Przejście laminarno-turbulentne w warstwie przyściennej indukowane śladami spływowymi

• Autorzy: Wierciński Z.
• Języki publikacji: PL

Abstrakty

EN

The state of the art in the field of experimental investigation of the laminar-turbulent transition induced by wakes in the boundary 1ayer of a flat plate is presented. Results of the investigation of the unsteady boundary layer carried out in the subsonic wind tunnel of the Institute of Fluid-Flow Machinery are reviewed. The purpose of the investigation is to analyse some phenomena ( e.g. influence of the negative and positive jets, the nature of the disturbance caused by a wake in the boundary layer, critical layer with a phase shift) of the in stationary boundary layer transition induced by wakes. This investigations is preceded by detailed investigation of the mean-time characteristics of the natural and induced transition of the boundary layer. Results of relevant comparative analysis are reported. The investigation has resulted in a new model of the induced boundary layer transition. The model is based on the observation that the velocity of a disturbance raised in the boundary layer by a wake is equal to the velocity of the wake outside the boundary layer. The turbulisation of the boundary layer between the wake disturbances appears first in the critical layer of the boundary layer. So the cause for the turbulence inception in the induced boundary-layer is the instability mechanism in the flow, and not diffusion of the turbulence from the wakes into their neigh our hood or production of the turbulence at the edge of the wakes. A critical layer with a phase shift of the wake disturbance in the boundary layer is revealed. Besides the phase shift, the first high-frequency velocity fluctuations between the wake disturbances are also revealed. This critical layer 1ies beneath the layer with the phase shift of the Tollmien-Schlichting waves. The different influence of the negative and positive .yet of the wake on the boundary layer transition is also reported. The negative wake jet causes transition earlier than the positive jet. Moreover, it is shown that the velocity fluctuations can be amplified if the intersection of the two wakes is oncoming the leading edge of the flat plate. Additionally, the experimental correlations between the inception (and the completion) of the induced and natural transitions are determined.

• Wydawca: Wydawnictwo Instytutu Maszyn Przepływowych PAN
• Czasopismo: Zeszyty Naukowe Instytutu Maszyn Przepływowych Polskiej Akademii Nauk w Gdańsku
• Rocznik: 1999
• Tom: nr 499/1450
• Strony: 1--126
• Opis fizyczny: Bibliogr. 143 poz., rys., tab.

Twórcy

autor

Wierciński Z.

• Institute of Fluid-Flow Machinery, Polish Academy of Sciences, ul. Fiszera 14, 80-952 Gdańsk, Fax [phone]