Photographs are presented for secondary flow patterns in a straight tube (x/d = 0 ∼ 70) downstream of a 180 deg bend (tube inside diameter d = 2.54 cm, radius of curvature Rc = 12.7 cm) and in an isothermally heated horizontal tube (tube inside diameter d = 2.54 cm, heated length l = 46.2 cm) with free convection effects. Each test section is preceded by a long entrance length with air as the flowing fluid. For curved pipes, the Dean number range is K = 99 to 384. At the exit of the 180 deg bend, the onset of centrifugal instability in the form of an additional pair of Dean vortices near the central outer wall occurs at a Dean number of about K = 100. The developing secondary flow patterns in the thermal entrance region of an isothermally heated horizontal tube are shown for the dimensionless axial distance z = 0.8 × 10−2 to 1.83 (Re = 3134 ∼ 14) for a range of constant wall temperatures Tw = 55 ∼ 65° C with entrance air temperature at about 25° C. The secondary flow patterns shown are useful for future comparisons with predictions from numerical solutions.

This content is only available via PDF.
You do not currently have access to this content.