Computational Fluid Dynamics (CFD)--What is it?

Computational fluid dynamics, or CFD, are the methods of applying the laws of fluid mechanics and the underlying mathematical equations and principles to sophisticated computer algorithms to produce software or computer programs for visualizing data to render graphical expressions, or interpretations, of how liquids and gases interact in relation to being stored/travelling through a closed boundary—such as water in a pipe or jet fuel in an aircraft’s wing.

As a specialized branch of fluid mechanics, fluid dynamics’ overall mission is to understand and explain the physics that govern the flow of fluids such as water, oil, or ethanol. Professionals in the aerospace, mechanical engineering, car manufacture, aerodynamics, and civil engineering sectors commonly implement computational fluid dynamics software.

Initial and Boundary Conditions

CFD takes into account several factors that closely affect the behavior of fluids and helps to visualize them via graphical simulation. Some of these ‘factors’ include mass transfer, chemical reactions, heat flow, and changes in gas to liquid and liquid to gas phases. Furthermore, ‘initial’ and ‘boundary’ conditions contribute to the understanding of what solutions are possible. The ‘initial boundary’ is the known pressure (p) and the initial velocity (or rate of speed, or U). The boundary condition is a set of numbers based on complex equations and algorithms and, essentially, dictates the outcome of fluidic movement.


Two fundamental methods govern much of the CFD field: finite difference methods (FDM’s) and finite element methods (FEM’s). Both are umbrella terms that encompass a serious of equations and principles—some more complex than others—that measure and compare/contrast anything from Neumann boundary conditions, to vortex phenomena, to compressible/incompressible flows.

Other phenomena that’s studied in conjunction with FDM’s and FEM’s include slip surfaces, convection, turbulence, transonic flows, and mass transfer. Two equations that help solve CFD problems that are almost synonymous with fluid dynamics themselves are the Euler methods and the Navier-Stokes methods. From the latter, a number of “discrete” methods can be employed, including the: Finite Volume Method, Finite Difference, Method, Finite Element Method, and the Boundary-Element Method.

Computational solving and graphical modeling of boundary conditions of elements like water, turbulence, and viscous substance flows help professionals better understand how things work and how to improve or even replace them. Three phrases that will inherently come up in nearly any conversation on fluid dynamics include (in addition to the Navier-Stokes and Euler methods) “Riemann problem,” Riemann solver, “finite methods” and the Boltzmann method (LBM).

Uses for CFD in the Real Word

CFD’s enable scientists, physicists, and chemists (among others) to effectively simulate the flow of fluids and gases, chemical reactions, fluid-boundary interactions and moving objects. With a CFD program, prototypes of many different kinds of systems or devices can be virtualized—which allows professionals to study certain phenomenal insight that the data and graphical renderings give. They then apply this insight—a mixture of Newtonian physics, statistical mechanics, thermodynamics, and chemistry, among others—to real-world scenarios to fix or improve things, create better efficiency in products or services, and invent new methodologies and/or products.

Computational fluid dynamics are used in a variety of applications and industries. Automobile manufacturers rely heavily on CFD principles, and the aviation industry would be virtually impossible without CFD’s (which is heavily used in aerodynamics and aerospace). It’s also widely used in several other industries such as: pharmaceuticals, plumbing, hydraulics, food processing and production, genetic engineering, ship/boat manufacturing, aeronautical, and chemical/biochemical industries. Also, oil conglomerates use computational fluid dynamics to study everything from deep-sea drilling, to petroleum physics and chemistry, to petroleum refinement.

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Copyright Gary Norton Developments 2010