The basis of Vivana
The hydrodynamic model in Vivana is based on empirical coefficients, while the structural model applies a non-linear 3-dimensional finite element formulation.
The program is able to work with an arbitrary distribution of tension, mass, stiffness, buoyancy and diameter.
Response frequencies are identified while considering a frequency dependent hydrodynamic mass along the structure.
Response amplitudes are calculated at the discrete frequencies by the frequency response method
The excitation force model includes a lift coefficient that is a function of the response amplitude and the response frequency.
Damping outside the excitation zone is introduced by high and low velocity damping terms.
What will Vivana provide for the user
- Free variation of all parameters (diameter, Strouhal number, coefficients etc.) along the riser
- Frequency dependent hydrodynamic mass matrix
- Identification of dominating and possible response frequencies
- Identification of excitation and damping zones for all response frequencies
- Calculation of response amplitude
- Calculation of fatigue damage
- Calculation of drag amplification