Speaker: Veljko Samardzic Advisor; Dr. Ernest Geskin
Investigation of impulsive water jets puzzled many scientists since 1950’s (Landau, Coles). Water which is conventionally considered incompressible actually is compressible when exposed to high pressure variations. High speed water slug investigated in this study is a discreet quantity of water which is propelled by combustion of gun powder. Conceptually, a launcher of the impulsive jet (IJ) termed a water cannon constitutes a barrel with an attached nozzle. Energy provided by powder combustion is injected at an extremely high rate into a water projectile located in a barrel. This brings about water acceleration. Consequently water can be accelerated to the speed of 3000 m/s and perhaps much more.
Water slug impacting a solid surface at speeds of 1000 m/s and more act as an explosive which detonates on the target surface. As a result the slug demolishes brittle materials such as rock and concrete. The metal deformation during the slug’s impact is similar to that of explosive forming. However, the high energy liquid impact has unique features which enable us to improve existing and create novel forming technologies. Investigation of production and behavior of high speed water slugs in the air and at the target surface are topics of my research. In order to understand energetic potential of high speed water slugs their behavior in the air must be studied. I conducted water slug velocity measurements and slug image monitoring and filming. I used laser particle image velocimeter for laboratory scale investigation and high speed filming for industrial scale investigation of water slug’s transformation in the air. In both cases development of slugs in the air was monitored and their axial and radial velocity components were measured. Industrial scale device generated slugs which were moving with velocity between 1500 and 1700 m/s.
Water slug target interaction was investigated with several objectives such as: metal piercing, concrete demolition, explosive set up neutralization, metal forming, welding and metal coating. Investigation of deformation and failure of ductile and brittle materials was performed including characterization of investigated samples. Among tested materials are: steel, aluminum, copper, concrete, wood, soil, and wax. Characterization of deformation of tested materials was investigated by: ultrasound devices, scanning electron microscope, optical microscope and visual investigation. Fractography analysis was performed to evaluate modes of failures of tested materials. Characterization results were used to simulate deformed samples and enhance deformation studies. As a result feasibility of material forming (piercing, punching, extrusion, stamping, forging, bending, coining), welding, coating using the liquid impact will be presented. Future prospective of investigation will be presented.