| dc.description.abstract |
Flight tests on the Handley Page suction wing showed that turbulence,
generated at the wing root, can propagate along the leading edge and
cause the whole flow to be turbulent. The flow on the attachment line of
a swept wing was studied in a low speed wind tunnel with particular reference
to the problem of turbulent contamination.
The critical Reynolds number, R9L, of the attachment line boundary
layer for the spanwise spread of turbulence was found to be about 100 for
sweep angles in the range 40°- 60°. A device was developed to act as a
barrier to the turbulent root flow 30 that a clean laminar flow could exist
outboard. This device was shown to be effective up to an Re of at least
170. With the aid of this bump experiments were Possible on L laminar
boundary layer at Reynolds numbers above the lower critical value. A spark
was used to introduce spots of turbulence into the attachment line boundary
layer and the propagation speeds of the leading and trailing edges were
measured. The spots expanded, the leading edge moving faster than the
trailing edge, at high Reynolds numbers, and contracted at low values.
The behaviour of Tollmien-Schlichting waves was also investigated by
exciting the flow with sound emanating from a small hole on the attachment
line. Measurements of the perturbation phase and amplitude were made
downstream of the source and although accurate values of wave length and
propagation speed could be found no difficulties were experienced in evaluating
the amplification ratio. Nevertheless, all small disturbances decayed at
a sufficient distance from the source hole up to the highest Reynolds number
tested of 170. |
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