High fidelity CFD methods were used to assess the current situation and determine the most practical CFD method for landing gear CFD simulations for application to aerodynamic loading. The geometry and experimental database was based on the LAGOON two-wheel nose landing gear, which includes details of the steering/lighting system and tow bar. SRANS, URANS and DES simulations were performed on a high quality hybrid mesh. The CFD results were validated against experimental measurements including PIV and static pressure measurements. The results show that given a high quality mesh the SRANS approach can deliver reasonable results for steady aerodynamic loading, however, the unsteady methods provide improved accuracy and resolution of the loading mechanisms.
Landing gear unsteady loading is a fundamental problem affecting the correct design and performance of an aircraft and it systems. The correct prediction of large scale flow separation around the main landing gear components presents a formidable challenge in terms of the understanding of the aerodynamic field around the complete configuration. Better upfront prediction will enable less conservatism in the design and thus potentially lighter airframe structures.
The main aim of this research is to explore some high fidelity CFD methods in order to assess the current situation and determine the most practical CFD method for landing gear CFD simulations with the main application towards aerodynamic loading.
The simulations were performed on a single high quality 25 million cell hybrid mesh consisting of a high quality fully structured surface mesh, a fully structured boundary layer mesh, a predominantly isotropic structured near-field volume mesh and an unstructured far-field mesh for efficiency. The simulations were performed using a second-order finite volume CFD solver (OpenFOAM) in parallel on the Iridis 3 cluster at Southampton University. Flow conditions: Mach = 0.23, Re = 1.75 x 106 based on wheel diameter (0.3m).
The results show that the unsteady methods (especially DES) offer an improvement in the prediction of the landing gear flow field for loading. However SRANS was shown to capture the same trends as the more expensive unsteady simulations at a much reduced cost.