Representing fluid dynamics as a many - body dynamics problem : a vehicle fording analysis test case

In this report we present the outcome of a study that attempted to answer the following question: for complex fluid-solid interaction problems, can the fluid be represented as a large number of rigid spheres that mutually interact via contact forces? We set out to answer this question by first describing the approach used in Chrono::FSI to analyze coupled fluid-solid interaction problems. This framework can be leveraged to investigate applications that include (i) rigid bodies; (ii) bilateral constraints (joints); (iii) unilateral constraints associated with impact and contact phenomena; (iv) and friction/cohesion. Subsequently, a river fording scenario is simulated using two different approaches. The first relies on a Lagrangian method for the fluid dynamics; i.e., the smoothed particle hydrodynamics (SPH) method. The second approach uses frictionless rigid spheres which interact mutually through contact and mimic the motion of the fluid. The two approaches, which fall back on entirely different physics and rely on completely different numerical algorithms, are producing surprisingly similar results.