Glossary

 

Chaos: When the present determines the future, but the approximate present does not approximately determine the future [46].
 

CFD: acronym for Computational Fluid Dynamics. It is a branch of fluid mechanics that uses numerical analysis and data structures to solve and analyze problems that involve fluid flows [91].

​

DNS: acronym for Direct Numerical Simulation. This corresponds to solving the Navier–Stokes equations on a digital computer using sufficient resolution to capture all physically important scales from the largest to the dissipation scales. It is to be emphasized that no modeling is employed for DNS; there is no closure problem. Thus, the only problem with this approach is that current computers are not sufficiently large and fast to permit the necessary resolution if Re is high and/or the problem possesses other physical/geometric complications [15].

 

LES: acronym for Large-eddy simulation. This form of turbulence calculation lies between DNS and RANS methods, both with respect to form and cost to compute. In particular, in LES the large-scale, energy-carrying motion is directly simulated while the small (mainly dissipative) scales are modeled [15].

 

RANS: acronym for Reynolds-Averaged Navier–Stokes approaches to turbulence calculation. RANS approaches are essentially the opposite of DNS, namely, nearly all scales of the solution must be modeled; only mean quantities are directly computed [15].

​

Eddy, Whirl, Vortex: In fluid dynamics, a vortex is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved [92].

 

Reynolds Number: The Reynolds number (Re) is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. The Reynolds number is the ratio of inertial forces to viscous forces within a fluid. Typically, a high Re is associated to a turbulent flow [93].

 

Boundary Layer: In physics and fluid mechanics, a boundary layer is an important concept and refers to the layer of fluid in the immediate vicinity of a bounding surface where the effects of viscosity are significant [94].

 

Turbulent Energy Cascade: Energy cascade refers to the transfer of kinetic energy from large, macroscopic scales of motion, where it is presumed to be input to the flow, through successively smaller scales, ending with viscous dissipation and conversion to heat (thermal energy) [15].