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NOMENCLATURE M Magnetic moment H Applied field B Theoretical value of magnetic field density without any core m o Permeability of the free space= 4π x 10-7 I Current Δp Pressure difference R Radius of capillary tube L Length of the capillary tube where magnetic field applied Q Volumetric flow rate of MR fluid in the capillary S w Shear stress of the fluid at the wall of the capillary g Shear rate 1. INTRODUCTION Magnetorheological fluid (MR), a class of smart materials ,has been in use as dampener for landing gears of military aircraft. The MR technology is well developed in USA, Canada and some European countries. It is widely incorporated in MR brakes, MR clutches, and MR suspension systems of automobiles. It is widely used in military vehicles due to their sudden response and remotely-controllable behaviour. MR fluid consists of three constituents namely; carrier liquid, suspension and additive. Carbonyl iron particles are widely used suspensions because of their high magnetic permeability, low remanant magnetisation, and also these are magnetically multidomain. When the magnetic field is applied, the suspended particles present in the MR fluid become magnetised and align themselves like a chain in the directions of the magnetic field 1. This transforms the MR fluid from fluid state to solid like state within milliseconds. It increases the viscosity and yield stress with the formation of columnar structures, parallel to the applied magnetic field, and which must be broken for the fluid to flow. The increase in yield stress, however, is not linear, since the particles are ferromagnetic or ferrimagnetic and the magnetisation in different parts of the particles occurs non-uniformly 2. The additive, the other constituent, helps to decrease sedimentation, prevents both agglomeration and oxidation, modifies viscosity, and inhibits wear. Carrier liquid is the major constituent of MR fluids (50-80 per cent by volume) which greatly influences the rheological properties of MR fluids. Its primary function is to provide a medium for magnetically active particulates to remain suspended during the absence of a magnetic field and to facilitate realignment once magnetic field is applied. But the type of carrier liquid used in a MR fluid may differ. In literature, different carrier liquids have been considered in the preparation of MR fluids and some are detailed here. These are polyvinyln-butyl and naphthol-thickened kerosene 3 , silicon oil 4, 5 , white and light grade mineral oils 6 , a combination of synthetic oil, water and organic liquids 7 , etc. MR fluids are also available commercially which contain hydrocarbon-based fluid, siliconbased fluid, etc. but these options are very costly. The literature review reveales that mineral oil, silicon oil and synthetic oil are commonly-used carrier liquids. The mineral oils, which are derived from petroleum, are neither biodegradable nor environmentally friendly, and likely to be depleted within few years. Silicone oil has low surface

Recent advances in drop-on-demand (DOD)-type inkjet printing techniques have increased research activities in the area of direct ceramic inkjet printing. In an attempt to develop a ceramic inkjet printer for the manufacture of ceramic components with their sizes in micro scale, the formation of ceramic ink droplet (ethyl alcohol loaded with different volume fractions of alumina particles) and its spread from a reservoir using piezoelectric actuation are simulated. The properties of the ceramic ink are taken from the data reported in literature. The simulations were performed with computational fluid dynamics software (CFD-ACE+), CFDRC. This study gives details of the interaction among different physical phenomena that contribute to the droplet formation and ejection process. The results from this study are being used for a preliminary design of nozzle and for the preparation of ceramic inks to achieve the desired droplet characteristics.