Landslides into water can generate massive tsunamis which are major natural hazards in coastal regions. In this study, waves were generated in a series of 41 laboratory experiments by releasing 4 ...different slide volumes ranging from 0.1-0.4 m3 of highly mobile material down a 6.73 m long slope into a reservoir of depth varying from 0.15-0.65 m, to achieve a wide range of dimensionless landslide parameter values. Water is used as the sliding material and with zero internal shear strength it is representative of the upper limit of high landslide mobility. The slide characteristics of thickness and velocity were measured at impact using high speed cameras and the time series of the resulting changes in water surface elevation were measured using nine wave probes along the 33.8 m long flume. The experimental results indicate that in the near-field the maximum wave amplitude is dependent on the landslide thickness and velocity and is relatively independent of the reservoir water depth. As waves propagate to the far-field, the depth-limited breaking reduces the wave amplitude, such that the maximum wave amplitude is highly dependent on the reservoir depth. The wave breaking limit, which differentiates the breaking from the non-breaking waves, is defined by the relationship am/h = 0.6 that is very closely adhered to for all source volumes and reservoir depths. The time and length over which the waves are generated are determined from the digital imagery, and are used to describe the scales of the momentum transfer. These observations are compared with previously published empirical and theoretical equations for granular landslides and positively buoyant avalanches, indicating that water is a useful source material for simulating highly mobile landslides. Since these parameters are difficult to obtain in field cases, a simplification of the theoretical equation is presented and this yields reasonable results for the maximum wave amplitude generated by slides with high mobility.
•Amplitudes of near-field waves generated by highly mobile flows are independent of slide volume for a given reservoir depth.•Depth-limited breaking is the primary control on the wave amplitude as waves propagate into the far-field.•Effective time and length of forcing are important factors that influence momentum transfer.
Assessment of strength anisotropy has been one of the most challenging subjects in rock mechanics and civil engineering. The orientation of the discontinuity plane, the aggregate distribution, and ...the specimen size have a significant influence on the mechanical properties of rock and cementitious materials. This study aims to evaluate the effect of anisotropy on uniaxial compressive strength, elastic constants, and destruction-specific energy using physical modeling. For this purpose, different concrete blocks were produced in which aggregate sizes of 9.5, 12.5, and 19 mm were used. Different cylindrical specimens with diameters of 45, 69, and 94 mm were prepared. A suite of laboratory testing was performed on prepared concrete samples as a function of discontinuity plane angle (α=30°,45°, and 60°), including uniaxial compressive strength and deformability tests. The results obtained have shown that the mechanical properties of cementitious materials have different values concerning the banding plane, aggregate size, and specimen volume. It was shown that the uniaxial compressive strength and tangent modulus of elasticity show the highest values in low discontinuity plane angle than those obtained in the other directions. However, in concrete mixtures with a grain size of 0-19 mm, an increasing-decreasing trend of strength behavior was observed with ascending the orientation of the discontinuity plane from 30° to 60°. The findings presented indicated that with increasing aggregate size, strength properties descend due to the rise in heterogeneities that affect failure modes. Finally, it was revealed that when specimen size increases from 69 to 94 mm in diameter, led to significant rises in the values of compressive strength and elasticity modulus in cementitious materials.
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•Strain sensors comprising polydopamine(PDA)-coated textiles with incorporated silver nanowires(AgNWs) were developed.•3.37 wt.% AgNWs and1.39 wt.% PDA gave 99 % antibacterial effect ...against E.coli and S. aureus, a fracture strain of 400 %.•99% SE against X-band EM waves, a strain sensitivity up to 457.1 and a strain sensing range up to 300 %.•Mathematical methods developed to analyze strain-resistivity correlation and address signal drift under cyclic strain.
For wearable smart textile sensors, stability, accuracy and multi-functionality are key objectives. Achieving the optimal application requires delicately balancing the crucial physical properties of strain sensors, presenting a key technological challenge. This study addresses these challenges by presenting several properties and potential applications of a triple hierarchic polymeric knitted fabric. The fabric incorporates an internal conductive network constructed with silver nanowires (AgNWs) and polydopamine (PDA) coating on its outer surface. This innovative textile successfully strikes a balance between strain sensing and electromagnetic interference shielding while concurrently exhibiting biocompatibility and antimicrobial properties. Significantly, acknowledging the susceptibility of measurements from polymer-based strain sensor materials to time drift, we introduce both a modeling approach and a novel calibration technique. This advancement facilitates the generation of stable cyclic sensing signals, even under substantial deformations of up to 80 % at a high stretching speed. Importantly, it provides a practical solution for addressing signal drift observed in flexible sensors when utilized in environments characterized by long-term and large deformations.
Tropical peat swamp forest becomes degraded through forest removal and drainage, usually followed by land use change and fire. Restoration of the degraded peatland requires rewetting, which involves ...canal blocking and water level management. The purpose of canal blocking is to rewet the peat so that peat-forming trees can re-establish or crops be grown with minimal greenhouse gas emissions and peat subsidence. In addition, wet peat is more fire resistant than degraded dry peat. Canal construction faces several technical problems, including stress that causes bending, water seepage under the dam, and erosion of peat by water forcing its way around the sides when the water level upstream exceeds the dam height. This research examined the behaviour of water flows in canals in peatland in Central Kalimantan after blocking with dams of different designs. This study used a survey method and hydraulic physical model test with a horizontal scale of 1:30 and a vertical scale of 1:10. Field measurements were carried out on the primary canal of the former Mega Rice Project (MRP) Block C to build a physical model test prototype for laboratory research, includes measurement of cross-sections, canal length and water flow for a distance of 100 metres upstream and downstream of the construction. The test included three types of the physical model, reviewed for the effect of flow patterns caused by flood discharge frequencies of 5, 25, 50 and 100 years. The effects of flow patterns on canal dam construction in peatland were obtained from the physical model test.
Driftwood is abundant in coastal zones, and is increasingly being incorporated in nature-based shore protection and restoration projects. However, accumulations of driftwood, and their mobilization ...by storms or other disturbances, can pose hazards to coastal communities, infrastructure, and ecosystems. An improved understanding of driftwood dynamics in nearshore, wave-dominated environments is needed to inform sustainable use and management of wood in coastal zones. An optical tracking technique was applied to quantify mean transport and dispersion of driftwood in a 1/30 Froude-scaled coastal model exposed to oblique waves. The results provided new insight to factors controlling driftwood mobility and dispersion on beaches exposed to oblique waves, including the effects of sea state, wave-induced currents and circulation, water levels, driftwood length, driftwood roughness, driftwood buoyancy, and coastal structures.
•Surf-zone driftwood transport correlates with Hs2Tp−1 when unconstrained by shore interactions.•Offshore transport by rip currents is countered by breaking waves, Stokes drift, and beach friction.•Vertical profiles of wave-induced velocities affect driftwood interactions with the shore.•Structure length at the water line relative to driftwood length influences trapping potential.•Driftwood length, roughness and buoyancy all influence beaching and mobility.
The applicability of pressure-impulse theory is evaluated for predicting wave impact loading magnitudes for non-breaking standing wave impacts on vertical hydraulic structures with relatively short ...overhangs. To this end, tests were carried out on a schematized but realistic configuration with low steepness regular wave impacts on a straight overhang perpendicular to a vertical wall. This paper aims to fill the existing knowledge gap on this type of wave impact with reliable and simple expressions. Pressure-impulses and force-impulses are the wave impact loading magnitudes considered in this study, which are defined as the integral of the impulsive pressures/forces over time during a wave impact. These impulses can be used to determine the resulting stresses in a structure for sudden, impulsive loads. The proposed theoretical model is based on the pressure-impulse theory and validated with laboratory experiments. The laboratory tests are done with regular waves for relatively short overhangs, with ratios of wave length to overhang length between 12.1 and 43.6, and ratios of overhang height to overhang length of 3 and 6. Thus, the theory is verified for conditions where the wave impact takes place along the full length of the overhang. From the experimental results, a mean effective bounce-back factor β=1.17 is obtained, accounting for the bounce-back effect of entrapped air and other secondary sources of discrepancies between theoretical and experimental results. The standard deviation of β for all the different tests is σβ=0.11. This method seems suitable for carrying out preliminary loading estimations, including the pressure-impulse profile at the wall and the total force-impulse at the wall. This study also shows that the force-impulse is a more stable magnitude compared with the force peaks, with about half the relative standard deviation. The impulses predicted by this model are recommended to be coupled with fluid-structure interaction models for analysing the response of the loaded structure.
•This paper addresses wave impacts on vertical hydraulic structures with overhangs caused by standing waves.•Pressure-impulse theory is thoroughly validated for standing wave impacts on vertical structures with short overhangs.•The effective bounce-back factor for standing wave impacts on short overhangs is determined at β = 1.17 (σβ = 0.11).•Pressure-impulse theory is a promising method to determine wave impact loadings on hydraulic structures with overhangs.•The peak forces are confirmed to have a larger variability than the force-impulses.
A combination of physical modeling, computational fluid dynamics modeling, and economics with plant trial studies was performed for quality improvement of Special Bar Quality (SBQ) and Oil Country ...Tubular Goods (OCTG) grade tundish steels. The present study consists of operating parameters like inert gas shrouding, non-isothermal conditions, and flow control devices (FCD) used on the billet product and slab quality. This work uses mathematical modeling using the fluid volume and discrete phase method (DPM) and the standard k-ε turbulence model validated with one-third scale physical water model experiments. A strong correlation between the physical model and computational simulation was found with rejection ratio and inclusion counts. Data about customer demands correlated with operating parameters for proper plant insights with an economic study to predict the cost-related issue. With the incorporation of FCD, the weight of the tundish skull was reduced by 6–10 M USD/year with a simulation studies expenditure of around 200 K. FCD also reduced the customer complaint index (CCI).
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Two-step thermochemical water splitting using concentrated solar power offers promising potential for green hydrogen production as a part of a future sustainable energy economy. In this study, a ...system and energy flow analysis of a large scale 250 kW reactor prototype is presented by using a complex 3D-simulation model. Thus, the physical dynamic system behavior and potential efficiency improvements are discussed with respect to plant design and operational strategy. Regarding the plant design, different kind of heat losses as well as the influence of reactor design parameters and material modifications are analyzed. Regarding the operational strategy, crucial control parameters as cycle durations, temperatures, and mass flow rates are varied in a broad range and analyzed with respect to plant efficiency. By comparing commonly used operational strategies, the temperature swing operation turns out to be by far more efficient than any isothermal or near-isothermal operation for the current plant concept.
•Solar-driven thermochemical water splitting as a perspective for efficient hydrogen production.•System and energy flow analysis of a large scale fixed-bed thermochemical reactor prototype.•System analysis regarding different temperatures, mass flow rates and design modifications.•Potential efficiency improvement is determined regarding plant design and operational strategy.
Air compressibility is often neglected in experimental work due to practical difficulties, even though it is known to affect the performance of OWC wave energy converters. The key question, of ...course, is to what extent. In this work the impact of air compressibility on the capture width ratio is thoroughly quantified by means of a comprehensive experimental campaign, with no fewer than 330 tests encompassing a wide range of wave conditions and levels of turbine-induced damping, and two experimental set-ups: one designed to account for air compressibility, the other to neglect it. This approach is complemented with the use of the RANS-based CFD model OpenFOAM® to calibrate the pressure-vs-flowrate curves, which enables the flowrate to be determined based on the pressure drop measurements from the physical model. We find that the errors that derive from disregarding air compressibility may lead to either under- or over-predictions of power output, and are highly dependent on the operating conditions, more specifically the wave conditions (sea state) and turbine-induced damping.
•Air compressibility is often neglected in assessing OWC converters' efficiency.•We quantify the effects of this neglect on the capture width ratio assessment.•Using an extensive laboratory programme (330 tests) and state-of-the-art CFD.•We find that the effects depend primarily on sea state and turbine damping.•We prove that neglecting air compressibility results in significant errors.
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