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*VDP

Data format:

A single line with 11 values:

GRP_ID EPS NU KHI A0 NPT ST INI_WAKE CL0 K_IN CD_0

Status :

Optional

Purpose :

To define the parameter for the VIV analysis based on the Van der Pol wake oscillator model.

Details :

Parameter	Description
GRP_ID	the group number onto which the VDP analysis
is carried-out
EPS	value of the eps coefficient in the wake equation (see eq. in the note)
NU	value of the nu coefficient in the wake equation (see eq in note)
KHI	value of the khi coefficient in the wake equation (see eq in note)
A0	forcing term coefficient A0
NPT	number of time step per wake period npT. This value is automatically doubled in case in-line analysis is required
ST	Strouhal number St
INI_WAKE	initial uniform wake value
CL0	lift coefficient CL0
K_IN	switch k_in for using an in-line approach. '1' is for in-line and cross-flow while '0' is for cross-flow solely
CD_0	drag coefficient which corresponds to that on a fixed structure subjected to vortex shedding

Note

the Van der Pol oscillator for the wake variable q is defined as :

\(\frac{\partial^2 q}{\partial t^2} + \epsilon \omega_W(z) (q^2 - 1) \frac{\partial_q}{\partial_t} \omega^2_W (z) q - v \frac{\partial^3 q}{\partial t \partial z^2} - \chi \frac{\partial^2 q}{\partial t \partial z^2} = f(y)\)

where \(f(y) = A_0 \frac{\partial^2 y}{\partial t^2}\)

Example :

Default values are as follows :

*VDP 1 0.3 0.001 0.001 12.0 8 0.2 0.1 0.3 0 1.0