Cavitation Models

1. Cavitation Models Roman Samulyak, Yarema Prykarpatskyy Center for Data Intensive Computing Brookhaven National Laboratory U.S. Department of Energy rosamu@bnl.gov, yarpry@bnl.gov

2. Talk outline • Modeling of the equation of state for two-phase fluid systems • Numerical simulation of the interaction of mercury with a proton pulse in a thimble (BNL AGS and CERN ISOLDE experiments) • Conclusions • Future research

3. The system of equations of compressible hydrodynamics • The system is solved using the front tracking technique for free surfaces

4. Isentropic two phase EOS model for cavitating liquid • Approach: connect thermodynamically consistently different models for different phases • Pure liquid is described by the stiffened polytropic EOS model (SPEOS) • Pure vapor is described by the polytropic EOS model (PEOS) • An analytic model is used for the mixed phase • SPEOS and PEOS reduced to an isentrope and connected by the model for liquid-vapor mixture • All thermodynamic functions depend only on density

5. The EOS • does not take into account drag forces, viscous and surface tension forces • does not have full thermodynamics Current work on improved models will be discussed in section Future Research

6. Simulation of the Mercury SplashSchematic of the experiment

7. Mercury splash (thimble): experimental data Mercury splash at t = 0.88, 1.25 and 7 ms after proton impact of 3.7 e12 protons

8. Mercury splash (thimble): numerical simulation

9. Mercury splash (thimble): numerical simulation

10. Increasing the spot size of the proton beam results in a decrease of the splash velocities

11. The splash velocity of mercury depends linearly on the proton intensity Numerical simulations Approximation from experimental data

12. Conclusions • Numerical simulations show a very good agreement with experimental data at early time. • The lack of full thermodynamics in the EOS leads to some disagreements with experiments for the time evolution of the velocity. Can be corrected by the energy deposition. Experimental data on the evolution of the explosion velocity (from Adrian Fabich’s thesis) • Equation of states needs additional physics (better mechanism of mass transfer, surface tension, viscosity etc.)

13. Future Research • Further work on the EOS modeling for cavitating and bubbly flows. • a) Direct method: study a liquid-vapor gas mixture as a system of one phase domains separated by free surfaces using FronTier’s code interface tracking capability a) b) c) Direct numerical simulation of the pressure wave propagation in a bubbly liquid: a) initial density; red: mercury, blue: gas bubbles, b) initial pressure; the pressure is 500 bar at the top and 1 bar at the bottom, c) pressure distribution at time 100 microseconds; pressure is 6 bar at the bottom. Future problem: develop a nonlocal Riemann solver for the propagation of free interfaces which takes into account the mass transfer due to phase transitions

14. b) Homogeneous method: use a continuous description of the liquid-vapor gas mixture by means of homogeneous equation of state models and the Rayleigh-Plesset equation for the average gas bubble size evolution Future problem: include terms describing the mass transfer due to phase transitions

15. Further studies of the muon collider target issues. Studies of the cavitation phenomena in a magnetic field. • Studies of hydrodynamic aspects of the cavitation induced erosion in the SNS target.