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	Gränsskikts teori	Direkt numerisk simulering
Ämnesområde	Strömningsmekanik	Strömningsmekanik
Familj	Process / pipeline	Process / pipeline
Ursprungsår	1904	1971
Upphovsperson	Ludwig Prandtl	Steven Orszag
Typ	Analytical framework and approximation method	Full-scale turbulence resolution method
Ursprungskälla	Prandtl, L. (1904). Über Flüssigkeitsbewegung bei sehr kleiner Reibung. In Verhandlungen des 3. Internationalen Mathematiker-Kongresses in Heidelberg (pp. 484-491). Teubner.	Orszag, S. A. (1971). Numerical simulation of incompressible flows within simple boundaries: accuracy. Journal of Fluid Mechanics, 49(1), 75-112.
Alias	BL theory, Prandtl boundary layer, viscous layer	DNS, resolved turbulence simulation
Närliggande	5	5
Sammanfattning	Boundary Layer Theory is the analytical and approximate framework for understanding viscous flow near solid surfaces, pioneered by Ludwig Prandtl in 1904. The central insight is that at high Reynolds numbers, viscous effects are confined to a thin layer near walls (the boundary layer), while the flow outside remains essentially inviscid. This separation enables powerful approximations: the boundary layer equations reduce the full Navier-Stokes to a parabolic system solvable via streamwise marching, yielding analytical or semi-analytical solutions for many practical cases. Boundary layer theory remains fundamental to aerodynamics, hydrodynamics, and heat transfer.	Direct Numerical Simulation (DNS) is a computational approach that solves the Navier-Stokes equations without turbulence models, resolving all scales of motion from the largest energy-containing eddies down to the smallest dissipative scales (Kolmogorov microscales). Pioneered by Steven Orszag in 1971, DNS provides complete information about turbulent flow fields and serves as a reference solution for validating turbulence models. However, extreme computational demands limit DNS to relatively simple geometries and low to moderate Reynolds numbers.