scholarly journals Estimation of energy dissipation in step-pool reaches of mountain river - a field investigation

2021 ◽  
Author(s):  
Abbas Torabizadeh ◽  
Hamid-Reza Ghafouri ◽  
Mohamadreza Majdzadehtabatabai ◽  
Ahmad Tahershamsi
Keyword(s):  
Energy Dissipation ◽  
Field Measurements ◽  
Step Length ◽  
Field Investigation ◽  
Mountain River ◽  
Mountainous Areas ◽  
Flow Conditions ◽  
Effective Parameters ◽  
Mountain Rivers ◽  
Height Difference

The bed of the step-pool rivers is adapted to the flow conditions in terms of the topographic position and the steep slope of the path in such a way to dissipate the water energy, along the river. The beds of these rivers is sinusoidal like the meander rivers. However, as the river banks are mostly rocky in mountainous areas and the erosion in these areas is less, the bed fluctuation of these reaches is mainly vertical. When the water flow streams from the step crest into the pool, most of the water energy dissipates. In addition to the height difference, other factors contribute to the energy dissipation in the step pool reaches. The present study examines the energy dissipation by determining its effective factors, including step height (H), step length (L), hydraulic radius (R), sediment material diameter (d84), velocity in the step (V), etc. by field measurements in three reaches of mountain rivers. In the same vein, an equation is provided to estimate energy dissipation in the step pool reaches, by considering measurable effective parameters.

scholarly journals Sediment Transport and Water Flow Resistance in Alluvial River Channels: Modified Model of Transport of Non-Uniform Grain-Size Sediments

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2038
Author(s):  
Gennady Gladkov ◽  
Michał Habel ◽  
Zygmunt Babiński ◽  
Pakhom Belyakov
Keyword(s):  
Sediment Transport ◽  
Water Flow ◽  
Transport Model ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Field Investigation ◽  
Empirical Modeling ◽  
River Channels ◽  
Channel Deformations ◽  
East European

The paper presents recommendations for using the results obtained in sediment transport simulation and modeling of channel deformations in rivers. This work relates to the issues of empirical modeling of the water flow characteristics in natural riverbeds with a movable bottom (alluvial channels) which are extremely complex. The study shows that in the simulation of sediment transport and calculation of channel deformations in the rivers, it is expedient to use the calculation dependences of Chézy’s coefficient for assessing the roughness of the bottom sediment mixture, or the dependences of the form based on the field investigation data. Three models are most commonly used and based on the original formulas of Meyer-Peter and Müller (1948), Einstein (1950) and van Rijn (1984). This work deals with assessing the hydraulic resistance of the channel and improving the river sediment transport model in a simulation of riverbed transformation on the basis of previous research to verify it based on 296 field measurements on the Central-East European lowland rivers. The performed test calculations show that the modified van Rijn formula gives the best results from all the considered variants.

scholarly journals Field Investigation and Rapid Deterioration Analysis of Heavy Haul Corrugation

2021 ◽  
Vol 11 (14) ◽  
pp. 6317
Author(s):  
Feng Jin ◽  
Hong Xiao ◽  
Mahantesh M Nadakatti ◽  
Huiting Yue ◽  
Wanting Liu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Cracks ◽  
Field Measurements ◽  
Field Investigation ◽  
The Finite Element Method ◽  
Rail Corrugation ◽  
Rapid Deterioration ◽  
Heavy Haul

In this study, the rapid growth of corrugation caused by the bad quality of grinding works and their wavelength, depth, and evolution processes are captured through field measurements. The residual grinding marks left by poor grinding quality lead to further crack accumulation and corrugation deterioration by decreasing plastic resistance in rails. In this case, the average peak-to-peak values of corrugation grow extremely fast, reaching 1.4 μm per day. The finite element method (FEM) and fracture mechanics methodologies were used to analyze the development and trends in rail surface crack deterioration by considering rails with and without grinding marks. Crack propagation trends increase with residual grinding marks, and they are more severe in circular curve lines. To avoid the rapid deterioration of rail corrugation, intersections between grinding marks and fatigue cracks should be avoided.

scholarly journals Experimental and field verifications of radial gates as flow measurement structures

2021 ◽  
Author(s):  
Hossein Khalili Shayan ◽  
Javad Farhoudi ◽  
Alireza Vatankhah
Keyword(s):  
Field Measurements ◽  
The United States ◽  
Data Series ◽  
Flow Conditions ◽  
Flow Limit ◽  
Before And After ◽  
Energy And Momentum ◽  
Extensive Experimental Data ◽  
Radial Gate ◽  
Discharge Curves

Abstract Radial gates are common structures in irrigation projects. This paper presents some theoretical-based equations for explicit estimation of the discharge from the radial gate under free and submerged flow conditions using Energy and Momentum (E-M) principles. The proposed equations were calibrated using extensive experimental data collected from the literature and this study for three types of radial gates under free and submerged flow conditions. The submergence threshold of radial gates is concluded, based on the concepts of hydraulic jump and the intersection of free and submerged head-discharge curves. The results indicated that the error in estimating the discharge increases under transition ( − 2.5 ≤ Sr% ≤ + 2.5), gate lip (1 < y0/w ≤ 2), and high submerged (yt/y0 ≥ 0.95) flow conditions. However, in these flow limit conditions, the discharge error can be considerably decreased by adjusting the tailwater depth to flow depth just after the gate and using the energy equation for the sections before and after the gate. The efficiency of the proposed methods was evaluated based on the data series from field measurements of radial gates in 29 check structures at irrigation canals in the United States and Iran. The results showed that the discharge could be estimated using the proposed equations in field conditions with acceptable accuracy.

SEL VƏ DAŞQIN AXINLARINDA DAĞ ÇAYLARI MƏCRASININ YUYULMA DƏRİNLİYİNİN TƏYİNİ

2021 ◽  
Vol 1 (1) ◽  
pp. 82-88
Author(s):  
F.Ş., Əhmədov ◽  
R.K., Quliyev ◽  
R.Ü Əbdüləzimov
Keyword(s):  
Average Velocity ◽  
Average Diameter ◽  
Average Depth ◽  
Mountain River ◽  
Mountain Rivers ◽  
Cross Sectional ◽  
Average Width ◽  
Caucasus Mountains ◽  
Flood Flow

Abstract. The article is dedicated to the determination of the wash depth of mountain rivers in floods and overflows. As well-known, hydrotechnical equipment is exposed to destructive damages of the floods and overflows. The undersurface of bridge basement and coast guards are washed away, the surface of drainage devices in water supply and dams (Düker) at river crossings are opened up. Therefore, the protection of the equipment against the destructive damage of the floods and overflows should be ensured. To this aim, first of all, the depth of the fortification of the equipment basement in riverbeds and the width through which the river can flow should be determined and the works of installing coast guards should be accordingly implemented. Since the flow regime of rivers due to floods in the course of mountain riverbeds dramatically changes, the width, depth, roughness and cross-sectional area of the riverbed also changes. To that reason, in the smallest case, calculation formulas includes the average width and wash depth of the riverbed in the course of the floods and overflows, average diameter of undersurface soils, the slope of the location of hydrotechnical structures, velocity due to the average diameter of the riverbed soils and so on. The article contains the analyses of theoretical and practical materials about the floods and overflows in mountain rivers. For the rivers flowing through the southern hills of Great Caucasus Mountains, the expressions for determining the riverbed parameters and hydrological parameters of rivers are used. According to the expressions, average width due to non-washing of the riverbed in floods in accordance with flood flow and slope of the studied part of the riverbed, the average depth of the riverbed crossing the flood, the average velocity of the flow and the wash depth in accordance with them are determined. basing on all these, the determining method of the wash depth of mountain riverbeds in floods have been worked out and determining the wash depth have been recorded. The studied methodology can be used in determining the riverbed parameters in floods and overflows. Keywords: Flood, riverbed deformation, mountain river, wash depth, average diameter of undersurface sediments, riverbed stability, flood velocity

Sediment size and shape observation in a mountain river, southern Brazil

2021 ◽  
Author(s):  
Danrlei Menezes ◽  
Masato Kobiyama
Keyword(s):  
Multiple Regression ◽  
Annual Rainfall ◽  
Mountain River ◽  
Southern Brazil ◽  
Mountain Rivers ◽  
Bed Sediments ◽  
Mean Values ◽  
Monitoring Period ◽  
Size And Shape ◽  
The Mean

<p>The aim of the present study was to characterize the size and shape of sediments along a reach of a mountain river in Maquiné municipality, southern Brazil, to establish an efficient methodology in river sediments analysis. In Brazil, this might be a pioneering study of mountain rivers characterized by the presence of gravel, cobble, and boulders sediments. The study catchment, covered by Dense and Mixed Rain Forest and high-altitude grasslands (Campos de Cima da Serra), has an altitude difference of 900 m. Its geology is characterized by the Serra Geral Formation (basaltic rocks) and pedology by Cambisols and Neossols. The mean annual rainfall is 1200 mm. According to the Köppen classification, the regional climate is humid subtropical with hot summers (Cfa) in lower areas and humid subtropical with mild summers and cold winters (Cfb) in higher areas. The catchment outlet has a fluviometric station, and at its headwater, there is a rainfall gauge, both of which perform automatic measurements every 10 min. For the bed sediments diameter analysis, 500 grains were sampled, following the Wolman Pebble Count methodology. The measurements were carried out along the same reach (100 m) in five stages (December 2019; February, May, August, and November 2020) to observe sediment dynamics over time. During these measurements, the mean values of water depth and discharge were 0.4 m and 0.8 m³/s, respectively. To determine the size and shape, the three axes A (longest), B (intermediate), and C (shortest) were measured by using the tree caliper. With the axes’ values, the sediment shape was classified into four types: sphere, rod, disc, and blade. Linear correlation and multiple regression analyses were performed to evaluate the influence of each sediment axis on determining the nominal diameter (D<sub>n</sub>). The mean values of D<sub>max</sub>, D<sub>90</sub>, D<sub>84</sub>, D<sub>50</sub>, D<sub>16,</sub> and D<sub>10</sub> of all the sampled sediments were 290.61, 114.40, 103.52, 56.27, 35.89, 28.0, and 18.40, respectively. Preliminary results indicate that 38% of the sampled sediments corresponded to the disc format and did not vary over the year. The characteristic diameters remained constant throughout the monitoring period, even though strong rainfall-runoff events sometimes occurred (~ maximum runoff was 33 m²/s in July 2020). The D<sub>n</sub> values calculated with the multiple regression model based on the analysis of the axes (D<sub>n</sub> = f (A, B, f (A, B))) were very close (R² = 0.95) to those calculated through an original definition of D<sub>n</sub>, i.e., D<sub>n</sub> = (A·B·C)<sup>1/3</sup>. During the monitoring period, notable changes in the size and shape of the sediments were not observed. The axes analysis confirms that the D<sub>n</sub> value can be estimated only with the measurement of axes A and B, without axis C. Therefore, this methodology (without the axis C) may be recommended to characterize the size and shape of bed sediments in mountain rivers. Finally, the present study highlights the importance of fieldwork to advance basic river sciences in Brazil.</p>

scholarly journals EXTERNAL BALLISTICS TASK MODELLING FEATURES / IŠORINĖS BALISTIKOS UŽDAVINIO MODELIAVIMO YPATUMAI

Aviation ◽  
2012 ◽  
Vol 15 (4) ◽  
pp. 112-116 ◽  
Author(s):  
Albertas Pincevičius ◽  
Vaclovas Jonevičius ◽  
Romualdas Baušys
Keyword(s):  
Computer Control ◽  
Mountainous Area ◽  
Mountainous Areas ◽  
Height Difference ◽  
Control Programs

Based on the solutions of an external ballistics task, tables are made for firearms and tables or computer control programs for heavy weapons. If you shoot in a mountainous area where the height difference between gunner and target can be about a hundred meters, defined skills for firing are necessary. We can make specific tables of firing with firearms in mountainous areas. Mortars are relatively simple and inexpensive weapons, and therefore their management has never been computerised. We have shown that this deficiency can be corrected. The programs described above calculate the required parameters very quickly. Santrauka Remiantis išorinės balistikos uždavinio sprendimais, šaulių ginklams sudaromos lentelės, o sunkiesiems ginklams – lentelės arba kompiuterinės valdymo programos. Jeigu šaudoma kalnuotoje vietovėje, kur aukščių skirtumas tarp šaulio ir taikinio siekia net šimtą metrų, reikia konkrečių įgūdžių. Galima sudaryti specifines šaudymo šaulių ginklais kalnuose lenteles. Minosvaidis yra santykinai paprastas ginklas, todėl jo valdymas nebūna kompiuterizuotas. Parodyta, kad šį trūkumą galima pataisyti. Aprašytos programos per kelias dešimtis sekundžių suskaičiuoja reikiamus parametrus.

An Infrared Interferometer for Elastoplastic Crack-Tip Field Investigation of Homogeneous and Bimaterial Beams: A Study of Three-Dimensional Effects and J-Dominance

1998 ◽  
Vol 65 (4) ◽  
pp. 1032-1041
Author(s):  
J. K. Sinha ◽  
H. V. Tippur
Keyword(s):  
Plane Deformation ◽  
Three Dimensional ◽  
Surface Preparation ◽  
Field Measurements ◽  
Sample Surface ◽  
Field Investigation ◽  
Crack Tip Field ◽  
Full Field ◽  
Infrared Wavelength ◽  
Dimensional Effects

An infrared interferometer capable of performing real-time full-field noncontacting deformation field measurements on optically rough surfaces is proposed as a tool for elastoplastic fracture mechanics investigations. The choice of the infrared wavelength allows interferometric measurements on fracture samples with little or no surface preparation and is more tolerant of the damage accumulation near the crack. The interferometer also bridges a sensitivity gap among existing techniques for out-of-plane deformation measurement. First, a rigorous Fourier optics analysis is provided for the interferometer and the range of surface roughness that can be studied using this interferometer is examined. The interferometer is then used for mapping deformations near elastoplastically deformed cracks in aluminum beams and solder-copper bimaterials. The regions of dominant three-dimensional effects and J-dominance are examined on the sample surface by evaluating measurements along with companion finite element analyses and the HRR fields.

Bayesian Prediction of Structural Response Under Crowd-Induced Walking Load

2018 ◽  
Vol 18 (03) ◽  
pp. 1850039 ◽  
Author(s):  
Lu Dai ◽  
Na Yang ◽  
Qingshan Yang
Keyword(s):  
Bayesian Method ◽  
Structural Response ◽  
Step Length ◽  
Field Investigation ◽  
Bayesian Theory ◽  
Acceleration Response ◽  
Design Standards ◽  
Heritage Building ◽  
Walking Velocity ◽  
Beam Bridge

Research on modeling the walking-induced dynamic load and its effects on structures has been increasing in recent years. Existing standards for estimating the acceleration response excited by crowd takes [Formula: see text] ([Formula: see text] is the number of walking persons in a crowd) times the single pedestrian load as the crowd load, neglecting uncertainties in the related parameters. This paper proposes a method for predicting the crowd-induced structural acceleration response based on the Bayesian theory. Parameters of the crowd include the distribution of stepping frequency, the interval of arriving time and the weight of pedestrians. By combining the existing methods for calculating the structural response to a pedestrian load and the Bayesian theory, the root-mean-square acceleration along with the crowd parameters are obtained. A field investigation is conducted to study the walking characteristics of pedestrians, including the distribution of stepping frequency, walking velocity and step length. The case of a crowd moving across a simply supported beam bridge is taken for illustration. The acceleration response under the crowd load with different stepping frequencies is calculated. A comparison between the results from the Bayesian method and the design standards is conducted. The proposed method is found to yield acceptable results, and is then applied to estimating the acceleration response of a typical Tibetan heritage building, with the result compared with a field measurement.

Resilience of the macroinvertebrate community of a small mountain river (Mau River, Portugal) subject to multiple stresses

2014 ◽  
Vol 65 (7) ◽  
pp. 633 ◽  
Author(s):  
Tânia Vidal ◽  
Joana I. Santos ◽  
Catarina R. Marques ◽  
Joana L. Pereira ◽  
Maria Teresa Claro ◽  
...  
Keyword(s):  
Ecological Status ◽  
Macroinvertebrate Community ◽  
Mountain River ◽  
Mountain Rivers ◽  
Multiple Stresses ◽  
Mining Areas ◽  
Multiple Stressor ◽  
Potential Source ◽  
Strong Current ◽  
Legislative Framework

Freshwaters commonly face human pressure, which produces multiple stressor scenarios that may threaten their ecological status. Biotic community assessments are useful tools to monitor such changes, and the European Water Framework Directive (WFD) has brought this into the legislative framework. The present study focused on a small mountain river facing multiple stresses, with the purpose of (1) evaluating the sensitivity of the macroinvertebrate community to the stresses, (2) assessing whether the ecological status was impaired in different years and (3) comparing the WFD approach with more refined community analyses. The river was generally in a very good ecological state. Despite seasonal and inter-annual fluctuations, no evident stressor-related effects were detected. We hypothesise that the observed resilience was the result of (1) the current dormant state of the abandoned mining areas (the most relevant potential source of contamination) and (2) the naturalness and strong current of the river, which buffered the impacts of contamination. Such a pattern may be generally valid for small mountain rivers, making them therefore more resilient to stresses. Nevertheless, small changes in community structure in the lowest reach of the river – undetected by the WFD assessment scheme – suggest that some disturbance was present, signalling the need for intervention by managers.

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