Braking System Cooling Time Simulation

Aircraft braking pads are subject to an extremely severe thermal environment. During a typical landing the carbon brake pads can reach temperatures up to 700–800 K or even more. Between landings during the taxi and parking phase the brakes have to cool off back to their operational limits in a time interval consistent with the average operational time. In order to evaluate the impact of design modifications on the wheel mounting and fairings, without the need of extensive laboratory and flight campaigns, a CFD (Computational Fluid Dynamics) based methodology was developed. Due to the geometry complexity the need of a geometrically representative, but simplified model comes up, in order to capture the major features of the natural convection flow and temperature fields and can be used to evaluate the influence of design changes on the braking system cooling times. A calibration procedure is carried out, aiming a better representation of the transient phenomenon, using a thermal resistances setting up feature from the solver used. An example of the application of this methodology is presented. A computational grid of over 700,000 tetrahedral elements was constructed and the Navier-Stokes equations are solved using a commercial package (FLUENT). The computational cost for a time accurate solution demands the use of parallel processing in order to complete the analysis in a typical industrial environment timeframe. Comparison with both laboratory and flight data calibrate and validate the results of the computational model. This paper describes the details of the construction of the CFD model, the setting of the initial and boundary conditions and the comparison between measured and simulated parameters.