No description available.

No description available.

No description available.

No description available.

No description available.

Computational Fluid Dynamics (CFD) modelling has been widely used within the automotive environment for areas such as the enhancement of the external aerodynamic performance of automobiles and the optimisation of the combustion process. More recently, however, the study of vehicle thermal management systems (VTMS), an area which encompasses the cooling, air conditioning and underhood airflow of vehicles, has embraced the use of CFD in an attempt to refine designs. Additionally, with continuing emphasis being placed on noise, vibration and harshness (NVH), engine design has tended towards neater, more integrated packages with a minimum of mechanical ancillaries; such as brackets. One of the significant aspects of this design philosophy is that there is now a proliferation of electronics in modern vehicles. One of the solutions to increasingly complex wiring harnesses has been to decentralize and migrate control units to the engine and the powertrain. This development has had consequent effects on environmental factors related to the powertrain control unit (PCU) itself as increasingly strict legislation limits the kind of design solutions which may be employed to overcome these effects, the underhood area has had to be researched thoroughly. For the work described herein, a CFD package and associated pre- and post-processors was used to assess the underhood flow characteristics with a view to determine the optimum positioning of these component packages. A further goal arose from the opportunity to check if the CFD package would be suitable for a non-specialist operator to use. To achieve these goals, the underhood volume of a vehicle was modelled both numerically and experimentally. The experiments were carried out using a physical instrumented model in the smooth controlled flow of the Department's Handley Page wind tunnel. This provided the analogue model for a generic car, against which the numerical results could be compared. The numerical modelling was performed using the commercial CFD package FLUENT 5.5. It was envisaged that the data gained from the two models could be used to enhance current design procedures and influence future design methodologies in engine compartment layout, with regard to the placement of electronic devices. It may also serve to validate the integration of data provided by simulation and experiment. It must be noted that the work was essentially an assessment of the usefulness of the methodology. Albeit the comparisons between CFD and experiment appear to possess significant differences, this early work illustrates the potential of the procedure and suggests the "follow-on" research that is required.

No description available.

No description available.

A method for the estimation of transient aerodynamic data from dynamic wind tunnel tests has been developed and employed in the study of the unsteady response of simple automotive type bodies. The experimental setup consists of the test model mounted to the oscillating model facility such that it is constrained to oscillate with a single degree of freedom of pure yawing motion. The yaw position is recorded from a potentiometer and the time response provides the primary measurement. Analysis of the wind-off and wind-on response allows the transient aerodynamic loads to be estimated. The frequency of oscillation, (synonymous with the frequency of disturbing wind input) is modified by altering the mechanical stiffness of the facility. The effects of Reynolds number and oscillation frequency are considered and the model is shown to exhibit damped, self-sustained and self-excited behaviour. The transient results are compared with a quasi-steady prediction based on conventional tunnel balance data and presented in the form of aerodynamic magnification factor. The facility and analysis techniques employed are presented and the results of a parametric study of model rear slant angle and of the influence of C-pillar strakes is reported. The results are strongly dependent on shape but for almost all rear slant angles tested the results show that the transient response exceeds that predicted from steady state data. The level of unsteadiness is also significantly influenced by the rear slant angles. The addition of C-pillar strakes is shown to stabilise the flow with even small strakes yielding responses below that of steady state. From the simulation results the self-sustained oscillation is shown to occur when the aerodynamic damping cancels the mechanical damping. The unsteadiness in the oscillation can be simulated by adding band-limited white noise with an intensity close to that of the turbulence intensity found in the wake. From vehicle crosswind simulation results the aerodynamic yaw moment derivative and its magnification factor are shown to be the important parameters influencing the crosswind sensitivity and path deviation.

No description available.