FLUID-INDUCED STRUCTURAL FORCES
25
Figure 2.7 A cylinder with a helical strake to negate periodic vortices.
The last nondimensional fluid-loading parameter highlighted herein is the
Keulegan-Carpenter number, Kc, which arises when a free stream, plane, periodic flow is imposed on a stationary cylinder. If neither u or ù is constant, but
both are described by a single, simple, plane wave of time period T, then Kc
correlates well with the force data on the cylinder. This flow parameter is
„ U°T
Kc= —
(2.13)
where uq is the amplitude of the wave velocity (Keulegan and Carpenter, 1958).
Conservation of Linear Momentum and Flow Superposition
For a stationary cylinder in a plane flow field with the free stream velocity
u = u(t), the total time-varying load per unit length on the cylinder may be
expressed by superimposing the two flow models described by Figures 2.3 and
2.5. Thus, by adding their respective drag and inertial loadings expressed by
équations (2.10) and (2.7), the resuit becomes
q = CDp^\u\u + CM p7r—ù
(2.14)
Equation (2.14) was first proposed by Morison and his colleagues (1950) as an
empirical resuit, and that équation now bears his name.
Figure 2.8 A rigid, circular cylinder in a flow field.
25
Figure 2.7 A cylinder with a helical strake to negate periodic vortices.
The last nondimensional fluid-loading parameter highlighted herein is the
Keulegan-Carpenter number, Kc, which arises when a free stream, plane, periodic flow is imposed on a stationary cylinder. If neither u or ù is constant, but
both are described by a single, simple, plane wave of time period T, then Kc
correlates well with the force data on the cylinder. This flow parameter is
„ U°T
Kc= —
(2.13)
where uq is the amplitude of the wave velocity (Keulegan and Carpenter, 1958).
Conservation of Linear Momentum and Flow Superposition
For a stationary cylinder in a plane flow field with the free stream velocity
u = u(t), the total time-varying load per unit length on the cylinder may be
expressed by superimposing the two flow models described by Figures 2.3 and
2.5. Thus, by adding their respective drag and inertial loadings expressed by
équations (2.10) and (2.7), the resuit becomes
q = CDp^\u\u + CM p7r—ù
(2.14)
Equation (2.14) was first proposed by Morison and his colleagues (1950) as an
empirical resuit, and that équation now bears his name.
Figure 2.8 A rigid, circular cylinder in a flow field.