Page 292 - Fluid-Structure Interactions Slender Structure and Axial Flow (Volume 1)

PIPES CONVEYING FLUID: LINEAR DYNAMICS I1 273

\

Well control equipment

L

Submarine base

Figure 4.40 Diagrams of two possible deep-water flexible risers.

all such occurrences must be known at the design stage, predicted by the same computer
codes. Therefore, understanding and modelling the effects of pressure and internal flow
are essential building blocks in the development of these codes.

4.7.5 High-precision piping vibration codes

As has already been remarked, for most industrial applications the effect of steady internal
flow in piping is not crucial. However, in specific applications, the piping is sufficiently
flexible and failure sufficiently undesirable to make it important to develop high-precision
computer codes for free, forced and transient vibration of pipes, talung internal flow effects
into account. Such applications are those just discussed in offshore risers, ocean mining
systems (Section 4.3), and special designs such as that discussed in Section 5.5.4, where
long unsupported spans make the pipes effectively very flexible. Another example is
a special low-cost condenser involving plastic tubes, designed by the French concern
Ecopol, to be discussed in Chapter 9 (Volume 2). Other applications are in aircraft and
rocket fuel lines, where the piping is very flexible because of weight considerations.
Computational tools for piping vibration have been developed, for example, by Ting &
Hosseinipour (1983), Nakra & Kohli (1984), Dang et al. (1989), Piet-Lahanier & Ohayon
(1990), Sallstrom (1990, 1993) and Sallstrom & BLkesson (1990). An example of the
type of complex piping structures that can be handled is shown in Figure 4.41, analysed
via an exact finite element formulation based on Timoshenko beam theory - Le. using