Part V of the present five-part paper focuses on a research project designed to uncover new and innovative means of increasing airflow to the engine within NASCAR rules. Computational Fluid Dynamics (CFD) offers an alternative to the current “build-and-bust” technique reducing costs and time per design iteration, and provides the sponsor with a physics-based design tool with true predictive capability. Armed with a validated CFD based design system, the team could respond quickly to rule changes by analyzing new configurations through simulations avoiding the fabrication and track testing that is currently necessary.
A robust and easy-to-use CFD methodology for this class of problems was developed and implemented to understand the flow physics and explore novel configurations, as described in Part I. Specifically, these problems involve external flow around a racecar traveling at 180 mph. One critical issue attracting attention in this research was the link between external high speed flow and how it negotiates a hairpin turn into the intake cowl.
This comprehensive computational methodology was used to reduce or eliminate errors due to geometry, grid, discretization, false diffusion, and turbulence modeling. The RANS equations were solved on an exact electronic replica of the geometry. A multi-block, multi-topology, unstructured, adaptive grid made up of high-quality, high-density finite volumes was created for use in all the simulations presented here. Fully converged and grid-independent solutions based on strict convergence criteria were obtained for all the cases without an exception. Turbulence closure was obtained through the realizable k-ε turbulence model with non-equilibrium wall functions to account for curvature and pressure gradient effects.
Through detailed analysis of flow physics novel configurations were identified and analyzed to determine intake cowl systems that produced the highest flow rate. Performance was improved significantly above the baseline configuration; flow rate was improved as much as 222% in one case. A new phenomenon was discovered that directly coupled external aerodynamics with intake cowl flow. For the first time in the open literature, detailed physics involving intake cowl flow phenomena are described in detail.