Large-scale dynamic structures in turbulent boundary layer

Yu.I.Khlopkov, V.A.Zharov, S.L.Gorelov

Moscow Phisical-Technical University

Currently there is a great deal of data about turbulent motion dynamics in incompressible fluid in boundary layer on the plate, in which there have been discovered structural elements of interaction of flow with surface. A number of experiments have been carried out by different researchers making use of different methods. The results of those experiments reveal a number of general and the most important properties of this interaction. Now it is time for fundamental understanding of these results and constructing a global theory of turbulent motion based on them. Below we will consider briefly the main results of the experiments, which, from our point of view, can be taken into consideration while constructing mathematical models.

Experimental results considered in this review have relation to the research of fundamentБl phenomena which take place in the thin layer of fluid or gas f1owing close to Б solid surface, i.e. in boundary layer. It is suggested that gas the fluid is in the complex time-dependent motion (turbulent) state. These phenomena were discovered in the middle of tl1c whole century and were for Б long time subjects Пf experimentalist investigation of entire world because or their complexity and experimentalist wishes to get more accurate data.

Long period cumulated experimental data about vorticity generation and moment transfer in turbulent boundary layer well founded prove the existence of large scale vortical structures (coherent structures) that can bЕ governed bХ autonomous dynamical equations. These structures are responsible for many turbulent boundary layer properties. Practice requirement contains necessity of coherent structure properties control. For example the reduction of aerПdХnБmiУs drag, aircraft noise or increase of effectiveness of fuel combustion an so on is reduced to structure control. Experimental results allow us to give Б definition of the structure and describe some of its details.

From the author's theoretica1 point Пf view experimental and computational works, carried out recently, do not bring essential changes to such views and add only ФПЗЕ precise definition. So results described in the review provide powerful basis for theoretical work because this information is sufficient for Б theory construction. This is especially important in connection with appearance of strong theoretical base which gives possibility to describe dynamical structures in dissipative media as well as in connection with appearance of theoretical methods of fluid motion description with continuous spectrum (renormalized group method and so on). Joining of these two directions which are supplemented with fundamental experimental data will possibly enable to create adequate theory of turbulent boundary layer.