Simulations on Rice cluster show tiny marine organisms can influence mixing where they concentrate in large numbers

February 23, 2016

Complex systems like oceans are driven by myriad factors and interactions that need to be understood in order to better understand the whole.

In the case of the oceans, even some of the smaller organisms swimming there may have significant impacts, computer modeling by Purdue Professor Arezoo Ardekani and her lab using the Rice community cluster indicates.

Research by Ardekani, an assistant professor of mechanical engineering, is centered on fluid mechanics and solving problems involving fluid flow using computational tools. The ocean, clearly, is one place with plenty of fluid flow problems to solve.

The kinds of fluid dynamics calculations employed by Ardekani and her students can be complex enough inherently to require high-performance computing systems like Rice, which rated as one of the 500 most powerful supercomputers in the world in 2015. Equations like these are used to model ocean currents, water flow in a pipe, the weather, air flow around an aircraft’s wing, distribution of pollutants, and blood flow, among many other things.

Demand for computational muscle only increases when the codes Ardekani’s lab develops are applied to a situation as intricate as the impact of numerous tiny organisms swimming in an ocean.

“We need to discretize them on hundreds of millions or even billions of grid points,” says Ardekani, winner of a 2016 Presidential Early Career Award for Scientists and Engineers (PECASE). “We need to solve these equations on each of these grid points so that needs very large computational power.”

In one paper, published in the journal Scientific Reports in December 2015, simulations by doctoral student Shiyan Wang and Ardekani, showed that small marine life contributed to the distribution of nutrients in the water, especially in localized “hotspots” where the swimming organisms are highly concentrated.

The research indicates that, like wind and waves, concentrations of organisms such as zooplankton contribute to the mixing of nutrients in the water, particularly from nutrient-rich bottom regions, through a layer called the “pycnoline” that marks a sharp density change, to the more nutrient-depleted upper regions, where marine life tends to consume all the nutrients available to it.

Zooplankton-sized organisms are key players because they are numerous enough and large enough to have an effect. Tinier organisms are too small to create much mixing as they swim and larger fishes and marine mammals aren’t sufficient in number. Ardekani came to Purdue from Notre Dame and some of the research also took place on high-performance computing clusters at the Center for Research Computing there.

Research by Ardekani’s lab using computer modeling of fluid dynamics has applications in other areas including the formation of biofilms by bacteria as well as flow through porous media for enhanced oil recovery applications.

For information about Rice and Purdue’s other Community Cluster Program research supercomputers, email rcac-help@purdue.edu or contact Preston Smith, director of research services and support for ITaP Research Computing, 49-49729 or psmith@purdue.edu.

Originally posted: February 23, 2016  11:04am