共查询到20条相似文献，搜索用时 31 毫秒
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This paper proposes a novel strategy for the investigation of displacement amplitude () near and along an oblique-truncated semicircular canyon subjected to shear horizontal (SH) waves. Transfinite interpolation (TFI) was used to obtain the coordinates of nodes and determine the sequence of node numbering in the inner finite region including the canyon. The hybrid method, comprising finite element method and a Lamb series, was applied in conjunction with TFI to study the effects of canyon geometry, incident angle of SH waves (), and dimensionless frequency () on . We detailed the amplification of in the illuminated zone and variations in due to canyon-decay-effect along the canyon surface as well as the decay of resulting from the shield effect in the shadow zone. Interestingly, oblique-effects play an important role in the magnification of along the inclined bottom of canyons, and variations in and dominate the patterns of . 相似文献
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One-dimensional flows of gravity currents within horizontal and inclined porous channels are investigated combining theoretical and experimental analysis to evaluate the joint effects of channel shape and fluid rheology. The parameter governs the shape of the channel cross section, while the fluid rheology is characterised by a power-law model with behaviour index n. Self-similar scalings for current length and height are obtained for horizontal and inclined channels when the current volume increases with time as .For horizontal channels, the interplay of model parameters , and governs the front speed, height, and aspect ratio of the current (ratio between the average height and the length). The dependency is modulated by two critical values of and . For all channel shapes, discriminates between currents whose height decreases () or increases () with time at a particular point. For all power-law fluids, discriminates between decelerated currents, with time-decreasing aspect ratio (), and accelerated currents, with time-increasing aspect ratio (). Only currents with time-decreasing height () and aspect ratio () respect model assumptions asymptotically; the former constraint is more restrictive than the latter.For inclined channels, a numerical solution in self-similar form is obtained under the hypothesis that the product of the channel inclination and the slope of the free-surface is much smaller than unity; this produces a negligible error for , and is acceptable for . The action of gravity in inclined channels is modulated by both the behaviour index n and the shape factor . For constant flux, the current reaches at long times a steady state condition with a uniform thickness profile. In steep channels and for sufficiently long currents, the free-surface slope becomes entirely negligible with respect to channel inclination, and the constant thickness profile depends only on n.Theoretical results are validated by comparison with experiments (i) in horizontal and inclined channels with triangular or semicircular cross-section, (ii) with different shear-thinning fluids, and (iii) for constant volume and constant flux conditions. The experimental results show good agreement with theoretical predictions in the long-time regime.Our analysis demonstrates that self-similar solutions are able to capture the essential long-term behaviour of gravity currents in porous media, accounting for diverse effects such as non-Newtonian rheology, presence of boundaries, and channel inclination. This provides a relatively simple framework for sensitivity analysis, and a convenient benchmark for numerical studies. 相似文献
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It is important to examine the ratio of measured to total sediment discharge to determine the error in measured sediment transport rates from depth-integrated samplers. The ratio of measured to total sediment discharge as well as the ratio of suspended to total sediment discharge are examined based on the Modified Einstein Procedure. Both ratios reduce to a function of the ratio of shear velocity, , to the fall velocity, , of suspended material, , and the ratio, , of flow depth, h, to the median grain size of bed material, . In rivers transporting fine material (such as silt or clay), the ratio of suspended to total load is a function of the ratio, . In this study, it is found that the ratio of measured to total load becomes a simple function of flow depth. For fine sediment transport, with a Rouse number (Ro) , at least 80% of sediment load is in suspension when , and at least 90% of sediment load is measured from depth integrating samples when . Detailed measurements from 35 river stations in South Korea demonstrate that sand sizes and finer fractions predominantly are transported in suspension. Also, at least 90% of sand and finer fractions are transported in suspension in gravel and sand bed rivers when the discharge is larger than the mean annual discharge. 相似文献
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