Froude–Krylov force

In

forces acting on a floating body in regular waves. The diffraction force is due to the floating body disturbing the waves.

Formulas

The Froude–Krylov force can be calculated from:

${\displaystyle {\vec {F}}_{FK}=-\iint _{S_{w}}p~{\vec {n}}~ds,}$

where

• ${\displaystyle {\vec {F}}_{FK}}$ is the Froude–Krylov force,
• ${\displaystyle S_{w}}$ is the wetted surface of the floating body,
• ${\displaystyle p}$ is the pressure in the undisturbed waves and
• ${\displaystyle {\vec {n}}}$ the body's
  normal vector
  pointing into the water.

In the simplest case the formula may be expressed as the product of the wetted surface area (A) of the floating body, and the dynamic pressure acting from the waves on the body:

${\displaystyle F_{FK}=A\cdot p_{dyn}}$

The dynamic pressure, ${\displaystyle p_{dyn}}$, close to the surface, is given by:

${\displaystyle p_{dyn}=\rho \cdot g\cdot H/2}$

where

• ${\displaystyle \rho }$ is the sea water density (approx. 1030 kg/m³)
• ${\displaystyle g}$ is the acceleration due to the earth's gravity (9.81 m/s²)
• ${\displaystyle H}$ is the wave height from
  trough
  .

See also

• Response Amplitude Operator

References

• Faltinsen, O. M. (1990). Sea Loads on Ships and Offshore Structures.
  ISBN 978-0-521-45870-2
  .