Wake-boundary Layer Interaction Research Articles

Unsteady Boundary Layers on a Flat Plate Disturbed by Periodic Wakes: Part II—Measurements of Unsteady Boundary Layers and Discussion

As the second part of the study, detailed hot-wire anemometry measurements of wake-affected boundary layers on the flat plate are made. These measurements are organized in order, first, to check the standpoint of the modeling of the wake-induced transition proposed in Part I, and second, to observe wake–boundary layer interaction in detail from a viewpoint of direct and indirect effect of the wake passage upon turbulent spot generation within the boundary layer, as described by Walker (1993). The validity of the presumed state of the wake-affected boundary layer in the distance–time domain, which constitutes the basis of the transition model, is confirmed to great extent. However, it is also found that the criterion for the onset of the wake-induced transition adopted in Part I should be reconsidered. Some successful attempts are therefore made to specify the transition onset.

Studies of the Unsteady Boundary Layer on a Flat Plate Subjected to Incident Wakes. 3rd Report. Hot-Wire Probe Measurement of the Unsteady Boundary Layer.

Detailed hot-wire probe measurements of unsteady boundary layer on a flat plate, which is affected by wakes generated from the rotating circular cylinders, are made. These measurements are organized in order, firstly, to investigate wake-boundary layer interaction behavior, considering the forced boundary layer transition model proposed in the previous paper, and secondly to determine the transition starting point and wake duration time by defining the threshold value for the wake-induced turbulent region in comparison with the data of time-averaged heat transfer distribution. It is consequently found that the forced transition tends to occur where Reynolds number based on the momentum thickness is around 160.

Viscous corrections on wings in incompressible flow

Numerical methods have been developed to analyse incompressible viscous flows past three dimensional wings with deflected flap using viscous-inviscid interaction techniques. By using a surface transpiration technique, a panel method for external potential flow calculation is combined with a boundary-layer calculation based on an integral method. For the clean wing case, both three dimensional boundary layer corrections and two dimensional boundary layer corrections are applied in a strip theory sense and compared with experimental results in the literature. It is found that for wings with moderate aspect ratio and sweep angle, viscous corrections at low incidences by the two methods are of the same order. Based on this observation, a two dimensional boundary layer correction method (strip theory sense), including the wake-boundary layer interaction, is developed for the case of wings with a deflected flap of similar planform. Experiments have been conducted to assess the accuracy of the calculation methods for wings with deflected flap; comparison between the experimental and predicted results is encouraging.

Paper 36: Wake—Boundary Layer Interaction in Tandem Cascades

The performance of a tandem cascade in a cascade wind-tunnel is discussed and the characteristics of a given cascade are presented ( a) without end wall suction and ( b) with suction, in order to produce two-dimensionality as closely as possible. Necessary criteria for the existence of two-dimensional conditions are stated. A discussion is given of the development of the boundary layer on the second blade as affected by the wake based on hot wire anemometer investigations. In addition, a separate experiment is described in which a wake is allowed to impinge on a flat plate, subject to an adverse pressure gradient. From both experiments the influence of the size of slot between the tandem aerofoils is assessed.