An investigation of flow in circular and annular 90 degrees bends with a transition in cross section

Stafford W. Wilbur
naca-tn-3995
Aug 1957


An investigation at low speed of the performances of circular and annular 90 degree bends of simple shapes was conducted for configurations for which the cross-sectional area was constant, expanding, and contracting. Two series of transition bends (circular to annular and annular to circular) were included, in which the transition occurred upstream of the bend, within the bend, and downstream from the bend. The data presented include the exit velocity profiles, the relative total-pressure-loss coefficients measured at the exit station, and an index for the exit total-pressure distortion. Separation of the flow in the bend occurred for all configurations except those with a contracting area. With the transition in cross section downstream of the bend proper, the separated region was removed by natural mixing but was accompanied by high pressure losses. Certain locations of the transition produced higher performances than others.

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