Kayaking with Bernoulli

Baschek, B. and D.M. Farmer

The Oceanography, 22, 2, 220-225, 2009.

In the narrow channels along the coast of British Columbia, Canada, spectacular rapids are generated by powerful tidal currents sometimes exceeding 8.6 m s-1. The Nakwakto tidal rapids are an especially impressive natural fluid mechanics laboratory and a beautiful example of Daniel Bernoulli's famous principle of energy conservation in a fluid. Boundary layer separation from irregular shorelines generates intense shears with highly energetic whirlpools that draw gas bubbles to great depth enhancing aeration of the water. Large standing waves form in the wake of an island. In these environments, fresh surface water from the extensive inlets of the mainland coast and saltier water from the Pacific Ocean are mixed thoroughly throughout the water column. In this report we describe unusual measurements acquired in Nakwakto Rapids, which provide an outstanding educational laboratory with unique opportunities for studying hydrodynamics.