Experimental investigation of the wave structure of a supersonic boundary layer

Abstract

At present there are a number of theoretical techniques to predict laminar boundarylayer transition to turbulence based on different criteria. In order to develop a general theory for transition it is necessary to have a detailed description of wave processes in the boundary layer and theoretical and experimental results on stability. The growth of natural disturbances [i] is, as a rule, studied in experimental investigations on the stability of supersonic boundary layers. The shortcoming of such studies is the absence of the complete three-dimensional characteristics of the disturbance field in the boundary layer. Hence it is possible to expect only qualitative agreement between theory and experiments. A more accuracy quantitative comparison is possible with controlled artificial disturbances modeling wave growth in the boundary layer. An alternate approach (in the study of the development of natural disturbances) consists of corresponding correlation measurements followed by an evaluation of wave spectra. Such an approach was partially realized in [2]. A point disturbance source was used in [3] to study the stability of incompressible boundary layers. The wave field created by it (amplitude and phase distribution of fluctuations in space) was recorded by hot-wire anemometry. The results of the study reflect the evolution of monochromatic plane waves in the boundary layer. A method similar to [3] was used in [4, 5] to study the stability of supersonic boundary layers. An electric arc was used as the disturbance source. It is shown that the given method makes it possible to study the growth of characteristic waves in supersonic boundary layers. Some problems that arise while obtaining experimental data and also during their analysis have been discussed in [4]. The present study extends the approach of [3, 4] and new experimental results have been obtained. Stability analysis of the boundary layer using linear approximation has been carried out on the basis of the experimental data.