Page 391 - Fluid-Structure Interactions Slender Structure and Axial Flow (Volume 1)

PIPES CONVEYING FLUID: NONLINEAR AND CHAOTIC DYNAMICS 367

are studies of inherently nonconservative such systems, exemplified by Dowell’s (1982)
work on flutter of a buckled plate, and that described here on a magnetically buckled
cantilevered pipe conveying fluid (Tang & Dowell 1988).+
The experimental system, shown in Figure 5.41, consists of a Tygon pipe (L = 545 mm,
Do = 12.7 mm) conveying water, fitted with a ferromagnetic metal strip, similar to that in
Section 5.8.1, and fitted with an end-nozzle. Two permanent magnets on either side of the
straight equilibrium position provide two potential wells, into one of which the system
buckles statically. The system would ordinarily stay buckled unless excited, either by
flow-induced flutter in the case of the autonomous version of the system, or mechanically
by a force Fo 6(e - 6~) sin wt. In the experiments this force is provided by a shaker at
e~ = 0.11, while pipe motion is sensed at es = 0.92. In the absence of flow, this system,

Magnet I Magnet
4 wb 4

Figure 5.41 Diagram of the magnetically buckled, mechanically excited pipe conveying fluid
(Tang & Dowell 1988).

+Apart from the work on the motion-constrained pipe described in Section 5.8.1; PaYdoussis & Moon’s
(1988) paper was published six months after Tang & Dowell’s.