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There is a need to reduce vehicle's running resistance through aerodynamic performance in terms of having less negative impact on the global environment. In the Accord full model change, the package design is changed, so it is an opportunity to propose methods for improving aerodynamic performance. During the preliminary study, phenomenon analyses were conducted to identify areas that have a significant effect on aerodynamics by using a 25% scale model of the previous model. Based on more than 500 variation measurements as parameter study, the analysis was conducted using computational fluid dynamics (CFD). A proposal was made to the package design. For development that began with the fundamental frame proposed in preliminary studies, wind tunnel testing using 25% scale model was conducted jointly with the Styling Design Office to achieve enhancement styling while also increasing aerodynamic performance.

Racing engines are required to be developed quickly in order to adapt to ever-changing regulations. A CFD-based optimization would be a useful tool to discover the best solution given the restrictions of the regulations. However, a CFD approach requires repeated trials and errors until the best solution is found because the numerical goal is unknown and the specifications required for the goal are never calculated back when using CFD. Therefore, this paper proposes an Empirically Integrated CFD Method. It is a combination of a one-dimensional CFD and several empirical equations that are derived from the racing engine database with physical meanings. These empirical equations give the CFD-based optimization a proper goal and primary specifications so as to make the optimization loop converge rapidly. This method is experimentally verified for its practical application with a prototype engine.

Larger outboard motors are usually equipped with “power trim and tilt” mechanism (referred to as “FIT”). The mechanism plays an important role to attain good performance and proper function of the craft. (See Fig. 1) Basically, PTT has not been evolved out of its original configuration for 15 years or so. It consists of three hydraulic cylinders positioned in parallel; one of them is used for tilting, and other two for trimming. In recent years, however, the outboard motor market had a strong demand for PTT on mid and small size outboard motors. Such, demand necessitated a new type of PTT that is more compact and less expensive than conventional PTT, and still retains equivalent function and performance. This paper describes first-in-industry coaxial double cylinder PTT (referred to as SPTT; abbreviation of Single-cylinder Power Trim and Tilt), especially focusing on its unique design and layout.

There have been not many fundamental researches reported on practical supercavitating foils until now. Therefore, we have investigated the lift and drag performances of three types of supercavitating foil, which have been successfully applied to several high-speed boat propellers. The test was conducted in the closed type cavitation tunnel with two-dimensional foils of those blades. As a result, those foils show fairly large values of the lift coefficient CL compared to the existing foils. In addition, it proves that there is a linear relationship between the cavitation numbers σ and CL in the supercavitating region. Conversely, the values of the drag coefficient CD are rather higher than those of the existing foils, so that there is much room for further drag reduction. Besides, the moment photographs of the cavitation aspects show the fact that the cavity is filled with a bubble cloud even in the supercavitating region, what is called, “pseudo-supercavitation”.