Being able to predict how boats respond to a variety of ocean conditions determines if multimillion-dollar vessels will sink or swim. To reliably mimic specific flow conditions in the ocean, researchers typically rely on artificial ocean basins—facilities equipped with wave and current generation systems.
“Artificial ocean basins use multiple-channel inlets to send smooth, fast flows of water into the test area, where researchers can test how boats and marine structures will respond,” said My Ha Dao, a Group Leader at the Institute of High Performance Computing (IHPC), A*STAR. “However, as slower, wall-hugging layers of water emerge from the inlets, they combine into slow layers of reduced flow that can propagate throughout the test area and affect experiments adversely.”
To maintain the velocity of water entering the artificial ocean basin, Dao’s team proposed using a ‘barrier’ resembling a honeycomb. The barrier was designed using computational fluid dynamics for modeling and predicting how turbulent flows of air or water will move around obstacles or through channels.
After optimizing for parameters such as the radii of arcs and the dimensions controlling honeycomb shape, Dao and his team eventually settled on a honeycomb with 4 mm-diameter holes in it. They also demonstrated, via simulation, that the structure would reduce deficit and fluctuations in the velocity distribution of water downstream of the inlet.
Seeking to validate their model, the researchers 3D-printed their prototype honeycomb and tested it in the lab. “We were able to verify the results of our computational fluid dynamics models; the 3D-printed honeycomb mitigated the velocity deficit while improving the uniformity of velocity of water flowing through our system,” Dao said, adding that the velocity variation decreased from 7-8 percent without the honeycomb to just 1-2 percent with the honeycomb in place.
The methodology developed by Dao is currently being used to design honeycomb shapes for the inlets of the deep-water basin at the Technology Centre for Offshore and Marine Singapore (TCOMS), a joint R&D center by A*STAR and the National University of Singapore.
Going forward, Dao intends to use his technique to solve more difficult problems that have a flow element to them. “In principle, our method can be used to cover more complex geometries, such as corners where horizontal and vertical walls meet. In addition, the shaped honeycomb method can be used for more than simply smoothing out flow profiles—it could also be used to produce flow profiles of any desired shape to further expand the capabilities of artificial ocean basins.”
The A*STAR-affiliated researcher contributing to this research is from the Institute of High Performance Computing (IHPC) and the Technology Centre for Offshore and Marine Singapore (TCOMS).
