Crest Length Research Articles

Discharge Estimation over Piano Key Weirs: A Review of Recent Developments

The piano key (PK) weir has advanced over the labyrinth weir to increase the discharge capacity. Piano key weirs exhibit nonlinear flow behavior and are easy to place on the existing spillway or newly constructed dam with less base area. Various investigators are given equations to calculate the discharge coefficient for free and submerged flow conditions. The study focuses on reviewing the impacts of the PK weir geometry on the weir flow discharge coefficient, including weir length and height, upstream and downstream key widths, and apex overhangs. In this study, all possible aspects of PK weirs were briefly reviewed. From sensitivity analysis, it is observed that the discharge coefficient of the PK weir is more sensitive for the L/W dimensionless ratio followed by the B/P ratio. L is total length of the weir crest, W is width of the weir, B is total width of PK weir and P is height of the weir. This review paper is intended to serve as an accessible resource for hydraulic structures researchers and hydraulic engineering professionals alike interested in the hydraulics of PK weirs.

Morphometric Study of Proximal End of the Fully Ossified Human Femur: A Cross-Sectional Study.

Introduction The femur or thigh bone is the longest and strongest bone in the body. It provides skeletal support for the thigh. Weight-bearing and stability of gait are the essential functions of the femur. Aim To construct the baseline data on different dimensions of the proximal end of the fully ossified human femur and determine any significant differences between the right and left femora. Objective To measure the total length of the femur, proximal breadth, vertical diameter of the head, transverse diameter of the head, the circumference of the head, the vertical diameter of the neck, the transverse diameter of the neck, the circumference of the neck, anterior length of the neck, neck-shaft angle, length of the intertrochanteric crest and correlate the different dimensions of the proximal end with the total length of the femur. Result The variables of the proximal end of the left femora like proximal breadth (PB), the circumference of the head (CH), vertical diameter (VDN), the transverse diameter of the neck (TDN), the circumference of the neck (CN), neck length (NL), neck-shaft angle (NSA), length of an intertrochanteric crest (LITC) showed highly significant positive linear correlation with the length of the femur. Circumference of the neck showed the highest degree of correlation with the length of the femur (correlation coefficient 0.839). Conclusion The statistically significant difference between right and left femora was found between the length of the femur, the vertical diameter of the neck of the femur, the transverse diameter of the neck of the femur, and the length of the intertrochanteric crest of the femur. The mean value of proximal breadth, the vertical diameter of the head, the transverse diameter of the head, the circumference of the head, the circumference of the neck, anterior length of the neck of the femur, and neck-shaft angle of the right and left femora to have no statistically significant differences.

CFD analysis of Fe transfer on roughened wall caused by turbulent lead-bismuth eutectic flow

Structural material compatibility with lead bismuth eutectic is one of the main challenges for design and operation of the LBE-cooled nuclear systems. To better understand the mechanisms of stainless steel corrosion behavior in LBE flow, the iron mass transfer phenomenon on roughened walls under various LBE pipe flow conditions are numerically investigated in this study. CFD simulations are performed, by applying a low Reynolds number k-ε model, in a range of Reynolds number from 5 × 103 to 105. Meanwhile, various pipe wall roughness conditions are considered, which are simulated by crests with different depths and periodic lengths. Effects of roughness dimensions and Reynolds numbers on the near-wall mass transfer rate are investigated. Results showed that higher flow velocities and shorter crest length led to higher mass transfer coefficient. On the basis of the results, the mass transfer coefficients are proposed both for smooth wall and roughened walls. The mass transfer enhanced by wall roughness is characterized by the ratio of rough-to-smooth mass transfer coefficient, and this ratio is demonstrated by a regression equation, in which dimensionless roughness number, Reynolds number and geometrical ratio of the roughness are included. Moreover, it is found that the ratio of rough-to-smooth mass transfer coefficient is relatively more dependent on Reynolds number.

Flow over embankment gabion weirs in free flow conditions

In this study, a series of laboratory tests were performed to investigate the effects of side ramp slope, crest length, and porous media properties on the flow regimes, water-surface profiles, discharge coefficients, and energy dissipation in embankment gabion weirs with upstream and downstream slopes. 24 physical models of solid and gabion weirs with three different upstream/downstream slopes (90°, 45° and 26.5°) were created. To investigate the complexity of flow over the porous-fluid interface and through the porous material, three-dimensional (3D) numerical simulations were developed. In numerical simulation, the standard k-ε turbulence model was utilized. A structured mesh domain was used to simulate the physical model. Water surface profiles above the porous weirs were used for comparison between the numerical simulations and measured data. These comparisons helped determine variables in the numerical simulations. Numerical simulation enables visualization of streamlines around and through the gabion weirs. In addition, mean stream wise velocity profiles above and within the porous structures were obtained. Numerical simulations showed that a reduction in the slope of the upstream face leads to an increased curvature of streamlines and the velocity distribution exhibits a non-uniform wavy shape due to the geometrical properties of the weirs. As the velocity profiles move downstream, the velocity distribution within the porous structures were more affected by the presence of the pores. The experimental results show that decreasing upstream slopes, from 90° to 26.5°, leads to decreased discharge coefficients. However, in all cases, gabion weirs lead to greater discharge coefficients than those of similar solid weirs. For milder side slopes, discharge ratios (flow passing through all faces of the gabion weirs over the inlet discharge) decreased nonlinearly. Moreover, with increasing the inlet discharge, relative energy dissipation was reduced up to 45% in gabion weirs.

Earlier appearance of Risser sign on ultrasound versus radiograph in adolescent idiopathic scoliosis.

ObjectiveThe usefulness of ultrasound in the detailed assessment of the Risser sign is still unclear. The purpose of this study was to analyze the usefulness of ultrasound for determining the Risser sign compared with that determined by conventional radiography by each Risser grade.Materials and MethodsEighty-eight iliac crests from 44 adolescent patients who visited the scoliosis clinic with Risser grades 0-4 were evaluated. The ultrasound probe was placed vertically on the iliac crest and the point where iliac apophysis ossification ended was marked. The length of ossification relative to the length of the iliac crest was calculated.ResultsAgreement between radiographic and ultrasound images were found in 58/86 iliac crests (67%). Kappa value was 0.565. Agreement between the two methods with regard to Risser grade was 53% for grade 0, 43% for grade 1, 47% for grade 2, 88% for grade 3, and 90% for grade 4. With additional analysis by integrating grades into two groups, the agreement rate was 47.7% and the Kappa value was 0.288 in the grade 0-2 group, and 88% and 0.703 in grades 3-4 group, respectively. In cases of disagreements, 93% of the iliac crests were judged as having higher Risser grades by ultrasound than by radiograph.ConclusionRisser sign evaluation by ultrasound demonstrated a higher agreement rate in grades 3 and 4, whereas less agreement was found in grades 0-2. In the majority of cases with disagreement, ultrasound showed a higher grade than radiography, suggesting that ossification can be detected earlier with ultrasound than with radiography.

PERANCANGAN GEOMETRIK JALAN ANTAR KOTA MENGGUNAKAN AUTOCAD CIVIL 3D STUDENT VERSION (STUDI KASUS JALAN MANDEH PROVINSI SUMATERA BARAT)

The roadway geometric designing must consider as optimal as possible time spent in designing and building a road. This study aims to determine the results of road geometric design using manual calculation methods and calculations by using AutoCAD Civil 3D Student Version 2016 with a case study of St. Mandeh STA 30 + 000 - STA 37 + 000. The design scope consists of horizontal alignment design, superelevation, and vertical alignment. The method used by reference standard of AASHTO 2011, and for criteria design used by Bina Marga 1997 standard. The results of the horizontal alignment design, obtained 6 SCS curves, 3 FC curves, and 5 SS curves. The manual calculation results are the same as the results of AutoCAD Civil 3D calculations for FC curves and SCS curves. For the SS curve, the result difference is <0.2 m. AutoCAD Civil 3D only calculates the superelevation of FC curve and SCS curve, then the calculation of SS curve have done by manual design. In the vertical alignment design there were 4 crest vertical curves and 3 sag vertical curves with a slope of 0.02% - 5.23% approprite the maximum slope requirement of 11%. The length of crest and sag vertical curve Lv approprite the K value requirement for stopping visibility and preceding visibility

Failure of the Downstream Shoulder of Rockfill Dams Due to Overtopping or Throughflow

This paper presents the results of an extensive laboratory set of tests aimed to study the failure of the downstream shoulder of highly permeable rockfill subjected to overflow. The experimental research comprised testing 114 physical models by varying the following elements: (i) the median size of the uniform gravels (7 to 45 mm); (ii) the configuration of the dam, i.e., upstream and downstream shoulders and crest or just the downstream shoulder; (iii) the dam height (from 0.2 to 1 m), (iv) the crest length (from 0.4 to 2.5 m), (v) the downstream slope (from 1 to 3.5 H:V), (vi) the type of impervious element (i.e., central core, upstream face, and no impervious element). The tests allowed us to identify two failure mechanisms, slumping and particle dragging. In addition, the downstream slope was observed to be one of the most important variables in this parametric study, as it influenced the pore water pressures inside the dam, the failure discharge, and the occurrence of one or the other mechanism of failure.

Stacking ensemble-based hybrid algorithms for discharge computation in sharp-crested labyrinth weirs

Labyrinth weirs are utilized to transport a greater discharge during floods in contrast to conventional weirs due to their increased weir crest length. Nevertheless, due to the increased geometric complexity of labyrinth weirs, determination of accurate discharge coefficients and accordingly, head-discharge ratings are quite essential issues in practical application. Hence, as a first step the present study proposes the following eight standalone algorithms: decision table (DT), Kstar, least median square (LMS), M5 prime (M5P), M5 rule (M5R), pace regression (PR), random forest (RF) and sequential minimal optimization (SMO). Then, applying the stacking (ST) algorithm, these standalone models were hybridized to predict the discharge coefficient (Cd) for sharp-crested labyrinth weirs. Potential/effective variables were constructed in the form of several independent dimensionless parameters (i.e., θ, h/W, L/B, L/h, Froude number (Fr), B/W and L/W) to predict Cd as an output. The accuracy of the developed models was examined in terms of different statistical visually based and quantitative-based error measurement criteria. The results illustrate that h/W and B/W parameters have the highest and lowest effect on the Cd prediction, respectively. According to NSE, all developed algorithms provided accurate performances, while ST-Kstar had the highest prediction power.

Numerical Simulation And Experimental Study of Hydraulic Performance of Circular Crested Normal Weirs

Weirs are simple control structures usually built across channels for water storage and measurementof flow rates. The main target of the present study is to numerically simulate and experimentally study thehydraulic performance of circular crested normal weirs. For numerical simulation, the commercialpackage ANSYS CFX is utilized adopting tetrahedrons mesh with a maximum total number of 1932301elements, while, for the experimental study nine physical models are manufactured and tested havingdifferent crest diameters and various weir heights. Numerical simulation results demonstrated that theANSYS CFX software is highly capable for simulating circular crested normal weirs showing quite goodagreements in water surface profiles and 4.3% mean percentage error in upstream head above crest,while, the software showed 6.8% mean percentage error in estimating discharge coefficient. A simpleempirical expression is obtained for the estimation of coefficient of discharge in terms of ratio of upstreamhead to weir height and the ratio of upstream head to crest diameter with a coefficient of correlation =0.88. The flow rate magnification is found increasing with the increase of upstream relative head and thebest performance of the weir is found when the ratio of crest diameter to weir height = 0.33 at which thehighest increase in flow rate is observed ranging between 25.41% and 32.14% compared with sharpcrested weirs having the same height and the same length of crest

Numerical investigation of the effect of geometric parameters on discharge coefficients for broad-crested weirs with sloped upstream and downstream faces

Weirs are structures that are important for measuring flow and controlling water levels. Research has shown that the discharge coefficient is not constant and depends on the crest length, the height of the weir, the upstream head, and the upstream and downstream slopes. In this study, the effect of these parameters on the discharge coefficient (Cd) is investigated by numerical simulation. The current study present numerical simulation using the ANSYS FLUENT software. The total number of simulations is 432 which includes: 4 upstream slopes, 4 downstream slopes, 3 weir heights, 3 upstream heads (h1) and 3 weir crest lengths. It was found that the downstream face slope has little effect on Cd. For 0.1 < H1/w < 0.4 by decreasing the upstream slope, Cd increases, where H1 is the water head on the weir crest and w is the length of the crest. Also, for the same range, by decreasing the height of the weir (p), the Cd increases. For 0.16 < H1/p < 2, as the length of the crest decreases, the Cd increases. By comparing the numerical simulation results to physical measurements, multi-variable regression equations for estimating Cd are presented. In addition to Cd, extraction of other more detailed information such as water level profiles and velocity profiles at different locations is provided.

Geometric and Hydraulic Properties of Arced Labyrinth Weirs

Weirs serve a critical role in dam safety. Numerous reservoirs' flood projections used in hydraulic design have risen in magnitude in recent years. As a result, many current spillways are no longer adequate since they do not fulfill current discharge capacity standards. Labyrinth weirs are frequently used to rehabilitate existing fixed width spillways. Weirs come in a variety of shapes and sizes, including labyrinth, linear, piano key, and more. Labyrinth weirs enhance the weir crest length for a given width, which increases the weir flow capacity. The majority of labyrinth weirs are designed in linear designs. An Arced cycle layout can boost the discharge capacity and hydraulic efficiency of a labyrinth weir. The article cites an arced geometric layout for labyrinth weirs, as well as nomenclature for arcspecific geometric variables. Experimental studies in the literature are presented by discussing and comparing.

Estimation of Femur Length From Its Fragments in an Iranian Population

Stature is one of the important variables to identify an individual, and the previous reports show that intact femur has the highest correlation with stature. But the femur is usually damaged in forensic cases. Hence in the present study, the femur length is estimated from proximal and distal femoral fragments in the Iranian population. Sixty-four dry femora (32 from each side) without sex determination were studied. The variables were measured by using the osteometric board and digital vernier caliper. The bones with visible abnormalities were excluded from the study. The measured values were analyzed by SPSS 25 software. The linear regression is used for estimating maximum femur length from the other measurements of femoral fragments. The result of this study showed that the value of segmental measurements was different between the right and left sides, but it was not statistically significant. All segmental measurements were positively correlated and found to have a linear relationship with the maximum femoral length (P&lt;0.05) except for femoral neck circumference, which was not significantly different. The regression equation suggested that the intertrochanteric crest length is the best estimator of maximum femur length. The data of this study showed that the femoral length could be estimated from proximal and distal femoral fragments with the help of a regression equation. Then femoral length can be used to estimate the stature. The result of this study can be used in the analysis of forensic bone remains.

Hydraulic Performance of Sharp-Crested Labyrinth Weir

Weirs are used as a control structure in the waterways. Among the influencing geometrical parameters on the weir performance is the total crest length. Experimental work on 27 geometric models of two-cycle Labyrinth shape crest weir is tested. The tested physical models consist of three weir heights, three apex widths and the sidewall angle is between (4.67°≤ α ≤ 19°), with three models of rectangular labyrinth weirs. The weirs of the wider apex and the same total length perform better and its coefficient of discharge is higher. Labyrinth weirs of longer sidewall length and contents same apex width performance batter. The larger value of sidewall angle and for a constant apex width reduces the value of discharge coefficient. The value of Cd range from (0.34-0.83) for the ratio of upstream head to the weir height (h/P) is ranged (0.08-0.48). The equations to predict the value of the discharge coefficient are suggested within the limitations of the present study.

Internal Solitary Wave Activities near the Indonesian Submarine Wreck Site Inferred from Satellite Images

In the early morning of 21 April 2021 local time, the Indonesian Navy submarine KRI nanggala-402 crashed in the Bali Sea (BS). As internal solitary waves (ISWs) are a great threat to submarine navigation, this paper analyzes the characteristics of ISWs in the BS by surveying satellite remote sensing images collected from 12–21 April 2021. The satellite images revealed active ISWs in the BS near the submarine wreck site with crest lengths approaching 200 km. Originating from the Lombok Strait (LS), the waves travelled northwestward across the BS deep basin, passed through the submarine wreck site, and shoaled onto the continental shelf west of the Kangean Islands, during which process, the propagation speed reached 2.69 m/s in the deep basin and 0.71 m/s in the shallow water. Based on the satellite images, the wave amplitude near the wreck site was reconstructed to be 41 m, and the reconstructed underwater wave structure showed a maximum vertical velocity of 10 cm/s. Satellite images also demonstrated the near-source evidence of ISWs near the Nusa Penida sill of the LS, and their generation were estimated to be related to the southward tidal current troughs.

A Sensitivity Analysis of Piano Key Weir Overhang Crest Length

In the scope of dam rehabilitation to manage floods increase or to increase storage, the Piano Key Weir is a good solution for concrete dams. The efficiency of Piano Key Weirs is now well demonstrated through various experimental studies. Until now most of the Piano Key Weir prototypes close to the Piano Key Weir Type A using symmetrical up- and downstream overhangs for structural reasons. The position of the overhangs influences the inlet and outlet key slopes and cross section as well as the side crest length influenced by these slopes and cross sections. On this paper, the influence of these main parameters has been studied on several models considering variation of the overhang lengths.

An iterative hydraulic design methodology based on numerical modeling for piano key weirs

Piano Key Weir (PKW) is a special type of overflow weir which provides an improved discharge capacity with its increased crest length. Increased discharge capacity makes this weir an attractive alternative in the rehabilitation of existing spillways. After the introduction of this new weir type, many experimental and numerical studies are conducted to understand the effect of the numerous geometrical parameters on the discharge capacity. However, empirical discharge formulas suggested by different researchers are not conforming to a unique expression mostly due to dependence on the experimental conditions from which they are derived. A numerical approach is used in the present study to investigate the dependence of discharge capacity of a PKW unit on several geometric parameters. Numerical models are developed and three-dimensional velocity fields are computed using FLOW-3D® software. Discharge efficiency of a PKW over an equivalent linear sharp-crested weir is evaluated within the practical range of parameters from 145 numerical solutions for 29 different PKW models. Numerically obtained data is used to form dimensionless expressions for the weir height and length as function of discharge efficiency which are proposed to facilitate an iterative numerical solution to meet the design requirements of a given project. This approach allows cost optimization while dimensioning the PKW for the required hydraulic capacity. The design procedure based on iterative numerical solutions is described and exemplified.

Determination of Discharge Coefficient for both Semicircular and Triangular Labyrinth Weirs

A Labyrinth weir is a type of nonlinear weir folded in plan-view, with the ability to pass a large flow at low heads due to an increase in the effective length of the weir crest for a given channel width. The discharge coefficients (Cd) were experimentally determined for both semicircular and triangular labyrinth weirs of varying sidewall angles (α) under free-flow conditions using eight physical models. Dimensional analyses are conducted using the Buckingham π theorem to find the dependent and non-dependent variables. A nonlinear empirical equation was developed using (Statistical Package for the Social Sciences 22) software. The findings show that the discharge coefficient decreases with the increase of headwater to (Ht/P) for both types of labyrinth weir with different plan forms. It is found that the efficiency of the semicircular and triangular labyrinth is higher than linear weir for (Ht/P ≤ 0.45) and decreases with increasing the value of (Ht/P) due to interference of flow between the layers in downstream. The obtained results revealed that the discharge coefficient (Cd) values obtained empirically using multivariable power regression and 5th degree polynomial equations considerably agree with the experimental data, for both of the semicircular and triangular labyrinth weirs. Furthermore, the correlation coefficient R2was (0.9951) and (0.9637) using 5th degree polynomial equation, and their values were (0.9643) and (0.9274) using multivariable power regression equation for both semicircular and triangular labyrinth weir models, respectively. The results in the present study compared quite well with the predicted results of the proposed equations obtained by other investigators.

Simulation of energy dissipation downstream of labyrinth weirs by applying support vector regression integrated with meta-heuristic algorithms

In this study, multi-tracker optimization algorithm (MTOA), particle swarm optimization (PSO), and differential evolution (DE) algorithms were integrated with support vector regression (SVR) to predict energy dissipation downstream of labyrinth weirs (ΔE). In order to evaluate the performance of these methods, the results are compared with corresponding outcome obtained by applying two other methods, namely, multilayer perceptron neural network (MLPNN) and multiple linear regressions methods (MLR). The input parameters comprise the discharge, the upstream flow depth, the crest length of a single cycle of the labyrinth weir, the width of a single cycle of the labyrinth weir, the apex width, the number of labyrinth weir cycles, the sidewall angle, and the height of weir. The results indicate that the meta-heuristic algorithms substantially improve the performance of SVR. The results show that the integrative methods, SVR-MTOA, SVR-PSO, and SVR-DE, are more accurate than the MLPNN and the MLR. In average, the integrative methods provide 39.63% more accurate results than the MLPNN and 79.34% more accurate results than the MLR. The average RMSE and R2 for the integrative methods are 0.0054 m and 0.977, respectively. Among all integrative methods, the SVR-MTOA yields the best results, with RMSE = 0.0044 m and R2 = 0.986.

Submerged Flow over Barrage Weirs: A Computational Fluid Dynamics Model Study

AbstractBarrage weirs, which are trapezoidal-sectioned sharp-crested weirs having finite crest length, are primarily used in the Indian subcontinent for diverting water for irrigation. This study p...

Comparative study of experimental and CFD analysis for predicting discharge coefficient of compound broad crested weir

Abstract Present study highlights the behavior of the weir crest head and width parameter on the discharge coefficient of a compound broad crested (CBC) weir. Computational fluid dynamics model (CFD) is validated with laboratory experimental investigations. In the discharge analysis through broad crested weirs, the upstream head over the weir crest (h) is crucial, where the result is mainly dependent upon the weir crest length (L) in the transverse direction to flow, water depth from channel bed. Currently, minimal investigations are known for CFD validations on compound broad crested weirs. The hydraulic research for measuring discharge numerically is carried out using FLOW 3D software. The model applies renormalized group (RNG) using the volume of fluid (VOF) method for improved accuracy in free surface simulations. Structured hexagonal meshes of cubic elements define discretized meshing. The comparative analysis of the numerical simulations and experimental observations confirm the performance of the CBC weir for precise measurement of a wide range of discharges. Series of CFD model studies and experimental validation have led to constant range of discharge coefficients for various heads over the weir crest. The correlation coefficient of discharge predictions is 0.999 with mean error of 0.28%.