Simulation of Turbulent Convection at High Rayleigh Numbers

The paper considers the possibility of using different approaches to modeling turbulence under conditions of highly developed convection at high Rayleigh numbers. A number of industrially oriented problems with experimental data have been chosen for the study. It is shown that, at Rayleigh numbers from 109 to 1017, the application of the eddy-resolving LES model makes it possible to substantially increase the accuracy of modeling natural convection in comparison with the linear vortex viscosity model SST. This advantage is most pronounced for cases of a vertical temperature difference with the formation of a large zone of convection of strong intensity. The use of the Reynolds stress model EARSM is shown for cases of natural convective flow in domains with dihedral angles in the simulated region and the predominance of secondary currents. When simulating a less intense convective flow, when the temperature difference is reached at one boundary, the differences in the approaches used to model turbulence are less significant. It is shown that, with increasing values of Rayleigh numbers, errors in the determination of thermohydraulic characteristics increase and, for more accurate determination of them, it is expedient to use eddy-resolving approaches to the modeling of turbulence

Studies of turbulent coolant mixing flows in the new generation reactors

Due to studying of the flow parameters in the downcomer the bottom plenum of the nuclear reactor can be carried out with the help of CFD programs, the work is devoted to experimental researches in the field of pressurized water reactor with the purpose of creation of benchmarks for verification of domestic codes of computational hydrodynamics. Such data must have high spatial resolution, high resolution and high accuracy of the measurements. It makes necessary to apply complex experimental methodologies, measurement instrumentation and careful adjustment of experimental methodology. So a brief description of the experimental stand and its research methodology is given. A spatial conductometric measuring system that allows to study the processes of turbulent mixing of flows in the complex geometry of the nuclear reactor is presented. The description of experimental research and their results are presented. Conclusions are drawn about the prospects of using spatial conductometry as a vortex-resolving measurement method

Experimental studies and numerical simulation of coolant hydrodynamics in the inlet area of nuclear reactor fuel assembly

An innovative core with an increased energy resource was used when designing RITM-200 reactor unit. The paper presents the results of experimental and numerical simulation of hydrodynamic processes occurring in the inlet region of the RITM reactor fuel assembly model. Computational mesh of fuel assembly, containing ~ 22 million elements was created using Ansys ICEM CFD. The values of relative axial velocities in several cross sections at the inlet to the bundle of fuel elements are obtained. At the inlet to the fuel rods bundle the velocity field is not uniform, due to the complex geometry of the fuel assembly. The obtained results of CFD-simulation can be used to determine the input boundary conditions for subchannel programs of the core thermal-hydraulic analysis. This allows taking into account uneven flow rate distribution in subchannels due to the complex geometry of the fuel assembly inlet region

Studies of turbulent coolant mixing flows in the new generation reactors

Due to studying of the flow parameters in the downcomer the bottom plenum of the nuclear reactor can be carried out with the help of CFD programs, the work is devoted to experimental researches in the field of pressurized water reactor with the purpose of creation of benchmarks for verification of domestic codes of computational hydrodynamics. Such data must have high spatial resolution, high resolution and high accuracy of the measurements. It makes necessary to apply complex experimental methodologies, measurement instrumentation and careful adjustment of experimental methodology. So a brief description of the experimental stand and its research methodology is given. A spatial conductometric measuring system that allows to study the processes of turbulent mixing of flows in the complex geometry of the nuclear reactor is presented. The description of experimental research and their results are presented. Conclusions are drawn about the prospects of using spatial conductometry as a vortex-resolving measurement method

Experimental studies and numerical simulation of coolant hydrodynamics in the inlet area of nuclear reactor fuel assembly

An innovative core with an increased energy resource was used when designing RITM-200 reactor unit. The paper presents the results of experimental and numerical simulation of hydrodynamic processes occurring in the inlet region of the RITM reactor fuel assembly model. Computational mesh of fuel assembly, containing ~ 22 million elements was created using Ansys ICEM CFD. The values of relative axial velocities in several cross sections at the inlet to the bundle of fuel elements are obtained. At the inlet to the fuel rods bundle the velocity field is not uniform, due to the complex geometry of the fuel assembly. The obtained results of CFD-simulation can be used to determine the input boundary conditions for subchannel programs of the core thermal-hydraulic analysis. This allows taking into account uneven flow rate distribution in subchannels due to the complex geometry of the fuel assembly inlet region