Wave breaking over a submerged step with a steep front slope and a wide horizontal platform is studied by smoothed particle hydrodynamic (SPH) method. By adding a momentum source term and a velocity attenuation term into the governing equation, a nonreflective wave maker system is introduced in the numerical model. A suitable circuit channel is specifically designed for the present SPH model to avoid the nonphysical rise of the mean water level on the horizontal platform of the submerged step. The predicted free surface elevations and the spatial distributions of wave height and wave setup over the submerged step are validated using the corresponding experimental data. In addition, the vertical distributions of wave-induced current over the submerged step are also investigated at both low and high tides.
Ultrathin
two-dimensional (2D) metal–organic framework (MOF)
nanosheet membranes have shown significant promise for gas separation
application because of their excellent molecular transport characteristics.
However, the preparation of oriented 2D MOF membranes by direct growth
remains challenging, especially on tubular substrates. In this study,
we propose a bottom-up strategy to prepare a highly oriented 2D Co2(bIm)4 (bIm = benzimidazole) membrane via the conversion
of Co(OH)2 sheets with assistance from graphene oxide (GO)
in organic ligand synthetic solution. Both the introduced GO and Co(OH)2 layers play important roles in inducing the highly oriented
growth of stable 2D Co2(bIm)4 membranes. The
obtained 2D Co2(bIm)4 membrane of around 210
nm in thickness displays outstanding separation properties. The permeance
for H2 is 2.54 × 10–7 mol·m–2·s–1·Pa–1, and the ideal selectivities for H2/CO2, H2/N2, and H2/CH4 are as high
as 23.1, 18.5, and 28.7, respectively. This approach opens up a new
avenue via a direct growth method for preparing highly oriented MOF
nanosheet tubular membranes for efficient gas separation.
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