Trans RINA, Vol 161, Part A4, Intl J Maritime Eng, Oct-Dec 2019


FLOW FIELD ON HELODECK OF A FRIGATE: A REVIEW (DOI No: 10.3940/rina.ijme.2019.a4.550)


B Praveen, Naval Ship Repair Yard, Karwar, R Vijayakumar, Dept of Ocean Engineering, IIT Madras, S N Singh, Dept of Applied Mechanics, IIT Delhi, and V Seshadri, MIT Mysore; Dept of Applied Mechanics, IIT Delhi


SUMMARY


The various functions desired from a frontline warship such as a frigate, corvette or a destroyer, coupled with the requirement of very high speeds and economic viability restricting the size, necessitates a very dense arrangement of weapons and sensors on the top deck and superstructure. Accordingly, Navies across the world have faced several problems with respect to functions for which a good aerodynamic design for these structures is essential. Major issues include smoke nuisance created due to impinging of the ship's exhaust gases on to the top deck leading to possible suction by engine intakes and high turbulence in the ship's air-wake leading to ship aircraft interface concerns. The flow field on the helodeck is extremely complex due to its geometry and interaction with the wake of the ship’s superstructure. A knowledge of this complexity is essential for ensuring safe helo operations on the helodeck. The problem of ship helicopter interaction has hogged the lime light in recent times, due to rising demand for design of warships for increased stealth, especially in the past two decades. Consequently, several researchers in countries with advanced Navies have invested considerable resources towards evolving both experimental and numerical solutions for the problem. However, given the military nature of the operations, open literature on the subject containing details of such research, which can be used as reference material for present work, are limited. Considering the complexities involved in the problem, an attempt has been made in this paper to holistically review the widely scattered and limited literature in this field. A good amount of literature on marine helo applications emerge from the offshore industry. Keeping in mind that the fields of warship design and offshore structures are dissimilar and have their peculiar problems, informed conclusions have been made in drawing lessons from available literature.


NOMENCLATURE


WOD Wind Over Deck RCS NPS


k I


Radar Cross Section Naval Postgraduate School, USA


CAA Civil Aviation Authority, UK FPSO Floating Production Storage and Offloading Platform


Turbulent Kinetic Energy Turbulence Intensity


u,v,w Velocity component in x, y, z directions u′u′


̅̅̅̅̅, v′v′̅̅̅̅̅, w′w′ Uref


̅̅̅̅̅̅̅ Diagonal components of Reynold's stresses


RANS Reynold's Averaged Navier Stokes Equations Sw


Standard Deviation of Vertical Velocity w Undisturbed Flow Velocity (m/s)


SHOL Ship Helo Operating Limit NATO North Atlantic Treaty Organisation NLR


INTRODUCTION National Aerospace Laboratory, Amsterdam


TTCP The Technical Co-operation Program 1.


Helicopter operations from warships form an integral part of modern Naval Warfare. Equipping frontline warships with the ability to undertake helo (short for helicopter) operations at sea, reinforces the truly three- dimensional nature of a nation's Navy. Countries with modern navies have bestowed several spheres of responsibilities on helo operations from frontline warships, both in war and peace. The surveillance and reconnaissance ability of a warship expands


©2019: The Royal Institution of Naval Architects


exponentially with the presence of a helicopter onboard. When required, helicopters can be deployed as an eye in the sky for long distances away from the warship with their own sensor payload which are much more effective than shipboard sensors, due to increased height and range. In wartime, helicopters are used for detection and destruction of enemy forces by use of weapon payload such as torpedoes and missiles. Helicopters have proved to be most effective in undertaking Search and Rescue operation (S&R) missions at sea for most Navies and Coast Guards across the world, owing to their agility and hovering capability. History of naval aviation dates back to early 1900s with advanced countries like United States, Britain and Germany taking lead in making naval aviation a vital part of naval war strategy. However, it is pertinent to mention that the early roles envisaged for the naval warfare favoured use of airplanes from warships. This led to the development of aircraft carriers, which later became an important instrument of power projection for advanced countries and were effectively used as weapons during many naval wars which followed. VS-300, designed by Igor Sikorsky, was the world's first practical helicopter which took flight in 1939. Following this development, during the middle of 20th century, amidst the aura of fighter planes operating from aircraft carriers, helicopters carved their own niche for specialised aerial functions which could not be performed easily by the former. Introduction of helicopters opened a new chapter in the history of naval aviation, by allowing the use of smaller warships for aerial operations with much lesser limitations as compared to use of a national asset such as an aircraft


A-401


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