Joseph Gorski

Simulation of surface ship dynamics

We present a summary of the three-year Challenge Project (C68), begun in 2001, with the objective of demonstrating a capability to simulate time-dependent six-degree-of-freedom motions of ships in waves and the associated near-field flow using unsteady Reynolds-Averaged Navier-Stokes (RANS) codes. The efforts involved a team of researchers using two state-of-the-art unsteady RANS codes for a progression of building-block simulations at both model- and full-scales and for practical configurations including detailed resolution of propulsors and appendages. The two RANS codes used for this project are UNCLE, developed at the Mississippi State University, and CFDSHIP-IOWA, developed at the University of Iowa. The three-year efforts have successfully demonstrated a capability to simulate coupled pitch/heave motions, coupled pitch/heave/roll motions, maneuvers in the horizontal plane, and near-field wake, including propeller and viscous effects. The predictive capability demonstrated in this project has clearly paved the way for more challenging computations that involve large-amplitude motions in high sea states for a new generation of naval ships, including surface combatant and other future hull forms.

HPCMP CREATE-SH Integrated Hydrodynamic Design Environment

The HPCMP CREATE-SH Integrated Hydrodynamic Design Environment (IHDE) is a workbench-like desktop application that integrates a suite of hull form design and analysis tools allowing a user to execute round-trip evaluations of hydrodynamic performance, including visualization, in a simplified and timely manner. Ship hull designers are able to assess ship performance in areas of resistance, seakeeping, hydrodynamic loads, and operability for several different mission types. The development plan calls for additional capabilities related to maneuvering performance and multi-objective optimization. The IHDE also includes an analysis tool validation engine, which provides the user with validation information by leveraging historical model test data for comparisons. The advantages of the IHDE include automated analysis preparation, automated grid generation, and integrated visualization. The IHDE has been used to support several Navy design studies and this paper describes the capabilities of IHDE and shows examples of typical workflow processes and sample analysis results.

Development and Application of an Incompressible Strand Solver

Computational fluid dynamics (CFD) is an ever-increasing component of the naval design and analysis process. Most current high-fidelity CFD methods used by the US Navy require body-fitted volume grids, which are time-consuming and depend on seasoned engineers with significant grid generation experience. Automated grid generation using a strand gridding approach is a relatively new concept that could transform the role of higher fidelity CFD within the Navys design and analysis process. The HPCMP CREATE-SH team seeks to expand the compressible strand solver under development as part of the HPCMP CREATE-AV effort to incompressible flow problems for applications of interest to the Navy. The completed incompressible strand solver would allow quicker turnaround time for experienced CFD engineers while allowing more naval architects to use higher fidelity CFD as a part of the overall design process. The incompressible strand solver is a new development of the HPCMP CREATE-SH Hydro team, and this work will demonstrate the solver on validation cases of naval interest.

Powering and Motion Predictions of High Speed Sea Lift (HSSL) Ships

High Speed Sea Lift (HSSL) is an important area of interest for the US Navy. Computational tools are needed to predict the hydrodynamics of these configurations for their proper design and analysis in many areas including: resistance and powering, motions and habitability, loads in service and maneuverability. In particular, computational approaches requiring a minimum of empiricism are desired as there is a limited experimental database available for these ship concepts. To achieve this, efforts are underway to apply high-end unsteady Reynolds-Averaged Navier-Stokes (URANS) computations to these configurations in nearly all aspects relevant to their hydrodynamics analysis and design. The present effort concentrates on ship operations and the use of controllers for maneuvering and powering. Results are demonstrated for a 30 degree change of heading for a destroyer as well as a waterjet equipped HSSL concept accelerating from rest to the self propulsion point for a given speed. These predictions are computationally intensive and thus require high performance computing resources, but they are paving the way for a computational capability to aid in the design and analysis for a new generation of naval ships.

A Scalable and Extensible Computational Fluid Dynamics Software Framework for Ship Hydrodynamics Applications: NavyFOAM

The main challenge facing simulation-based hydrodynamic design of naval ships comes from the complexity of the salient physics involved around ships, which is further compounded by the multidisciplinary nature of ship applications. Simulation of the flow physics using “first principles” is computationally very expensive and time-consuming. Other challenges largely pertain to software engineering, ranging from software architecture, verification and validation (V & V), and quality assurance. This article presents a computational fluid dynamics (CFD) framework called NavyFOAM that has been built around OpenFOAM, an open source CFD library written in C that heavily draws upon object-oriented programming. In the article, the design philosophy, features, and capabilities of the software framework, and computational approaches underlying NavyFOAM are described, followed by a description of the V&V effort and application examples selected from Navy’s recent R&D and acquisition programs.

The Increasing Use of Visualization in Ship Hydrodynamics

Flow field visualization is an important part of the study of fluid dynamics and ship hydrodynamics. The field of computational fluid dynamics has provided an unprecedented ability to explore the hydrodynamics of marine vehicles through visualization. Many examples of this exist in the literature for steady flow field situations. However, unsteady visualization provides both challenges and opportunities to extract meaningful physical insight and information from computational simulations. This paper discusses some of these issues along with approaches being pursued to obtain adequate flow field information using remote high performance computing resources as well as concurrent visualization using local resources. A number of examples of flow field computations being pursued are discussed including: cavity flow, ship roll motions, trailing edge vortex shedding, ballast water exchange and crashback