Software Design Document for a Six DOF Unsteady Simulation Capability in ANSYS-CFX


  1. Gerber, A.G.
  2. Godine, P.G.
  3. Dajka, S.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN)
This report presents the software design for a 6 degree-of-freedom submarine simulation capability in ANSYS-CFX (“CFX”). It documents the underlying theory, implementation in the CFX software system, verifies the algorithms, and presents a preliminary validation. Two main approaches to the problem are considered, both using a body fixed mesh. In one, the mesh is rigid and moves in 6 DOF with the submarine so that apparent body forces for 6 DOF motion must be accounted for in the fluid equations of motion solved by CFX. In the other, the mesh translates but does not rotate with the submarine; it deforms to follow the submarine locally using the CFX Arbitrary-Langragian-Eulerian (moving mesh) formulation of the fluid equations and requires only the apparent body force terms for the linear accelerations. In either approach the equations of motion for the submarine (solid body model) are also solved to determine the apparent body forces and, if required, any mesh motion. The rigid mesh approach is chosen for initial evaluation. In this approach CFX solves the flow about the submarine, then passes the unsteady hydrodynamic forces on the submarine surface to its solid body model (which account for submarine inertia, buoyancy, propulsion, control forces, etc.), and receives back the solid body kinematic information needed to propagate the next coefficient update loop/time step. A second order scheme is used to integrate the fluid and solid body equations of motion in parallel. T

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Report Number
DRDC-ATLANTIC-CR-2007-020 — Contractor Report
Date of publication
01 Jan 2007
Number of Pages

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