A new mechanical engineering and physics study recently delved into the dynamics of heat transport in tilted porous materials, like Earth’s soil, uncovering how imperfections in boundaries can induce traveling behavior of localized convective cells that transfer heat across the porous material. Using U.S. National Science Foundation (NSF) ACCESS allocations on Advanced Research Computing at the Johns Hopkins (ARCH) core facility and Purdue University’s Anvil supercomputer, the scientists’ findings could pave the way for a better understanding of heat transfer in various systems – ranging from industrial applications to natural phenomena.

Recently published in the Bulletin of the American Physical Society, the research was presented at the 77th Annual Meeting of the Division of Fluid Dynamics. The work was conducted by Zhiwei Li (University of Washington), Chang Liu (University of Connecticut), Adrian van Kan (University of California at Berkeley) and Edgar Knobloch (University of California at Berkeley).

When the bottom of an inclined porous layer is heated while the top is cooled, the resulting convection takes the form of distinct patterns of spatially localized clusters of convection cells that transfer heat across the layer. Previous research revealed that these structures can coexist in surprising ways, but until now, scientists haven’t explored what happens when the upper boundary is partially insulating.

Liu, an assistant professor of mechanical engineering, said the team used ACCESS allocations on ARCH and Anvil to create advanced computer simulations examining how localized heat patterns behave when the boundary at the top is partially insulating. “It turns out that different values of the Biot number in the top and bottom boundaries, which measures how well heat is conducted at the boundary, break the symmetry between the lower and upper boundaries,” he said. “The effect is striking: as the symmetry of the system was disrupted, the heat pulses started to ‘drift’ either upslope or downslope, depending on the number of pulses and the symmetry-breaking parameter, among others.”

He said that the heat pulses consistently moved upslope for small domains, but in larger domains the travel direction and speed became more complex.

The team’s study also used simulations on ARCH and Anvil supercomputers to uncover a key transition point: when the conductivity of the boundary crosses a critical threshold, the behavior of flow patterns changes dramatically. Below this threshold, convection cells can cluster tightly and interact in dynamic ways, including bouncing off each other to form new patterns. Above it, they spread out, repelling each other, forming equispaced configurations.

The results could inform designs for efficient heat management in engineering and improve models of natural processes like subsurface heat flow in Earth’s crust.

-Chang Liu, Assistant Professor of Mechanical Engineering at University of Connecticut

“Our findings provide a clearer picture of how fluid flows, which transfer heat, evolve in real-world systems where boundaries have imperfect conductivity,” Liu said. “The results could inform designs for efficient heat management in engineering and improve models of natural processes like subsurface heat flow in Earth’s crust.”

Resource Provider Institution(s): Johns Hopkins (ARCH), Purdue University (Anvil)
Affiliations: University of Washington, University of Connecticut, University of California at Berkeley
Funding Agency: NSF
Grant or Allocation Number(s): PHY230056

The science story featured here was enabled by the U.S. National Science Foundation’s ACCESS program, which is supported by National Science Foundation grants #2138259, #2138286, #2138307, #2137603, and #2138296.