star-ccm+ in nswccd cfd applications
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Minyee Jiang Naval Surface Warfare Center at Carderock
September 1, 2009STAR Global Forum 2009
STAR-CCM+ in NSWCCD CFD Applications
Hull Resistance prediction
CFD Validations
Internal flow plus ship-wave interaction
Wave slap prediction
Background
Traditional Submarine Mission: Prior to the end of the Cold War conflict between two super powers, anti-submarine warfare and the delivery of massive nuclear fire power were the major roles for U.S. submarines. The “Silent Service” was the major concern for submarine operations. Opportunities for submarine to encounter waves were very rare .
New Missions: . Now dealing with multiple small conflicts through out the world, U.S. submarines are more multi-mission oriented, including assisting Special Operating Forces. Submarine operation is no longer completely silent in deep sea. More often submarines encounter waves.
New configurations: Dry Deck Shelter (DDS) and Advanced Seal Delivery System (ASDS) mounted on host submarines.
ASDS Wave Slap Simulation
Task Title: Initial Investigation of Wave Impact Loading Trends on the ASDS
Objective: Simulate forces on ASDS under various wave height, wavelength, and wave
heading to identify trends where ASDS systems may experience significant forces.
Results could lead to identification of potential problem areas with high loading
Approach: Computational Fluid Dynamics approach for pressure loading by
simulation of the interaction of the wave field with the ASDS mated to the host ship
Numerical Tool and MethodSTAR-CCM+
A Reynolds Averaged Navier-Stokes (RANS) code, developed by CD-Adapco, was designed to solve wave interaction problems and is applicable to surface ships and submarines.
VOFVolume of fluid (VOF) is one of the approaches for accurately computing free surface flows and breaking waves. Grid cells near the free surface are filled partially with air and water and computed appropriately based on VOF.
Volume of Fluid Free Surface Capturing
water
air
Geometries for the Numerical ModelASDS on a submarine
The propellers of ASDS and submarine are not included in the numerical model
Still water line
ASDS Wave Slap Simulation
Close up View on ASDS
ASDS was raised few inches for grid generation purpose
Control surfacesASDS Hull
Pylons and Matting trunk
Computational Domain and GridLocal Grid RefinementCell Zones
Region of interest
Cells near ASDSInlet
Interest
Damping
Grid Topology I (Single region with stretched wave damping zone)
Velocity Inlet
Pressure outlet
velocity inlet
Velocity inlet
Grid Topology II (Embedded mesh with stretched wave damping zone)
Velocity Inlet
Pressure outlet
velocity inlet
Interface
Grid Topology III (Single region without stretched wave damping zone)
Velocity Inlet
Pressure outlet
Velocity Inlet
Velocity inlet
Grid Topology I (Single region)
Because the outlet boundary is located far downstream, free surface is outside the fine grid region even for small pitch angle
d =20L
Grid Topology I (Single region)
Free surface enters coarse grid region
Grid Topology II (Embedded Grid)
Interface for grid rotation
Free surface stays in fine grid region
Grid Information 2 - 6 M cells Evenly distributed cells in the inlet region Stretched grid size in the damping zone
Wave Conditions Averaged Wave Height (H=20 feet) Averaged Wave Length (λ=262 feet) Wave Heading: (Beam Sea) Positions : broach Forward speeds : 0 knot
Submarine and ASDS at Broach ConditionFree Surface
Wave direction
Sample of the Surface Pressure
Areas with High impact load
Pressure Animation
Wave Slap Peak Pressure on ASDS
Large peak pressure with small duration
More sustain load
Wave Slap Peak Pressure on ASDS Elements
More vulnerable element
Conclusions STAR-CCM+ has been successfully applied to several Navy
vessels for resistance prediction and wave impact analysis. More wave slap/slam validations and simulations are in
progress. Simulation of LCS-2 requires modeling of interaction of
ship with wave as well as internal flow We are gradually increasing our usage at DoD-HPC. We are
expecting to have more allocation available at several computing centers next year.
Fluid-Structure Interaction (FSI): We are currently waiting for the release of STAR-CCM+ coupled with ABAQUS for accurately prediction of wave impact load.
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