scholarly journals Development of algorithms for constructing two-dimensional optimal boundary-adaptive grids and their software implementation

2021 ◽  
Vol 21 (3) ◽  
pp. 222-230
Author(s):  
A. E. Chistyakov ◽  
V. V. Sidoryakina ◽  
S. V. Protsenko
Keyword(s):  
Test Problem ◽  
Complex Geometry ◽  
Adaptive Grid ◽  
Software Implementation ◽  
Computational Algorithms ◽  
Computational Domain ◽  
Two Dimensional ◽  
Adaptive Grids ◽  
Qualitative Properties ◽  
Optimal Boundary

Introduction. It is noted that the use of adaptive grids in calculations makes it possible to improve the accuracy and efficiency of computational algorithms without increasing the number of nodes. This approach is especially efficient when calculating nonstationary problems. The objective of this study is the development, construction and software implementation of methods for constructing computational two-dimensional optimal boundary-adaptive grids for complex configuration regions while maintaining the specified features of the shape and boundary of the region. The application of such methods contributes to improving the accuracy, efficiency, and cost-effectiveness of computational algorithms.Materials and Methods. The problem of automatic construction of an optimal boundary-adaptive grid in a simply connected region of arbitrary geometry, topologically equivalent to a rectangle, is considered. A solution is obtained for the minimum set of input information: the boundary of the region in the physical plane and the number of points on it are given. The creation of an algorithm and a mesh generation program is based on a model of particle dynamics. This provides determining the trajectories of individual particles and studying the dynamics of their pair interaction in the system under consideration. The interior and border nodes of the grid are separated through using the mask tool, and this makes it possible to determine the speed of movement of nodes, taking into account the specifics of the problem being solved.Results. The developed methods for constructing an optimal boundary-adaptive grid of a complex geometry region provides solving the problem on automatic grid construction in two-dimensional regions of any configuration. To evaluate the results of the algorithm research, a test problem was solved, and the solution stages were visualized. The computational domain of the test problem and the operation of the function for calculating the speed of movement of interior nodes are shown in the form of figures. Visualization confirms the advantage of this meshing method, which separates the border and interior nodes.Discussion and Conclusions. The theoretical and numerical studies results are important both for the investigation of the grids qualitative properties and for the computational grid methods that provide solving numerical modeling problems efficiently and with high accuracy.

Comparison of DSMC and CFD Models of Heat Transfer in a Rarefied Two-Dimensional Geometry

2018 ◽  
Author(s):  
Dilesh Maharjan ◽  
Mustafa Hadj-Nacer ◽  
Miles Greiner ◽  
Stefan K. Stefanov
Keyword(s):  
Heat Transfer ◽  
Rarefied Gas ◽  
Complex Geometry ◽  
Direct Simulation Monte Carlo ◽  
Accurate Method ◽  
Vacuum Drying ◽  
Helium Pressure ◽  
Two Dimensional ◽  
Dsmc Method ◽  
Cfd Simulations

During vacuum drying of used nuclear fuel (UNF) canisters, helium pressure is reduced to as low as 67 Pa to promote evaporation and removal of remaining water after draining process. At such low pressure, and considering the dimensions of the system, helium is mildly rarefied, which induces a thermal-resistance temperature-jump at gas–solid interfaces that contributes to the increase of cladding temperature. It is important to maintain the temperature of the cladding below roughly 400 °C to avoid radial hydride formation, which may cause cladding embrittlement during transportation and long-term storage. Direct Simulation Monte Carlo (DSMC) method is an accurate method to predict heat transfer and temperature under rarefied condition. However, it is not convenient for complex geometry like a UNF canister. Computational Fluid Dynamics (CFD) simulations are more convenient to apply but their accuracy for rarefied condition are not well established. This work seeks to validate the use of CFD simulations to model heat transfer through rarefied gas in simple two-dimensional geometry by comparing the results to the more accurate DSMC method. The geometry consists of a circular fuel rod centered inside a square cross-section enclosure filled with rarefied helium. The validated CFD model will be used later to accurately estimate the temperature of an UNF canister subjected to vacuum drying condition.

Methods to Accelerate Ray Tracing in the Monte Carlo Method for Surface-to-Surface Radiation Transport

2006 ◽  
Vol 128 (9) ◽  
pp. 945-952 ◽  
Author(s):  
Sandip Mazumder
Keyword(s):  
Monte Carlo ◽  
Ray Tracing ◽  
Radiation Transport ◽  
Three Dimensional ◽  
Intersection Point ◽  
Surface Radiation ◽  
Computational Domain ◽  
Two Dimensional ◽  
Spatial Partitioning ◽  
The Monte Carlo Method

Two different algorithms to accelerate ray tracing in surface-to-surface radiation Monte Carlo calculations are investigated. The first algorithm is the well-known binary spatial partitioning (BSP) algorithm, which recursively bisects the computational domain into a set of hierarchically linked boxes that are then made use of to narrow down the number of ray-surface intersection calculations. The second algorithm is the volume-by-volume advancement (VVA) algorithm. This algorithm is new and employs the volumetric mesh to advance the ray through the computational domain until a legitimate intersection point is found. The algorithms are tested for two classical problems, namely an open box, and a box in a box, in both two-dimensional (2D) and three-dimensional (3D) geometries with various mesh sizes. Both algorithms are found to result in orders of magnitude gains in computational efficiency over direct calculations that do not employ any acceleration strategy. For three-dimensional geometries, the VVA algorithm is found to be clearly superior to BSP, particularly for cases with obstructions within the computational domain. For two-dimensional geometries, the VVA algorithm is found to be superior to the BSP algorithm only when obstructions are present and are densely packed.

Two Dimensional Simulations of Enhanced Heat Transfer in an Intermittently Grooved Channel

2000 ◽  
Author(s):  
M. Greiner ◽  
P. F. Fischer ◽  
H. M. Tufo
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Spectral Element ◽  
Local Heat ◽  
Navier Stokes ◽  
Computational Domain ◽  
Two Dimensional ◽  
Number Range ◽  
Element Technique ◽  
Outflow Boundary

Abstract Two-dimensional Navier-Stokes simulations of heat and momentum transport in an intermittently grooved passage are performed using the spectral element technique for the Reynolds number range 600 ≤ Re ≤ 1800. The computational domain has seven contiguous transverse grooves cut symmetrically into opposite walls, followed by a flat section with the same length. Periodic inflow/outflow boundary conditions are employed. The development and decay of unsteady flow is observed in the grooved and flat sections, respectively. The axial variation of the unsteady component of velocity is compared to the local heat transfer, shear stress and pressure gradient. The results suggest that intermittently grooved passages may offer even higher heat transfer for a given pumping power than the levels observed in fully grooved passages.

An adaptive grid scheme applied to two-dimensional airfoil problems

1984 ◽  
Author(s):  
J. STEINBRENNER ◽  
D. ANDERSON ◽  
Y. TASSA
Keyword(s):  
Adaptive Grid ◽  
Two Dimensional ◽  
Grid Scheme

Design and Deformation of CAD Surface Models With Haptics

2004 ◽  
Author(s):  
X. Liu ◽  
G. Dodds ◽  
J. McCartney ◽  
B. K. Hinds
Keyword(s):  
Shape Control ◽  
Force Feedback ◽  
Complex Geometry ◽  
Virtual Space ◽  
Cad Model ◽  
Two Dimensional ◽  
Shape Functions ◽  
Ship Hulls ◽  
Control Functions ◽  
Surface Models

With traditional two-dimensional based interfaces, many CAD surface models, such as automobile bodies and ship hulls, are difficult to design and edit due to their 3D nature. This paper discusses the haptic-based deformation for the design of CAD surface models. With haptic devices (force feedback interfaces) designers can, in virtual space, touch a native B-rep CAD model, and use their tactile senses to manipulate it by pushing, pulling and dragging its surfaces in a natural 3D environment. The paper presents shape control functions. By using the shape functions, designers can directly manipulate and deform a selected region of a surface to the desired shape, and generate complex geometry with simple operations. Force feedback gives designers the greatest flexibility for the design of complex surfaces.

Transient Flow Field on Containment Floor Predicted by Two-Dimensional Shallow Equation Solver

2009 ◽  
Author(s):  
Young Seok Bang ◽  
Gil-Soo Lee ◽  
Byung-Gil Huh ◽  
Deog-Yeon Oh ◽  
Sweng-Woong Woo
Keyword(s):  
Flow Field ◽  
Transient Flow ◽  
Complex Geometry ◽  
Solid Wall ◽  
Shallow Water Equation ◽  
Water Reservoir ◽  
Two Dimensional ◽  
Pressurized Water ◽  
Fast Running ◽  
Propagation Of Waves

For the analysis of debris transport on containment floor, a model to predict the flow field should have a fast-running capability and high accuracy. A model is developed to calculate the transient flow field on the containment floor involving a complex geometry in the advanced pressurized water reactor (PWR) such as Advanced Power Reactor (APR)-1400, which does not have a switchover from injection to recirculation following a loss-of-coolant accident (LOCA). Two-dimensional shallow water equation (SWE) is solved using the finite volume method (FVM). Unstructured triangular meshes are used to simulate the complex structures on the containment floor. Harten-Lax-van Leer (HLL) scheme, one of the approximate Riemann solver, is adopted to capture the dry-wet interface and to determine the momentum flux at the interface. An experiment of a sudden dam break having water reservoir and L-shape open channel is simulated and compared with the calculated result, which supports the validity of the present model. The model is also applied to calculation of the flow field of APR-1400. The calculated flow field can be characterized by the propagation of waves generated by surface level difference and by the reflection of waves from solid wall. The transient flow rates entering to the Holdup Volume Tank (HVT) can be predicted within a practical limit of computational resource.

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