Three-dimensional Method Of Characteristics Research Articles

Time-dependent neutron transport method based on three-dimensional method of characteristics

The 3D Method of Characteristics (MOC) has high numerical accuracy, geometrical flexibility, making it suitable for the simulation of advanced reactors with complex geometry, while the development of transient solvers based on it is still relatively limited. In this work, transient method was developed based on 3D MOC solvers of OpenMOC and predictor–corrector quasi-static method and the C5G7-TD benchmark problems were used to verify the implementation. In 2D cases and 3D moderator density change cases, the results of OpenMOC were in good agreement with the results of other transient codes. In 3D control rods movement cases, there are oscillation errors between the existing results of different transient codes due to the control rod cusping effect. This work is based on the refined axial modeling of 3D MOC, which avoids the cusping effect and provides new results of C5G7-TD benchmark.

High-Fidelity Neutron Transport Solution of High Temperature Gas-Cooled Reactor by Three-Dimensional Linear Source Method of Characteristics

Recently, a three-dimensional method of characteristics (MOC) code called Advanced Reactor CHaracteristics tracER (ARCHER) has been developed by the Institute of Nuclear and New Energy Technology, Tsinghua University, to solve the neutron transport problem in high-temperature gas-cooled reactors (HTRs) with explicit pebble-bed geometry. Although the spatial domain decomposition using the message passing interface (MPI) and the ray parallel using OpenMP have been implemented in the previous version of ARCHER, in order to simulate practical HTR problems it is still necessary to reduce the great computational burden through efficient algorithms. Therefore, the linear source approximation (LSA) scheme, which allows coarser transport calculation grids while maintaining high accuracy, has been added in the latest version of ARCHER to relieve memory pressure together with the MPI-based spatial domain decomposition. Moreover, on-the-fly calculation of the relative position coordinates of the ray segment center can further reduce the memory for storing segment information under LSA. In addition, time-consuming MOC transport sweeps can be reduced greatly with coarse-mesh finite difference (CMFD) acceleration. Numerical results show that both LSA and CMFD acceleration contribute to simulate the practical HTR-10 problem successfully.

A Time-Dependent Computaional Method for Blunt Body Flows

The steady blunt body problem is solved using a time-dependent technique. The steady solution is reached asymptotically. The computation is performed in the shock layer only, assuming that the shock wave is a discontinuity surface, dependent on time. A technique similar to the one used by Richtmyer, Lax, and Wendroff is applied to the points between shock and body, whereas the shock and body points are analyzed with a three-dimensional method of characteristics. In this way a coarse mesh can be used, and little time is needed on the computer to achieve accurate results. Detailed results for two-dimensional (symmetric and asymmetric) blunt bodies and for axisymmetric ones are given and compared with experimental data. A brief critical comparison of the present technique with other methods also is given.

Calculation of three-dimensional flowfields by the unsteady method of characteristics

A numerical algorithm based on the unsteady three-dimensional method of characteristi cs is presented for calculating unsteady three-dimensional subsonic/transonic inviscid flowfields. The flowfield unit processes are based on a local network consisting of six bicharacteristics and the pathline. The algorithm is an explicit secondorder accurate predictor-corrector procedure. An inverse-march ing method is employed, wherein the solution grid in physical space is prespecified. Steady flow solutions are obtained as the asymptotic solution in time. Results are presented for spherical supersonic source flow, for axisymmetric supersonic flow in a conical nozzle, for three-dimensional supersonic flow in a superelliptical nozzle, and for three-dimensional subsonic/transonic flow in a superelliptical nozzle. Solutions obtained by the present method agree well with solutions obtained by steady flow method of characteristi cs algorithms and experimental data.

Linearized Solutions for the Supersonic Flow Through Turbomachinery Blade Rows (Using Actuator Disk Theory)

An actuator disk method is developed for calculating the flow through the blade rows of a turbomachine in which the velocity relative to the blading may be supersonic. The method is compared with calculations of the fully supersonic flow through a twisted blade row using a three-dimensional method of characteristics.

Spatial Supersonic Flow Through Annular Cascades

The spatial supersonic flow through rotating and stationary annular cascades is analyzed by means of a nonlinear three-dimensional method of characteristics. Three-dimensional corrections for flow quantities referred to a quasi-three-dimensional approximation method are determined depending on geometric and gas dynamical parameters. Characteristic properties of spatial supersonic flow through annular cascades are analyzed, leading to guiding principles for practical design purposes.

A new algorithm for three-dimensional method of characteristics.

A new algorithm for three-dimensional method of characteristics.

Viscous Flowfield Calculations on Pointed Bodies at Angle of Attack in Nonuniform Freestreams

determined from Eq. (1) and the condition of constant static pressure and total enthalpy. The inviscid flowfield is then calculated from a modified form of Rakich's three-dimensional method of characteristics (NASA TN D-5341). Typical results for the non-dimensional pressure (pb — Pb/p^v^) and inviscid surface Mach Number (Mb) are shown in Fig. 2 for a 20° half-angle cone at a = 10° and Mx = 3. For a velocity defect of A = 0.2 the surface Mach number goes to unity at x = 0.95 (based on B = 10) in the windward plane, and the three-dimensional method of characteristics cannot be continued beyond this point. Member AIAA.

Stability of some numerical schemes of the three-dimensional method of characteristics

Stability of some numerical schemes of the three-dimensional method of characteristics