The Lagoon case is a simplified landing gear. During the landing phase, landing gear is an important source of noise and produce a non-trivial turbulent flow.
It is convenient to bench CFD codes since the geometry is simple and a large experiment database is available for both aerodynamic and acoustic. Hence Lagoon is a good non-trivial test case to benchmark a CFD software for both precision and performance.
More information on the Lagoon programme here.