484 research outputs found
A Coupled Lattice Boltzmann-Volume Penalization for Flows Past Fixed Solid Obstacles with Local Mesh Refinement
A coupled Lattice Boltzmann-Volume Penalization (LBM-VP) with local mesh refinement is presented to simulate flows past obstacles in this article. Based on the finite-difference LBM, the local mesh refinement is incorporated into the LBM to improve computing efficiency. The volume penalization method is introduced into the LBM by an external forcing term. In the LBM-VP method, the processes of interpolating velocities on the boundaries points and distributing the force density to the Eulerian points near the boundaries are unnecessary. Performing the LBM-VP on a certain point, only the variables of this point are needed, which means the whole procedure can be conducted parallelly. As a consequence, the whole computing efficiency can be improved. To verify the presented method, flows past a single circular cylinder, a pair of cylinders in tandem arrangement, and a NACA-0012 are investigated. A good agreement between the present results and the data in the previous literatures is achieved, which demonstrates the accuracy and effectiveness of the present method to solve the flows past obstacle problems
Progress in particle-based multiscale and hybrid methods for flow applications
This work focuses on the review of particle-based multiscale and hybrid methods that have surfaced in the field of fluid mechanics over the last 20 years. We consider five established particle methods: molecular dynamics, direct simulation Monte Carlo, lattice Boltzmann method, dissipative particle dynamics and smoothed-particle hydrodynamics. A general description is given on each particle method in conjunction with multiscale and hybrid applications. An analysis on the length scale separation revealed that current multiscale methods only bridge across scales which are of the order of O(102)−O(103) and that further work on complex geometries and parallel code optimisation is needed to increase the separation. Similarities between methods are highlighted and combinations discussed. Advantages, disadvantages and applications of each particle method have been tabulated as a reference
Topology-free immersed boundary method for incompressible turbulence flows: An aerodynamic simulation for 'dirty' CAD geometry
To design a method to solve the issues of handling 'dirty' and highly complex
geometries, the topology-free method combined with the immersed boundary method
is presented for viscous and incompressible flows at a high Reynolds number.
The method simultaneously employs a ghost-cell technique and distributed
forcing technique to impose the boundary conditions. An axis-projected
interpolation scheme is used to avoid searching failures during fluid and solid
identification. This method yields a topology-free immersed boundary, which
particularly suits flow simulations of highly complex geometries. Difficulties
generally arise when generating the calculation grid for these scenarios. This
method allows dirty data to be handled without any preparatory treatment work
to simplify or clean-up the geometry. This method is also applicable to the
coherent structural turbulence model employed in this study. The verification
cases, used in conjunction with the second-order central-difference scheme,
resulted in first-order accuracy at finer resolution, although the coarser
resolution retained second-order accuracy. This method is fully parallelized
for distributed memory platforms. In this study, the accuracy and fidelity of
this method were examined by simulating the flow around the bluff body, past a
flat plate, and past dirty spheres. These simulations were compared with
experimental data and other established results. Finally, results from the
simulation of practical applications demonstrate the ability of the method to
model highly complex, non-canonical three-dimensional flows. The countermeasure
based on the accurate classification of geometric features has provided a
robust and reasonable solution.Comment: 33 pages, 23 figure
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