Numerical study of CFD simulations for compact counter-recoil design of EOD water cannon
Explosive Ordnance Disposal (EOD) robots armed with a water cannon are deployed to disarm the improvised explosive devices. It is critical that the water cannon produces as little recoil force as possible when fired. Otherwise, the robot may be rendered immobile or damaged. In a previous work, a recoilless water cannon was designed through a specific combination of firing experiments and Computational Fluid Dynamics (CFD) simulations. The final design was conceived, prototyped and tested with real bullets. The testing results were found to be satisfactory. In this work, the CFD simulations of the final design was carried out and closely investigated. Numerical study and error analysis were performed in an attempt to find the most suitable and efficient CFD setups for this problem. Two different CFD programs, three different flow domains, and various mesh resolutions were tested.
Compact counter-recoil design of water cannon using a single nozzle with backward spray
A novel design of water cannons using off-the-shelf bullet and barrel was conceptualized, analyzed, prototyped and field-tested. The cannon was designed to be mounted on a remotely controlled carrier robot and its main propose was to utilize water impact to defuse explosives usually placed in metal or wooden containers. In the previous design, the firing created a large recoil force, which was likely to damage and/or immobilize the robot. In the new design presented here, the primary objective was to significantly reduce the recoil force by using backward spray near the muzzle, which allowed the cannon to maintain its destructive power without increasing the robot's payload. In this paper, the design process using a combination of Computational Fluid Dynamics simulations and experiments were presented. The combination was nontrivial but essential due to the limited prior knowledge of the employed bullet (for simulations) as well as firing safety regulation and high prototyping cost (for experiments). The final prototype of the cannon was field-tested and shown to be capable of reducing the recoil force to such an extent that the robot was visibly stationary.
Tests of composite beams with web holes
Tests of composite beams comprising a concrete slab supported on a steel deck and a steel wide-flange shape containing large web openings are described. Special attention is directed to the amount of shear connection between slab and steel section in the region of a web hole, and on the effect of construction loads acting on the steel section prior to composite action being effective.It is shown that limited shear connection at the hole will significantly affect the strength when loading produces a high shear-to-moment ratio, and a theory is presented which conservatively takes this into account. The effect of construction loads on unshored construction is shown to be small when these do not exceed 60% of the non-composite beam resistance at the hole.