Search Results

Convertible vehicle hoods are known to deform away from their designated showroom shape as a result of aerodynamic loading. The ultimate aim of the work is to produce a computer-based methodology to model the fluid-structure interaction over a convertible vehicle hood. To develop an appropriate flow-structure coupling methodology, steady-state computations have been carried out for a two-dimensional model geometry. A commercial computational fluid dynamics (CFD) package is used to calculate the pressure on the model roof. This CFD package is coupled to an in-house structural code that models the structural mechanics of the flexible roof. Furthermore, a very rapid hybrid means of generating the aerodynamic loading is developed because the multiple solutions required in a complete wall-flow iteration procedure can be computationally very expensive. Solutions generated using the modelling concepts have been compared with wind-tunnel testing on a physical model.

Simulations have been carried out for the flow through a throttle valve to determine the flow mechanisms for various blade angles. In all cases, the time-dependence of the flow had to be accounted for. From this the relationship between blade angle and frequency of oscillation has been found. Comparisons have also been made between solutions with tetrahedral unstructured meshes and hexahedral structured meshes. Finally, it has been found that adding a breather pipe to the throttle removes the oscillation entirely.

The steady flow through a plenum-runner system within an inlet manifold has been measured experimentally and also predicted with computational fluid dynamics (CFD). This paper reviews the experiment and computation before presenting the results of simulations that assess the effect of various geometries at the plenum-runner interface. It has been found that careful experiments are needed to produce reliable experimental data and that CFD can be used to produce accurate predictions. In terms of the losses due to various interfaces, the sharp-edged simple interface is the worst case, with a protrusion giving a slight reduction in loss and various forms of rounding significantly reducing the losses.

For Computational Fluid Dynamics (CFD) to be influential in designing new engines, it has to be capable of providing useful design information to engineers in a short space of time. It is usual for several months to elapse from the time it is first decided to carry out a CFD simulation to obtaining the results. This is not acceptable and a target simulation turnaround time of one day is more appropriate. This work has investigated ways in which computational models, and especially meshes, can be built quickly both using commercial software and software written in-house. Simulations using these models have been carried out and this study shows that models with distorted cells can be built with ease by one person in a few days. Some current generation flow simulation packages cannot produce results using these models, but models with acceptable distortion are now built routinely and solved within two weeks.

Many computational techniques are now available that provide solutions to the problem of the external airflow over vehicle shapes. For such techniques to be of use within the automotive design process, not only must the solutions provide useful aerodynamic information, but also they must be successfully integrated into the design process. This paper relates the limited experiences in this field of one automotive user, highlighting the possible benefits of such techniques, as well as areas that have deficiencies at present.