To initialize a random velocity field with components in the range [0,1) using funkySetFields, add this in funkySetFieldsDict

U { field U; expression "vector (rand(N1), rand(N2), rand(N3))"; }

where N1, N2, N3 are three arbitrary integers used as seeds to generate three different random scalar fields.

To obtain velocity components in a different range:

U { field U; expression "vector (0.01*rand(N1)-0.005, 0.01*rand(N2)-0.005, 0.01*rand(N3)-0.005)"; }

transforms the range from [0,1) to [-0.005,0.005).