Ocean models are not yet powerful enough to resolve small-scale mixing processes on a global scale. Shear brilliance Reviewing some of the data results from the VMP and CTD, instruments that are used to profile the ocean. The science party on Falkor will use this concept to analyze the data being collected on the cruise in order to advance our understanding of turbulent mixing. Later theory showed that a necessary condition for instability is that the Richardson number is less than a quarter. The Richardson number essentially is the ratio of the vertical density gradient, squared, to the shear, squared. These observations inspired him to consider the energetics of flow and to encapsulate the physics in a number, now known as the Richardson number. On the other hand, when the temperature of the air closer to the ground became colder than that above, the fluctuations decreased. In looking at measurements of the wind at two different heights above the ground he noted the fluctuations in wind increased as the difference in wind speed at the two heights increased. The billows undergo further instabilities leading to turbulence and the mixing of properties such as heat, water vapor (in the atmosphere) and salt (in the ocean).Īnother significant player was Lewis Fry Richardson. Under the right conditions these billows are seen in cloud formations in the sky. The mechanism is known as Kelvin-Helmholtz instability which when active forms beautiful “billows”. The battle between these two forces (shear and buoyancy) decides if the flow will go unstable. light fluid overlays heavy fluid) there is a tendency to damp any disturbance. They found that a velocity difference (or shear) at different heights in a fluid flow can induce the flow to become unstable, while if the density of the fluid decreases with height (i.e. Lord Kelvin and Hermann von Helmholtz made significant contributions to fluid dynamics. ![]() Mixing celebrities Mixing celebrities (from left to right) Kelvin, Helmholtz, and Lewis Fry Richardson. The namesake of Lord Kelvin, it is no coincidence that small scale ocean mixing is his passion. Richards is curious to see if the same physics he is witnessing there extend into the central Pacific. After working in the western equatorial Pacific for many years, Dr. For him, this cruise is a significant step forward, or east, to obtain long awaited information. Kelvin Richards, the Principal Investigator on the Mixing Up The Tropical Pacific Cruise beams with excitement at the prospect of collecting new data. Kelvin Richards awaits on the VMP to see what kind of data they can find.
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