Visualization of the velocity field in a moderately turbulent Kolmogorov flow (spatial resolution 128^3). The  flow is sustained by a steady unidirectional force (here along the X axis)  with a monochromatic sinusoidal dependence proportional to  sin(k Y).  The sinusoidal profile is clearly reflected in the large scale velocity field in the X-Y planes (visible at the beginning and at the end of the movie).