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Qualitative Features of Boundary Layer Separation

Here X is the curvilinear coordinate along the surface of the body and Y is the coordinate normal to the surface. [Pg.45]

The boundary layer equations are valid only in the region between the front stagnation point and the separation point. Behind the separation point there is a wake region with absolutely different hydrodynamic laws. The position of the separation point can be determined either experimentally or by using numerical or approximate analytical methods. [Pg.45]

As Re increases, the adjacent vortices are elongated and shedding of vortices occurs (Karman s vortices are formed). Finally, for Re 1000, the remote wake becomes completely turbulent [117]. At the same time, the separation point moves toward the midsection and even a bit farther upstream. For such values of Re, we can speak about a pronounced boundary layer. In a large part of the boundary layer, the flow remains laminar [486], Strong turbulence within the boundary layer occurs for considerably higher Reynolds numbers (Re 2x 105), at which the cylinder drag drops rapidly [117], This phenomenon is called the drag crisis. [Pg.45]

In what follows we consider the laminar boundary layer in a cross flow past a circular cylinder. This problem is also of practical importance, since tube elements are widely used in industrial equipment. [Pg.46]

Cross flow past a cylinder. The problem on a cross flow past a cylinder comprises Eqs. (1.8.1) and boundary conditions (1.8.2)—(1.8.3). For a circular cylinder, we have [427] [Pg.46]


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