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This is a personal recollection on the Move fire on May 13, 1985
| Gerris | |
|---|---|
 | |
 Air flow around RV Tangaroa | |
| 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,[a] 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):
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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.
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.
This is a list of free and open-source software (FOSS) packages, computer software licensed under free software licenses and open-source licenses. Software that fits the Free Software Definition may be more appropriately called free software; the GNU project in particular objects to their works being referred to as open-source. For more information about the philosophical background for open-source software, see free software movement and Open Source Initiative. However, nearly all software meeting the Free Software Definition also meets the Open Source Definition and vice versa. A small fraction of the software that meets either definition is listed here. Some of the open-source applications are also the basis of commercial products, shown in the List of commercial open-source applications and services.
Software prototyping is the activity of creating prototypes of software applications, i.e., incomplete versions of the software program being developed. It is an activity that can occur in software development and is comparable to prototyping as known from other fields, such as mechanical engineering or manufacturing. A prototype typically simulates only a few aspects of, and may be highly different from, the final product. Prototyping has several benefits: the software designer and implementer can get valuable feedback from the users early in the project. The client and the contractor can compare if the software made matches the software specification, according to which the software program is built. It also allows the software engineer some insight into the accuracy of initial project estimates and whether the deadlines and milestones proposed can be successfully met. The degree of completeness and the techniques used in prototyping have been in development and debate since its proposal in the early 1970s.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
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