40,403 research outputs found
MFC: An open-source high-order multi-component, multi-phase, and multi-scale compressible flow solver
MFC is an open-source tool for solving multi-component, multi-phase, and bubbly compressible flows. It is capable of efficiently solving a wide range of flows, including droplet atomization, shock–bubble interaction, and bubble dynamics. We present the 5- and 6-equation thermodynamically-consistent diffuse-interface models we use to handle such flows, which are coupled to high-order interface-capturing methods, HLL-type Riemann solvers, and TVD time-integration schemes that are capable of simulating unsteady flows with strong shocks. The numerical methods are implemented in a flexible, modular framework that is amenable to future development. The methods we employ are validated via comparisons to experimental results for shock–bubble, shock–droplet, and shock–water-cylinder interaction problems and verified to be free of spurious oscillations for material-interface advection and gas–liquid Riemann problems. For smooth solutions, such as the advection of an isentropic vortex, the methods are verified to be high-order accurate. Illustrative examples involving shock–bubble-vessel-wall and acoustic–bubble-net interactions are used to demonstrate the full capabilities of MFC
Flow visualization using momentum and energy transport tubes and applications to turbulent flow in wind farms
As a generalization of the mass-flux based classical stream-tube, the concept
of momentum and energy transport tubes is discussed as a flow visualization
tool. These transport tubes have the property, respectively, that no fluxes of
momentum or energy exist over their respective tube mantles. As an example
application using data from large-eddy simulation, such tubes are visualized
for the mean-flow structure of turbulent flow in large wind farms, in fully
developed wind-turbine-array boundary layers. The three-dimensional
organization of energy transport tubes changes considerably when turbine
spacings are varied, enabling the visualization of the path taken by the
kinetic energy flux that is ultimately available at any given turbine within
the array.Comment: Accepted for publication in Journal of Fluid Mechanic
Afivo: a framework for quadtree/octree AMR with shared-memory parallelization and geometric multigrid methods
Afivo is a framework for simulations with adaptive mesh refinement (AMR) on
quadtree (2D) and octree (3D) grids. The framework comes with a geometric
multigrid solver, shared-memory (OpenMP) parallelism and it supports output in
Silo and VTK file formats. Afivo can be used to efficiently simulate AMR
problems with up to about unknowns on desktops, workstations or single
compute nodes. For larger problems, existing distributed-memory frameworks are
better suited. The framework has no built-in functionality for specific physics
applications, so users have to implement their own numerical methods. The
included multigrid solver can be used to efficiently solve elliptic partial
differential equations such as Poisson's equation. Afivo's design was kept
simple, which in combination with the shared-memory parallelism facilitates
modification and experimentation with AMR algorithms. The framework was already
used to perform 3D simulations of streamer discharges, which required tens of
millions of cells
Kinematics of Clustering
The dynamical system for inertial particles in fluid flow has both attracting
and repelling regions, the interplay of which can localize particles. In
laminar flow experiments we find that particles, initially moving throughout
the fluid domain, can undergo an instability and cluster into subdomains of the
fluid when the flow Reynolds number exceeds a critical value that depends on
particle and fluid inertia. We derive an expression for the instability
boundary and for a universal curve that describes the clustering rate for all
particles.Comment: 13 pages, 6 figure
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