in determining the total drag, and the variation of pressure distribution along the blunt body is not the direct presentation of drag reduction performance. The opposing jet has the highest drag reduction efficiency, and lateral jet has the highest heat flux reduction. However, compared with the lateral and rear jets, the opposing jet has better thermal protection performance from the overall perspective as it can also protect the aerodome head from severe aerodynamic heating.

CFD Investigations of the Effect of Rotating Wheels, Ride Height and Wheelhouse Geometry on the Drag Coefficient of Electric Vehicle

The development of electric vehicles demands minimizing aerodynamic drag in order to provide maximum range. The wheels contribute significantly to overall drag coefficient value because of flow separation from rims and wheel arches. In this paper various design parameters are investigated and their influence on vehicle drag coefficient is presented. The investigation has been done with the help of computational fluid dynamics (CFD) tools and with implementation of full vehicle setup with rotating wheels. The obtained results demonstrate changes in drag coefficient with respect to the change of design parameters.

Victims crossing overflowing watercourses with vehicles in Spain

AbstractHeavy rainfall causes many watercourses to overflow. In these circumstances, crossing by car even on a road, can be extremely dangerous; however, dozens of drivers are swept away every year in their vehicles. This paper analyses this type of accident in Spain between 2008 and 2018, recording the date, location, number of victims, age and gender, and rainfall during the event. The results show that 125 accidents occurred with 200 victims including 45 fatalities. Most accidents occurred in E, S and SE Spain, where the rainfall irregularity is greater, during December, October and March, although fatalities were concentrated in September and October. Among the victims male drivers dominated, with an average age of 52 years. The main cause of these accidents was the drivers' behaviour due to: underestimating risk, overconfidence, overvaluation of their driving skills, an excess of trust in the authorities, ignorance about vehicle drag and buoyancy risks, and, social pressure. To reduce these risks, it is necessary to increase adaptation and protection measures on roads, but above all, a change in drivers' behaviour to stop them trying to cross‐flooded rivers.

Quantitative Analysis of Drag Reduction Methods for Blunt Shaped Automobiles

In fluid mechanics, drag related problems aim to reduce fuel consumption. This paper is intended to provide guidance for drag reduction applications on cars. The review covers papers from the beginning of 2000 to April 2020 related to drag reduction research for ground vehicles. Research papers were collected from the library of Science Direct, Web of Science, and Multidisciplinary Digital Publishing Institute (MDPI). Achieved drag reductions of each research paper was collected and evaluated. The assessed research papers attained their results by wind tunnel measurements or calculating validated numerical models. The study mainly focuses on hatchback and notchback shaped ground vehicle drag reduction methods, such as active and passive systems. Quantitative analysis was made for the drag reduction methods where relative and absolute drag changes were used for evaluations.

Efficiency Analysis and Integrated Design of Rocket-Augmented Turbine-Based Combined Cycle Engines with Trajectory Optimization

An integrated analysis method for a rocket-augmented turbine-based combined cycle (TBCC) engine is proposed based on the trajectory optimization method of the Gauss pseudospectral. The efficiency and energy of the vehicles with and without the rocket are analyzed. Introducing an appropriate rocket to assist the TBCC-powered vehicle will reduce the total energy consumption of drag, and increase the vehicle efficiency in the transonic and the mode transition. It results in an increase in the total efficiency despite a reduction in engine efficiency. Therefore, introducing a rocket as the auxiliary power is not only a practical solution to enable flight over a wide-speed range when the TBCC is incapable but also probably an economical scheme when the the TBCC meets the requirements of thrust. When the vehicle drag is low, the rocket works for a short time and its optimal relative thrust is small. Thus, the TBCC combined with a booster rocket will be a more simple and suitable scheme. When the vehicle drag is high, the operating time of the rocket is long and the optimal relative thrust is large. The specific impulse has a significant impact on the flight time and the total fuel consumption. Accordingly, the combination form for the rocket-based combined cycle (RBCC) engines and the turbine will be more appropriate to obtain higher economic performance.