 | |
 Air flow around RV Tangaroa | |
| Initial release | 2001 |
|---|---|
| Written in | C |
| Operating system | Unix, Linux |
| Successor | Basilisk |
| Type | CFD |
| Licence | GPL |
| Website | gfs |
Gerris is computer software in the field of computational fluid dynamics (CFD). Gerris was released as free and open-source software, subject to the requirements of the GNU General Public License (GPL), version 2 or any later.
Gerris solves the Navier–Stokes equations in 2 or 3 dimensions, allowing to model industrial fluids (aerodynamics, internal flows, etc.) or for instance, the mechanics of droplets, thanks to an accurate formulation of multiphase flows (including surface tension). Actually, the latter field of study is the reason why the software shares the same name as the insect genus.
Gerris also provides features relevant to geophysical flows:
Flow types #1 to #3 were studied using the shallow-water solver included in Gerris, case #4 brings in the primitives equations and application #5 relies on the spectral equations for generation/propagation/dissipation of swell (and/or wind sea): for this purpose Gerris makes use of the source terms from WaveWatchIII. [8]
Lastly, one can note that the (non-hydrostatic) Navier–Stokes solver was also used in the ocean to study:
On the contrary Gerris does not allow the modeling of compressible fluids (supersonic flows).
Several methods can be used to provide a numerical solution to partial differential equations:
Gerris belongs to the finite volumes family of CFD models.
Most models use meshes which are either structured (Cartesian or curvilinear grids) or unstructured (triangular, tetrahedral, etc.). Gerris is quite different on this respect: it implements a deal between structured and unstructured meshes by using a tree data structure, [lower-alpha 1] allowing to refine locally (and dynamically) the (finite-volume) description of the pressure and velocity fields. Indeed, the grid evolves in the course of a given simulation owing to criteria defined by the user (e.g. dynamic refinement of the grid in the vicinity of sharp gradients).
Gerris mainly aims at DNS; the range of Reynolds available to the user thus depends on the computing power they can afford (although the auto-adaptive mesh allows one to focus the computing resources on the coherent structures). According to the Gerris FAQ [12] the implementation of turbulence models will focus on the LES family rather than RANS approaches.
Gerris is developed in C using the libraries Glib (object orientation, dynamic loading of modules, etc.) and GTS. [13] The latter brings in facilities to perform geometric computations such as triangulation of solid surfaces and their intersection with fluid cells. Moreover Gerris is fully compliant with MPI parallelisation (including dynamic load balancing).
Gerris does not need a meshing tool since the local (and time dependent) refinement of the grid is on charge of the solver itself. As far as solid surfaces are concerned, several input formats are recognized:
Among the various ways to output Gerris results, let us just mention here:
CFD software, as any software, can be developed in various "realms":
As far as CFD is concerned, a thorough discussion of these software development paths can be found in the statement by Zaleski. [14]
Gerris was distributed as free and open-source software right from the onset of the project. [15] [16]
Following a redesign of the software organization, Gerris became Basilisk, [17] which allows one to develop its own solver (not necessarily in fluid mechanics) using various data structures (including of course the quadtree/octree) and optimized operators for iteration, derivation, etc. Solvers are written in C, more specifically the Basilisk C. However many solvers are available "turnkey", including Navier-Stokes et Saint-Venant.
Other computing software are freely available in the field of fluid mechanics. Here are some of them (if the development was not initialized under a free license, the year when it moved to Open Source is mentioned in parentheses):
Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate the free-stream flow of the fluid, and the interaction of the fluid with surfaces defined by boundary conditions. With high-speed supercomputers, better solutions can be achieved, and are often required to solve the largest and most complex problems. Ongoing research yields software that improves the accuracy and speed of complex simulation scenarios such as transonic or turbulent flows. Initial validation of such software is typically performed using experimental apparatus such as wind tunnels. In addition, previously performed analytical or empirical analysis of a particular problem can be used for comparison. A final validation is often performed using full-scale testing, such as flight tests.
In numerical analysis, adaptive mesh refinement (AMR) is a method of adapting the accuracy of a solution within certain sensitive or turbulent regions of simulation, dynamically and during the time the solution is being calculated. When solutions are calculated numerically, they are often limited to predetermined quantified grids as in the Cartesian plane which constitute the computational grid, or 'mesh'. Many problems in numerical analysis, however, do not require a uniform precision in the numerical grids used for graph plotting or computational simulation, and would be better suited if specific areas of graphs which needed precision could be refined in quantification only in the regions requiring the added precision. Adaptive mesh refinement provides such a dynamic programming environment for adapting the precision of the numerical computation based on the requirements of a computation problem in specific areas of multi-dimensional graphs which need precision while leaving the other regions of the multi-dimensional graphs at lower levels of precision and resolution.
Mesh generation is the practice of creating a mesh, a subdivision of a continuous geometric space into discrete geometric and topological cells. Often these cells form a simplicial complex. Usually the cells partition the geometric input domain. Mesh cells are used as discrete local approximations of the larger domain. Meshes are created by computer algorithms, often with human guidance through a GUI, depending on the complexity of the domain and the type of mesh desired. A typical goal is to create a mesh that accurately captures the input domain geometry, with high-quality (well-shaped) cells, and without so many cells as to make subsequent calculations intractable. The mesh should also be fine in areas that are important for the subsequent calculations.
Fluid–structure interaction (FSI) is the interaction of some movable or deformable structure with an internal or surrounding fluid flow. Fluid–structure interactions can be stable or oscillatory. In oscillatory interactions, the strain induced in the solid structure causes it to move such that the source of strain is reduced, and the structure returns to its former state only for the process to repeat.
Bram van Leer is Arthur B. Modine Emeritus Professor of aerospace engineering at the University of Michigan, in Ann Arbor. He specializes in Computational fluid dynamics (CFD), fluid dynamics, and numerical analysis. His most influential work lies in CFD, a field he helped modernize from 1970 onwards. An appraisal of his early work has been given by C. Hirsch (1979)
Computational magnetohydrodynamics (CMHD) is a rapidly developing branch of magnetohydrodynamics that uses numerical methods and algorithms to solve and analyze problems that involve electrically conducting fluids. Most of the methods used in CMHD are borrowed from the well established techniques employed in Computational fluid dynamics. The complexity mainly arises due to the presence of a magnetic field and its coupling with the fluid. One of the important issues is to numerically maintain the (conservation of magnetic flux) condition, from Maxwell's equations, to avoid the presence of unrealistic effects, namely magnetic monopoles, in the solutions.
The material point method (MPM) is a numerical technique used to simulate the behavior of solids, liquids, gases, and any other continuum material. Especially, it is a robust spatial discretization method for simulating multi-phase (solid-fluid-gas) interactions. In the MPM, a continuum body is described by a number of small Lagrangian elements referred to as 'material points'. These material points are surrounded by a background mesh/grid that is used to calculate terms such as the deformation gradient. Unlike other mesh-based methods like the finite element method, finite volume method or finite difference method, the MPM is not a mesh based method and is instead categorized as a meshless/meshfree or continuum-based particle method, examples of which are smoothed particle hydrodynamics and peridynamics. Despite the presence of a background mesh, the MPM does not encounter the drawbacks of mesh-based methods which makes it a promising and powerful tool in computational mechanics.
A CFD-DEM model is suitable for the modeling or simulation of fluid-solids or fluid-particles systems. In a typical CFD-DEM model, the phase motion of discrete solids or particles is obtained by the Discrete Element Method (DEM) which applies Newton's laws of motion to every particle and the flow of continuum fluid is described by the local averaged Navier–Stokes equations that can be solved by the traditional Computational Fluid Dynamics (CFD). The model is first proposed by Tsuji et al. The interactions between the fluid phase and solids phase is better modeled according to Newton's third law.
In computational fluid dynamics, the immersed boundary method originally referred to an approach developed by Charles Peskin in 1972 to simulate fluid-structure (fiber) interactions. Treating the coupling of the structure deformations and the fluid flow poses a number of challenging problems for numerical simulations. In the immersed boundary method the fluid is represented in an Eulerian coordinate system and the structure is represented in Lagrangian coordinates. For Newtonian fluids governed by the Navier–Stokes equations, the fluid equations are
In applied mathematics, the name finite pointset method is a general approach for the numerical solution of problems in continuum mechanics, such as the simulation of fluid flows. In this approach the medium is represented by a finite set of points, each endowed with the relevant local properties of the medium such as density, velocity, pressure, and temperature.
In computational fluid dynamics, TELEMAC is short for the open TELEMAC-MASCARET system, or a suite of finite element computer program owned by the Laboratoire National d'Hydraulique et Environnement (LNHE), part of the R&D group of Électricité de France. After many years of commercial distribution, a Consortium was officially created in January 2010 to organize the open source distribution of the open TELEMAC-MASCARET system now available under GPLv3.
KIVA is a family of Fortran-based computational fluid dynamics software developed by Los Alamos National Laboratory (LANL). The software predicts complex fuel and air flows as well as ignition, combustion, and pollutant-formation processes in engines. The KIVA models have been used to understand combustion chemistry processes, such as auto-ignition of fuels, and to optimize diesel engines for high efficiency and low emissions. General Motors has used KIVA in the development of direct-injection, stratified charge gasoline engines as well as the fast burn, homogeneous-charge gasoline engine. Cummins reduced development time and cost by 10%–15% using KIVA to develop its high-efficiency 2007 ISB 6.7-L diesel engine that was able to meet 2010 emission standards in 2007. At the same time, the company realized a more robust design and improved fuel economy while meeting all environmental and customer constraints.
SU2 is a suite of open-source software tools written in C++ for the numerical solution of partial differential equations (PDE) and performing PDE-constrained optimization. The primary applications are computational fluid dynamics and aerodynamic shape optimization, but has been extended to treat more general equations such as electrodynamics and chemically reacting flows. SU2 supports continuous and discrete adjoint for calculating the sensitivities/gradients of a scalar field.
Regional Ocean Modeling System (ROMS) is a free-surface, terrain-following, primitive equations ocean model widely used by the scientific community for a diverse range of applications. The model is developed and supported by researchers at the Rutgers University, University of California Los Angeles and contributors worldwide.
Ocean general circulation models (OGCMs) are a particular kind of general circulation model to describe physical and thermodynamical processes in oceans. The oceanic general circulation is defined as the horizontal space scale and time scale larger than mesoscale. They depict oceans using a three-dimensional grid that include active thermodynamics and hence are most directly applicable to climate studies. They are the most advanced tools currently available for simulating the response of the global ocean system to increasing greenhouse gas concentrations. A hierarchy of OGCMs have been developed that include varying degrees of spatial coverage, resolution, geographical realism, process detail, etc.
Nektar++ is a spectral/hp element framework designed to support the construction of efficient high-performance scalable solvers for a wide range of partial differential equations (PDE). The code is released as open-source under the MIT license. Although primarily driven by application-based research, it has been designed as a platform to support the development of novel numerical techniques in the area of high-order finite element methods.
FEATool Multiphysics is a physics, finite element analysis (FEA), and partial differential equation (PDE) simulation toolbox. FEATool Multiphysics features the ability to model fully coupled heat transfer, fluid dynamics, chemical engineering, structural mechanics, fluid-structure interaction (FSI), electromagnetics, as well as user-defined and custom PDE problems in 1D, 2D (axisymmetry), or 3D, all within a graphical user interface (GUI) or optionally as script files. FEATool has been employed and used in academic research, teaching, and industrial engineering simulation contexts.
In geology, numerical modeling is a widely applied technique to tackle complex geological problems by computational simulation of geological scenarios.
A blade vortex interaction (BVI) is an unsteady phenomenon of three-dimensional nature, which occurs when a rotor blade passes within a close proximity of the shed tip vortices from a previous blade. The aerodynamic interactions represent an important topic of investigation in rotorcraft research field due to the adverse influence produced on rotor noise, particularly in low speed descending flight condition or maneuver, which generates high amplitude impulsive noise.
WindStation is a wind energy software which uses computational fluid dynamics (CFD) to conduct wind resource assessments in complex terrain. The physical background and its numerical implementation are described in. and the official manual of the software.
