Experiments on buoyant-parcel motion and the generation of internal gravity waves

Abstract

Laboratory experiments were conducted to study the motion of miscible buoyant fluid parcels in both homogeneous and stratified media, and were complemented with numerical experiments using the model of Orlanski & Ross (1973). Parcel motion in the homogeneous case was found to be shape-preserving, in agreement with the large body of data for such motion. The stratified medium experiments were such that the parcel attained equilibrium positions. It was found that the time for the parcel to reach maximum depth was approximately 0·7 times the buoyancy period, independent of that depth. The subsequent collapse of the parcel and generation of internal gravity waves was observed. Ray-like patterns of waves propagated out from the collapse region, and wave frequencies near 0·7 times the Brunt-Väisälä frequency were predominant. The internal wave energy radiated away from the collapsed parcel was estimated and found to be 20 to 25% of the change in the system potential energy.