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Hermann Schlichting studied from 1926 till 1930 mathematics, physics and applied mechanics at the University of Jena, Vienne and Göttingen.In 1930 he wrote his PhD in Göttingen titled Über das ebene Windschattenproblem and also in the same year passed the state examination as teacher for higher mathematics and physics.
The boundary layer around a human hand, schlieren photograph. The boundary layer is the bright-green border, most visible on the back of the hand (click for high-res image). In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by
The boundary layer thickness, , is the distance normal to the wall to a point where the flow velocity has essentially reached the 'asymptotic' velocity, .Prior to the development of the Moment Method, the lack of an obvious method of defining the boundary layer thickness led much of the flow community in the later half of the 1900s to adopt the location , denoted as and given by
A shear layer develops viscous instability and forms Tollmien–Schlichting waves which grow, while still laminar, into finite amplitude (1 to 2 percent of the freestream velocity) three-dimensional fluctuations in velocity and pressure to develop three-dimensional unstable waves and hairpin eddies. From then on, the process is more a breakdown ...
At this moderate free-stream turbulence level, he observed a velocity perturbation signal with a frequency under 12 Hz, much smaller than the usual Tollmien-Schlichting wave frequency. He also observed fluctuations in boundary layer thickness , which does not occur in low-turbulence free-stream flow.
This turbulent boundary layer thickness formula assumes 1) the flow is turbulent right from the start of the boundary layer and 2) the turbulent boundary layer behaves in a geometrically similar manner (i.e. the velocity profiles are geometrically similar along the flow in the x-direction, differing only by stretching factors in and (,) [5 ...
However, using his hypothesis (and backed up by experiments) Prandtl was able to derive an approximate model for the flow inside the boundary layer, called boundary-layer theory; while the flow outside the boundary layer could be treated using inviscid flow theory. Boundary-layer theory is amenable to the method of matched asymptotic expansions ...
A simple example is a semi-infinite domain bounded by a rigid wall and filled with viscous fluid. [12] At time t = 0 {\displaystyle t=0} the wall is made to move with constant speed U {\displaystyle U} in a fixed direction (for definiteness, say the x {\displaystyle x} direction and consider only the x − y {\displaystyle x-y} plane), one can ...