FoamFile
{
    version     2.0;
    format      ascii;
    class       uniformDimensionedVectorField;
    object      g;
}

dimensions      [0 1 -2 0 0 0 0];
value           (0 -0.98 0);
// Hysing 无量纲 g*=-0.98; 有量纲值 g = g* × U_ref^2 / L_ref
// = -0.98 × 1^2 / 1 = -0.98 m/s^2