What is Computational Fluid Dynamics?
Computational Fluid Dynamics (CFD) is the French acronym for Mécanique des Fluides Numérique (MFN). CFD is numerical computation applied to fluid mechanics. CFD software can be used to solve the fundamental equations of fluid mechanics, which can be coupled with heat transfer or chemical reaction equations. Numerical simulations take into account numerous parameters such as fluid volume, physico-chemical properties such as Reynolds number, viscosity and Mach number.
With this 8-minute lecture, discover the applications of CFD in industry!
Basic fluid mechanicsFluid mechanics is a physical discipline devoted to the study of fluid behavior : liquids (considered incompressible), gases (considered compressible), or more rarely in the form of plasma. It can be divided into two categories:
- Fluid statics (hydrostatics): study of a system at rest. This is the historic beginning of the discipline, with the study of pressure and buoyancy.
- Fluid dynamics: the study of a system in motion.
- Newtonian fluids : these include water, air and most gases. Their viscosity is constant, varying only with temperature.
- Non-Newtonian fluids: all other fluids such as blood, gels, emulsions, pastes… The viscosity of these fluids varies not only with temperature, but also with speed and the stresses experienced during flow.
- fundamental law of fluid statics ;
- Euler equation ;
- Bernoulli theorem and Bernoulli relations ;
- Navier-Stokes equations.
Details on the perfect fluidA perfect fluid is an idealized fluid (it does not exist naturally) to facilitate its study. Its movement is studied without taking into account its viscosity and thermal conductivity parameters. Added to this is the assumption of conservation of mass. The perfect fluid is an approximation.
Computational fluid mechanicsComputational fluid mechanics is a progression of classical fluid mechanics in which numerical analysis is used to visualize and study the behavior of fluids under real-life conditions. This discipline has undergone significant development over the last thirty years, and has become essential in many business sectors. Numerical simulation methods are applied to fluid mechanics for analytical purposes: as a complement to physical experiments, but also for predictive purposes. Visit CFD simulation software are widely used, and are becoming a must for manufacturers. They make it easier for engineers to understand physical phenomena on simulated models before carrying out experimental tests on physical models… Visit CFD software predict the performance of complex systems before installing an infrastructure or using a product, in order to limit faults that could be detrimental from a safety point of view. During the test phases, the numerical calculation is carried out using the parameters of real operating conditions. Design engineers modify the data until correct models are obtained. Several alternative designs can be studied before validating the final solution and moving on to the production stage. Generally speaking, computational fluid mechanics meets two major challenges for companies:
- Solve problems of ever-increasing complexity, due to the physical phenomena involved.
- Improve problem-solving efficiency: not only through faster computation times, but also through higher-quality results.
- Reduce the number of prototypes (digital prototypes).
Further reading: rheology as an extension of fluid mechanicsRheology is defined as the science of material deformation and flow. More specifically, the study of the mechanical behavior of matter: relationships between stresses and strains. Rheology is a branch of mechanics that relates the viscosity, plasticity and elasticity of matter. This discipline therefore calls on knowledge of materials resistance (RDM) and hydraulics for practical calculations. There are three levels to rheology studies:
- experimental materials research ;
- theoretical study based on the laws of behaviour of these materials;
- microscopic study of the influence of structure on the behavior of matter: geometry, meshing, etc.
CFD applications in engineering
CFD tools are used right from the product design phase to validate the viability of a physical model. Computational fluid mechanics is particularly well suited to predicting the performance of applications for which experimental measurements are difficult to make.
Depending on the CFD software, you may have access to a variety of features, selected according to your needs:
- heat transfer ;
- stationary (stable) and transient (time-varying) ;
- pressure losses ;
- turbulence models ;
- aerodynamic analysis ;
- movements of moving or rotating parts ;
- fluid interactions with a structure ;
- multiphase flows (several liquid, solid or gaseous phases coexist and interact);
- chemical reaction ;
- particle tracking ;
- solidification or fusion…
After design ideas, an industry’s objective is to rapidly commercialize high value-added products that meet market demand. Anticipating failure scenarios and unsatisfactory performance is one of the success factors in developing a new industrial solution. CFDs are very useful for any industry seeking to mitigate potential risks as far as possible before going to market.
Here are some concrete industrial applications of numerical modeling of thermo-fluidic phenomena:
- Automotive: air conditioning systems, exhaust gases, vehicle aerodynamics, gearboxes, engine cooling systems…
- Aerospace and defense: aerodynamics of airborne vehicles (subsonic and supersonic fluid flows).
- Electronics: thermal analysis of printed circuits, system cooling, LEDs…
- Energy: nuclear, wind, energy recovery, solar, etc.
- Naval: cavitation studies (creation of bubbles in a liquid subjected to negative pressure), propeller design…
- Industry: pumps, turbocompressors, fans, gas or steam turbines…
- Various consumer goods: building or object acoustics, refrigerators, motorcycle helmets…
CFD Computational Fluid Dynamics: benefits for manufacturers
Lower development costs
- uncertainties are identified earlier :
- risks are eliminated when it’s possible and quicker to make changes.
Improving product quality