Current Research Activities
The current research activities can be broadly grouped into four headings namely
(i) Green ship initiative
(ii) Ship Aerodynamics
(iii) Development of underwater glider
(iv) Astern maneuverability of the vessel.
The brief description is given below.
1) Application of Green technologies like energy saving devices like vortex generators or flaps for improving propulsion efficiency.
(a)Experimental and numerical investigation of fitment of stern flaps to improve propulsive efficiency of high speed displacement vessel is being investigated under INTB (Indian naval technology board) projects. Research in this area for fitment of such devices for commercial and naval vessels are explored. This is more effective in reducing the wave making resistance of (above 0.25 Froude number) of high speed displacement vessel.( Research funding through INTB in progress)
(b)In order to reduce the frictional resistance component for lower Froude number vessels, Investigation of Bubble Drag reduction methodology in reducing frictional drag of vessels operating both in deep and shallow water is being investigated. This also involves both experimental and CFD investigation.(Research funding through Ministry of Shipping in progress)
(c)The need for a quiet marine propeller is paramount today. A low noise propeller is needed as underwater noise generated by propeller and machinery is threat to marine life particularly the marine mammals. IMO has come up with guidelines for reduction of underwater noise from commercial shipping to address this problem. These guidelines have been adopted in 2014 and though non-statutory may be enforced in future. So the technology has to be ready for this. Reducing noise by 06 dB from the loudest 16% of all vessels result in 60% reduction in marine noise pollution. Merchant shipping presently differ by 40dB between quietest and noisiest vessels so there is lot of room for improvement as far as noise mitigation measures are concerned. Research in the area of propeller noise reduction in non cavitating regime is being carried out.(Research funding through NRB in progress)
2) Ship Aerodynamic:
(a) Smoke nuisance problem on naval ships: To model and study the flow characteristics of the exhaust from the funnel of the ship and its interaction with the ship deck/GT intake which would facilitate in proper positioning of the funnel and rest of the structures of Naval Ships. This work was completed as part of my doctoral research work at IITD( Funded by NRB – completed )
(b) Ship helo interface: The modern naval ships have been experiencing the problem of safe helo(helicopter) operation on its deck. A significant number of helo blade strikes have been reported in various Navies while rotor operating inside the engage/disengage envelope of helo operational area. The research in this area deals with finding safe helo operation limits.
The research work involves both experimental and CFD simulation on helo deck of a generic warship. The experimental work on generic frigate model is being carried out in a wind tunnel to measure the velocity field over helo deck. Using the experimental data, the commercially available CFD code being used to study the effect of various active and passive flow control devices in reducing the size of the separation zones and the levels of turbulence encountered on the helicopter deck. (The research work is being carried out at IITD being funded by NRB – completed in 2019)
(c) Ship aircraft interface: Flow structures and air wake studies are crucial features which need thorough understanding in the initial stages of design, to enhance the primary role of aircraft carriers- to launch and recover aircraft, safely and swiftly. The project aims to study and analyse the air flow over an aircraft carrier, especially the wake region along the flight approach zone. The regions of separated flow created by the geometrical features of the carrier greatly augment workload of the pilot approaching the carrier for landing. The project aims to study the causal factors that generate the turbulent wake and parametrically analyse whether it can be improved by changes in carrier geometry. The project intends to derive useful guidelines from the study which would be beneficial for aerodynamic design of future aircraft carrier flight decks. It is a collaborative effort between the Department of Applied Mechanics, IIT Delhi and the Department of Ocean Engineering, IIT Madras. (The funding for the project has been approved by NRB hydrodynamics panel. IITM share is 11 lakhs. The fund will be released on submission of completion report of 2(b))
3) Astern Maneuverability: The assessment of the maneuverability of a vessel is inherently complex, and the complexity of assessment increases when ship enters the shallow waters and require to move astern. Research in the area of maneuvering in astern motions of vessels are not studied much. The research focus on the estimation of hydrodynamic derivative by captive model testing in shallow water and in astern conditions to focus on improving the direction stability of vessels in astern motions.( The funding proposal has been forwarded to INTB)
4) Development of UW glider: Underwater Gliders are autonomous underwater vehicles which execute long endurance mission (up to 6 months) in a glide profile without conventional propeller. These gliders collect oceanographic data and transmit to shore at regular using satellite communication. The concept design of such a glider is underway under my guidance. The proof of concept of a UW glider is designed and fabricated and presented to Prime minister in 2015. Now the research is focused on
(a)Study of maneuverability of autonomous underwater gliders with focus on spiral glide maneuver and effects of glider parameters on the maneuver. The spiral maneuver of different underwater gliders will be studied for identifying the parameters that affect the duration and radius of the spiral glide. Effect of hull form on these parameters will be studied by experimental and numerical methods. Hydrodynamic coefficients and their effect on glider maneuver will be quantitatively studied and observed.
(b)Study of blended wing underwater gliders for assessment of the hull form on maneuverability and the operational range of the glide path. Blended wing hull form will be studied for performance in maneuverability of the vehicle. Parameters that affect the gliding performance will be identified and observed numerically and experimentally. Hull form, inspired from underwater gliding fishes is aimed to be achieved for energy efficient gliding motion and maneuvers