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 aplitudes are calculated at the discrete frequencies by the frequency response method

The excitattion 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