Dimensionless Unit Research Articles

Integrated Prediction Model for Upstream Reservoir Sedimentation in a Weir: A Comprehensive Analysis Using Numerical and Experimental Approaches

In this study, a new empirical equation was established to predict the sedimentation volume resulting from the construction of a multi-purpose weir or low-head dam using experimental approaches. Applying the 1-D numerical model (STAFF), which is based on Exner’s equation, 2545 cases were simulated and laboratory experiments were conducted with various sediment particle sizes, channel slopes, inlet discharge, and outlet water elevation. Short-term predictions were conducted through laboratory experiments with movable bed, and the results indicated that dimensionless unit stream power and the Shields parameter exhibited the most significant correlation with dimensionless deposition volume. In particular, we analyzed the phenomenon in which the backwater effect and reservoir delta. Using a multiple regression approach, the developed empirical equation was validated for predicting sedimentation in the upstream reservoir of the weir.

The UV Index color palette revisited

The UV Index (UVI), standardized by the World Health Organization (WHO) in 2002, is an internationally accepted reference for disseminating information on solar UV radiation levels with the purpose of preventing the harmful effects on human health by sun overexposure. The UVI is the erythemal irradiance expressed in a dimensionless unit, with numerical values adapted to a risk scale that considers the “Extreme” level from a UVI value equal to 11 upwards. This scale is linked to a color palette by health risk ranges, and to a graded color palette by units of UVI for more details. Both the numerical scale and its associated risk levels were universally adopted by the scientific community and by global information systems to the population. However, inconsistencies and limitations persist between both UVI color palettes, making their interpretation and application difficult. In the present work all these aspects are addressed, proposing a revised color palette for unit UVI values that resolves each of them. Based on the WHO risk-ranges UVI color palette, the new color palette for unit UVI values gives coherence to both color charts, allowing reliable identification of the risk level bands and of each unit UVI level within them, and solves the need to distinguish between units for numerical values of UVI higher than 11 that are registered daily in many regions of the world.

Prediction of Continuous Rainfall-Runoff Scenarios for Snow-Fed Watershed of Himachal Pradesh, India using Geographical Information System GIS based on Hydrological Modelling

Rainfall runoff modeling is one of the most complex hydrological modeling due to the involvement of different watershed physical parameters. It is essential for the analysis of watershed hydrological response towards the received precipitation under the influence of watershed variables. As it is a replica of watershed hydrological response, Rainfall-Runoff modeling is essential to evaluate the general characteristics of total surface runoff at catchment’s outlet. The main objective of this study was prediction of rainfall runoff using Hydrologic Engineering Center-Hydrologic Modeling System [HEC-HMS] model for Rampur watershed which was covered in Kullu and Shimla districts situated at Upper Sutlej sub-basin of Himachal Pradesh, India. Geo-spatial data of Digital Elevation Model,LandUse-LandCover (LU-LC) map, Soil map and Hydro-meteorological data of rainfall were collected from different open source web portals to utilise as input parameters for modeling. Soil Conservation Service-Curve Number (SCS-CN) for precipitation loss modeling, Soil Conservation Service–Dimensionless Unit Hydrograph [SCS-UH] for transform modeling, Muskingum method for Runoff routing were used as input parameters of respective components of HEC-HMS model. This article proposes a methodology for generating hourly rainfall data from daily rainfall data using Intensity-Duration-Frequencycurves in Meteorological model of HMS. The simulation results of runoff with 5 different return period scenarios are follows the return period frequency tendency, such as 1000 year return period runoff peak delivers 4729.5 m3/s, 500 year return period delivers a peak runoff of 4263.9 m3/s, 100 year return period gives a peak runoff of 3196.5 m3/s, 50 year return period runoff deliver 2745.3 m3/s and 10 year return period deliver 953.7 m3/s runoff at the outlet of Rampur watershed.

RAINFALL-RUNOFF SIMULATION OF A SUB-CATCHMENT USING HEC-HMS

Hydrological data in the form of stream flow is very scarce in most developing countries. This affects the planning and management of urban watersheds. Therefore, it is necessary to estimate peak discharge from rainfall using hydrologic models based on some measurable watershed characteristics. This study aims to model the rainfall-runoff process from a typical urban watershed using Hydrologic Engineering Center Hydrological Modeling System (HEC-HMS) software. The catchment basin has a total area of 21.91 km2, and a dendritic stream system. Soil Conservative Services (SCS) Curve number was used for getting excess rainfall from total rainfall, SCS dimensionless unit hydrograph for converting the excess rainfall to direct runoff and Muskingum for the channel routing. The rainfall-runoff simulation was conducted using six (6) rainfall events. Model calibration and validation were done using optimized parameters and the result shows a reasonable fit between the observed and simulated hydrograph. The model result has an RMS error of 1.5 m3/s, and a Nash-Sutcliff of 0.585. It is concluded that the model can be used to predict runoff from rainfall with reasonable accuracy. The result can be used for watershed planning and management.Keywords: HEC HMS, rainfall, runoff

Flow resistance in a subtropical canyon river

We conducted several field surveys to measure velocity and channel geometry in 15 cross-sections distributed along three reaches in the Boi River (Southern Brazil), a canyon river that belongs to the most extensive canyon chain in South America. The three reaches present, respectively, canyon, transition, and floodplain landscapes. The resulting data were used to compute the flow resistance. A downstream hydraulic geometry analysis indicates that the exponent describing the velocity increases with the discharge and that these values were between 0.3043 and 0.3507. A downstream hydraulic geometry analysis indicates that changes in velocity with discharge are greater than the rate of change of width or depth. It is typically found in steep mountain streams laterally confined, and it was verified in the canyon reach. However, despite the transition presents a considerable lateral constriction and the floodplain reach presents mountain river characteristics, both reaches did not present such behavior. The findings are coherent with other mountain river datasets, although the Boi River presents distinct geomorphic units such as glide-runs. In contrast, other available datasets are usually characterized by step-pool channels. Flow resistance in the canyon and transition reaches differ in many ways from floodplain reach, indicating larger resistance inside the canyon than outside, probably related to the landform and grain size in the canyon. Regression analysis of the combined field dataset indicated that dimensionless unit discharge is an important independent variable to explain variations in velocity and flow resistance. We also verified that the use of Rickenmann's Equation can be helpful to estimate velocity in canyon rivers. Our findings include: i) canyon landscape presents higher friction factors than floodplain landscape; and ii) canyon and transition landscapes are similar in terms of flow resistance during high-flow conditions, while floodplain present remarkably differences.

The NRCS Peak Rate Factor for Severe Storms

AbstractThe Natural Resources Conservation Service's Dimensionless Unit Hydrograph is used extensively in industry by design engineers for the purpose of determining the runoff hydrograph from a rainfall event. As part of the methodology, the user is required to input a Peak Rate Factor (PRF) which describes the runoff response (volume distribution) of the corresponding unit hydrograph. Unfortunately, little guidance is given in the literature for selecting an appropriate PRF for a given watershed. Additionally, consideration has not been given to determine if the PRF should remain constant for a given watershed or be allowed to vary as a function of return period. The goal of this study was to back‐calculate site‐specific PRFs for various watersheds which have experienced two or more significant rain events since the year 2000. A total of 14 watersheds were investigated with results showing PRFs remained consistent for five of the watersheds regardless of the storm event. Nine of the watersheds showed a significant variation in PRF with an average variation of approximately 440 across all storm events within a given watershed. Additional analysis showed there is a general trend of increasing PRF with decreasing storm‐specific curve number. Finally, the complacent‐violent runoff response was shown to occur for storms with resulting PRF's in excess of 1,000.

Flow Resistance in Lowland Rivers Impacted by Distributed Aquatic Vegetation

This study addressed a research concern that employing a fixed value for the bed roughness coefficient in lowland rivers (mostly sand-bed rivers) is deemed practically questionable in the presence of a mobile bed and time-dependent changes in vegetation patches. Accordingly, we set up 45 cross-sections in four lowland streams to investigate seasonal flow resistance values within a year. The results revealed that the significant sources of boundary resistance in lowland rivers with the lower regime flow were bed forms and aquatic vegetation. The study then used flow discharge as an influential variable reflecting the impacts of the above-mentioned sources of resistance to flow. The studied approach ended up with two new flow resistance predictors which simply connected the dimensionless unit discharge to flow resistance factors, Darcy-Weisbach (f) and Manning (n) coefficients. A comparison of the computed and measured flow resistance values also indicated that 87–89% of the data sets were within ± 20% error bands. The flow resistance predictors were also verified against large independent sets of field and flume data. The obtained predictions using the developed predictors might overestimate flow resistance factors by 40% for other lowland rivers. Based on a different view, according to the findings of this research, seasonal variation of vegetation abundance could show the augmentation in flow resistance values, both f and n, in low summer flows when vegetation covers river bed and side banks. The highest amount of flow resistance was observed during the summer period, during the July–August period.

Measurement of Mach probe on plasma flow velocity in highly collisional plasma jet

A normalized plasma flow velocity in highly collisional plasma formed by a microwave plasma jet, which is dimensionless unit for plasma flow velocity/ion acoustic velocity, was measured by the parallel Mach probe. To deduce the normalized plasma flow velocity under highly collisional plasma conditions, the collisional model of a Mach probe was proposed. In addition, neutral gas flow velocity which assumed to be plasma flow velocity was calculated by the turbulent model. The results for the two different models were compared with those for the collsionless models of the Mach probe. The turbulent model produced 2–4 times reduced values than by measurements with collsionless models. The measured results with the collisional model were shown as approximately 100–250% lower than those for collsionless models. They were obtained to be in good agreement with difference rate of 10–30% when compared to those for the turbulent model.

A critical evaluation of air quality index models (1960-2021).

The formulation of an adequate and practical Atmospheric Air Quality Management Plan at different spatial scales at local (micro), city (medium), national (macro)), and temporal (short and long term) is an indispensable solution to prevent the public from air pollution health risk. The air quality monitoring system provides regulatory agencies a comprehensive data of current air contaminants in a particularlocation. Then, air monitoring data of pollutants is processed into a dimensionless unit called the "Air Quality Index" (AQI); it serves as an information medium for the people to know the air quality health of their location and takes preventative steps accordingly (public participation). Thus, the AQI is a beneficial tool for the public, stakeholders, and regulators to understand the current state of air quality. AQI across the globe considers the number of pollutants (most of the developed countries and some developing countries considers PM2.5 to measure the overall status of air quality being monitored), averaging time for which pollutants are measured, calculation method to compute air quality indices for each pollutant, calculation mode to aggregate the overall index, scale of an index, categories, colour coding scheme, and related descriptive terms of the pollutants. This article presents rationalized and extensive reviews of various Air Quality Index (AQI) models utilized worldwide from 1960 to 2021, comparing them based on several parameters such as types and number of pollutants (criteria or hazardous air pollutants), averaging time (long-term or short-term), calculation methods (linear or nonlinear), calculation modes [single-pollutant (maximum value) or multi-pollutants (combined effect)]. By analysing the strengths and flaws of all the AQI models developed so far, it is recommended to develop a more reliable, extensible, and comparable AQI model to be employed as an executive tool for designing strategic pollution abatement programs to preserve public health.

Construction of mammographic findings simulators to study the interference of silicone implants in the diagnosis of breast cancer

Introduction: Breast cancer is the most prevalent malignant neoplasm among women, presenting itself, in 99% of cases, in females. Augmentation mammoplasty is the most performed aesthetic surgical intervention in the world. Objective: This study aims to improve the search for biomaterials compatible with mammographic findings suggestive of malignancy, to further study the interference of silicone implants in mammography exams. Methods: To make the simulators of mammographic findings, a bibliographic study of possible biomaterials that presented compatibility with the breast tissue and with possible neoplastic findings was carried out. The validation process of the simulators made in this work was carried out in two stages. Results: The result found was a density variation between 2.54 and 2.57 (dimensionless unit). For the second plate, the individual optical density of each material was analyzed. The results found for fiberglass ranged between 1.95 and 2.63. For chicken eggshells between 0.59 and 0.80. For the glycerin suppository, values between 1.43 and 2.29 were found. And for plastic PVC film 1.78 to 2.53. Conclusion: Given the above, it is observed that the first plate as a whole is compatible with mammographic studies. However, on the second plate, when the materials were analyzed separately, it was observed that fiberglass and plastic PVC film were the closest to compatibility with the commercial phantom, being compatible materials to simulate breast neoplasms in possible further studies.

The Role of Interleukin-1-Receptor-Antagonist in Bladder Cancer Cell Migration and Invasion.

Background: The interleukin-1-receptor antagonist IL1RA (encoded by the IL1RN gene) is a potent competitive antagonist to interleukin-1 (IL1) and thereby is mainly involved in the regulation of inflammation. Previous data indicated a role of IL1RA in muscle-invasive urothelial carcinoma of the bladder (UCB) as well as an IL1-dependent decrease in tissue barrier function, potentially contributing to cancer cell invasion. Objective: Based on these observations, here we investigated the potential roles of IL1RA, IL1A, and IL1B in bladder cancer cell invasion in vitro. Methods: Cell culture, real-time impedance sensing, invasion assays (Boyden chamber, pig bladder model), qPCR, Western blot, ELISA, gene overexpression. Results: We observed a loss of IL1RA expression in invasive, high-grade bladder cancer cell lines T24, UMUC-3, and HT1197 while IL1RA expression was readily detectable in the immortalized UROtsa cells, the non-invasive bladder cancer cell line RT4, and in benign patient urothelium. Thus, we modified the invasive human bladder cancer cell line T24 to ectopically express IL1RA, and measured changes in cell migration/invasion using the xCELLigence Real-Time-Cell-Analysis (RTCA) system and the Boyden chamber assay. The real-time observation data showed a significant decrease of cell migration and invasion in T24 cells overexpressing IL1RA (T24-IL1RA), compared to cells harboring an empty vector (T24-EV). Concurrently, tumor cytokines, e.g., IL1B, attenuated the vascular endothelial barrier, which resulted in a reduction of the Cell Index (CI), an impedance-based dimensionless unit. This reduction could be reverted by the simultaneous incubation with IL1RA. Moreover, we used an ex vivo porcine organ culture system to evaluate cell invasion capacity and showed that T24-IL1RA cells showed significantly less invasive capacity compared to parental T24 cells or T24-EV. Conclusions: Taken together, our results indicate an inverse correlation between IL1RA expression and tumor cell invasive capacity and migration, suggesting that IL1RA plays a role in bladder carcinogenesis, while the exact mechanisms by which IL1RA influences tumor cells migration/invasion remain to be clarified in future studies. Furthermore, we confirmed that real-time impedance sensing and the porcine ex vivo organ culture methods are powerful tools to discover differences in cancer cell migration and invasion.

Verification of ansys and matlab Heat Conduction Results Using an “Intrinsically” Verified Exact Analytical Solution

Abstract A two-dimensional (2D) transient thermal conduction problem is examined, and numerical solutions to the problem generated by ansys and matlab, employing the finite element (FE) method, are compared against an “intrinsically” verified analytical solution. Various grid densities and time-step combinations are used in the numerical solutions, including some as recommended by default in the ansys software, including coarse, medium, and fine spatial grids. The transient temperature solutions from the analytical and numerical schemes are compared at four specific locations on the body, and time-dependent error curves are generated for each point. Additionally, tabular values of each solution are presented for a more detailed comparison. Two different test cases are examined for the various numerical solutions using selected grid densities. The first case involves uniform constant heating on a portion of one surface for a long duration, up to a dimensionless time of 30. The second test case still involves uniform constant heating but for a dimensionless time of one, immediately followed by an insulated condition on that same surface for another duration of one dimensionless time unit. Although the errors at large times for both ansys and matlab are extremely small, the errors found within the short-duration test are more significant, in particular when the heating is suddenly set “on.” Surprisingly, very small errors occur when the heating is suddenly set “off.” The solution developed using the matlab differential equation solver is found to have errors an order of magnitude larger than those generated using ansys with a similar mesh size and same FE type (quadratic triangular). This occurs not only during the transient but also for steady-state problems. However, the matlab computational efficiency is superior. Also, when using ansys, at early times the numerical errors are very sensitive to the time-step chosen rather than the spatial discretization. Therefore, the time-steps have to be very small near a singularity.

Theoretical Investigation of Equilibrium Dynamics in Braided Gravel Beds for the Preservation of a Sustainable Fluvial Environment

Gravel bars have an important role in the exchange between surface and subsurface waters, in preventing and mitigating riverbank erosion, in allowing the recreational use of rivers, and in preserving fluvial or riparian habitats for species of fishes, invertebrates, plants, and birds. In many cases, gravel bars constitute an important substrate for the establishment and development of ground flora and woody vegetation and guarantee higher plant diversity. A sustainable management of braided rivers should, therefore, ensure their ecological potential and biodiversity by preserving a suitable braiding structure over time. In the present study, we propose an analytical–numerical model for predicting the evolution of gravel bars in conditions of dynamical equilibrium. The model is based on the combination of sediment balance equation and a regression formula relating dimensionless unit bedload rate and stream power. The results highlight the dependence of the evolving sediment particles’ pattern on the ratio of initial macro-bedforms longitudinal dimension to river width, which determines the gradual transition from advective and highly braiding to diffusive transport regime. Specifically, the tendency to maintain braiding and flow bifurcation is associated with equilibrium average bed profiles and, therefore, equilibrium average stream power characterized by the maximum period that does not exceed transverse channel dimension.

Weighted GDoP for improved position accuracy using NavIC and GPS hybrid constellation over Indian sub-continent

Positioning accuracy of any navigation system plays a vital role in precise positioning applications like CAT-1 aircraft landings, surveying, etc. GNSS positioning accuracy can be affected by many factors like multipath, refraction in atmospheric layers, and satellite-receiver geometry. As Geometric Dilution of Precision (GDoP) is a dimensionless unit, which characterizes the geometry of satellite-receiver. For enhancing the position accuracy over low latitude Indian sub-continent, satellite-receiver geometry is investigated using weighted least squares-based Dilution of Precision (WGDoP) algorithm using GPS and NavIC combined constellation over Hyderabad region. The results are validated with IGS data of the receiver located at Navigation and Communication Research Centre (NCRC), Chaitanya Bharathi Institute of Technology (CBIT), Hyderabad.

Estimation of Surface Water Runoff for a Semi-Arid Area Using RS and GIS-Based SCS-CN Method

The proper planning of storage structures, waterways, irrigation schemes, water harvesting, erosion control structures, and groundwater development strategies requires accurate estimation of surface runoff. However, hydrologists in Saudi Arabia face serious challenges, specifically due to the rare availability of surface runoff data. In this study, the soil conservation service-curve number (SCS-CN) method integrated with geographic information system (GIS) and remote sensing (RS) was utilized to estimate the surface runoff in Wadi-Uranah basin, in the western region of Saudi Arabia. Different thematic maps such as slope, hydrologic soil group (HSG), land use/land cover (LULC), and daily rainfall have been created in GIS environment and processed to generate the curve number (CN) and surface runoff maps. Based on the soil classification results, the study area was categorized into two HSGs (B and C). The dominant HSG was group C, representing about 98.8% of the total area. The LULC analysis showed four main land use types in the study region: urban, rocks, barren soil, and agricultural areas. Furthermore, the finding results showed that CN values for the normal conditions (CNII) ranged between 74 and 93 in agricultural and both urban and rock areas, respectively. The CNII values were further corrected using slope data to derive slope-adjusted CNII. Moreover, the rainfall-runoff results showed an increase in the daily runoff of the study region with a minimum of 15 mm to a maximum of 74 mm. Another interesting result was rainfall-runoff linear regression analysis that showed a good correlation of 0.98. Additionally, the peak runoff hydrograph flows for 10-, 50-, and 100-year return periods obtained from the SCS-based dimensionless unit hydrograph were 828, 1353, and 1603 m3/s, respectively. Therefore, this study highlights that the SCS-CN method integrated with RS and GIS deserves further attention for estimating runoff of ungauged basins for better basins management and conservation purposes.

تحليل المعطيات المورفومترية لأحواض التصريف بمدينة حفر الباطن - شمال شرق المملكة العربية السعودية باستخدام نظم المعلومات الجغرافية (GIS)

تقدم هذه الدراسة تحليلا جيومورفولوجياً لخصائص الأودية الداخلة على مدينة حفر الباطن باستخدام تقنيات نظم المعلومات الجغرافية التي ساعدت على استخلاص الخصائص التضاريسية والخصائص المورفومترية المستخدمة في تطبيق نموذج SCS Dimensionless Unit Hydrograph لحساب تدفق الذروة لكل وادٍ. ولقد أظهرت نتائج تطبيق هذا النموذج أن سيول الأودية المدروسة تتدفق خلال فترات تتباين من حوض مائي لآخر بين 4.38 ساعات بالحوض (1) و26.44 ساعة بالحوض (9) وبحجم يتراوح بين 30.04 م3/ثانية بالحوض (1) و257.58 م3/ثانية بالحوض (10)، وبسرعة تتراوح بين 1.50 م/ثانية بالحوضين (2) و(5) و2.37 م/ثانية بالحوض (9). كما ساعدت مخرجات التحليل المكاني لبرنامج Arc GIS في استخلاص 12 متغيرات مورفومتريو 11 متغير تضاريسي ساعدت في تصنيف أحواض الروافد المدروسة حسب كل متغير.

Assessment of the Stability of an Unlined Rectangular Tunnel with an Overload on the Ground Surface

City tunnels are often constructed at shallow depths, and tunnel failure may be initiated by overloads resulting from surrounding buildings, structures, heavy‐haul trailers, and other installations. Although several works have been reported on tunnel stability, stability numbers have mainly been obtained for cases with fully cohesive soils. Moreover, little information has been presented about the influence of overloads on the failure patterns for unlined rectangular tunnels. This paper uses upper‐bound finite element methods to assess the stability of an unlined rectangular tunnel in cohesive‐frictional soils with an overload acting on the ground surface. A complete set of dimensionless parameters covering the tunnel size and shallow tunnel depth and Mohr‐Coulomb material parameters are determined to obtain the dimensionless overload. In addition, failure modes that are similar to slip line fields are acquired. A failure mechanism that may cause base heave is proposed in this paper to improve the accuracy of the results. These failure patterns are more complex for cases with larger dimensionless depth, larger internal friction angle, and smaller dimensionless unit weight. Compared with the rigid‐block mechanisms from the upper‐bound rigid‐block analysis method, these computed failure mechanisms are better suited for rectangular tunnel stability analysis.

A predictive power sequence equation for vapor pressures of pure organic fluids and partial pressures in multicomponent systems in equilibrium

The simplified Clausius-Clapeyron equation with the assumption of a constant molar enthalpy of vaporization is not adequate for general applications, despite the desirable need of using only two experimental values for the two integration constants. Therefore many correlations and models of equations of state with more than two necessary empirical constants are used. Here the critical state equation is used as a starting point, with a power sequence as a mathematical model for the estimation of the critical constants for small molecules and for homologous series. With the n-alkanes as reference class for all organic compounds, a reference vapor pressure equation has been defined as function of the relative molecular mass M, which represents principally the correct temperature dependence over the entire liquid state of n-alkanes. With an additional, temperature dependent structural increment U, with the same dimensionless unit as M, a generally applicable vapor pressure equation results for all organic fluids which needs only two specific experimental values. In this investigation principally liquids with freezing point, Tf < 298 K are discussed. The two experimental vapor pressures used are for T1 = 298.15 K and T2 = Tb (boiling point). The predicted values are reliable for the most part of the liquid state. The equation has been validated for alkanes, alkyl-benzenes, 2-ketones, esters, primary alcohols and carboxylic acids by comparing of predicted values with published data of high quality. The increment values for specific functional groups and branching groups can be used for pressure predictions only when the structure or the boiling point is known. An important application of the increments is the prediction of partial pressures in binary mixtures with specific fractions δ of the U-values. The determination of the corresponding δ-values from a set of experimental partial vapor pressures is very easy in comparison with other models. Prediction of partial pressures in multicomponent systems at equilibrium is possible with a good first approximation, without additional empirical constants.Most remarkably, for the application of the developed equation only a small number of easily available empirical parameters are needed as structure increments U and fractions δ of U. The qualitative relation of these parameters to the polarities and other properties of the investigated compounds allow a better understanding of the main reasons for the relative magnitude of vapor pressures and their interactions in mixtures.

A STUDY OF FERROFLUID LUBRICATION BASED ROUGH SINE FILM SLIDER BEARING WITH ASSORTED POROUS STRUCTURE

This paper attempts to study a ferrofluid lubrication based rough sine film slider bearing with assorted porous structure using a numerical approach. The fluid flow of the system is regulated by the Neuringer-Rosensweig model. The impact of the transverse surface roughness of the system has been derived using the Christensen and Tonder model. The corresponding Reynolds’ equation has been used to calculate the pressure distribution which, in turn, has been the key to formulate the load carrying capacity equation. A graphical representation is made to demonstrate the calculated value of the load carrying capacity which is a dimensionless unit. The numbers thus derived have been used to prove that ferrofluid lubrication aids the load carrying capacity. The study suggests that the positive impact created by magnetization in the case of negatively skewed roughness helps to partially nullify the negative impact of the transverse roughness. Further investigation implies that when the Kozeny-Carman’s model is used, the overall performance is enhanced. The Kozeny-Carman’s model is a form of an empirical equation used to calculate permeability that is dependent on various parameters like pore shape, turtuosity, specific surface area and porosity. The success of the model can be accredited to its simplicity and efficiency to describe measured permeability values. The obtained equation was used to predict the permeability of fibre mat systems and of vesicular rocks.

Regulation effectiveness of a window-check dam on debris flows

Window-check dams are widely used to regulate sediment transport in debris-flow hazard mitigation. However, the effectiveness of window-check dams on modulating debris flows is still unclear. In this study, dimensional analyses combined with physical experiments were conducted to evaluate the sediment-trapping and particle-regulating functions of a window-check dam. Results showed that both of the attenuation ratio of unit weight and (the difference between upstream and downstream divided by upstream) the retention ratio of mass (upstream divided by downstream) decreased with an increase in openings area, drain holes width, and bottom slope. However, the increase in inflow unit weight of debris-flow led to larger retention ratio of mass. Besides, an optimal attention ratio corresponding to dimensionless unit weight of 1.8 was found. Also, the particle sizes sorted by the window-check dam were found to be associated with the median grain size of sediment. Furthermore, two improved expressions were obtained to assess the effectiveness of window-check dams on trapping sediments. The comparison between these expressions and laboratory data is in reasonable agreement, serving a useful reference for the optimal design of check dams.