Bioluminescence is light produced by organisms through chemical reactions. In most cases, bioluminescent organisms produce light in response to mechanical stimulation, including from shear around objects moving in the water. Many phytoplankton and zooplankton are capable of producing bioluminescence, which is commonly measured as bioluminescence potential, defined as mechanically stimulated light measured inside of a chambered pump-through bathyphotometer. We have developed a numerical model of a pump-through bathyphotometer and simulated flow using Lagrangian particles as an approximation for bioluminescent marine plankton taxa. The results indicate that all particles remain in the detection chamber for a residence time of at least 0.25 s. This suggests that the total first flash of bioluminescent autotrophic and heterotrophic dinoflagellates will be measured based on the existing literature regarding their flash duration. We have found low sensitivity of particle residence time to variations in particle size, density, or measurement depth. In addition, the results show that a high percentage of organisms may experience stimulation well before the detection chamber, or even multiple stimulations within the detection chamber. The results of this work serve to inform the processing of current bioluminescent potential data and assist in the development of future instruments.

Drag reduction is of significant interest in the design of marine vehicles. Viscoelastic boundary materials and compliant surfaces, such as those found in dolphin skin, have the potential to reduce frictional drag by delaying the transition from laminar to turbulent flow and minimizing turbulence. To investigate the effect of boundary modulation on turbulence, we developed and tested a novel device that generates wave-like deformations on a flow boundary. This device, enabled by a 5×5 voice coil motor array, was embedded in the wall of a flow channel and overlaid with a flexible membrane in direct contact with the water. The boundary displacement was quantified using a computer vision approach. The deformable membrane system was tested across a range of flow tank speeds and boundary actuation patterns, and the impact on near-boundary velocity was assessed. The resulting data indicate that boundary actuation alters the boundary layer velocity and turbulent stresses both under the region of actuation and in its wake. The effect was most pronounced in regions with boundary layer coherent structures, and certain actuation parameters were consistent with a reduction in frictional drag. A numerical model of the flow tank showed a 10% reduction in average shear stress over the actuated boundary and one actuation wave period, supporting the laboratory experiments and corroborating the findings. This work supports efforts to develop dolphin-inspired methods to reduce near-boundary turbulence and drag, which, if successfully applied in a natural environment, can lead to more energy-efficient platforms and underwater vehicles.