Aerodynamic Considerations and Optimization in Vehicle Body Design

Designing an aircraft that operates optimally under various flight conditions requires the consideration of flight operational data in the aircraft design process. In this talk, I will discuss the evolution of aerodynamic shape optimization formulation from a single-point optimization (with nominal assumption) to a data-driven, operation-aware multipoint one – and the challenges to achieve the latter. The results show that integrating comprehensive aerodynamic considerations under various flight conditions in the optimization problem formulation can produce a more robust aircraft with more consistent fuel-efficient performance.

A 3D numerical simulation is built on heavy truck including cab, frame, and tires. And vehicle exterior flow field in steady state is computed by computational fluid dynamics software. In the computation process, the distribution of sound power levels on the surface of vehicle body as well as the connection between sound power level and vehicle speed are obtained from aerodynamic noise source, which is using broadband noise source models. Taking the steady flow field results as original values, the exterior flow field computations in transient state are performed by large eddy simulation. Based on the transient fluid field, the near field aerodynamic noise from cab accessories is predicted using FW-H model, and the comparison of the simulation results and the test results is carried out. The results show that the aerodynamic noise sources are from the upwind side with a great pressure gradient. Attentions should be paid more on rearview mirror, diversion trench and sun visor for Aerodynamic noise optimization of heavy truck. The maximum sound power level of aerodynamic noise in vehicle body accessories is quadratic to vehicle speed. And the aerodynamic noise of heavy trucks is analysed by numerical simulation, in which noise distribution law is consistent with the test. Therefore, the numerical simulation can be adopted to provide the guidance for the design of vehicle body with low noise.

The aerodynamic characteristics are concerned with the fuel consumption rate and the stability of a high speed vehicle. The current research aims at studying the aerodynamic behavior of a typical SUV vehicle model mounted with the vortex generator (VG) at various linear positions with reference to its rear roof edge. The flow field around the vehicle model was observed at different wind speed conditions. It had been determined that at the instance of lower wind speed, the VG had minimal effects of aerodynamic drag on the vehicle body. However, at the instance of higher wind speed conditions the magnitude of the drag force decreased significantly. Vehicles move at higher speeds in the highways, location of the VG varied towards the upstream of the vehicle due to early flow separation. Therefore test were conducted at different wind speeds and locations of VG. The numerical simulation conduced in this study provides flow characteristics around the vehicle model for different wind speeds. The realizable k−ε model was used to simulate and validate the empirical results in an effective manner. By using experimental data, the drag was reduced by 9.04 % at the optimized VG location. The results revealed that the induced aerodynamic drag would determine the best car shape. This paper provides a better understanding of VG positioning for enhanced flow separation control.

The aircraft industry supports aviation by building aircraft and manufacturing aircraft parts for their maintenance. Fuel economization is one of the biggest concerns in the aircraft industry. The reduction in specific fuel consumption of aircraft can be achieved by a variety of means, simplest and more effective is the one to impose minor modifications in the aircraft main wing or the parts which are exposed to the air flow. This method can lead to a reduction in aerodynamic resistance offered by the air and have a smoother flight. The main objective of this study is to propose geometric design modifications on an existing aircraft wing which acts as a vortex generator and it can reduce the drag and increase lift to drag ratio, leading to lower fuel consumption. The NACA 2412 aircraft wing is modified and designed. Rigorous flow analysis is carried out using computational fluid dynamics based software Ansys Fluent. Results show that saw tooth modification to the main wing shows the best aerodynamic efficiency as compared to other modifications.

Rapid prediction of unsteady flow fields around airfoils is crucial for aerodynamic design and optimization of aircraft. However, traditional wind tunnel experiments and numerical simulation methods incur high computational costs for flow field calculations. This paper proposes an improved method based on deep neural operator networks for rapidly predicting unsteady flow fields of different symmetric airfoils under high angle-of-attack conditions. The method uses incoming flow conditions and airfoil parameters as inputs, reconstructing the flow field through spatiotemporal coordinates to achieve joint prediction of pressure and velocity. Experimental results demonstrate that this method accurately captures the unsteady flow field characteristics of different symmetrical airfoils at various high angles of attack. The inference time for a single time-step case takes only about 0.6 s, which is significantly faster than traditional numerical simulation methods. The proposed method can substantially enhance computational efficiency while maintaining flow prediction accuracy, offering a viable new approach for rapid flow field prediction and aerodynamic design optimization of aircraft.

<div class="section abstract"><div class="htmlview paragraph">One of the practical consequences of the development of low CO₂ emission cars is that many of the traditional NVH sound engineering processes no longer apply and must be revisited.</div><div class="htmlview paragraph">Different and new sound sources, new constraints on vehicle body design (e.g., due to weight) and new sound perception characteristics make that the NVH knowledge built on generations of internal combustion-powered vehicles cannot be simply transferred to Hybrid and Electric Vehicles (HEV). Hence, the applicability of tools must be reviewed and extensions need to be developed where necessary.</div><div class="htmlview paragraph">This paper focuses on sound synthesis tools as developed for ICE-powered vehicles. Because of the missing masking effect and the missing intake and exhaust noise of the Internal Combustion Engine (ICE) in electric vehicles, on one hand electric vehicles are quieter than traditional vehicles. On the other hand, other components such as HVAC system, alternator, vacuum pump, power-steering pump, cooling systems, transmission systems, inverter noise, etc., become more important and generate new complex sound signatures. Typically, their interior noise is well-defined by high-frequency noise components which can be subjectively experienced as annoying, hence the increased importance put to sound quality aspects and perceptual-relevant NVH studies.</div><div class="htmlview paragraph">In the paper, a Virtual Car Sound (VCS) synthesis technique for HEV is designed. This approach turns out to be a very helpful engineering tool to design a brand specific sound and allows reproducing typical sound features of HEV during real-time driving simulation based on a Sound Quality Equivalent Model (SQE). Several SQE models were constructed for different powertrains of HEV in various engine conditions. Finally, the results of the sound metrics and listening tests indicate a comparison between the synthesized sounds and the original sound recordings.</div></div>

10 - Mechanical fastening techniques for advanced high-strength steels (AHSS)

<div class="section abstract"><div class="htmlview paragraph">Multidisciplinary Design Optimization (MDO) has been widely used in the automotive industry to balance overall weight and stringent vehicle attributes, such as safety, NVH, durability, etc. To improve product quality and shorten product development cycle, a comprehensive MDO-based platform for vehicle attribute integration is developed in this paper. Some key issues in the platform development are addressed: Parameter model synchronization, Metamodel predictive capabilities, and Pre/post processing, etc. In addition, a strategy for body design is proposed to achieve weight targets while meeting other vehicle attributes. Lastly, the proposed methodology is demonstrated by a real world example for vehicle body design.</div></div>

Heart Rate Variability (HRV) has been a growing major health concern worldwide. It is a key factor to determine an individual's cardiovascular condition. The imbalance in the heart rate has profound impact in causation of several heart diseases. This study aimed to investigate the HRV risk factors that are predominant in the development of heart diseases in motorbike riders. It involves 10 healthy subjects riding five different Indian make motorbikes. Photo plethysmography signal was recorded in three different conditions such as before, during and after motorbike riding using pulse oximeter. The acquired physiological signals from different motorbike riders were processed to determine the variability in the heart rate. The parameters such as systolic amplitude, diastolic amplitude and dicrotic notch for all considered motorbikes were extracted. The results of this study shows an exceptionally high risks of variation in the heart rate among motorbike riders for vehicles having overall kerb weight of 187 kg, moderate risks for kerb weight between 144-145 kg and low risks for motorbikes having kerb weight between 132-137 kg. Body vibration too had an impact on the heart rate variability. Our study thus, reveals that existence of abnormal HRV owing to increase in motorbike kerb weight and speed. The other factors such as vehicle suspension, body design and wheels dimension also indirectly influences HRV. We suggest that essential ergonomic interventions are required to eliminate HRV exposure risks in motorbikes.

Development of lightweight materials onto vehicle bodies, especially in the automotive sector is seen as one of the best alternative solutions in order to reduce fuel consumption and decrease harmful emissions produced by the emission. Reducing in weight of a vehicle can improve fuel efficiency with no prejudice to safety strength requirements. Fibre metal laminate (FML) is hybrid composite structure based on thin sheet of metal alloys and plies of fibre reinforced polymeric materials which offer the ability of superior mechanical properties such as lightweight, high fatigue growth resistance and high strength and stiffness. Multi-material auto bodies will allow optimal material selection in structural components for higher performance and lower cost. This study aims to fabricate and investigate the failure behaviour of a 3/2 layer fibre metal laminate subjected to the quasi-static indentation test. The FML is constructed from aluminium 2024-T3 and layered with composite materials CFRP, GFRP and SRPP. The crosshead speed test analysis ran in different parameters on 1 mm/min, 5 mm/min, 10 mm/min and 50 mm/min, respectively in quasi-static indentation test. The experimental performances of each specimen were compared to predict the behaviour and performance of the FML composite. The test indicates that varying crosshead speeds have influenced the affected region of the FML, causing debonding on the laminate as a result of continued loading.

Aiming at the problems of control accuracy reduction and component fatigue damage caused by driving vibration of flat grain vehicle, multi-body dynamics simulation is carried out for the vehicle body under four working conditions of straight running, turning, tilting and climbing in grain depot environment to identify the vibration limit working conditions; The effects of track preload, part spacing between two tracks and the number of driving teeth on the driving vibration degree of vehicle body under extreme working conditions are analyzed respectively. The simulation results show that when the flat grain vehicle is driving, with the increase of track preload, the acceleration amplitude of vehicle body centroid first increases and then decreases; With the increase of the two crawler parts, the acceleration amplitude of the vehicle body centroid first decreases and then increases; With the reduction of driving wheel teeth, the acceleration amplitude of vehicle body centroid increases gradually. The simulation results show that due to the change of three influencing factors of crawler walking mechanism, the vibration of vehicle body has changed obviously and regularly. Therefore, by selecting appropriate values, the vibration of vehicle body can be effectively reduced, which provides a theoretical basis for vehicle body design and optimization.

The research aims at designing a solar endurance glider for an increased flight time. The constraints for design include reduction in weight compared to a typical glider and improving its aerodynamic performance by application of vortex generators on its wingspan. The design of each component was performed through various stages of similitude cases; furthermore, the components, such as solar panels and vortex generators were selected based on a decision matrix design process. This research utilized ANSYS 18.1 K-Omega SST turbulence simulation techniques to successfully simulate the glider at different speeds along with various angle of attacks for aerodynamics optimization. The results show an improvement in lift force from 160 N to 192 N once the vortex generators were installed. 16 solar cells are installed on the glider’s wings providing 57.6 Watts of power. This study faced a limitation on the physical testing using a wind tunnel for validation; therefore, the team relied on CFD simulations verification from published data. This report details the concept of boundary layer, design process, glider simulation as well as glider configuration, such as the wingspan and total length. The glider should be able to maintain a flight time of at least 6 hours with vortex generators and solar panels.

<div class="htmlview paragraph">The high-speed three-dimensional measurement segment is associated with the introduction of both in-line and off-line production measurement technology. This segment forms the core strategy in a large number of industries, notably the automotive and aviation sectors.</div> <div class="htmlview paragraph">The demand for high-speed three-dimensional measurement systems is particularly strong in the automotive sector, for a range of applications from sheet metal working to mechanical machining. There is a need for such systems in bodywork assembly and stamping applications to perform controls on both full vehicle body - Body-in-White - and on “subunits” - body sides, doors, etc. The control systems used to inspect Body-in-White are usually called “measurement tunnels”. They are found at the production prototype stage as much as they are on the production line where they provide quality improvement led by continuous in-line inspection.</div> <div class="htmlview paragraph">ActiCM has designed and is developing a non-contact measurement tunnel as part of its partnership with Renault’s Vehicle Prototype Center/Technocentre. This tunnel uses AdventCR, optical technology that drastically reduces the duration to perform the 3D inspection of vehicle prototypes. The powerful image-processing and 3D calculation algorithms used by AdventCR offer faster three-dimensional controls than any current Coordinate Measurement Machines.</div> <div class="htmlview paragraph"> <figure id="F1" class="figure"><div class="graphic-wrapper"><img class="article-figure figure" src="2007-01-1382_fig0001.jpg" alt="No Caption Available"/></div></figure>Renault intends to use this technology to shorten the tryout phase for new vehicle designs that require exhaustive controls on a number of prototypes, and to benefit from the power of the post-measurement diagnostic tool. AdventCR gives significantly faster Body-in-White control measurements: a complete measurement process usually takes the prototype off-the-line for ten hours or more; with the AdventCR “non-contact tunnel measurement” system, the Body-in-White data acquisition is dramatically cut to less than one hour. The other substantial benefit of AdventCR is its ability to offer the image data and tools for performing post-acquisition measurement possibilities; unlike other three-dimensional measuring techniques, AdventCR enables the user to measure a geometric element that is not identified in the original control survey under the condition that the element is visible within the images of the images database.</div> <div class="htmlview paragraph">This document provides a detailed introduction to the AdventCR solution and its role in assembled body control applications, and then explains the qualification process established with Renault and the results.</div>

<div class="htmlview paragraph">Theoretical and experimental techniques in road data are needed for design of vehicle body and chassis according to nowadays technology concept. In this paper, both theoretical analysis and experimental accelerated techniques are explained considering domestic and export production of Anadolu ISUZU company urban type midi bus vehicle.</div> <div class="htmlview paragraph">First of all, the chassis and body (skeleton system) of the midi bus vehicle were modeled in 3D by using Catia program and then finite element model (FEM) of the chassis and the body were created by using Ansys, Workbench program. Static and dynamic loading models obtained from dynamic wheel loads acting on the vehicle were developed. In this model, during the service life of the vehicle under vertical and lateral dynamic loads (straight good road, straight bad road, cornering bad road, and singular obstacle road) arising from the road conditions were taken into account. The loading model basically had two different types of loading case, symmetrical loading case and asymmetrical loading case. After performing FEM analysis, critical areas/regions with high stress and deformation values were obtained.</div> <div class="htmlview paragraph">A prototype vehicle was run at IDIADA's (Barcelona/Spain) accelerated fatigue test track with a selected test cycle. The critical stress areas/regions obtained from the results of FEM analysis and results/inspections from accelerated fatigue test track were compared. Required design changes were applied to a second prototype vehicle, and this second prototype vehicle was run on selected Turkish roads in order to obtain road load data. The road load data was recorded by using strain gages on different 12 areas considering maximum stress areas on the chassis both obtained FEM results and accelerated fatigue test track at IDIADA in order to perform accelerated fatigue life test on the hydraulic four-poster test system at ITU Automotive Test Laboratory. During the road data collection, additionally displacement values on the front and on the rear suspension systems were also recorded by LVDT(Linear Variable Differential Transformer) sensors mounted two on the front axle and two on the rear axle. Next step was to collect strain and displacement data on the selected eleven different Turkish road routes, totally 650 km. These road load data were then processed by using nCode-ICE-FLOW 4.0 and LMS TecWare-FALANCS signal processing programs and the damage values of each channel for each different road were obtained. According to these damage values of strain measurements and also S-N diagrams of chassis material displacement signals were processed by rainflow analysis.</div> <div class="htmlview paragraph">The test chassis of the vehicle was produced and assembled at ITU's rig test bench with the construction of special jigs and fixtures for mounting the chassis to the test bench. For making the strain-gage measurement on the test chassis, the same points/areas as collecting the road load data on the road tests were used. Displacement signals were also arranged so that their damage values from real road conditions to accelerated fatigue test bench were equivalent. After arranging damages of different road signals according to their magnitudes eight big different damage road signals were selected as a driven matrix for four poster. Only rear axle side of the chassis were subjected to accelerated life test of total 150 hours and finally the results of FEM analysis and the results of the accelerated rig test were compared.</div>

Effective rear view vision from external mirrors is compromised at high speed due to rotational vibration of the mirror glass. Possible causes of the mirror vibration are reviewed, including road inputs from the vehicle body and a variety of aerodynamic inputs. The latter included vibrations of the entire vehicle body, vibrations of the mirror shell, the turbulent flow field due to the A-pillar vortex (and to a lesser extent the approach flow) and base pressure fluctuations. Experiments are described that attempt to understand the relative influence of the causes of vibration, including road and tunnel tests with mirrors instrumented with micro accelerometers. At low frequencies, road inputs predominate, but some occur at such low frequencies that the human eye can track the moving image. At frequencies above about 20Hz the results indicate that at high speeds aerodynamics play a dominant role. When the vehicle is yawed, significantly greater aerodynamic inputs arise from the leeside vortex than from the vortex on the upwind side. However since the mounting of the mirror glass is part of a complex dynamic system the results are configuration specific.