FULLY DEVELOPED TURBULENT FLOW IN STRAIGHT RECTANGULAR DUCTS--SECONDARY FLOW, ITS CAUSE AND EFFECT ON THE PRIMARY FLOW (thesis). Technical Report No. 2
The problem of fully developed turbulent flow in rectangular ducts is investigated principally by obtaining experimental measurements of the primary and secondary velocity distributions in ducts with aspect ratios of 1: 1, 2: 1, and 3: 1. Mean primary (axial) velocities are measured with both hot-wire annemometer and pitot-tube instrumentation. Secondary velocities are deternimed from observations of flow direction using a very sensitive hot-wire system. Secondary flows are found to behave in the manner originally suggested by Prandtl. They are about the same magnitude in all three ducts. Maximum secondary velocities of approximately 1 to 1 1/2% of the axial centerline velocity occur near the wall in the corner region where the large wall shear stress gradient is observed. The second ary flows, by convection of axial momentum, are seen to have a significa nt effect on the primary flow distribution, particularly by causing the wall shear stress to be nearly uniform around the duct periphery except for the corner region. An evaluation of the axial momentum terms from the experimental measurements shows the secondary convective terms to be important throughout much of the flow. The behavior near the wall of the transverse turbulents intensity components (v' and w') in the presence of a transverse gradient of wall shear is shown to be a major cause eof the secondary flow. Expressing these intensity components by a universal relation in the viscous wall region, itt is shown that wall shear gradients produce secondary moltion driving forces of significant magnitude. Mixture length theories are shown to be inadequate, and the need for measurements of turbulent stresses is discussed. (auth.)
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge
- DOE Contract Number:
- DA-19-020-ORD 4538
- NSA Number:
- NSA-15-005150
- OSTI ID:
- 4093197
- Report Number(s):
- OOR-1935.2
- Resource Relation:
- Other Information: DA Project No. DA599-01-004. Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- United States
- Language:
- English
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