Aerodynamic Analysis of an Airbrake System

Traditional flowfield analysis includes the predictions of design parameters such as surface pressures distributions, force (loading) responses, velocity profiles, three-dimensional flow visualizations for laminar or turbulent, incompressible or compressible, subsonic or supersonic, and steady or unsteady flows.

The following is an example for an airbrake system flowfield analysis. This is a braking system used by heavy vehicles. The geometry includes an external housing, a butterfly valve, a leakage flow path (a small gap between the butterfly valve and the external housing), a by-pass flow path, and a by-pass valve. The valves are used to control the mass flow split into the leakage and by-pass flow path.

The inflow speed at the external housing inlet is about 10 m/s, and the inlet pressure is 5 atm. Roughly about 60% of the flow will pass through the leakage path, while the remaining enters the by-pass flow path. Because the leakage gap is extremely small, the incoming flow pressure is high enough to choke the gap. The flow then continues to accelerate to a maximum Mach number of 1.85 before expanding to the vast exiting region downstream of the butterfly valve. Throughout the domain, the maximum flow speed exceeds over 700 m/s. The resultant surface pressure information can be used to analyze deformation based on the uneven aerodynamics loading on various parts. The CFD analysis successfully provides critical three-dimensional flowfield information for design engineers to improve existing designs.