Aeronautical Engineering: A special bibliography with indexes, supplement 62

This bibliography lists 306 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1975

Aeronautical Engineering: A special bibliography with indexes, supplement 67, February 1976

This bibliography lists 341 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1976

Review of Research on Vehicles Aerodynamic Drag Reduction Methods

Recent spikes in fuel prices and concern regarding greenhouse gas emissions, automotive design engineers are faced with the immediate task of introducing more efficient aerodynamic designs vehicles. The aerodynamic drags of a road vehicle is responsible for a large part of the vehicle’s fuel consumption and contribute up to 50% of the total vehicle fuel consumption at highway speeds. Review on the research performance of active and passive flow control on the vehicle aerodynamic drag reduction is reported in this paper. This review intends to provide information on the current approaches and their efficiency in reducing pressure drag of ground vehicles. The review mainly focuses on the methods employed to prevent or delay air flow separation at the rear end of vehicle. Researches carried out by a number of researchers with regard to active and passive flow controls method on vehicle and their effect on aerodynamic drag in terms of drag coefficient (CD) was highlighted. Passive methods i.e. Vortex Generator (VG), spoiler and splitter and active flow controls i.e. steady blowing, suction and air jet are among the methods had been reviewed. In addition several attempts to couple these flow control methods were also reviewed. Several aspects of aerodynamic drag that need for further investigation as to assist for vehicles aerodynamic design and for practical reasons were highlighted. Progressive research on active flow control was observed due to its flexibility for wide range of application without body shape modification

Future perspectives on automotive CAE

Computer Aided Engineering (CAE) is an integral part of today’s automotive design process. Very often OEM’s rely solely on software vendors to provide appropriate solutions. On the other hand, some companies still use in-house developed software for specific applications. It is, however, a combination of these two approaches that provides OEM’s with optimal leading edge software technology. This paper will present an overview of several relevant automotive CAE-methods that will illustrate this approach. Four important automotive software areas will be considered: vehicle CFD applications, aeroacoustics, vehicle crash analysis and occupant / pedestrian safety. The first two topics, CFD and aeroacoustics, are extensive subject areas in themselves, but will be dealt with by considering two specific topics, namely, numerical aerodynamic / flow optimization and aeroacoustic sound propagation into vehicle cabins, respectively. A more detailed focus will be placed on the two safety application areas: vehicle crash analysis and occupant safety using Human Body Models

Gear ratio optimization of one- and two-speed transmissions for fully-electric vehicles

Currently, electric vehicles use a transmission with a single-speed fixed gear ratio optimized for performance. This work features the development of a framework to optimize the gear ratio for a given vehicle design, motor efficiency map, motor noise spectrum, and transmission noise spectrum. The framework provides a methodology for designing the optimization problem to be solved using derivative-free optimization methods. As electric vehicles become increasingly prevalent in the global automotive market, the need to develop multi-speed transmissions to provide a competitive edge against other electric vehicles. This work also explores the optimization of gear ratios for a two-speed transmission and identifies a corresponding switching point to switch between the two ratios. Using the same methodology, the optimization problem is formatted such that derivative-free optimization methods can be used to solve the optimization problem quickly and efficiently. Utilizing the framework developed, the program was able to identify an optimal gear ratio for a single-speed transmission in about half the time it took a brute-force search method to the same. The two-speed optimization process completed about 50 times faster than the brute force search. In both cases, the result returned by the optimization process was compared against the brute force search result to confirm global optimality. The single-speed gear ratio optimization, the two-speed gear ratio optimization, and the two-speed switching point optimization reliably located a global optimum.Mechanical Engineerin

The GNAT method for nonlinear model reduction: effective implementation and application to computational fluid dynamics and turbulent flows

The Gauss--Newton with approximated tensors (GNAT) method is a nonlinear model reduction method that operates on fully discretized computational models. It achieves dimension reduction by a Petrov--Galerkin projection associated with residual minimization; it delivers computational efficency by a hyper-reduction procedure based on the `gappy POD' technique. Originally presented in Ref. [1], where it was applied to implicit nonlinear structural-dynamics models, this method is further developed here and applied to the solution of a benchmark turbulent viscous flow problem. To begin, this paper develops global state-space error bounds that justify the method's design and highlight its advantages in terms of minimizing components of these error bounds. Next, the paper introduces a `sample mesh' concept that enables a distributed, computationally efficient implementation of the GNAT method in finite-volume-based computational-fluid-dynamics (CFD) codes. The suitability of GNAT for parameterized problems is highlighted with the solution of an academic problem featuring moving discontinuities. Finally, the capability of this method to reduce by orders of magnitude the core-hours required for large-scale CFD computations, while preserving accuracy, is demonstrated with the simulation of turbulent flow over the Ahmed body. For an instance of this benchmark problem with over 17 million degrees of freedom, GNAT outperforms several other nonlinear model-reduction methods, reduces the required computational resources by more than two orders of magnitude, and delivers a solution that differs by less than 1% from its high-dimensional counterpart

Vehicle Fuel Economy Improvement through Vehicle Optimization in 1-D Simulation Cycle towards Energy Efficient Vehicle (EEV)

The high average of fuel consumption in vehicle for ASEAN countries compared to global average has led to the establishment of Energy Efficient Vehicle (EEV) by National Automotive Policy (NAP) 2014. PROTON Saga 1.3L 4-speed automatic transmission (4AT) with 6.80 L/100km fuel consumption, it is crucial to reduce the fuel consumption in order to fulfil the NAP 14 target which is 6.0 L/100km so that it stays competitive in the market and also to support the ASEAN emission legislation. The objectives of this research are to design and develop a 1-Dimensional 4-AT vehicle model for fuel economy and performance analysis as well as to evaluate and optimize vehicle model to achieve the product target and legislation requirements. The PROTON Saga 1.3L 4-AT vehicle model which is a B-Segment passenger vehicle will be developed using 1-Dimensional simulation software. The correlation between the base vehicle model and actual vehicle model is 0.14% for fuel consumption and 2.22% for 0-100km/h, since the value is less than 4%, the vehicle model can be concluded as valid and authentic. All the data and engine maps used in this research are provided by PROTON Engineering Department to support the accuracy of findings. For each parameter considered in this research, the optimization was performed in simulation where it begins from the current vehicle engine configuration and then applying each parameter at each step until the anticipated configuration of vehicle has achieved. The parameters involved in this research are vehicle weight, aerodynamic, rolling resistance, final gear ratio, and idle speed. Stop start system was used as an advanced alternative way to mitigate the fuel consumption since it is cost consuming. The fuel consumption for an optimized model is 6.01 L/100km with 0.17% difference with the real target which is 6.0 L/100km. The current vehicle model fuel consumption is 6.80 L/100km, thus, it has been successfully reduced to 6.01 L/100km which is equivalent to 11.62% without implementing stop start system and 25.03% with the implementation of stop start system. It seems that the beneficial to examine various possible solution concepts, and to establish understanding on the effectiveness and synergies between powertrain technologies and vehicle design in reducing the overall fuel consumption ad emission

Energy Optimization for Platooning through Utilizing the Road Topography

The road haulage industry is a fundamental part of today’s society. The companies of haulage stand before a challenge, as the environmental and economic sustainability demands are increasing. The automotive industry tries to meet these demands by developing intelligent systems that will decrease the fuel consumption. The two systems, predictive controller and platooning, are two intelligent solutions that help to decrease the fuel consumption. A predictive controller uses the knowledge of the future road topography to calculate an optimal velocity profile that utilizes the energy stored in the altitude differences. Platooning describes the concept of driving several vehicles in a close formation. The vehicles are controlled autonomously in the longitudinal direction, which enables a short intermediate distance between the vehicles and a reduction of the decelerating aerodynamic drag force. In this thesis, a predictive platoon controller has been developed that takes both the topography and the possible reduction of the aerodynamic drag force into account. Two main different platoon control strategies are evaluated. The result shows that the aerodynamic drag has a large influence of the fuel consumption and that a short intermediate distance between the vehicles will often reduce the consumption. However, the road topography has an influence on the driving profile and in some scenarios it would be beneficial to increase the intermediate distance to avoid using the vehicle’s brake. The result shows that predictive platoon control enables a fuelefficient velocity profile, though, more scenarios should be analysed to draw further conclusions about the strategy