scholarly journals REEF3D Wave Generation Interface for Commercial CFD Codes

2020 ◽  
pp. 1-12
Author(s):  
Csaba Pakozdi ◽  
Hans Bihs ◽  
Arun Kamath
Keyword(s):  
Cfd Simulation ◽  
Velocity Potential ◽  
Three Dimensional ◽  
Wave Theory ◽  
Far Field ◽  
New Approach ◽  
Cfd Models ◽  
Numerical Wave ◽  
The One ◽  
General Interface

Abstract In recent years CFD developments have shown a trend to combine RANS CFD simulation with other methods such as wave theories or velocity potential based numerical wave tanks, in order to reduce to computation costs. This is however not a new approach, and there exists a large amount of literature about domain decomposition techniques describing a two way coupling between the RANS CFD models and other methods. One can also observe an increasing popularity in the use of a less sophisticated technique where different fluid solvers are combined with one-way coupling. In these methods a predefined solution is provided in the far-field, while a three-dimensional (3D) CFD simulation is applied in a limited zone near the structure. The predefined solution is used to specify the background far-field solution. The published solutions use wave theory or a numerical wave tank where the predefined solution is calculated parallel to the RANS solver. In this way it is possible to reduce the interpolation inaccuracy and the amount of transferred data to the CFD simulation. The disadvantage of this technique is that the far field solver has to be prepared in order to run in parallel with the CFD solver. Due to the one way coupling it is possible to predefine this information in tables before the CFD simulation. This technique makes it possible to define a general interface between difference solvers without modifying existing codes. This paper presents such a technique where the predefined solution is stored into files.

scholarly journals REEF3D Wave Generation Interface for Commercial CFD Codes

2019 ◽  
Author(s):  
Csaba Pakozdi ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Elin Marita Hermundstad
Keyword(s):  
Cfd Simulation ◽  
Three Dimensional ◽  
Wave Theory ◽  
Far Field ◽  
New Approach ◽  
Field Solution ◽  
Cfd Models ◽  
Numerical Wave ◽  
The One ◽  
General Interface

Abstract In recent years CFD developments have shown a trend to combine RANS CFD simulation with other methods such as wave theories or velocity potential based numerical wave tanks, in order to reduce to computation costs. This is however not a new approach, and there exists a large amount of literature about domain decomposition techniques describing a two way coupling between the RANS CFD models and other methods. One can also observe an increasing popularity in the use of a less sophisticated technique where different fluid solvers are combined with one-way coupling. In these methods a predefined solution is provided in the far-field (ignoring the structure), while a three-dimensional (3D) CFD simulation is applied in a limited zone near the structure. The predefined solution is used to specify the background far-field solution. The governing equations are extended by the addition of a source term. The published solutions use wave theory or a numerical wave tank where the predefined solution is calculated parallel to the RANS solver. In this way it is possible to reduce the interpolation inaccuracy and the amount of transferred data to the CFD simulation. The disadvantage of this technique is that the far field solver has to be prepared in order to run in parallel with the CFD solver. Due to the one way coupling it is possible to predefine this information in tables before the CFD simulation. This technique makes it possible to define a general interface between difference solvers without modifying existing codes. This paper presents such a technique where the predefined solution is stored into files. An interpolation function delivers all data to the far-field solution for the CFD simulation. The paper analyses the necessary accuracy of the interpolation and the costs of the input/output operation of the CFD simulation through several verification cases.

Mixing Conditions in the Lower Plenum and Core Inlet of a BWR

2008 ◽  
Author(s):  
Hernan Tinoco ◽  
Stefan Ahlinder
Keyword(s):  
Boundary Conditions ◽  
Three Dimensional ◽  
Mean Value ◽  
Large Temperature ◽  
Inlet Temperature ◽  
Inlet Section ◽  
The Core ◽  
Cfd Models ◽  
Stable Temperature ◽  
The One

A thermal mixing analysis of the Downcomer, Main Recirculation Pumps (MRPs) and Lower plenum of Forsmark’s Unit 3 has been carried out with three separate CFD models. Several difficulties with the boundary conditions have been encountered, particularly with the MRP model. The results obtained predict stable temperature differences of around 8 K at the core inlet. Such large temperature differences have never been observed at Forsmark NPP. Temperature measurements at four positions above the Reactor Pressure Vessel (RPV) bottom give the mean value used as the core inlet temperature for core analyses with codes such as POLCA. The temperature transmitters used are rather slow and inaccurate. Still, they should be able to detect large stable temperature differences such as those predicted by the aforementioned computations. Indirect indication of the incongruity of these predictions is the possibility of fuel damage caused by such large temperature differences. Fuel damage other than the one caused by debris fretting (thread-like particles) through mechanical influence has not been reported at Forsmark NPP since the implementation of liner cladding in fuel design. Also, the aforementioned difficulties with the connection of the models throw some doubt upon the accuracy of these predictions. A completely connected model of the same RPV volume covered by the separate models predicts temperature differences at core inlet that are almost a fourth of those mentioned above, i. e. approximately 2.5 K. Most of the mixing occur downstream of the MRP diffusers, at the Lower Plenum “inlet”. The reason for this prediction divergence is an impossibility of a correct transfer of complete three-dimensional flow field properties by means of boundary conditions defined at a two-dimensional inlet section.

CFD Analysis of Turbulent Flow in a Nuclear Fuel Bundle With Mixing Vane

2002 ◽  
Author(s):  
Wang Kee In ◽  
Dong Seok Oh ◽  
Tae Hyun Chun
Keyword(s):  
Turbulent Flow ◽  
Nuclear Fuel ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Cfd Analysis ◽  
Mean Flow ◽  
Cfd Models ◽  
Fuel Bundle ◽  
Rod Array

A computational fluid dynamics (CFD) analysis was performed to investigate the coolant mixing in a nuclear fuel bundle that is promoted by the mixing vane on the grid spacer. Single and multiple subchannels of one grid span of the fuel bundle were modeled to simulate a 5×5 rod array experiment with the mixing vane. The three-dimensional CFD models were generated by a structured multi-block method. The standard k-ε turbulence model was used in the current CFD simulation since it is practically useful and converges well for the complex turbulent flow in a nuclear fuel bundle. The CFD predictions of axial and lateral mean flow velocities showed a somewhat large difference from the experimental results near the spacer but represented the overall characteristics of coolant mixing well in a nuclear fuel bundle with the mixing vane. Comparison of single and multiple subchannel predictions shows good agreement of the flow characteristics in the central subchannel of the rod array. The simulation of multiple subchannels shows a slightly off-centered swirl in the peripheral subchannels due to the external wall of the rod array. It also shows no significant swirl and crossflow in the wall subchannels and the corner subchannels.

scholarly journals Far-field representation for the vertical force on a floating structure

2012 ◽  
Vol 712 ◽  
pp. 661-670 ◽  
Author(s):  
M. McIver
Keyword(s):  
Velocity Potential ◽  
Three Dimensional ◽  
Low Frequency ◽  
Exciting Force ◽  
Far Field ◽  
Vertical Force ◽  
Floating Structure ◽  
Field Representation ◽  
Reciprocity Relations ◽  
Scattering Potential

AbstractEquations are derived that relate the vertical hydrodynamic force on two- and three-dimensional structures that are floating in a fluid of infinite depth to the far-field dipole coefficient in the velocity potential. By an application of Green’s theorem to the radiation or scattering potential and a suitable test potential, the heave added mass, the heave damping and the vertical exciting force are shown to be expressible in terms of the dipole coefficient in the relevant potential. The results add to the known reciprocity relations, which relate quantities such as the damping and the exciting force to the amplitude of the far-field radiated wave. The expressions are valid at all frequencies, and their high- and low-frequency asymptotics are investigated.

A CFD Simulation Analysis of the Water Volumetric Fraction Distribution in the Runner of a Turgo Type Turbine Designed With an Integrated Dimensional Methodology

2014 ◽  
Author(s):  
Jorge Luis Clarembaux Correa ◽  
Jesús de Andrade ◽  
Sergio Croquer ◽  
Miguel Asuaje
Keyword(s):  
Steady State ◽  
Cfd Simulation ◽  
Simulation Analysis ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Steady State Regime ◽  
Volumetric Fraction ◽  
Cfd Models ◽  
Fraction Distribution ◽  
State Regime

Our previous work, on development of a design methodology inspired in the analysis of One-Dimensional and Three-dimensional Theories [1], allowed to obtain a Turgo Type Turbine (TTT) bucket using 8 geometric parameters as a function of the jet diameter, and Rankine Ovoids potential flow. CFD models under steady state regime [2] made possible to verify deduced expressions for torque, output power and hydraulic efficiency. In this paper, the effects of the water volumetric fraction distribution in the runner have been included, which are significantly conclusive to understand the runner hydrodynamic behavior and highlighted several optimizations to the performance equations that could be considered as a potential novelty for these turbines. In the same way, an influence study of nozzle parameters determined that the most profitable performance is achieved for an absolute velocity angle coming from the jet of 19.8°. Finally, several differences in the flow distribution in the runner were evaluated through a non-steady state regime CFD simulation, when comparing with the steady state.

TRANSPORT EQUATIONS WITH UNBOUNDED FORCE FIELDS AND APPLICATION TO THE VLASOV–POISSON EQUATION

2009 ◽  
Vol 19 (02) ◽  
pp. 199-228 ◽  
Author(s):  
DELPHINE SALORT
Keyword(s):  
Initial Data ◽  
Poisson Equation ◽  
Force Fields ◽  
A Priori ◽  
Kinetic Equations ◽  
Three Dimensional ◽  
Transport Equations ◽  
New Approach ◽  
The One ◽  
The Cost

The aim of this paper is to give new dispersive tools for certain kinetic equations. As an application, we study the three-dimensional Vlasov–Poisson equation for initial data having strictly less than six moments in [Formula: see text] where the nonlinear term E is a priori unbounded. We prove via new dispersive effects that in fact the force field E is smooth in space at the cost of a localization in a ball and an averaging in time. We deduce new conditions to bound the density ρ in L∞ and to have existence and uniqueness of global weak solutions of the Vlasov–Poisson equation with bounded density for initial data strictly less than six moments in [Formula: see text]. The proof is based on a new approach which consists in establishing a priori dispersion estimates (moment effects) on the one hand for linear transport equations with unbounded force fields and on the other hand along the trajectories of the Vlasov–Poisson equation.

Diffraction contrast of dislocations in icosahedral quasicrystals

1990 ◽  
Vol 48 (4) ◽  
pp. 454-455
Author(s):  
K. Urban ◽  
Z. Zhang ◽  
M. Wollgarten ◽  
D. Gratias
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Complete Characterization ◽  
Extinction Condition ◽  
Burgers Vector ◽  
Diffraction Contrast ◽  
Lattice Geometry ◽  
Reference Space ◽  
Icosahedral Quasicrystals ◽  
The One

Recently dislocations have been observed by electron microscopy in the icosahedral quasicrystalline (IQ) phase of Al65Cu20Fe15. These dislocations exhibit diffraction contrast similar to that known for dislocations in conventional crystals. The contrast becomes extinct for certain diffraction vectors g. In the following the basis of electron diffraction contrast of dislocations in the IQ phase is described. Taking account of the six-dimensional nature of the Burgers vector a “strong” and a “weak” extinction condition are found.Dislocations in quasicrystals canot be described on the basis of simple shear or insertion of a lattice plane only. In order to achieve a complete characterization of these dislocations it is advantageous to make use of the one to one correspondence of the lattice geometry in our three-dimensional space (R3) and that in the six-dimensional reference space (R6) where full periodicity is recovered . Therefore the contrast extinction condition has to be written as gpbp + gobo = 0 (1). The diffraction vector g and the Burgers vector b decompose into two vectors gp, bp and go, bo in, respectively, the physical and the orthogonal three-dimensional sub-spaces of R6.

Exploring the Multidimensional Facets of Authoritarianism: Authoritarian Aggression and Social Dominance Orientation

2008 ◽  
Vol 67 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Stefano Passini
Keyword(s):  
Social Dominance ◽  
Factor Model ◽  
Three Dimensional ◽  
Social Dominance Orientation ◽  
Model Fit ◽  
Regression Analyses ◽  
One Dimensional ◽  
Confirmatory Factor ◽  
The One ◽  
Better Than

The relation between authoritarianism and social dominance orientation was analyzed, with authoritarianism measured using a three-dimensional scale. The implicit multidimensional structure (authoritarian submission, conventionalism, authoritarian aggression) of Altemeyer’s (1981, 1988) conceptualization of authoritarianism is inconsistent with its one-dimensional methodological operationalization. The dimensionality of authoritarianism was investigated using confirmatory factor analysis in a sample of 713 university students. As hypothesized, the three-factor model fit the data significantly better than the one-factor model. Regression analyses revealed that only authoritarian aggression was related to social dominance orientation. That is, only intolerance of deviance was related to high social dominance, whereas submissiveness was not.

Sea Urchins and Circuses: The Modernist Natural Histories of Jean Painlevé and Alexander Calder

2018 ◽  
Vol 13 (2) ◽  
pp. 187-211
Author(s):  
Patricia E. Chu
Keyword(s):  
New Media ◽  
Sea Urchins ◽  
Life Sciences ◽  
Three Dimensional ◽  
Machine Age ◽  
Avant Garde ◽  
History Of ◽  
And Performance ◽  
The One ◽  
Natural Historian

The Paris avant-garde milieu from which both Cirque Calder/Calder's Circus and Painlevé’s early films emerged was a cultural intersection of art and the twentieth-century life sciences. In turning to the style of current scientific journals, the Paris surrealists can be understood as engaging the (life) sciences not simply as a provider of normative categories of materiality to be dismissed, but as a companion in apprehending the “reality” of a world beneath the surface just as real as the one visible to the naked eye. I will focus in this essay on two modernist practices in new media in the context of the history of the life sciences: Jean Painlevé’s (1902–1989) science films and Alexander Calder's (1898–1976) work in three-dimensional moving art and performance—the Circus. In analyzing Painlevé’s work, I discuss it as exemplary of a moment when life sciences and avant-garde technical methods and philosophies created each other rather than being classified as separate categories of epistemological work. In moving from Painlevé’s films to Alexander Calder's Circus, Painlevé’s cinematography remains at the forefront; I use his film of one of Calder's performances of the Circus, a collaboration the men had taken two decades to complete. Painlevé’s depiction allows us to see the elements of Calder's work that mark it as akin to Painlevé’s own interest in a modern experimental organicism as central to the so-called machine-age. Calder's work can be understood as similarly developing an avant-garde practice along the line between the bestiary of the natural historian and the bestiary of the modern life scientist.

Mathematical Model Investigation of Far-Field Transport of Ocean-Dumped Sewage Sludge Related to Remote Sensing

1982 ◽  
Vol 14 (3) ◽  
pp. 33-39
Author(s):  
C Y Kuo
Keyword(s):  
New York ◽  
Sewage Sludge ◽  
Laboratory Data ◽  
Three Dimensional ◽  
Approximate Model ◽  
Transport Processes ◽  
Far Field ◽  
New York Bight ◽  
Mean Current

An existing, three-dimensional, Eulerian-Lagrangian finite-difference model was modified and used to examine the far-field transport processes of dumped sewage sludge in the New York Bight. Both in situ and laboratory data were utilized in an attempt to approximate model inputs such as mean current speed, vertical and horizontal diffusion coefficients, particle size distributions, and specific gravities. Concentrations of the sludge near the sea surface predicted from the computer model were compared qualitatively with those remotely sensed.

Sign in / Sign up

Export Citation Format

Share Document