Investigation of Buoyancy Driven Flow in a Simplified Full-Scale Underhood – Numerical Study

Abstract

Transient numerical results are presented for simulating buoyancy driven flow in a simplified full-scale underhood in automobile. The flow condition is set up in such a way that it mimics the underhood soak condition, when the vehicle is parked in a windbreak with power shut-down, after enduring high thermal loads due to performing a sequence of operating conditions, such as highway driving and trailer grade loads in a hot ambient environment. For validation, several experiments were conducted to measure the temperature and velocity fields. The simplified underhood geometry, although simplified, consists of the essential components in a typical automobile underhood undergoing the buoyancy driven flow condition. It includes an enclosure, an engine block and two exhaust cylinders mounted along the sides of the engine block. The calculated temperature and velocity were compared with the measured data at different locations near and away from the hot exhaust plumes. The numerical predictions reveal a complex, transient flow structure under the buoyancy condition, and the results show very favorable comparisons with the experimental velocity and temperature measurements. The transient numerical procedure developed for the current study would pave the way for the future numerical simulations of the practical real underhood soaking.