Generation and development of small-amplitude disturbances in a laminar boundary layer in the presence of an acoustic field

A low-turbulence subsonic wind tunnel was used to study the influence of acoustic disturbances on the development of small sinusoidal oscillations (Tollmien-Schlichting waves) which constitute the initial phase of turbulent transition. It is found that acoustic waves propagating opposite to the flow generate vibrations of the model (plate) in the flow. Neither the plate vibrations nor the acoustic field itself have any appreciable influence on the stability of the laminar boundary layer. The influence of an acoustic field on laminar boundary layer disturbances is limited to the generation of Tollmien-Schlichting waves at the leading-edge of the plate

Stability of an oscillating boundary layer

Levchenko and Solov'ev (1972, 1974) have developed a stability theory for space periodic flows, assuming that the Floquet theory is applicable to partial differential equations. In the present paper, this approach is extended to unsteady periodic flows. A complete unsteady formulation of the stability problem is obtained, and the stability characteristics over an oscillating period are determined from the solution of the problem. Calculations carried out for an oscillating incompressible boundary layer on a plate showed that the boundary layer flow may be regarded as a locally parallel flow

Openness of the insurance market for foreign entities: methodology and experience of Ukraine

The article is devoted to the development of methodical tools for determining the level of openness of the insurance market in Ukraine. The proposed level of openness of the insurance market of Ukraine should be considered as an opportunity (potential) for domestic insurers to interact effectively with foreign investors and financial intermediaries. It has been established that the mathematical tool for realizing the task should be a gravity modeling, which, taking into account the inflow and outflow of the characteristics of the openness of the insurance market of Ukraine, allows us to determine the degree of its remoteness from the insurance markets of Europe and the World. It is proved that the openness of the insurance market of Ukraine serves not only as an indicator of the level of readiness of the interaction of domestic financial intermediaries with foreign entities, but also fully characterizes the infrastructural level of the Ukrainian insurance market