The flow field behind non-planar porous fence of geometric porosity ε=0.273 with various bottom gaps (G) has been investigated by hot-wire anemometer velocity field measurement technique in a wind tunnel experiment. Seven gap ratios G/H=0.000, 0.025, 0.075, 0.125, 0.150, 0.175, 0.200 of non-planar porous fence were tested in this study with the free-stream velocity fixed at 10m/s. The experimental data were analyzed and the turbulence intensity and wind reduction ratios for different gaps of the porous fence were calculated to estimate the shelter effect of a non-planar porous fence model. The results show that the gap ratio G/H=0.150 gives the best shelter effect among the seven gaps of the non-planar porous fence tested in this study, having a better mean velocity and turbulence intensity as well as wind reduction ratio in a large area behind the non-planar porous fence.

The low-quality factor is a key bottleneck for the engineering and commercial application of graphene nanoelectromechanical resonators at room temperature. The hypothesis in dissipation dominated by the ohmic loss is difficult to cover this phenomenon. Mechanical loss may still be on the list of the main causes for the quality factor stress-modulation characteristics of graphene resonators. The dissipation dilution theory reveals the intrinsic energy and dissipation mechanism of the traditional high-stress silicon-based resonator, which may also be applied to two-dimensional (2D) materials if dominated by mechanical loss. Based on Zener’s model of anelasticity, combined with the edge-corrected mode shape, the stress dilution mechanism of the bending potential dissipation of the graphene resonator is revealed. On this basis, the resonator dissipation is decomposed into boundary dissipation and non-boundary dissipation parts, and the steep rise phenomenon of the bending dissipation density (curvature) in the boundary region is analyzed through theoretical calculation. The analysis reveals that boundary dissipation is dominant in bending dissipation. To effectively suppress the boundary dissipation, a novel design of a graphene resonator via soft-clamped phononic crystal (PnC) is proposed. The existence of localized mode (LM) and effective suppression of boundary dissipation are verified in the simulations of both triangular and honeycomb PnC lattices. The theoretical model developed in this paper provides a new window into the dissipation properties of graphene nanoelectromechanical resonators, and the design of graphene resonators via soft-clamped PnC is expected to provide a new route toward high-quality factors at room temperature.