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10). At A ---- 20 the base pressure is fairly uniform at -- 0.6 over the middle half of the span, with a sharp drop near tile tips. The level of the pressure over tile middle half of the span, although lower than on the lower aspectratio plates, is considerably higher than on t h e two-dimensional plate. Correspondingly the bubble length (expressed in terms of tile chord) is 4.29 for A ---- 20 and 2.82 for A ---- oo.
Behind the low-aspect-ratio plates (Figs. 5a to 5d) it will be seen that, at any one distance behind the plate, the static pressure is fairly constant within the bubble. There are staticpressure gradients between the bubble boundary and the total-head boundary and also down the length of the bubble.
Axial distributions of total head, static pressure and velocity are shown in Figs. l l a to 1 lc for all the rectangular plates. Between A = 1 and A = 10 t h e bubble length decreases from
2-96~/S to 2"26V'S but the distributions of pressure and velocity within the bubble do not change much. The static-pressure coefficient in the centre of the downstream face of the …show more content…
0.115
0.115
0"115
0.117
and more detailed comparisons of the nature of the flows are given in Figs. I3 to 15. These results differ by little more than the experimental accuracy. It is concluded that large charges in tile shape of the plate have only negligible effects on the aerodynamic characteristics.
Ref. 2 shows, however, that perforating the plate can prevent the formation of a bul~ble, and hence suppress the regular shedding of eddies and much of the random low-frequency velocity fluctuation. 6. Comlusio~s.--The effects of aspect ratio on drag, base pressure and flow pattern are small up to A --=- 10. All the plates shed turbulent eddies at particular frequencies; generally there are two shedding frequencies for each rectangular plate, one associated with the smaller dimension of the plate and a lower frequency associated with the longer dimension.
Large charges in the shape of low-aspect-ratio plates have very small effects on the aerodynamic characteristics but the regular Shedding of eddies call be eliminated by perforating the plate; this is accompanied by a reduction in tile random low-frequency velocity fluctuations.
6
LIST OF SYM.BOLS
C
Chord of plate
b
Span of
Behind the low-aspect-ratio plates (Figs. 5a to 5d) it will be seen that, at any one distance behind the plate, the static pressure is fairly constant within the bubble. There are staticpressure gradients between the bubble boundary and the total-head boundary and also down the length of the bubble.
Axial distributions of total head, static pressure and velocity are shown in Figs. l l a to 1 lc for all the rectangular plates. Between A = 1 and A = 10 t h e bubble length decreases from
2-96~/S to 2"26V'S but the distributions of pressure and velocity within the bubble do not change much. The static-pressure coefficient in the centre of the downstream face of the …show more content…
0.115
0.115
0"115
0.117
and more detailed comparisons of the nature of the flows are given in Figs. I3 to 15. These results differ by little more than the experimental accuracy. It is concluded that large charges in tile shape of the plate have only negligible effects on the aerodynamic characteristics.
Ref. 2 shows, however, that perforating the plate can prevent the formation of a bul~ble, and hence suppress the regular shedding of eddies and much of the random low-frequency velocity fluctuation. 6. Comlusio~s.--The effects of aspect ratio on drag, base pressure and flow pattern are small up to A --=- 10. All the plates shed turbulent eddies at particular frequencies; generally there are two shedding frequencies for each rectangular plate, one associated with the smaller dimension of the plate and a lower frequency associated with the longer dimension.
Large charges in the shape of low-aspect-ratio plates have very small effects on the aerodynamic characteristics but the regular Shedding of eddies call be eliminated by perforating the plate; this is accompanied by a reduction in tile random low-frequency velocity fluctuations.
6
LIST OF SYM.BOLS
C
Chord of plate
b
Span of