"With the North Sea as its last vacant lot,
And waves of dunes to hold back the waves,
And vague rocks that the tides wash over,
Their hearts forever at low tide."
Jacques Brel sang it with such conviction, and his imagery is so rich in meaning that it still shapes our vision today: Le Plat Pays (The Flat Country) is unimaginable without dune-fringed beaches ceaselessly confronting a more or less restless sea. As the poet observes, dunes can take the form of waves. And though dunes move more slowly, their motion is comparable as well. Science will show that he was partly right. To understand why, we must turn to fluid mechanics. This branch of mathematical physics is developing particularly rapidly today, finding new applications through computing and simulation processes that are especially useful in animation, where increasingly realistic rendering is required.
