Ongoing

Cable dynamics: Cables are useful for

(a) towing equipment -- e.g. underslung loads of helicopters, large array sonars of navy, mineral detectors, etc., 

(b) supporting objects -- e.g. bridges, elevators, aerostats, etc.

In these applications, cables twist, bend, and extend. Sometimes by amounts large enough to make traditional beam theories inapplicable. Additionally, as in aerostats, the cable's length can change. Air / fluid drag is often very important. We (me, Shakti Gupta, Fahad Anwer) are developing a fairly general computational model for cables incorporating large rotation and coupled interaction with air / fluid flow.  Immediate applications are to

(a) Underslung mineral detectors: We are a nuclear power with very little Uranium. What little we have needs to be found using large detectors carried by helicopters. The detectors need to be horizontal (parallel to the ground) during operation for accurate detection. However, it is noted in flight tests that these detectors tend to go unstable. Our computational model will help simulate and understand the dynamics and stability of this system.

(b) Aerostats: Kargil happened because in winters we didn't keep an eye on what happened on the other side of the mountain. This is because it is not nice to park humans in winters at high altitudes. At least in civilized nations. This is where high-altitude aerostats (balloons anchored by cables) can help. They give you an eye in the sky. But, they suffer from instabilities in deployment at high altitudes. These instabilities could be due to wind flow across the cable and/or the aerostat body. An additional challenge is that during deployment the length of the cable changes. These aspects are being investigated computationally through our cable dynamics simulation.

(c) Optical fibers: Optical fibers are, basically, cables. These fibers are subjected to various mechanical stresses that, in turn, causes a change in their refractive index profiles leading to power loss. The industry has become very competitive and understanding every aspect of power loss is now important. We (me, Shakti Gupta, and Pradeep Kumar) are coupling the cable dynamics code (its static version) with electro-magnetic (EM) calculations to predict power loss in optical cables. This research is supported by Sterlite Ltd.

Future applications are envisaged in the areas of

(a) Air-to-air refueling: No body has time these days. Even aircrafts. Especially those employed in the Air Force. They would rather refuel mid-air. This also increases their deployment range. But to do this we have to master Air-to-Air refueling systems, many of which rely on our ability to contril cables. Hence, Cable Dynamics!

Dormant

Thermal ratcheting:  It is observed that pipes exposed to a sharp and oscillating temperature front in the axial direction bulge radially outwards. This bulging is tangible and irreversible and occurs within a few cycles of the thermal oscillation. Obviously, such a deformation is undesirable in general, and in particular in the walls of, say, a fast-breeder reactor. In the latter, the fluctuating level of the hot Sodium fuel drives thermal ratcheting. The aim is to ultimately develop a predictive design tool hopefully of use in an actual FBR.

Dynamics of non-ideally cantilevered beams: In a fast-breeder reactor, the nuclear fuel assembly consists of very many hexagonal rods held vertically by inserting one end into a cylindrical bearing. Because it is often necessary to take these rods out for cleaning, some clearance is maintained in the bearing. However, this clearance greatly influences the vibrations of these fuel rods.

The ultimate aim is to model the dynamical response of the fuel subassembly due to vertical and horizontal base excitation.

Simplified models for rolling: The need of the hour, for all people interested in toys, is a simplified model for rolling contact. Most famous toys, like the celt, the tippy-top, or the spinning egg cannot be explained by assuming idealized rolling. They require us to realize that two bodies cannot contact at only one point; there is a zone of contact, within which slipping necessarily takes place at most points. This slipping leads to a frictional moment. The extent of slipping and the magnitude of the frictional torque depend on the rolling speed, the local geometry and also the rigidity of the objects. This is a complicated relationship, as evinced by the presence of a tyre-modeling industry. I want to develop a simplified model that may be employed to gauge the mechanics underlying toys. We should not require recourse to complicated tyre models.