5 research outputs found
Automatic grid refinement criterion for lattice Boltzmann method
In all kinds of engineering problems, and in particular in methods for
computational fluid dynamics based on regular grids, local grid refinement is
of crucial importance. To save on computational expense, many applications
require to resolve a wide range of scales present in a numerical simulation by
locally adding more mesh points. In general, the need for a higher (or a lower)
resolution is not known a priori, and it is therefore difficult to locate areas
for which local grid refinement is required. In this paper, we propose a novel
algorithm for the lattice Boltzmann method, based on physical concepts, to
automatically construct a pattern of local refinement. We apply the idea to the
two-dimensional lid-driven cavity and show that the automatically refined grid
can lead to results of equal quality with less grid points, thus sparing
computational resources and time. The proposed automatic grid refinement
strategy has been implemented in the parallel open-source library Palabos
Local mesh refinement sensor for the lattice Boltzmann method
A novel mesh refinement sensor is proposed for lattice Boltzmann methods (LBMs) applicable to either static or dynamic mesh refinement algorithms. The sensor exploits the kinetic nature of LBMs by evaluating the departure of distribution functions from their local equilibrium state. This sensor is first compared, in a qualitative manner, to three state-of-the-art sensors: (1) the vorticity norm, (2) the Q-criterion, and (3) spatial derivatives of the vorticity. This comparison shows that our kinetic sensor is the most adequate candidate to propose tailored mesh structures across a wide range of physical phenomena: incompressible, compressible subsonic/supersonic single phase, and weakly compressible multiphase flows. As a more quantitative validation, the sensor is then used to produce the computational mesh for two existing open-source LB solvers based on inhomogeneous, block-structured meshes with static and dynamic refinement algorithms, implemented in the Palabos and AMROC-LBM software, respectively. The sensor is first used to generate a static mesh to simulate the turbulent 3D lid-driven cavity flow using Palabos. AMROC-LBM is then adopted to confirm the ability of our sensor to dynamically adapt the mesh to reach the steady state of the 2D lid-driven cavity flow. Both configurations show that our sensor successfully produces meshes of high quality and allows to save computational time
Matrisome Profiling During Intervertebral Disc Development And Ageing
Abstract Intervertebral disc (IVD) degeneration is often the cause of low back pain. Degeneration occurs with age and is accompanied by extracellular matrix (ECM) depletion, culminating in nucleus pulpous (NP) extrusion and IVD destruction. The changes that occur in the disc with age have been under investigation. However, a thorough study of ECM profiling is needed, to better understand IVD development and age-associated degeneration. As so, iTRAQ LC-MS/MS analysis of foetus, young and old bovine NPs, was performed to define the NP matrisome. The enrichment of Collagen XII and XIV in foetus, Fibronectin and Prolargin in elder NPs and Collagen XI in young ones was independently validated. This study provides the first matrisome database of healthy discs during development and ageing, which is key to determine the pathways and processes that maintain disc homeostasis. The factors identified may help to explain age-associated IVD degeneration or constitute putative effectors for disc regeneration