Coupling Discrete Element Models of Ceramic Breeder Pebble Beds to Thermofluid Models of Helium Purge Gas Using Volume-Averaged Navier-Stokes and the Lattice-Boltzmann Method

2015 ◽  
Vol 68 (2) ◽  
pp. 288-294 ◽  
Author(s):  
Jon T. Van Lew ◽  
Alice Ying ◽  
Mohamed Abdou
Author(s):  
Joris C. G. Verschaeve

By means of the continuity equation of the incompressible Navier–Stokes equations, additional physical arguments for the derivation of a formulation of the no-slip boundary condition for the lattice Boltzmann method for straight walls at rest are obtained. This leads to a boundary condition that is second-order accurate with respect to the grid spacing and conserves mass. In addition, the boundary condition is stable for relaxation frequencies close to two.


2014 ◽  
Vol 554 ◽  
pp. 665-669
Author(s):  
Leila Jahanshaloo ◽  
Nor Azwadi Che Sidik

The Lattice Boltzmann Method (LBM) is a potent numerical technique based on kinetic theory, which has been effectively employed in various complicated physical, chemical and fluid mechanics problems. In this paper multi-relaxation lattice Boltzmann model (MRT) coupled with a Large Eddy Simulation (LES) and the equation are applied for driven cavity flow at different Reynolds number (1000-10000) and the results are compared with the previous published papers which solve the Navier stokes equation directly. The comparisons between the simulated results show that the lattice Boltzmann method has the capacity to solve the complex flows with reasonable accuracy and reliability. Keywords: Two-dimensional flows, Lattice Boltzmann method, Turbulent flow, MRT, LES.


Author(s):  
Felipe A. Valenzuela ◽  
Amador M. Guzmán ◽  
Andrés J. Díaz

During the last years the aerodynamics characteristics of airfoils have been studied solving numerically the Navier-Stokes (NS) equations. These calculations require a significant computational cost due to both the second order and the nonlinear characteristics of the NS partial differential equations. Therefore, efforts have been devoted to reduce this cost and increase the accuracy of the numerical methods. The Lattice-Boltzmann Method (LBM) has become a great alternative to simulate this problem and a variety of fluid flows. In this method, the convective operator is linear and the pressure is calculated directly by the equation of state without implementing iterative methods. This work represents a preliminary investigation of a laminar flow over airfoils under low Reynolds number conditions (Re = 500). Solutions are obtained using a Multi-Block mesh refinement method. In order to validate the computational code, calculations are performed on a SD7003 airfoil at an angle of attack of 4° and 30°, which corresponds to the available numerical and experimental results. The results of this study agree well with previous experimental and numerical studies demonstrating the capabilities of the LBM to simulate accurately laminar flows over airfoils as well as capturing and predicting the laminar separation bubbles.


Author(s):  
Ru Yang ◽  
Chin-Sheng Wang

A Lattice Boltzmann method is employed to investigate the flow characteristics and the heat transfer phenomenon between two parallel plates separated by a micro-gap. A nine-velocity model and an internal energy distribution model are used to obtain the mass, momentum and temperature distributions. It is shown that for small Knudsen numbers (Kn), the current results are in good agreement with those obtained from the traditional Navier-Stokes equation with non-slip boundary conditions. As the value of Kn is increased, it is found that the non-slip condition may no longer be valid at the wall boundary and that the flow behavior changes to one of slip-flow. In slip flow regime, the present results is still in good agreement with slip-flow solution by Navier Stokes equations. The non-linear nature of the pressure and friction distribution for micro-channel flow is gieven. Finally, the current investigation presents a prediction of the temperature distribution for micro-channel flow under the imposed conditions of an isothermal boundary.


Author(s):  
KUN QU ◽  
CHANG SHU ◽  
JINSHENG CAI

In this paper, a new flux solver was developed based on a lattice Boltzmann model. Different from solving discrete velocity Boltzmann equation and lattice Boltzmann equation, Euler/Navier-Stokes (NS) equations were solved in this approach, and the flux at the interface was evaluated with a compressible lattice Boltzmann model. This method combined lattice Boltzmann method with finite volume method to solve Euler/NS equations. The proposed approach was validated by some simulations of one-dimensional and multi-dimensional problems.


Respati ◽  
2017 ◽  
Vol 12 (3) ◽  
Author(s):  
Kumara Ari Yuana

 INTISARIKomputasi dan eksperimental dalam dunia teknik permesinan (mechanical engineer) merupakan bidang yang saling melengkapi. Komputasi dilakukan untuk memberikan gambaran dan penjelasan rasional dari fenomena yang dihasilkan pada eksperimen. Komputasi juga memberikan prediksi sebelum dilakukan eksperimen untuk lebih mematangkan kondisi-kondisi dari sebuah eksperimen. Komputasi dengan metode Lattice Boltzmann adalah metode yang relatif baru dan menjanjikan di dunia komputasi aliran fluida atau CFD (Computational Fluid Dynamics), sebagai alternative metode yang sudah lama dikembangkan dari persamaan kontunum Navier-Stokes. Metode Lattice Boltzmann berangkat dari logika interaksi sekumpulan partikel dan ditelusuri pola interaksinya melalui bantuan pola jaringan (lattice). Pada riset ini akan digunakan metode Lattice Boltzmann untuk membuat model matematis dan algoritmanya pad aliran fluida yang mengalir di sekitar External Ballistics model G1-Standard-Bullet. Tahap riset selanjutnya adalah pengembangan pembuatan coding pemrograman dan simulasi visual untuk mengetahui pola aliran dan analisis-analisis aerodinamisnya. ABSTRACTComputational and experimental in the world of mechanical engineering is a complementary field and providing a picture and a rational explanation of the phenomena generated from the experiment. Computation with the Lattice Boltzmann method is a relatively new and promising method in the world of fluid flow computation or CFD (Computational Fluid Dynamics), as an alternative to the long-established method of the Navier-Stokes continuum equation. The Lattice Boltzmann method departs from the logic of the interaction of a set of particles and traces its interaction pattern through the aid of a network pattern (lattice). In this research we will use the Lattice Boltzmann method to create a mathematical model and algorithm for the flow of fluid flowing around External Ballistics model G1-Standard-Bullet. The next stage of research is developing the development of coding programming and visual simulation to know the flow pattern and aerodynamic analysis.


2015 ◽  
Vol 799-800 ◽  
pp. 784-787
Author(s):  
Wen Qin Liu ◽  
Yong Li

The main objective of this work is to develop a new approach based on the Lattice Boltzmann method (LBM) to simulate the extrudate swell of an Oldroyd B viscoelatic fluid. Two lattice Boltzmann equations are used to solve the Navier-Stokes equations and constitutive equation simultaneously at each time iteration. The single LBM model is used to track the moving interface in this paper. To validate the accuracy and stability of this new scheme, we study the steady 2D Poiseuille flow firstly, finding the numerical results be in good accord with the analytical solution. Then the die-swell phenomenon is solved, we successfully acquire the different swelling state of an Oldroyd B fluid at different time.


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