GPUSPH at Northwestern University

Waves Propagating over a Reef

This project, lead by Dr. Rozita Jalali Farahani, used GPUSPH to examine the wave breaking over a reef, comparing the results to a laboratory wave tank test. The work showed the ability of the SPH model to replicate wave processes, such as wave breaking, setup, wave-induced nearshore circulation, and wave-current interaction. See Jalali Farahani, R., R.A. Dalrymple, A. Hérault, and G. Bilotta, “Three Dimensional SPH Modeling of a Bar/rip Channel System,” Journal of Waterways, Ports, Coastal Engineering, 140 (1), 82-99, 2014.
Journal paper (ASCE $$$)

Coherent Turbulent Structures

GPUSPH was used to examine the coherent turbulent structures under a breaking solitary wave. The image above shows the evolution of the coherent turbulence under the breaking wave crest as seen by an observer moving with the wave crest, and how these eddies can be an explanation for obliquely descending eddies. (Jalali Farahani, R. and R.A. Dalrymple, “Three-dimensional horseshoe vortex structures under a broken solitary wave,” Coastal Engineering, 91, 261-279, 2014.)
Journal paper

Tsunami Impact on Column

GPUSPH was used to model the experiments of Arnason, Petroff, and Yeh (2009), which examine the forces exerted on various shaped columns by a surge of water from a dam break (simulating a tsunami). Wei, Z., R.A. Dalrymple, A. Hérault, G. Bilotta, E. Rustico, H. Yeh, “SPH modeling of dynamic impact of tsunami bore on bridge piers,” Coastal Engineering, 104, 26-42, 2015.
Journal paper

Tsunamis at the Shoreline

This validation work led by Zhangping Wei compares GPUSPH solitary wave calculations to laboratory experiments of Hsiao and Lin (2010). The snapshots above show the evolution of wave breaking on a dike on a slope. (Wei Z., R. A. Dalrymple, E. Rustico, A. Hérault, G. Bilotta, “Simulation of Nearshore Tsunami Breaking by Smoothed Particle Hydrodynamics Method,” Journal of Waterway, Port, Coastal, and Ocean Engineering, 142, 4, 2016.)\\

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Journal paper (ASCE $$$)

Intersecting Waves and Nearshore Circulation

This project examined the surf zone when the waves are short-crested, here due to synchronous intersecting waves. The surprising nonlinear diffraction of waves across the nodal lines (dashed red lines) led to isolated wave crests that, in turn, diffracted. This phenomena led to the increase in the alongshore wave number closer to shore and an increase in the number of rip current cellular structures.
Wei, Z., R. A. Dalrymple, M. Xu, R. Garnier, and M. Derakhti, “Short-crested waves in the surf zone,” Journal of Geophysical Research, Oceans, 122, DOI:10.1002/2016JC01248, 2017.
Journal paper

Tsunami Attack on a Bridge

This project examined the tsunami attack on bridges with different cross-sections. The image shows various times of a tsunami impact, colored by fluid velocity. The flow under the bridge is shown to be much faster than in the near field, leading to low pressure under the bridge, due to Bernoulli effects. Reference: Wei, Z., and R.A. Dalrymple, “Numerical study of mitigating tsunami forces on bridges by an SPH model,” J. Ocean Engineering and Marine Energy, DOI 10.1007/s40722-016-0054-6, 2016.
Journal paper

Lava Flowing over Topography

Flowing lava is a far more complex fluid than water. The very high viscosity of lava is temperature dependent and the lava can solidify. A temperature equation is an additional computation step to allow for the correct flow of the lava. The figure above shows lava flowing down a smooth valley and one with topographic variation. The colors denote the lava temperature, which is cooling as it moves away from the volcanic source. The high viscosity of the lava requires very small time-steps and so an implicit method is used to integrate the equations. ( Zago, V., G. Bilotta, A. Hérault, R.A.Dalrymple, L. Fortuna, A. Cappello, G. Ganci, C. Del Negro, Semi-implicit 3D SPH on GPU for lava flows, J. Computational Physics, 375, 854-870, 2018.)
Journal paper

Modeling Wave Energy Converters with GPUSPH

The coupling of GPUSPH with Project Chrono for rigid body dynamics allows the modeling of moving fixed or floating structures. Above is a simulation of waves overtopping a bottom-mounted flap, like the Oyster device. (Wei, Z., B.E. Edge, R.A. Dalrymple, and A. Hérault, Modeling of wave energy converters by GPUSPH and Project Chrono, Ocean Engineering, 183, 2019.)
Journal paper