CRNavies
CRNavies
Cooperative Research Navies (CRNAV)

The Cooperative Research Navies (CRNAV) consortium was established in 1990 to study the mechanisms of capsizing and to develop guidelines for safe ship design and operation at sea, including extreme conditions. The CRNAV group comprises the following participants:

Canadian Navy (DRDC-Atlantic, Dartmouth, and DMSS, Hull)
French Navy (Bassin d'Essais des Carènes, Val de Reuil)
Royal Australian Navy (Dept. of Defence, Canberra)
Royal Netherlands Navy (Mar. Tech. Dept., The Hague)
Royal UK Navy (UK MOD and QinetiQ, Haslar)
U.S. Coast Guard (EngineeringLogisticsCenter, Baltimore)
U.S. Navy (Naval SurfaceWarfareCenter Carderock Division, and NAVSEA)
MARIN, Wageningen, the Netherlands
USCG Engineering Logistics Center,Naval Architecture Branch (ELC-023), (Baltimore, USA)


All participants contribute their expertise and relevant technology to the group's research efforts. MARIN provides the CRNAV chairmanship and secretariat, as well as overall project management.


Background

Navy ships have been designed and operated for the past 40 years in accordance with empirically based stability criteria which were derived for wall-sided and flared monohull vessels of World War II vintage. See Figure 1.

Figure 1. World War II USN <i>Farragut Class</i> Destroyer Figure 1. World War II USN Farragut Class Destroyer
















Existing ship stability criteria do not adequately address dynamic stability, or the stochastic nature of the wave environment. These criteria are typically based on hydrostatics and include margins, which are only approximate means of accounting for ship dynamics. The stability criteria do not account for a ship’s dynamic behaviour in extreme seas. Even modern hull forms may capsize under certain extreme conditions, as illustrated by model experiments shown in figure 2.
As warships must be able to operate in high sea states and at high speeds, this problem is of particular concern to navies. Stability requirements can have a major impact on decisions made during the design of these ships, such as the location of the center of gravity. In addition, such criteria dictate the inherent levels of safety against capsizing. Therefore, there is a clear need to develop dynamic stability criteria for practical design purposes on a rational basis.

  Figure 2. Capsize Experiments Figure 2. Capsize Experiments
The objective of the Dynamic Stability Simulation project is to develop physics-based stability criteria for intact and damaged ships based on realistic and validated computer modeling in order to assess capsize risk associated with new ship designs over the life cycle of the ship. The Naval Stability Standards Working Group (NSSWG) provides the framework for CRNAV with regard to the development of design criteria.
Safe operation of a ship in extreme seas in combination with highest possible speeds and various loading conditions requires sound knowledge of the expected dynamic behavior of the vessel. Operational procedures will benefit from knowledge gained on the dynamic stability related risk in various operational environments. The Operator Guidance and Training Working Group (OGTWG) provides the framework for CRNAV with regard to research aimed at improving operational issues.

CRNAV website (www.crnav.org)

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