TURBULENT BOUNDARY-LAYER ON A FLAT-PLATE

Four algebraic models, based on the use of Prandtl's mixing length formula with Loitsyanskii's damping factor in the inner domain and on different relationships for turbulent viscosity in the outer domain, are analyzed. An analysis has resulted in a conclusion that the so-called problem of ''small'' Reynolds numbers is a consequence of nonuniversality of the scales used in the outer domain. It is shown that the universal scales of the outer domain are the dynamic velocity v* and the boundary layer displacement thickness delta*. Out of four treated relations for the turbulent viscosity in die outer domain, based on the use of different linear and velocity scales, it is only the relation v(t) = Kv*delta* (K = const = 0.4), referred to as the Clauser-3 formula, that possesses the property of universality (irrespective of the Reynolds number) in the entire range of Reynolds numbers being treated: 320 less than or equal to Re** = U delta**/v less than or equal to 2 x 10(4) (U is the velocity at the outer bound of the boundary layer, delta** is the momentum thickness, and v is the kinematic viscosity). For the remaining three models, approximations are proposed that take into account the dependence of the empirical ''constants'' on the Reynolds number. The boundary layer structure is analyzed, including its specific features in the region of small Reynolds numbers. It is shown that, for Re** > 10(3), the inner domain thickness is equal to the boundary layer displacement thickness.