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This paper describes a system for measuring unsteady pressure at up to 256 spatial points and at frequencies up to 300 Hz. The system consists of commercially available equipment for measuring steady pressures. It is based on the use of electronically scanned pressure (ESP) sensors, 16 A/D converters, and a personal computer to control the whole system and acquire data. The signal outputs through the tubes connecting the pressure taps and the ESP sensors are compensated, as are the phase delays between the scanned signals and the gain variation. A 1/5 scale model of a sedan was used in this experiment. The passenger car model was placed in a wind tunnel equipped with a moving belt, which was operated at the same speed as the uniform flow in the wind tunnel. Pressure measurements were obtained at 252 points in a plane behind the model perpendicular to the uniform flow. Measurements were made with the belt turned on and off.

Among the various methods for measuring flow velocity vectors, multi-holed pitot tubes offer the advantages of facilitating pressure measurements, low cost and ease of use. On the negative side, the range of measurable flow angles is limited (e.g., to ± 40° with 5-hole tubes) and pitot tubes require time-consuming calibration before use. The authors have developed a new pitot tube with a spherical head and 13 holes arranged such that the pitot head shows a 5-hole pattern when viewed from different right angles. This hole arrangement is equivalent to having several multi-holed pitot tubes connected to one pitot head and expands the measurable range of flow angles substantially to ± 135°. In addition, a robot is used to achieve fully automatic calibration. These two improvements overcome the traditional drawbacks of multi-holed pitot tubes.

A two-channel LDV system is used to obtain accurate airflow measurements around scale models of passenger cars in wind tunnel tests at the Nissan Research Center. A 2-watt argon-ion laser is employed as the light source. The main optical unit and probe head are connected by optical fibers. The probe head consists of a compact LDV probe with a beam expander and focusing lens with a long focal length can be easily traversed. A new type of signal processor, performing a digital autocorrelation function, is employed to process the Doppler signals. Mean airflow velocities and turbulence intensities are calculated by a micro computer to evaluate the flow fields. The results of preliminary experiments conducted with this system indicate that the system is not only capable of measuring the mean velocity components, including reverse flow, it can also provide accurate estimation of turbulence components.

Incompressible viscous unsteady airflow around three types of automobiles are simulated. A thirdorder upwind-difference scheme is used in these simulations. In all the analyses, computational grids are generated by a multi-block transformation and a transfinite method in each block. The first two types of automobile have almost the same shape in the front half of the body, and the accuracy of predicting the difference in drag coefficient is investigated. In this case, the bodies are simplified. They have flat under-floors and no wheels. These calculated results are compared with experiments using 1/5 scale models. The difference in drag coefficient between the two types agrees well with the experiments, and also the values themselves agree well. In the last case, a car with wheels and an under-floor resembling a production model is studied. Simulated results are compared with experiments using a real production car with closed front opening and without mirrors.

The main function of automobile heat exchangers is to transfer residual heat from the engine to the open air so as to keep running the engine at its best condition. In order to efficiently transport heat from the heat exchanger to the air, extended surfaces (e.q., fins) are usually provided over the outer surface of the water tube in the heat exchanger. Moreover, many bent out plate louvers are manufactured on the fin safaces. In order to obtain higher rate of heat transmission in a more compact heat exchanger, many experimental and analytical studies have been carried out up to the present. However, there are many difficult problems to be resolved so far in finding the obtimum louver profile because of the complexity of air flow around small-scale louver assemblies. In the present paper, the characteristics of air flow as well as heat flow around louver assemblies are analysed by the numerical analysis code developed at the Central Engineering Laboratory of the Nissan Motor Co., Ltd.

It is very difficult to measure and analyze the internal flows of torque converters because of their complicated construction. In this report, an attempt is made to calculate the characteristics of torque converters by the combination of a one-dimensional flow theory and a finite difference calculation. From the computed results however, it is significant to note, that this experimental result is more useful as a rational design procedure than the pure angular momentum theory.

This paper describes a preliminary study of the role of computational fluid dynamics in analyzing the aerodynamic characteristics of a heavy-duty truck body. Among truck related aerodynamic problems, we selected the soil problem on the vehicle side surfaces as the analysis subject. Because of computer capacity limitations, a half-truck-cab model with a tire and mud guard are used and created by using the multi-block transformation technique. The flow around the cab is simulated by directly integrating the Navier-Stokes equations, approximated by finite-difference equations. Calculated results on the flaw structures around the vehicle body surface where it becomes dirty under wet weather conditions provide some useful information in the search for understanding of soil problems.

The computation of the Navier-Stokes equations through the three torque converter components (i.e., the pump, the turbine and the stator) is shown. A third-order-upwind scheme is used in the computation. The flow in each component is first calculated individually. Then, the calculation results for each outlet condition are used as the inlet condition of the next component, and the flow in each component is calculated again. This iterative procedure is terminated when the loss of flow pressure in the three components reaches a steady state. The torque converter performance predicted with this method agrees well with experimental data.

It is essential for today’s sports car to have excellent aerodynamic characteristics and a sophisticated style. These factors are dependent and often inconsistent with each other. It is desirable that they are integrated rather than compromised in such cases. In the early stages of development of the 280ZX, we thoroughly investigated the relationship between a style and its aerodynamic characteristics. A three-dimensional smoke tunnel and a 1/5-scale model was used for this purpose. Several improvements were examined mainly on the front end of the model, which strongly affect both aerodynamic characteristics and styling, such as the hood, bumper, chin spoiler, engine-compartment opening and others. The resultant values of the principal aerodynamic coefficients of the realized 280ZX are CD=0.385, CLF=0.11 and CYM=0.04 (CD and CLF at a yaw angle of 0 degree and CYM at 10 degrees).