Rough Surface Effect Research Articles

An improved B-L model for dynamic stall prediction of rough-surface airfoils

The Beddoes-Leishman (B-L) semi-empirical model is a classical method for predicting the dynamic stall of wind turbine airfoils. However, the model performs poorly for rough-surface airfoils due to the premature entry of turbulence and stall condition under the roughness effect. In this study, an improved dynamic stall model is developed for rough-surface airfoils. Two corrections are involved in the modifications. First, the calculation of flow separation points is corrected considering the difference between the normal and tangential separation points, and then an attenuation coefficient is introduced for the effective angle of attack to account for the rough-surface effect. Subsequently, the proposed model is extensively verified by experimental data of S-series airfoils with rough surfaces. Results show that the proposed model can well predict the dynamic stall characteristics of rough-surface airfoils with a higher accuracy than that of the original B-L model under various mean angle of attacks, oscillating amplitudes and reduced frequencies. At last, the model is utilized to predict the operating loads of a wind turbine using the Blade-Element Momentum theory. Significant difference between the dynamic loads predicted by smooth and rough models is observed. This indicates that the roughness effect on the dynamic stall model as well as the prediction of the operating loads on wind turbines cannot be ignored.

Rough surface effect in terahertz near-field microscopy: 3D simulation analysis.

Terahertz scattering-type scanning near-field optical microscopy (THz-s-SNOM) has emerged as a powerful technique for high-resolution imaging. However, most previous studies have focused on simplified smooth surface models, overlooking the realistic surface roughness induced by contamination during sample preparation. In this work, we present a novel 3D model, to the best of our knowledge, that combines the point dipole model with the finite element method to investigate the influence of sample morphology on scattered signals. We explore surfaces with a protrusion, a depression, and random roughness, characterizing the variations in scattered signals and highlighting the role of higher-order scattering in mitigating surface roughness effects. Our findings provide valuable insights into the impact of sample morphology on THz-s-SNOM imaging.

Rough-surface effect on sputtering of Cr bombarded by low-energy He plasma

• Microscopic cones grow on a Cr surface during He plasma exposure. • Angular distribution of sputtered atoms becomes more over-cosine-like (narrower). • Sputtering yield is significantly reduced. • GITR coupled with SDTrimSP simulations reproduce the experimental findings. The formation of microscopic cone-like structures on a Cr surface is observed under He plasma exposure at a low incident ion energy of ∼106 eV in the PISCES-A linear plasma device. 2D emission profiles of the Cr I line intensity, measured with a hyperspectral imaging camera, are compared with those modeled using the GITR Monte Carlo impurity transport code coupled with the SDTrimSP binary collision code. With the growth of cones, the experimental 2D emission profile becomes axially elongated and the emission intensity significantly drops, and these observations are successfully reproduced in the simulation. The simulation reveals that the deposition of sputtered Cr atoms onto the neighboring cones results in a more over-cosine-like angular distribution, i.e., a narrower distribution with more particles ejected in the surface normal direction, of sputtered Cr atoms with a significant reduction of the sputtering yield.

Investigation of Sea Surface Effect on Shallow Water Reverberation by Coupled Mode Method

The effects of rough sea surface on the long-range bottom reverberation in shallow seas are studied by the coupled mode reverberation theory. The scattering effect caused by irregular rough sea surface is described by couple coefficients. The decaying rules of long-range bottom reverberation level are simulated at different sea states, and the rough sea surface effect on the coherence of distant bottom reverberation is also discussed. It is indicated that irregular upper boundary has changed the propagation effect of the shallow water waveguide, and bottom reverberation, which is dominated among other kinds of reverberation in shallow water, is affected by the sea surface scattering as the increasing sea state. Compared with other literatures, the emphasis of this paper is to present the mechanism of rough sea surface scattering by describing the transfer of energy between different modes, and the details of energy transitions between different modes which are caused by sea surface scattering are presented for different sea states. With the increasing sea state, stronger mode coupling caused by surface scattering would affect the intensity and its space coherence of bottom reverberation obviously.

Rough Surface Effect on a Broken Time-reversal Pairing State in d-wave Superconducting Films

We investigate the effect of a rough surface on the normal-superconducting phase transition in d-wave superconducting films on the basis of the quasiclassical theory of superconductivity with a boundary condition that allows us to treat the surface scattering from the specular limit to the diffusive limit. When the surfaces are specular, the film can exhibit a novel superconductivity that breaks continuous translational symmetry along the surface as well as time reversal symmetry. When the surfaces are rough, this superconducting phase is suppressed by diffusive surface scattering.

High-performance vertical hydrogen sensors using Pd-coated rough Si nanowires

We fabricated Pd-coated rough Si nanowires, using a combination of Si electroless etching and Pd sputtering. The semi-densely distributed, vertical-standing rough Si nanowires, which were clustered locally with inter-cluster distances of several nm to several μm, were selected as a basal platform. Pd was coated only on the upper part of the Si nanowires in the semi-dense configuration, and their surface profile replicated the surface morphology of Si nanowires. The Pd-coated rough Si nanowires showed good reversibility and excellent hydrogen-sensing performance in terms of sensitivity (>300%), response time (<3 s), and detection limit (∼5 ppm). These attributes are discussed in terms of the vertical-standing nanowire structures and the rough surface effect of the nanowires. Interestingly, the variation in sensitivity of the Pd-coated Si nanowire sensors was divided into two regimes, which appeared in the low and high hydrogen concentration ranges, respectively. A simple model is also provided to account for this unusual finding.

Improvement of Tear Strength using Dielectric Barrier Discharge Plasma

In the our study, an improvement of the tear strength of the bonded resin material using an atmospheric dielectric barrier discharge plasma treatment is described. The surface treatment experiments were carried out on the surface of the polyimid films with the air and the air with an argon as a operation gas for various treatment times. The 20 kVP-P, 2 AP-P and 45 kHz power supply was used to produce an atmospheric discharge plasma with the mixture of air and small amount of argon. The contact angle on the treated surface was significantly decreased from 40-50 degree to less than 10 degree by the this plasma treatment. This suggested the removal of the organic contaminant and the enhancement of the wettability to an adhesive. The peeling test of the bonded resin materials was adopted to study the tear strength in both cases with and without plasma treatment. The results showed that the tear strength was successfully improved by more than 3 times of that measured for the bonded un-treated films. We could conclude that the surface of the polyimid film was successfully treated by the atmospheric dielectric barrier discharge plasma and that the organic contaminants which inhibited the adhesion was removed. In addition, the adhesive property also affects rough surface effect and active effect of the surface(1)-(3). And the adhesive property can be improved by them. As a result, a significant improvement of the tear strength of the resin materials was achieved.

Water-scattered signal to compensate for the rough sea surface effect on bottom lidar imaging

We investigate the possibility of using the water-backscattered radiation from a bottom sounding airborne imaging light detection and ranging (lidar) system to determine the surface slope at the point where the laser beam intersects the surface. We show that the refraction angle of the beam can be determined using receivers whose sensitivities vary linearly over their field of view. Equations are derived to estimate the statistical mean and variance values of this refracted angle. We demonstrate that the proposed algorithm improves lidar imaging. Numerical examples with reference to typical marine conditions are given.

Rough Surface Effect on Diamagnetic Response of Normal-Superconducting Proximity Contact System with Arbitrary Concentration of Impurities

A quasi-classical theory of rough surface effect on diamagnetic response is developed for normal-superconducting proximity contact systems with arbitrary concentration of impurities. We calculate the diamagnetic current and the screening length of the normal layer taking into account the surface roughness by use of the thin dirty layer model. We propose an analytic treatment of the thin dirty layer model. The surface roughness has a considerable effect in the clean limit and also when the mean free path is comparable with the normal layer width. In dirty systems, while the diamagnetic current is significantly reduced near the rough surface, the screening fraction is not so much affected by the surface roughness in the whole temperature range.

Rough Surface Effect on Meissner Diamagnetism in Normal-Layer of N–S Proximity-Contact System

Rough surface effect on the Meissner diamagnetic current in the normal layer of proximity contact N-S bi-layer is investigated in the clean limit. The diamagnetic current and the screening length are calculated by use of quasi-classical Green's function. We show that the surface roughness has a sizable effect, even when a normal layer width is large compared with the coherence length $\xi =v_{\rm F}/\pi T_{\rm c}$. The effect is as large as that of the impurity scattering and also as that of the finite reflection at the N-S interface.