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Buoy properties

The buoy properties tab is provided to enter a number of mechanical and hydrodynamic properties for your buoy.

  • Net buoyancy force (N): The net buoyancy force is the buoyancy minus the weight in air. The value may be positive or negative depending on whether the buoy has a negative or positive submerged weight.

  • Horizontal drag global coefficient (kg/m): COEFH can be calculated for example with the following relationship : COEFH = 0.5rsea waterCdHS . Where CdH is the dimensionless normal drag coefficient, and S is the cross section perpendicular to the direction (HD). A standard value of CdH is 1.2 for a vertical cylinder.

  • Vertical drag global coefficient (kg/m): COEFV can be calculated for example with the following relationship : COEFV = 0.5rsea waterCdV*S where CdV is the dimensionless axial drag coefficient, and S is the cross section perpendicular to the direction (pD2/4). A standard value of CdV is 1.4 for a vertical cylinder with two hemispherical caps.

  • Horizontal inertia global coefficient (kg): CINH can be calculated for example with the following relationship : CINH = rsea waterCiHV where CiH is the dimensionless normal inertia coefficient, and V is the volume displaced by the floater. A standard value of CiH is 1.7 for a vertical cylinder with two hemispherical caps.

  • Vertical inertia global coefficient (kg): CINV can be calculated for example with the following relationship : CINV = rsea waterCiVV where CiV is the dimensionless axial inertia coefficient, and V is the volume displaced by the floater. A standard value of CiV is 1.3 for a vertical cylinder with two hemispherical caps.

  • Mass and inertia matrix (kg and kg.m): Attention must be paid to the fact that this mass is not taken into account in the apparent weight calculation (directly defined by the net buoyancy force). The mass terms are only used in dynamic to model the inertia loads (those loads that are proportional to the acceleration of the buoy). These inertia terms must include both the mass of the buoy in air and the added mass of the buoy in water.

    Note

    The 6 terms of the matrix must be expressed in the local coordinates system of the buoy component.

  • Lift global coefficient (kg/m): COEF is used to compute the lift load F = COEF*|Vr|2, where Vr is the relative fluid velocity projected on the horizontal plane.