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The article examines the simulation of pressurized thermal shock (PTS) within the European Integrated Project nuclear reactor simulations(NURESIM). It discusses the involvement of two-phase conditions in the geometric region of the nuclear reactor. Furthermore, it describes the advances in the understanding of cold leg and downcomer conditions and discusses the computational fluid dynamics (CFD) simulation tools' capabilities to capture each basic conditions.

The article provides an analysis on the thermal-hydraulic phenomena of pressurized thermal shock (PTS) in pressurized water reactors under the Nuclear Reactor Simulations (NURESIM) Project of the European Commission. It explores the two-phase phenomena in the cold leg and downcomer regions of the nuclear reactor through computational fluid dynamics (CFD) simulation. It shows the involvement of several two-phase subphenomena, but limitations on its performance and interaction were observed.

The impact of interfacial dynamics on turbulent heat transfer at a deformable, sheared gas-liquid interface is studied using Direct Numerical Simulation (DNS). The flow system comprises a gas and a liquid phase flowing in opposite directions. The governing equations for the two fluids are alternately solved in separate domains and then coupled at the interface by imposing continuity of velocity and stress. The deformations of the interface fall in the range of capillary waves of waveslope ak=0.01 (wave amplitude a times wavenumber k), and very small phase speed-to-friction velocity ratio, c/u[sub*]. The influence of low-to-moderate molecular Prandtl numbers (Pr) on the transport in the immediate vicinity of the interface is examined for the gas phase, and results are compared to existing wall-bounded flow data. The shear-based Reynolds number Re[sub*] is 171 and Prandtl numbers of 1, 5, and 10 were studied. The effects induced by changes in Pr in both wall-bounded flow and over a gas-liquid interface were analyzed by comparing the relevant statistical flow properties, including the budgets for the temperature variance and the turbulent heat fluxes. Overall, Pr was found to affect the results in very much the same way as in most of the available wall flow data. The intensity of the averaged normal heat flux at high Prandtl numbers is found to be slightly greater near the interface than at the wall. Similar to what is observed in wall flows, for Pr=1 the turbulent viscosity and diffusivity are found to asymptote with z&sup+3;, where z[sup+] is the distance to the interface, and with z[sup+n], where n>3 for Pr=5 and 10. This implies that the gas phase perceives deformable interfaces as impermeable walls for small amplitude waves with wavelengths much larger than the diffusive sublayers. Moreover, high-frequency fluctuating fields are shown to play a minor role in transferring heat across the interface, with a marked filtering effect of Pr. A new scaling law for... [ABSTRACT FROM AUTHOR]