Bed Conditions Research Articles

TSUNAMI RUN-UP CONSIDERING TIME VARIATION OF DENSITY OF INUNDATION WATER

Aiming for the advancement of tsunami load, historical and/or prospective tsunami scale evaluations, practical empirical formulas for evaluating friction factor K of inundation flow and density ρ of inundation water over a movable bed, which can be applied to a tsunami run-up theory, are proposed using experimental data whose amount (range) is increased (expanded) by carrying out additional experiments on ρ and run-up of inundation flow with sediment, and verification data of the above theory under a uniformly sloping movable bed condition are provided. Series solutions with a higher universality to the run-up of tsunami inundation flow with sediment over a uniformly sloping movable bed, in which both K and ρ depend on time, are derived under the conditions depending on an incident bore height h1 at shoreline (or an initial stored water depth), bed slope i, median particle diameter d50 of initial bed material, and examples of the solutions are shown. The solutions are applicable to the case that ρ is independent on time, i.e., the case of inundation flow without sediment over a movable bed or fixed bed. Including the case of inundation flow without sediment, validity of one of the solutions is also verified through a comparison with the verification data on run-up distance.

Effect of channel bed sediment on the transport behaviour of superparamagnetic silica encapsulated DNA microparticles in open channel injection experiments

AbstractRecently, superparamagnetic silica encapsulated DNA microparticles (SiDNAFe) were designed and in various experiments used as a hydrological tracer. We investigated the effect of bed characteristics on the transport behaviour and especially the mass loss of SiDNAFe in open channel injection experiments. Hereto, a series of laboratory injection experiments were conducted with four channel bed conditions (no sediment, fine river sediment, coarse sand, and goethite‐coated coarse sand) and two water qualities (tap water and Meuse water). Breakthrough curves (BTCs) were analysed and modelled. Mass loss of SiDNAFe was accounted for as a first‐order decay process included in a 1‐D advection and dispersion model with transient storage (OTIS). SiDNAFe BTCs could be adequately described by advection and dispersion with or without a first‐order decay process. SiDNAFe mass recoveries exhibited a wide range, varying from 50% to 120% from sediment‐free conditions to coarse (coated) sediment. In 6 out of 8 cases, SiDNAFe mass recovery was complete. Retention of SiDNAFe was 1–2 orders of magnitude greater than gravitational settling rates, as determined in Tang et al. (Hydrological Processes, e14801, 2023). We reason this was due to grain‐scale hyporheic flows and coupled water‐sediment‐particle interactions. The dispersive behaviour of SiDNAFe generally mimicked that of NaCl tracer. We concluded that SiDNAFe can be used in tracing experiments. However, water quality and sediment characteristics may affect the fate of SiDNAFe in river environments. SiDNAFe is a promising tool for particulate multi‐tracing in large rivers.

Effect of Lubrication Pattern on the Performance of a Small Turbojet Engine

A small turbojet engine has been designed for UAV application and is intended to operate at high altitude and high subsonic speed. The mist lubrication system adopted initially for bearing to support a rotor speed of about 30000 rpm has exhibited good performance under test bed condition but incurs oil starvation during altitude operation. The present paper evaluates the performance of a mist lubrication system during flight and its limitations and drawbacks. The paper also highlights the performance of a close-loop system at altitude operating conditions enabling the system to meet the flight goal. The effect of lubrication pattern on bearing performance has been studied during this exercise. The bearings are found to be cooler with respect to engine speed as well as with altitude when working with closed loop system within the operating range.

Ice-flow perturbation analysis: a method to estimate ice-sheet bed topography and conditions from surface datasets

Abstract One of the largest contributors to uncertainty in predictions of sea-level rise from ice-sheet models is a lack of knowledge about the bed topography beneath ice sheets. Bed topography maps are normally made by interpolating between linear radar surveys using methods that include kriging, mass conservation and flowline diffusion, all of which may miss influential mesoscale (2–30 km) bedforms. Previous works have explored an Ice-Flow Perturbation Analysis (IFPA) approach for estimating bed topography using the surface expression of these mesoscale bedforms. Using regions of Pine Island Glacier that have been intensively surveyed by ice-penetrating radar as test sites, and a refined IFPA methodology, we find that IFPA detects bedforms capable of influencing ice flow which are not represented in Bedmachine Antarctica and other interpolated bed products. We further explore the ability of IFPA to estimate relative bed slipperiness, finding higher slipperiness in the main trunk and tributaries. Alongside other methods which estimate ice thickness, bed topography maps from IFPA have the potential to constrain projections of future sea-level rise, especially where radar data are sparse.

Effect of soil on leakage rates in water distribution pipes

Abstract This paper describes an experimental and analytical study that examined the effects of soil on leakage rate from defective water pipes. An experimental model was designed and constructed to simulate idealized cracks in defective water pipes discharging into a bed of granular materials. Tests were run on three different materials: LBS-B, LBS-A, and glass ballotini with different characteristics. The results reveal that the presence of bedding material surrounding a leaking pipe causes a significant change in the leakage rate versus free flow conditions. The bedding has a greater impact on larger defect openings. There was a significant drop in the values of the coefficient of discharge (Cd) when the pipe discharged into a soil bed versus free flow conditions; this value was 38% lower for coarse particles and 70% for finer particles. The results also showed that high leakage rates could flow from the defective pipe without fluidization of the bedding materials. An analytical model based on the method of fragments was presented to predict the leakage rate after which the predicted results were compared with values measured experimentally.

The structural and textural characteristics of limestones and the effectiveness of SO2 sorption in fluidized bed conditions

The structural and textural characteristics of limestones and the effectiveness of SO2 sorption in fluidized bed conditions

Assessment and analysis of load-settlement characteristics for square model footings on sand beds enhanced with vertical pultruded fibreglass reinforced helical piles

ABSTRACT This article introduces an innovative ground enhancement technique using vertically oriented fiberglass pultruded pipes with helical bottoms. The study focused on prefabricated helical piles of varying lengths and cross-sectional areas as reinforcement in sandy soil. Experimental investigations were conducted on a laboratory model square footing on sand with Pultruded Fiber Reinforced Helical (PFRH) piles installed beneath. A parametric study analyzed the effects of PFRH pile slenderness ratio, sand bed conditions, and helical plate diameters using model plate load tests. Results showed significant improvements in settlement characteristics and load-carrying capacity with PFRH piles. Load capacity increased with the slenderness ratio up to 20, beyond which improvements were minimal. Denser sand enhanced bearing capacity without reinforcement, while PFRH piles performed best in medium-density sand. Larger helical plates also increased load capacity. Multivariate linear regression confirmed the reliability of the findings, highlighting the potential of prefabricated helical piles for soil reinforcement.

Impact of human wound exudate on the bactericidal efficacy of commercial antiseptic products.

By default, the antimicrobial efficacy of antiseptics used in wound management is tested in vitro under standardised conditions according to European standard DIN EN 13727, with albumin and sheep erythrocytes used as organic challenge. However, it is not clear whether these testing conditions adequately reflect the wound bed environment and its interaction with antiseptic products intended to be used in wounds in humans. This study compared the efficacy of different commercial antiseptic products based on octenidine dihydrochloride (OCT), polyhexamethylene biguanide (PHMB) and povidone-iodine under challenge with human wound exudate collected from the hard-to-heal wounds of patients, compared to the standardised organic load, in an in vitro setting according to DIN EN 13727. The bactericidal efficacy of the tested products was reduced to a different extent when challenged with human wound exudate, compared to the standardised conditions. Overall, OCT-based products showed the necessary germ count reductions at the shortest exposure times (e.g., 15 seconds for Octenisept (Schülke & Mayr GmbH, Germany)). PHMB-based products were the least efficient. In addition to the protein content, other components of wound exudate, such as the microbiota, seem to influence the efficacy of antiseptics. This study demonstrated that the standardised in vitro test conditions may only partially reflect actual wound bed conditions in humans.

Flow rate of solids through recycle chamber of loop seal in a circulating fluidized bed

This study investigated the flow rate of solids through the recycle chamber of a loop seal in a circulating fluidized bed (CFB) at atmospheric pressure and temperature. Flow characteristics of alumina particles were measured in the downcomer, horizontal passage, recycle chamber, and riser (0.05 m i.d., 2.7 m high).As the gas velocity in the riser increased, the pressure drop in the downcomer decreased, and thus, the aeration rate required at the bottom of the supply chamber to attain the minimum fluidization state for the bed of the downcomer increased. Based on experimental data, relationships that could predict the flow rate of solids through the recycle chamber Gs,r were derived by extending the correlation for the solids flow rate through the bubbling fluidized bed that discharged solids via overflow exit. Gs,r increased in proportion to the gauge pressure at the base of the recycle chamber. When the riser was under the fast bed condition, the back pressure against the flow of solids coming from the recycle chamber to the riser appeared significantly, and Gs,r was inversely proportional to the gauge pressure at the base of the riser. The derived relationships for Gs,r were in good agreement with measured data.

Bathymetry and bed conditions of Lago Subglacial CECs, West Antarctica

AbstractAlthough over 600 Antarctic subglacial lakes have been identified using radar and satellite observations, the bathymetry and bed properties, which are key to understanding conditions within the lake, have been determined in very few localities. We present measurements of water column thickness and lakebed properties from Lago Subglacial CECs (SLC), located beneath 2653 m of ice at the Rutford-Institute-Minnesota divide in Antarctica. Seismic profiles indicate a maximum water column thickness of 301.3 ± 1.5 m, at the widest part of the lake, with an estimated lake volume of 2.5 ± 0.3 km3. Seismic imaging and measurements of the reflection strength at the ice base and lakebed indicate >15 m of high-porosity fine-grained sediment in the central section of the lakebed, consistent with a depositional sequence with an age of up to 0.5 Ma. These observations, along with previous radar measurements and modelling, indicate a low-energy sedimentary environment with a long water-residence time. As such, SLC is a suitable target for exploration via direct access to recover sediment records of ice sheet and climate history and investigate microbial life with long periods of isolation.

Recoater crashes during powder bed fusion of metal with laser beam: simulative prediction of interference and experimental evaluation of resulting part quality

In powder bed fusion of metal with laser beam (PBF-LB/M), repetitive melting and solidification of newly added layers lead to thermal stresses and distortions during part build-up. Particularly at critical component features such as unsupported overhangs, super-elevated edges pose a risk in terms of crashes with the recoating system during powder spreading. Damaged recoater lips lead to irregularities in the form of stripes in the powder bed. These local inhomogeneities cause lack-of-fusion porosity and geometric defects on the part surface. However, quantitative information on important quality aspects, such as tensile properties, dimensional accuracy, roughness, and hardness of parts printed under irregular powder bed conditions is scarce. Here, we show that samples from build jobs with recoater crashes maintain their elastic tensile properties and hardness, but lose elongation at break. Finite-element simulations of in-process distortions are used to design an artifact that intentionally damages the silicone rubber lip of the recoater but does not cause machine breakdown. The lowest mean yield strength of the damage-affected samples is 243 MPa, which is still within the material data sheet limits for AlSi10Mg. Therefore, recoater crashes do not necessarily result in rejects, but users must consider the likely presence of porosity.

In Situ Analysis of Curling Defects in Powder Bed Fusion of Polyamide by Simultaneous Application of Laser Profilometry and Thermal Imaging

Additive manufacturing (AM) is one of the key technologies in the global manufacturing market within various application sectors. The unique capabilities of AM enable high structural and part complexity, low material waste, and benefits in productivity by reducing design cycles and time to market. Efficient real-time quality control is still an important challenge in AM. In this paper, a real-time and in situ approach for monitoring the process in powder bed fusion of polyamide (PBF-LB/P/PA12) is proposed using the simultaneous application of two individual sensors, enabling the overlay and direct comparison of independent output data. An industrial grade laser profilometer and a thermal infrared (IR) camera were successfully integrated into a commercial system for PBF-LB/P. Artificially created curling defects were induced in a reproducible way by the manipulation of process parameters. The radiometric data was evaluated and processed into 3D topology and profile measurements to highlight peaks and curling progression. The results measured using different powder bed conditions were contrasted with corresponding thermographic data to prove the thermal visibility of curling and the influence of inhomogeneous temperature distribution on geometrical powder surface defects. The experimental setup enables the measuring of the entire powder bed surface inside the machine, with no limitations to sub-areas. Results indicate the measurable presence of curling and related temperature influences. When curling reached maximum values, inverted warpage into the negative z-direction was detected at part center as a further effect. These results can be used for improving real-time quality control in AM.

MPS-based simulation of dam-break wave propagation over wet beds with a sediment layer

In this study, a two-phase mesh-free method is employed to simulate the dam-break wave propagation along different wet bed conditions in the presence of sediment. The method is based on the mixture theory and volume fraction is incorporated for both water and sediments. The pressure Poisson equation is explicitly solved to obtain the pressure field for the water and the pressure field for the sediment is calculated by using the rheology model. The method is validated by simulating submerged granular column collapse and dam-break flow over a sediment layer. The method can reproduce the interface variation between water and sediment. The validated model is then used to simulate the dam-break wave propagation in the presence of both downstream water and sediment. Different dam-break waves induced by the upstream water depths are simulated and it is found that the dam-break wave can make the sediment move violently. The larger downstream water depth can slow down the sediment movements while the sediment movements are violent for shallower water downstream.

Evaluating the effects of stream power on rill flow resistance

AbstractLimited information is currently available on how sediment transport affects rill flow resistance and the influence of hydraulic variables, as stream power, on sediment transport capacity for rill flows. In this paper, the available measurements of hydraulic variables (flow depth, channel slope, mean flow velocity, Reynolds number, Froude number, and Darcy–Weisbach friction factor) carried out by Ban et al. (Measurement of rill and ephemeral gully flow velocities and their model expression affected by flow rate and slope gradient. Journal of Hydrology, 589, 125172) and Ban (Measurements and estimation of flow velocity in mobile bed rills. International Journal of Sediment Research, 38(1), 97–104) for fixed and mobile bed rills are used to test the applicability of a theoretically deduced rill flow resistance equation based on a power‐velocity profile. The results allowed for stating that (i) the theoretical flow resistance approach can predict Darcy–Weisbach friction factor for flows over fixed and mobile beds, (ii) the stream power, dependent on flow discharge and slope, determines different flow behaviour, and (iii) the data are supportive of the slope independence hypothesis of rill velocity, for the mobile bed condition, only for the highest investigated discharge values (greater than 0.133 L s−1).

Mapping of seagrass ecosystem on Bontosua Island, Pangkep District, South Sulawesi, Indonesia

Abstract. Rosalina D, Jamil K, Arafat Y, Amalia R, Leilani A. 2023. Mapping of seagrass ecosystem on Bontosua Island, Pangkep District, South Sulawesi, Indonesia. Biodiversitas 24: 2023-2030. Bontosua Island is one of the islands in South Sulawesi, Indonesia, that has a seagrass ecosystem. The purpose of this study was to assess the density, cover, area, and condition of seagrass on Bontosua Island. The data collection involved the use of a quadratic transect method in the field and the Lyzenga method for remote sensing. The identification of seagrass areas was made using Landsat 8 OLI/TIRS satellite. Six seagrass species were identified, namely Cymodocea rotundata, Thalassia hemprichii, Halodule uninervis, Halodule pinifolia, Syringodium isoetifolium and Halophila sp. The results showed that C. rotundata had the highest density value of 89 Ind/m² and was categorized as rather dense, while C. rotundata also had the highest percentage cover of 58%, and Halophila sp. had the lowest percentage cover of 2%. The distribution area of seagrass beds on Bontosua Island was approximately 28.26 ha, out of a total area of 92 ha, of which approximately 6 ha was land. Observations on the condition of seagrass beds showed that 16.65 ha was healthy, 6.3 ha was unhealthy, while 5.31 ha was poor.

Comparison of fruit texture and aquaporin gene expression in papaya “Khak Nual” cultivated under varying conditions

ABSTRACT The effects of cultivation conditions on the texture of unripe papaya fruit ‘Khak Nual’ were investigated. Fruit from papaya cultivated using raised bed conditions were crisper than those cultivated under open field conditions. Conversely, fruit cultivated under open field conditions were firmer. In all cases, mesocarp cells and intercellular spaces were larger in papaya fruit cultivated in raised beds, reflecting the higher relative humidity (RH) of the cultivation conditions and greater water availability. At harvest, TIP2–1, TIP4–1, SIP1 and PIP1–3 expression was significantly higher in fruit cultivated under raised bed conditions, which correlated with the larger cells of the mesocarp, the RH and the ready availability of water. There also appeared to be a link between aquaporin gene expression and crispness in papaya fruit from both conditions. Expression of TIP2–1 and TIP4–1 correlated with papaya fruit under open field conditions while SIP1 and PIP2–5 correlated with papaya fruit under raised bed conditions. The results clearly demonstrate the effect of cultivation conditions on fruit texture, with water availability being critical in the production of market-preferred crisp fruit with the optimal conditions. These conditions are reflected in the higher expression of the water transport aquaporins which likely control crispness.

Establishing a Framework for Fused Filament Fabrication Process Optimization: A Case Study with PLA Filaments.

Developments in polymer 3D printing (3DP) technologies have expanded their scope beyond the rapid prototyping space into other high-value markets, including the consumer sector. Processes such as fused filament fabrication (FFF) are capable of quickly producing complex, low-cost components using a wide variety of material types, such as polylactic acid (PLA). However, FFF has seen limited scalability in functional part production partly due to the difficulty of process optimization with its complex parameter space, including material type, filament characteristics, printer conditions, and "slicer" software settings. Therefore, the aim of this study is to establish a multi-step process optimization methodology-from printer calibration to "slicer" setting adjustments to post-processing-to make FFF more accessible across material types, using PLA as a case study. The results showed filament-specific deviations in optimal print conditions, where part dimensions and tensile properties varied depending on the combination of nozzle temperature, print bed conditions, infill settings, and annealing condition. By implementing the filament-specific optimization framework established in this study beyond the scope of PLA, more efficient processing of new materials will be possible for enhanced applicability of FFF in the 3DP field.

Basal Melt Patterns around the Deep Ice Core Drilling Site in the Dome A Region from Ice-Penetrating Radar Measurements

Basal melt in the Dome A region will influence the deep-ice-core drilling at Kunlun Station. The melting point (wet bedrock) has a higher reflectivity than the surrounding area, which can be assessed using radar echoes from the bedrock. This paper uses a linear absorption model to determine wet and dry ice–bedrock interfaces around the Kunlun drilling site. In the determination process, an artificial intelligence model was applied to extract the ice–bedrock interface for inferring the ice thickness. Additionally, the various depth-averaged attenuation rates were used to identify the maximal range of basal melting. We mapped the patterns of the wet points on the bottom of the ice sheet and the modeled basal temperature to verify the results of the wet bed conditions. According to these maps of wet bed conditions, the areas with basal melting around the drilling site primarily appear in valley walls with low basal temperatures and are linked with hydraulic potential and bedrock elevation. Identifying the ice–bedrock interface is challenging in the valley bottom area, where the melting points are less than at the valley walls. Additionally, the melting proportions of 11.8% and 3.62% were calculated from two ice-penetrating radar data in this research. The mapped melting points around the site of Kunlun ice core drilling suggest complex ice flow effects and can be used to better interpret archives of old ice for paleoclimate research.

A study on characteristic indexes of railway ballast bed under high-frequency radar

PurposeIn this paper, a high-frequency radar test system was used to collect the data of clean ballast bed and fouled ballast bed of ballasted tracks, respectively, for a quantitative evaluation of the condition of railway ballast bed.Design/methodology/approachBased on original radar signals, the time–frequency characteristics of radar signals were analyzed, five ballast bed condition characteristic indexes were proposed, including the frequency domain integral area, scanning area, number of intersections with the time axis, number of time-domain inflection points and amplitude envelope obtained by Hilbert transform, and the effectiveness and sensitivity of the indexes were analyzed.FindingsThe thickness of ballast bed tested at the sleep bottom by high-frequency radar is up to 55 cm, which meets the requirements of ballast bed detection. Compared with clean ballast bed, the values of the five indexes of fouled ballast bed are larger, and the five indexes could effectively show the condition of the ballast bed. The computational efficiency of amplitude envelope obtained by Hilbert transform is 140 s·km−1, and the computational efficiency of other indexes is 5 s·km−1. The amplitude envelopes obtained by Hilbert transform in the subgrade sections and tunnel sections are the most sensitive, followed by scanning area. The number of intersections with the time axis in the bridge sections was the most sensitive, followed by the scanning area. The scanning area can adapt to different substructures such as subgrade, bridges and tunnels, with high comprehensive sensitivity.Originality/valueThe research can provide appropriate characteristic indexes from the high-frequency radar original signal to quantitatively evaluate ballast bed condition under different substructures.

Turbulent flow mechanisms in meandering channels with sediment transport

Abstract This research aims to investigate the near-bed turbulent flow characteristics in a meandering channel with both mobile bed and immobile bed conditions. Experiments were performed in a prismatic rectangular meandering channel with a non-uniform sand bed of size d50 = 0.523mm. The three-dimensional instantaneous fluid velocity was collected using the Acoustic Doppler velocimeter which will provide important results related to the flow turbulence such as mean flow velocity, turbulence intensity, Reynolds shear stress, turbulent kinetic energy, skewness, kurtosis and turbulent anisotropy. The secondary current flow and the exchange of momentum in the form of turbulence kinetic energy, Reynolds shear stress and turbulent intensity at the inner layer of the flow are identified more in a mobile bed condition as compared to an immobile condition, which causes sediment transport. For the inner layer of the flow, turbulence intensity and turbulent kinetic energy are decreased in magnitude and gradually increase in the outer layer of flow for both the bed conditions. Higher turbulence anisotropy is noticed in the mobile bed condition than in the immobile bed condition, which shows more nonuniformities near the bed level for the mobile bed condition. This study may help in understanding the effect of sediment transport due to a turbulent flow structure in a sinuous alluvial channel.