Development of a Numerical Design Tool for SNS Cavitation Mitigation

OakRidge National Laboratory (ORNL) has recognized that the generation of strong shock waves in the Spallation Neutron Source (SNS) can lead to cavitation and significant erosion of the wall of the liquid mercury target. Based on preliminary numerical and experimental work at ORNL and other laboratories, it has been proposed that the insertion of a cloud of small gas bubbles or a gas layer in the mercury target could absorb and deflect the shock waves and protect the walls from cavitation erosion. Another strategy would involve taking advantage of wall shaping/deformation characteristics and energy absorption to reduce cavitation. An accurate numerical code is required to select a proper mitigation solution and requires multiphase, shock wave, and fluid structure interaction capability. This project will develop a simulation package capable of modeling shock propagation in a multiphase media and interacting with a solid structure solver. In addition, the project will utilize two capabilities now under development for the US Navy: a multiphase flow model capable of representing bubble interactions at multiple scales and a method for fluid-structure coupling. These approaches will be combined with a shock capturing scheme and a model for discrete interfaces to generate a tool for mitigation design. Commercial Applications and other Benefits as described by the awardee: In addition to mitigating shock waves in the mercury targets at the SNS, the software should have multiple applications. These include naval applications where the mitigation of shock wave impact is of keen interest to vessel protection and to propeller blade design. The modeling capability also should be attractive to the chemical industry, to improve the performance of bubble column reactors and multiphase slurries. Also, minimally invasive medical techniques that use acoustic cavitation-based treatments such as HIFU and shock wave lithotripsy would benefit from the tool.