Direct CFD simulation of ship and submarine maneuvers including moving rudders

and propellers has become possible though it is still computationally expensive. The inclusion of waves results in further complexity and cost, essentially in the form of finer grids to allow transport of the waves through the domain without unacceptable loss of wave amplitude due to numerical diffusion. A complete turn or zigzag maneuver simulation can take 2 to 6 weeks, depending on the length of the simulation to perform and the computational resources available. This high
cost prevents direct CFD simulation from wider adoption in engineering design. However, use of coarser grids in calm water maneuvers still yields good quality results for forces, moments and motions, at a considerably lower computational cost. In this paper we present a series of
strategies designed to achieve the goal of dramatically reduce the computational time to perform direct CFD simulation of maneuvers by one order of magnitude or more. These strategies
include scalability improvements, decomposition of the overset process, serial performance
improvements, single precision floating-point operation, local partially rotating frame
for the propeller, etc. These strategies require considerable implementation work
but are an additional toward the elusive real time simulation. Demonstrations are performed for KCS in a 30-degree turn in regular and irregular waves.