Bed Dryer Research Articles

Bubble behaviour investigation in a wet fluidized bed using digital image analysis

AbstractDue to the presence of liquid bridge forces, wet particles reveal totally different fluidization behaviours than dry fluidized beds. This paper studies the bubble dynamics of wet Geldart‐D particles in a wet 2D fluidized bed. A digital image analysis method is adopted to identify bubbles and extract bubble properties based on MATLAB software. During fluidization, the bubble feature analysis of optimized binary images captures the bubble size variation, bubble fraction, and bubble shape. The results show that the increasing liquid saturation promotes the gas holding capacity of the emulsion phase, leading to the decreasing bubble fraction. When the particle size grows, the stability of the emulsion phase is promoted and hence the average bubble diameter increases. As the liquid saturation increases, the enhancing liquid bridge forces limit the bubble growth and promote the bubble breakage, which contributes to the small bubbles. With respect to the wet particles, of which the diameter is 1 mm and the liquid saturation is over 15%, slugging is likely to be observed, resulting in the increasing equivalent bubble diameter. The growing liquid saturation increases the wide aspect ratio, decreases the shape factor, and disperses the dependence between the two parameters. This indicates that small and irregular bubbles are likely to be seen in wet fluidized beds.

Design of Free Stalls for Dairy Herds: A Review

Lying is an important behavior of dairy cattle. Cows should spend more than 50% of a day lying as it has a high impact on their milk yield and animal welfare. The design, size, and flooring properties of the free stalls influence the time cows spend lying, the way they lie down, and their rising movements. The purpose of this review is to provide an overview of the currently available information with the aim to assist farmers and advisors to come to an optimal design of the free stalls. The design of the free stalls should enable the cows to move and lie in positions as natural as possible. Cows should rest, with all parts of the body, on a clean, dry and soft bed, be able to stretch their front legs forward, lie on their sides with unobstructed space for their neck and head, and rest with their heads against their flanks without hindrance from a partition. When they stand, they should not be hindered by neck rails, partitions, or supports. A comfortable place for cows to lie down helps cows to stay healthy, improve welfare, and increase milk yield. Hence, the probability of a longer productive life for the cows increases and the number of replacements per year decreases.

E. coli CB390 as an Indicator of Total Coliphages for Microbiological Assessment of Lime and Drying Bed Treated Sludge

The use of a single host strain that allows for an evaluation of the levels of total coliphages in any type of environmental sample would facilitate the detection of and reduction in complexity and costs, favoring countries or areas with technical and economic limitations. The CB390 strain is a candidate for this type of simultaneous determinations, mainly in water samples. The objective of the study was to establish the recovery capacity of the CB390 strain in solid and semi-solid samples and to evaluate the microbiological quality of the sludge generated and stabilized by lime and drying beds in two WWTPs in Colombia. The results of both matrices indicated that CB390 recovered similar numbers of total coliphages (p > 0.05) against the two host strains when evaluated separately. Only the drying bed treatment was able to reduce between 2.0 and 2.9 Log10 units for some microorganisms, while the addition of lime achieved a maximum reduction of 1.3 Log10 units for E. coli. In conclusion, the CB390 strain can be used in solid and semi-solid samples, and the treatment in a drying bed provided a product of microbiological quality. However, the results are influenced by the infrastructure of the WWTP, the treatment conditions, and the monitoring of the stabilization processes.

INFLUENCE OF THE SIDE VENTILATION ON THE DURABILITY OF THE FUNCTIONING OF DRYING BEDS WITH NON-SATURATED FLOW IN TREATEMENT OF SEPTIC TANK SLUDGE

The non-saturated Flow Drying Beds allow efficient treatment of septic tank sludge. However, they are vulnerable to clogging. To ensure the sustainability of this technology, through an additional supply of oxygen from the lateral surface, a flow model coupled with the variation of the biofilm has been developed. The calibration, validation and comparison of the simulated and experimental results were made from the NASH criterion. The simulations focused on two types of reactors. A reactor with pores on its side surface is called a ventilated reactor (VR). The second is then called an unventilated reactor (UVR). The results show that the maximum applicable organic load is 43.3 mgO2 / cm2 / d at the UVR level and 51.8 mgO2 / cm2 / d at the VR level. In addition, the reduction in free flow porosity is 93.33% at the UVR level and 81% at the AR level. In addition, the results show that when the hydraulic head is less than 5 cm / d, the COD removal efficiency is 96.19% at the UVR level and 95.64% at the VR level. But, when the load is greater than 5 cm / d, the yield is 92.65% at the level of the UVR and of 94.95% at the level of the VR. Thus, in the context of a large-scale operation, lateral ventilation is essential. It guarantees good purification efficiency, slows down internal clogging of beds and accelerates its reversibility when it occurs.

A New Dam-Break Outflow-Rate Concept and Its Installation to a Hydro-Morphodynamics Simulation Model Based on FDM (An Example on Amagase Dam of Japan)

Dams are constructed to benefit humans; however, dam-break disasters are unpredictable and inevitable leading to economic and human life losses. The sequential catastrophe of a dam break directly depends on its outflow hydrograph and the extent of population centers that are located downstream of an affected dam. The population density of the cities located in the vicinity of dams has increased in recent times and since a dam break hydrograph relies on many uncertainties and complexities in devising a dam-break outflow hydrograph, more researches for the accurate estimation of a dam-break flood propagation, extent and topography change becomes valuable; therefore, in this paper, the authors propose a novel and simplified dam-break outflow rate equation that is applicable for sudden-partial dam breaks. The proposed equation is extensively affected by a dam-break shape. Therefore, the inference of a dam-break shape on a dam-break outflow rate is investigated in the current study by executing hydraulic experiments in a long, dry bed, frictionless and rectangular water channel connected to a finite water tank to acquire a mean break-shape factor. The proposed equation is further validated by regenerating the Malpasset dam-break hydrograph and comparing it to the existing methods and also by installing it on an existing 2D hydro-morphodynamics flood simulation model. Finally, Amagase Dam’s (arch-reaction dam in Japan) break simulation is executed as a case study. The results of the simulations revealed that the greater the height of a dam-break section, the more devastating its flood consequences would be.

ALIGN-CCUS: Results of the 18-month test with aqueous AMP/PZ solvent at the pilot plant at Niederaussem – solvent management, emissions and dynamic behavior

After a 13,000-hour test campaign with aqueous 30 wt% MEA (2-aminoethanol) solvent at the CO2 capture pilot plant at Niederaussem, another long-term test was carried out as part of the ALIGN-CCUS project. This test ran for more than 12,275 hours with aqueous AMP/PZ (2-Amino-2-methyl-1-propanol/piperazine) solvent, named CESAR1 (3.0 molar AMP (~26.74 wt%) and 1.5 molar PZ (~12.92 wt. %)). A minimum specific reboiler duty of 2,970 MJ/tCO2 was identified for the capture plant operation with four active absorber beds (total 16 m packing height) and intercooling (40°C). Neither a lower desorber pressure of 1.5 bar(a), instead of 1.75 bar(a), nor a change of the different positions of intercooling had a significant effect on energy consumption. Reduction of the active packing height to three beds (i.e., 12 m), resulted in a moderately higher specific energy demand (+100 MJ/tCO2). Tests with CO2 capture rates between 90 and 98% showed only a small increase of the specific energy demand at 95% (+20 MJ/tCO2) and four active packings (98%: +250 MJ/tCO2). The average solvent consumption of CESAR1 during 400 days of operation was 0.45 kg/tCO2 and is lower than for MEA if the phase of accelerated non-linear degradation of MEA is taken into account. CESAR1 follows a slow-progressing linear degradation behavior; neither a critical metal ion concentration threshold value could be found that triggers fast degradation nor a correlation between accumulated trace components or metal ion concentrations in the solvent and the degradation rate was observed. Highly transient tests were conducted to investigate the dynamic behavior of the capture plant and subsequently special settings were chosen to stimulate high emissions for the investigation of aerosol-based emissions, connected with performance tests of several emission mitigation measures: single water wash, double water wash, acid wash, dry bed, wet electric precipitator and flue gas pre-treatment. When applying the dry bed configuration, emissions of AMP between 15 - 20 mg/Nm3, PZ between 3 - 7 mg/Nm3, and NH3 below 3 mg/Nm3 were achieved.

Simulation of Dam Breaks on Dry Bed Using Finite Volume Roe-TVD Method

Dams are one of the most important hydraulic structures. In view of unrecoverable damages occurring after a dam failure, analyzing a dams’ break is necessary. In this study, a dam located in Iran is considered. According to adjacent tourist and entertainment zones, the breaking of the dam could lead to severe problems for the area and bridges downstream of the river. To investigate the issue, a numerical FORTRAN code based on the 2D finite volume Roe-TVD method on a fixed bed is provided to assess the effects of the dam break. Turbulence terms and dry bed conditions were considered in the code. A numerical wave tank (NWT) with a triangular barrier in the bed was numerically modeled and compared with analytical models to verify the capability of the code. Comparing numerical, experimental and analytical results showed that estimated water level and mass conservation in the numerical model is in good agreement with the experimental data and analytical solutions. The 2D approach used has reduced the cost of computing compared to a 3D approach while obtaining accurate results. The code is finally applied to a full-scale dam-break flood. Six KM of the natural river downstream of the dam, including two bridges, B1 and B2, is considered. Flood flow hydrographs and water level variations at bridges B1 and B2 are presented. The results denoted that bridges B1 and B2 will be flooded after 12 and 21 min, respectively, and are at risk of the potential break. Thus, it is necessary to announce and possibly evacuate the resort area alongside the dam in order to decrease losses.

Study of coherent structures and heat flux transportation under different stratification stability conditions in the atmospheric surface layer

A field experiment was carried out on a dry flat bed of Qingtu Lake in Minqin, China to measure the velocity and temperature in the atmospheric surface layer at high Reynolds number. The facility, the Qingtu Lake Observation Array, permits synchronous multi-point measurements of three-dimensional wind velocity and temperature at different wall-normal and spanwise positions. Data were selected to analyze the characteristics of the large-scale coherent structures under different stratification stability conditions. The results confirm the previous findings that the positive buoyancy can be considered as a wall-normal force to have a “lifting” effect increasing the size of large-scale structures and further illustrate that negative buoyancy in the stable condition has an opposite effect leading to small structures with less wall-normal coherence. The stability dependence of structure inclination angles for all three velocity components is built by a parametric model indicating a log-linear trend under near-neutral and unstable conditions. In addition, the unique measurement array at this facility also permits us to study the three-dimensional form of these features and the associated temperature fluctuations. By computing the space average for momentum and heat flux, we found that the threshold stability parameter z/L=−0.1, where z = 2.5 m and L is the Obukhov length scale, can act as a role to determine the dominant flow by shear-driven and buoyancy-driven, respectively. Last, the streamwise length scales for temperature component are investigated where a smaller length scale corresponds to a stronger buoyancy condition, but with larger values at higher heights.

A Review on Formulation and Development of Solid Self-Nano Emulsifying Drug Delivery Systems

This article describes current strategies to enhance aqueous solubility and dissolution rate of poor soluble drugs. Most drugs in the market are lipophilic with low or poor water solubility. There are various methods to enhance solubility: co-solvency, particle size reduction, salt formation and Self Nanoemulsifying drug delivery systems, SEDDS is a novel approach to enhance solubility, dissolution rate and bioavailability of drugs. The study involves formulation and evaluation of solid self-Nano emulsifying drug delivery system (S-SNEDDS) to enhance aqueous solubility and dissolution rate. Oral route is the most convenient route for non-invasive administration. S-SNEDDS has more advantages when compared to the liquid self-emulsifying drug delivery system. Excipients were selected depends upon the drug compatibility oils, surfactants and co surfactants were selected to formulate Liquid SNEDDS these formulated liquid self-nano emulsifying drug delivery system converted into solid by the help of porous carriers, Melted binder or with the help of drying process. Conversion process of liquid to solid involves various techniques; they are spray drying; freeze drying and fluid bed coating technique; extrusion, melting granulation technique. Liquid SNEDDS has a high ability to improve dissolution and solubility of drugs but it also has disadvantages like incompatibility, decreased drug loading, shorter shelf life, ease of manufacturing and ability to deliver peptides that are prone to enzymatic hydrolysis.

Aeolian sand transport over a wet, sandy beach

• Substantial transport occurs below Belly’s (1964) fluid threshold. • Particles in transport exhibit high moisture contents. • Vertical flux profiles deviate from those observed over dry beds. • Transport flux models predict motion below the fluid threshold for wet beds. Quantifying aeolian transport within the intertidal zone is critical to understanding feedbacks between aeolian and nearshore processes in coastal environments. Here, we report a field study of aeolian transport over a wet bed in the intertidal zone. Predominate winds and beach orientation were aligned during all field observations. Mean grain size of bed samples were 0.18 mm and moisture content ranged from 16 to 17%. Velocity profiles were measured with a vertical array of cup anemometers. Sustained wind velocities were 9.5 m/s at 93 cm above the bed with gusts reaching 13.5 m/s. Five saltation traps captured particles in transport from the bed to a height of 15 cm. Particles in transport were wet and the highest moisture content of trapped sediments was found in the lowest saltation trap. Vertical flux profiles show a higher concentration of flux closer to the bed (81 to 89% below 5 cm) than those measured over dry beds. Power and exponential decay functions were fit to our vertical flux profiles; the exponential decay function best fit flux profiles with larger β coefficients and smaller α estimates than those fit to dry bed profiles. Total flux models predict transport below Belly’s (1964) fluid threshold of motion for moist beds and model performance improves when using a threshold for dry sand. Our results suggest transport over wet beds is fundamentally different from transport over dry beds. However, more research is needed to discern the mechanics driving deviations in flux profiles over wet beds in field environments.

Emergency Oil Spill Response: Data Collection Automation, and Dissemination

ABSTRACT The California Department of Fish and Wildlife (CDFW), Office of Spill Prevention and Response (OSPR) has employed Geographic Information System (GIS) technology for oil spill planning and response since the early 1990's, adding remote sensing tools to the mix by the turn of the Century. Discussed herein are OSPR's current smartphone and tablet-based field data collection applications. We use an off-the-shelf tool for pre-response protection strategy planning and use customized tools developed in-house for California Sea Otter Surveys, Wildlife Search and Collection and the Shoreline Cleanup Assessment Technique (SCAT). The benefits of automated field data collection include the omission of transcription errors during manual data input and streamlined data processing. This results in accurate and timely information delivered to responders, thus enhancing their capability for informed decision making. OSPR uses the National Oceanic and Atmospheric Administration's (NOAA) Environmental Response Management Application® (ERMA), a web-based GIS data viewer as the Common Operational Picture (COP) for data dissemination throughout the incident response community during an oil spill event, and for the post emergency response cooperative Natural Resource Damage Assessment (NRDA). OSPR also uses ERMA a planning tool by uploading significant data layers from the U.S Coast Guard's (USCG) six Area Contingency Plans (ACP) for coastal California and OSPR's Geographic Response Plans for inland waters of the state with higher risk of an oil spill. These response planning data are freely downloadable from the ERMA platform. In the Summer/Fall of 2019 at the Cymric Oil Field in Kern County, California, over 1,000,000 gallons of oil, mud and steam seeped into a dry stream bed from several “surface expressions”. Direct access to the spill site was not permitted for Health and Safety concerns. OSPR used an off-the-shelf small Unmanned Aerial System (sUAS, aka drone) equipped with a standard high definition (HD) camera and a thermal infrared camera for SCAT reconnaissance, resources at risk evaluations, and regularly scheduled mapping missions for overall site situational awareness.

Augmented HLL Riemann solver including slope source term for 1D mixed pipe flows

Abstract In this paper, the augmented version of finite volume Harten–Lax–van Leer (HLL) solver, including source terms, is extended to free-surface and pressurized mixed pipe flows over complex and frictional topography. This augmented HLL Riemann solver is employed for the flux approximation at the cell interface, where source terms are split into two parts based on the wave propagation speed. The friction term is treated using a splitting implicit method to maintain stability over dry beds. The Preissmann slot method is adopted to reproduce pressurized flow in the conduit. The performances of the numerical model are investigated by several numerical tests and compared with existing methods showing clear improvements.

Numerical simulation of non-rigid landslide into reservoir with erodible sediment bed using SPH method

Landslide phenomenon in accumulated erodible bed sediments in a reservoir is one of the issues in hydraulic and sedimentation sciences that has received little attention. We intend to model two-dimensional changes of the water surface in a reservoir and of an erodible bed caused by a non-rigid landslide using a particle-based meshless approach. In this study, a fully explicit three-step algorithm is used. In this method, approximate numerical solution to the equations of the fluid dynamics is obtained by replacing the fluid with a set of particles. The governing equations for water flow and sand mass movement are solved for each particle. The movement of each particle, which is in interaction with other particles, is tracked. Experiments of a dam break on a dry bed, and submarine rigid and non-rigid landslides have been used to validate the method. Results indicate that the model was successfully calibrated against the measured data. Moreover, good agreement with the measured data demonstrates high capabilities of this method in simulating free-surface flows and wave-related phenomena. After the model validation, changes of erodible bed in a reservoir due to a non-rigid landslide were modelled. In this study, non-rigid landslide masses and sediment materials were modelled by non-Newtonian Carreau-Yasuda fluid, which is the novelty in the analysis of this type of natural hazard. Two possible scenarios were analyzed—one with the sliding material lighter, and the other with the sliding material heavier than the deposited sediments. The model was run until the landslide completely collapsed and its full impact was applied to the reservoir bed sediments. Additionally, we waited until the water level reached a steady state. These examples demonstrate that the model presented in this paper can be used as a reliable tool for modelling these phenomena.

Studies on variations in Physico-chemical Properties of Mustard Seeds during Drying and Fluidized bed Drying Kinetics

Proper drying methods can prevent the damage of food grains by changing in physic-chemical properties and minimize the spoilage during storage and improve the nutrition quality of grain. Thus proper drying methods are very important to choose based on operating conditions and cost. In present work, the typical variations in physico-chemical properties of mustard seeds obtained from Varshakonda Village in Telangana State were investigated during drying in Hot Air Oven, Tray Drier and Fluidized Bed drier. Removal of moisture during fluidized bed drying is observed very effective. Also, nutritional properties like fat, protein, phosphorous & iron contents were found to decrease considerably low during drying in Fluidized bed comparatively in hot air oven and tray drier. Therefore, mustard seeds can effectively dried in Fluidized Bed. The fluidization characteristics of mustard seeds under different operating conditions were investigated in order to find out best drying method to dry mustard seeds.

The characteristics of swampland rice farming in South Sumatra: local wisdom for climate change mitigation

Swampland has been used for agriculture for hundreds of years, yet most still use traditional ways. In general, rice farming in swampland is cultivated once a year before the dry season depending on land classification. This paper presents the swampland rice farming system’s role as local wisdom that needs to be maintained for environment preservation and climate change mitigation. Data was collected through interviews with farmers and extension workers and reviews of relevant experimental studies and articles. The success of rice farming in swampland is primarily determined by nature such as sudden flood and drought. Swampland is divided into three typologies, namely shallow swampland, mid swampland, and deep swampland. The nursery system and rice variety selection are key for successful rice farming in swampland. There are dry and floating nursery systems in South Sumatra. The dry nursery is carried out in dry land and field beds, usually done for shallow swampland; floating nursery is carried out in higher water level swampland using rafts made from waterweeds. Some of superior adaptive varieties in swampland are Inpara-1, Inpara-2, Inpara-4, Batutegi, Limboto, Inpari-1, Inpari-4, Inpari-6, Inpari-9 and Mekongga which may increase production in swampland.

Factors affecting evaporation of water from cattle bedding materials

In livestock farming, maintaining dry bedding is considered to be important for maximising animal performance and welfare. A better understanding of the mechanisms that regulate drying has the potential to improve bedding management and reduce production costs. A custom laboratory-scale method was developed to explore the effects of environmental conditions and bedding characteristics on drying rate (DR). Samples (n = 256) of different types of bedding materials were exposed to controlled environmental conditions by using a climate chamber equipped with a custom cabinet capable of simulating different levels of air velocity and bedding temperature. The effects of the type of material, bedding moisture content, bedding temperature, air temperature, air relative humidity (RH) and air velocity were evaluated in a full factorial experimental design. Under the experimental conditions tested, DR ranged from 0.28 to 6.04 kg m −2 d −1 , with an average of 2.03 kg m −2 d −1 . All variables significantly affected DR, but large variation in the magnitude of effects was found. Bedding moisture content, air velocity and air RH had considerably larger effects than the other variables, together accounting for more than 70% of the variance in DR. The DR from bedding samples increased with bedding moisture content and air velocity but decreased with increasing air RH. The results of the current study may have important implications in the design and management of bedded pack barns. To increase the DR and keep bedding dry, producers should focus primarily on providing adequate barn ventilation (both in terms of air velocity and air exchange), whereas maintaining a high pack temperature may yield poorer-than-expected results. • Water evaporation from livestock bedding materials has been measured experimentally. • Drying rate depends on environmental conditions and bedding characteristics. • Bedding moisture content, air velocity and air RH are the most important factors. • Producers with bedded pack barns should focus on providing adequate ventilation.

Control of septage sanitization by limes and lactic acid fermentation

Considering low-cost and effective fecal sludge (FS) treatment alternatives is essential to avoid risk to human health and to ensure safe disposal in landfills and soils. This research assesses optimal pH adjustment of two techniques for sanitizing de-watered FS from a septic sewage-treatment plant. The preliminary analysis evaluated the efficiency of lactic acid fermentation (LAF) by two lactic acid strains: Lactobacillus casei and Lactobacillus acidophilus. The homofermentative strain was chosen to evaluate three supplementary sugars: smashed carrot, sugarcane-derived molasses, and anhydrous dextrose. Lime treatment was examined using two materials, CaO, 105% calcium carbonate equivalent (CCE), and Ca(OH)2, 75% CCE. Four samples were retrieved from a passive thermal drying bed, two characterized by its available nutrient content; all samples were analyzed for the pathogenic profile, and total coliforms (TC) were selected as indicators. For LAF, an inoculating rate of Lactobacillus casei 10 g/100 g sludge was found effective in decreasing the pH below 4.0 after 30 days of fermentation, using 22% w/w dextrose/septage and 20% w/w molasses/septage, where molasses contains 20.7% of soluble sugars. In the case of lime treatment, the pH was fitted by a power-law relationship to the rate of lime applied in a septage with an initial pH lower than 7.0. A Langmuir type equation fitted better the liming of two septages with initial pHs above 7.0. The rate of lime CaO 10% w/w was observed to increase the pH above critical value, 12, after 1 h and 24 h. Analysis confirmed the total elimination of TC in samples with pH < 4.0 and pH > 12, contrasting the respective controls. Rates of CaO considering the initial pH of the FS are recommended in order to reach pH 12. Septage sanitization can be completed using either CaO or lactic acid fermentation with molasses; selecting the ideal method will rely on cost-benefit analysis. Sanitization can be considered as well to improve safety soil nutrient recycling practices.

A three dimensional dam break flow: Small time behavior

Small time behavior of gravity driven free surface flows resulting from the collapse of a cavity is studied. Initially there is a rigid vertical cylinder of circular cross section starting from the free surface of a liquid and ending at the rigid bottom. The cylinder disappears suddenly and gravity driven flow of the fluid starts. The flow in early stage is described by the potential theory. Attention is paid to the singular behavior of the velocity field at the intersection line between the bottom and the free surface of the cavity. The leading order linear problem is solved by the Fourier series method. The flow velocity is log-singular at the intersection line. In the limiting case where the radius and the center of the cavity approach infinity, the problem is reduced to the classical two dimensional dam break problem where the fluid is initially on one side of a vertical wall (dry bed case). The flow resulting from cavity collapse is a three dimensional dam break flow. It is concluded that the three dimensional effects are important when the radius of the cavity is small compared with its depth and that the local flow near the intersection line of the cavity is governed only by the hydrostatic pressure.

A fully Lagrangian DEM-MPS mesh-free model for ice-wave dynamics

This paper develops and evaluates a novel three-dimensional fully-Lagrangian (particle-based) numerical model, based on the hybrid discrete element method (DEM) and moving particle semi-implicit (MPS) mesh-free techniques, for modeling the highly-dynamic ice-wave interactions. Both MPS and DEM belong to mesh-free Lagrangian (particle) techniques. The model considers ice-wave dynamics as a multiphase continuum-discrete system. While the MPS solves the continuum equations of free-surface flow in a Lagrangian particle-based domain, the DEM uses a multi-sphere Hertzian contact dynamic model to simulate the ice floes motion and interaction. The hybrid model predicts the motion and collision of ice floes as well as their interaction with water, boundaries, and any obstacle in their way. Considering the mesh-free Lagrangian nature of both DEM and MPS, the developed model has an inherent ability to predict the free-drift (absence of internal stress) movements of the ice floes, e.g., sliding, rolling, colliding, and piling-up, in violent free-surface flow. A small-scale and challenging experiment based on dam-break flow over dry and wet beds with floating block floes, which mimics the characteristics of an idealized jam release, has been conducted to provide useful and comprehensive quality data for the validation of the proposed model, as well as other numerical models. Experimental and numerical results of the free-surface profile and the position of the blocks are compared. The results show the ability of the model to numerically reproduce and predict the complex three-dimensional dynamic behavior of wave-ice floes interaction. Overall, this study is a first effort toward developing an ice-wave dynamic within a fully Lagrangian framework (i.e. both flow hydrodynamics and ice dynamics in the Lagrangian particle-based system), and its results can be extended to bring an in-depth understanding of the physics of the real-scale ice-wave or river ice dynamic problems in the future.

Measurements of bed shear stresses near the tip of dam-break waves on a rough bed

Shear plates have previously been used to measure bed shear stresses under swash and dam-break waves. The present study has been focused on the large bed shear stresses near the tip and even at distances less than one plate length from the tip. In order to resolve this rapid stress variation, the shear plate was calibrated with respect to its step response as well as statically. Step response calibration enables the effects of the time lag and the natural frequency of the shear plate system to be removed. Thus, the initial variation of the bed shear stress during and just after the rise of the water level is resolved and opens the opportunity to investigate the boundary layer development close to the tip where other measurements have not previously succeeded. The bed shear stress $$\tau_{{{\text{bed}}}} \left( t \right)$$ initially increases almost linearly with time to a maximum, which occurs about 0.2 s after the passage of the contact point, while it takes about 2.0 s for the water surface level h(t) to rise to a quasi-steady level under the present experimental conditions. Thus, with h(t) and $$\tau_{{{\text{bed}}}} \left( t \right)$$ varying with different timescales, the simple assumption of $$\tau_{{{\text{bed}}}} = \tau_{{{\text{bed}}}} \left( {\frac{{{\text{roughness}}}}{{{\text{depth}}}}} \right)$$ is not supported. For a given dam-break, the peak bed shear stress depends on the tailwater level. In our tests with initial dam depth 400 mm and bed roughness 84 mm, $$\tau_{{{\text{bed}}}}$$ peaks at 210 Pa ± 20 Pa on dry beds decreases to peak values of the order 40 Pa with 98 mm tailwater depths. Quasi-steady $$\tau_{{{\text{bed}}}}$$ -values reached while the water surface is still quasi-steady, which are of the order 5–10 Pa. For dry beds, $$\tau_{{{\text{bed}}}}$$ shows a single peak followed by a smooth monotonical decay, while tailwater depths above 40 mm may lead to two almost equal, successive $$\tau_{{{\text{bed}}}}$$ -peaks and an oscillating decay.