Wind and current#
Wind and current loads can be added to a model by defining:
wind/current areas
wind speed
wind direction
air density
current speed
current direction
water density
Wind and current areas are nodes. All the others are general settings of the Scene. directions is defined as going to in [deg] relative to the positive x-axis.
Wind speed and direction are constant.
The force acts in the direction of the wind/current and is equal to:
\(Force = {1 \over 2} * \rho * Cd * A_e * V^2\)
Cd#
Cd is the drag coefficient is a fixed coefficient and is user-provided. Typical values are 1.2 for a wire, 0.4 for a sphere, 2.0 for a flat plate perpendicular to the wind.
Effective Area#
The effective area is a combination of an area (A) and the orientation of that area relative to the wind/current.
The area A [m2] is fixed and user-defined.
The effective area \(A_e\) is calculated from the area and its orientation relative to the wind/current. In general \(A_e = A_0 * |sin(\alpha)|\) where the term \(\sin(\alpha)\) accounts for the orientation of the area relative to the wind/current direction. It is 1 if the wind/current is perpendicular to the surface and 0 if it is parallel.
The orientation of the surface can be defined in three ways:
No orientation
The area is the same from any direction:
This is the case for spheres.
Plane orientation
The area is a flat plane. The direction of the node is the normal of the plane:
The area is zero if the wind/current is perpendicular to the defined direction.
Cylindrical orientation
The area is constant around one axis, but plane-like about an axis perpendicular to that. In this case the direction defines the axis about which the area is constant (ie: the center-axis of the cylinder).
The effective area is zero if the wind/current is parallel to the defined direction.
Notebooks#
Wind demonstration
References:#
DNV-RP-C205 : ENVIRONMENTAL CONDITIONS AND ENVIRONMENTAL LOADS