atmCoriolisUSource

Table of Contents

Properties

  • The atmCoriolisUSource applies corrections to incorporate the horizontal and vertical components of the Coriolis force for which the rotating frame is Earth.
  • The Coriolis force is an inertial or fictitious force that acts on objects that are in motion within a frame of reference that rotates with respect to an inertial frame.
  • In the atmospheric boundary layer context, for the "Coriolis effect", the rotating reference frame implied is almost always Earth. Because Earth spins, Earth-bound observers need to account for the Coriolis force to correctly analyze the motion of objects. Earth completes one rotation per day, so for motions of everyday objects the Coriolis force is usually quite small compared with other forces; its effects generally become noticeable only for motions occurring over large distances and long periods of time, such as large-scale movement of air in the atmosphere or water in the ocean. Such motions are constrained by the surface of Earth, so only the horizontal component of the Coriolis force is generally important.
  • The atmCoriolisUSource can be applied on any RAS turbulence model.
  • The atmCoriolisUSource inherits the traits of the fvOption, and cellSetOption.

Corrections applied on: 

U    | Velocity                  [m/s]

Required fields: 

U    | Velocity                  [m/s]

Model equations

The model expression:

\[ f_M -= \alpha \rho ((2 \Omega) \times \u ) \]

where

\( f_M \) = fvMatrix of the velocity field
\( \Omega \) = Rotation vector of the rotating reference frame relative to the inertial frame [rad/s]
\( \u \) = Velocity field [m/s]
\( \alpha \) = Phase fraction in multiphase computations, otherwise equals to 1
\( \rho \) = Fluid density in compressible computations, otherwise equals to 1

Usage

Example of the fvOptions specification using constant/fvOptions file: 

atmCoriolisUSource1
{
    // Mandatory entries (unmodifiable)
    type                  atmCoriolisUSource;

    atmCoriolisUSourceCoeffs
    {
        // Mandatory (inherited) entries (unmodifiable)
        selectionMode    all;

        // Conditional mandatory entries (unmodifiable)
        // Select either of the below

        // Option-1: to directly input rotation vector
        Omega        (0 0 5.65156e-5);

        // Option-2: to indirectly input rotation vector
        // by a latitude-period pair
        latitude                   51.971;
        planetaryRotationPeriod    23.9344694;
    }

    // Optional (inherited) entries
    ...
}

where the entries mean:

Property Description Type Required Default
type Type name: atmCoriolisUSource word yes -
latitude Geographic coordinate specifying the north–south position of a point on the surface of a planetary body [degree] scalar conditional 0.0
planetaryRotationPeriod Rotation period of the planetary body [h] scalar conditional 23.9344694
Omega Rotation vector of the rotating reference frame relative to the inertial frame [rad/s] vector conditional (0 0 0)

The inherited entries are elaborated in:

Further information

Tutorials

Source code

History

  • Introduced in version v2006