Piano Key Weirs Research Articles

Unsteady Hydrodynamic Behavior at Piano Key Weirs

AbstractPiano key weirs (PKWs) are nonlinear hydraulic structures that exhibit unsteady hydraulic phenomena. A study incorporating both physical and numerical modeling was undertaken to identify in...

Physical and Numerical Modeling of the Hydraulic Characteristics of Type-A Piano Key Weirs

AbstractPiano key weirs (PKWs) have been introduced in recent years as a hydraulically efficient and cost-effective type of spillway, and there are more than 30 PKWs under construction or already c...

Experimental and numerical analysis of flow hydraulics in triangular and rectangular piano key weirs

ABSTRACT Piano key weir is a new type of spillways designed to improve the discharge capacity of dams. Generally, increasing the upstream hydraulic load in piano key weirs results in reduced discharge capacity of the weir. Accordingly, the present study investigated the effects of triangular notch on the discharge coefficient of piano key weirs. The 3D flow field over the piano key weirs was simulated in FLOW-3D software in order to study the flow hydraulics and compare the discharge rates, and the effect of each model on the flow field over the weirs and discharge coefficient was investigated. The results suggested that data of the numerical model were appropriately consistent with that of the laboratory model. According to the results, the discharge coefficient of the triangular piano key weirs was 25% higher than that of the rectangular piano key weirs. It was also observed that changing the notch shape of the piano key weir increased the discharge coefficient of the piano key weir by 36% and 13% for the heights of 5 cm of 7.5 cm, respectively.

Experimental study and modelling discharge coefficient of trapezoidal and rectangular piano key weirs

Crest length is an important parameter in influencing the discharge handling capacity of a weir. Nonlinear weirs with longer crests are cost effective alternatives for those existing dam structures which are more susceptible to failure due to loss of storage capacity by reservoir silting problem, and insufficiency of the structure in evacuating the updated flow due to the limited space. Piano key weir is a type of nonlinear weir designed in the form of piano keys, over-hanged from both the upstream and the downstream with sloping floors founded on a base or footprint. These weirs can be easily placed over gravity dams due to smaller footprint than labyrinth weirs. The present study’s focus is on the comparative analysis of identical configurations of trapezoidal and rectangular piano key (PK) weirs. The importance of (crest length to width) L/W ratio and weir height (P) in affecting the discharge efficiency of both types of PK weirs is investigated in the experimental study. Furthermore, soft computing approaches are applied to the current data set obtained from both types of weirs by considering discharge coefficient (C_{text{d}}) as a function of dimensionless geometric variables of PK weirs. The modelling performance of random forest regression and M5 tree approach is tested in order to estimate the values of discharge coefficient. The results conclude higher predictive accuracy of random forest model over M5 tree model.

Hydraulic Advantage of Piano-key Weir Over Ogee Weir

The piano-key weir is a new encouraging hydraulic structure yet to become a widespread usage due to limited knowledge of the hydraulic performance. A laboratory investigation on the hydraulic efficiency of the piano-key weir was compared with that of an ogee weir. The experiment data confirmed that the piano-key weir discharged more than ogee weir for the same upstream head. However, the coefficient discharge of the piano-key weir is extremely low compared to the ogee weir.

The effect of the inlet/outlet width ratio on the discharge of piano key weirs

A piano key weir (PKW) is a solution for improving the efficiency and safety of reservoirs and simplifying their management. To investigate the influence of the inlet/outlet width ratio on the discharge efficiency of PKWs, a three-dimensional numerical model based on a standard turbulence model and volume-of-fluid (VOF) method is employed, and the flow characteristics of nine laboratory-scale PKWs with different ratios are studied numerically. The results confirm that PKW configurations with are generally superior to those with in terms of discharge capacity. However, as the water head rises, the discharge efficiency of the PKW with a greater decreases more rapidly. By decomposing the total discharge into inlet, lateral and outlet components, according to the flow features of each overflow crest and their contributions to the total discharge, the intrinsic influencing mechanism of on the discharge performance of PKWs is revealed.

Experimental study of trapezoidal piano key side weirs in a curved channel

Side weirs are hydraulic structures usually used for flow diversion in irrigation, drainage and sewer networks. The piano key weir (PKW) is the newest form of labyrinth weir. It is more efficient and needs less reinforcing steel. PKW can be used as a side weir. The aim of this research is to study the geometric and hydraulic parameters of type-A trapezoidal piano key side weirs (TPKSWs) with two different total widths located on a curved channel. Dimensional analysis revealed that the discharge coefficient of TPKSW along the bend depends on the dimensionless parameters of the upstream Froude number (Fr1), ratio of total weir width to main channel width (W/b), ratio of upstream-downstream length of the TPKSW to weir height (B/P), ratio of weir height to upstream flow depth (P/y1), sidewall angle of the TPKSW (δ) and angle of the bend curvature (β). The effect of each parameter on the discharge coefficient was estimated by calculating the statistical parameters. It was found that β had the greatest effect on the discharge coefficient. An empirical equation is presented for the discharge coefficient of the TPKSW in a curved channel using the nonlinear regression module in Statistica software based on the experimental data. Error indices were employed to determine the precision of the equation. The equation was satisfactory with a high coefficient of determination (R2≈0.978). The experimental results showed that the average discharge coefficient of the TPKSWs was about 2.68 times higher than that of the linear rectangular side weirs (LRSWs) in the curved channel. In the intake channel, the scour potential downstream of TPKSWs was lower than that of LRSWs. Because of the increased intensity of the secondary current, the discharge coefficient (CdL) of TPKSWs with W/b = 1.43 was 1.3–2.1 times higher than that of TPKSWs with W/b = 0.71.

Comparison of Hydraulic Performance of Linear and Nonlinear Piano-Key Weirs in Plan

Comparison of Hydraulic Performance of Linear and Nonlinear Piano-Key Weirs in Plan

Hydraulics of Labyrinth and Piano Key Weirs: 100 Years of Prototype Structures, Advancements, and Future Research Needs

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

Application of Gaussian Process Regression Model to Predict Discharge Coefficient of Gated Piano Key Weir

The Piano Key (PK) weir is a new type of long crested weirs. This study was involved the addition of a gate to PK weir inlet keys. It was conducted by the Department of Water Engineering, University of Tabriz, Iran to determine if the gate increased hydraulic performance. A Gated Piano Key (GPK) weir was constructed and tested for discharge ranges of between 10 and 130 l per second. To this end, 156 experimental tests were performed and the effective parameters on the GPK weir discharge coefficient (Cd), such as gate dimensions (b and d), gate insertion depth in the inlet key (Hgate), the ratio of the inlet key width to the outlet key width (Wi/Wo) and the head over the GPK weir crest (H) were investigated. In addition, application of soft computing to estimate of Cd was carried out using MLP, GPR, SVM, GRNN, multiple linear and non-linear regressions methods using MATLAB 2018 software. This study suggests the relation for Cd with non-dimension parameters. The results of this study showed that H, Wi/Wo, Hgate and b and d, had the greatest effect on the GPK weir discharge coefficient, respectively. The GPR method was introduced as a new effective method for predicting discharge coefficient of weirs with RMSE = 0.011, R2 = 0.992 and MAPE = 1.167% and provided the best results when compared with other methods.

Experimental Study of Hydraulic Flow of Circular Piano-Key Inlet in Shaft Spillways

One of the most important conflicts that shaft spillways have to deal with is vortex formation. This phenomenon leads to some unfavorable effects such as vibration in the body of structures, air entrainment and reduced overflow capacity of the spillway. Among all solutions for disrupted vortex formation, an innovative one called circular piano-key spillway, based upon piano key weir principles has not been noticed as well as other solutions. Hence, in this study, experiments were conducted on circular piano-key spillway models. Results showed that in a constant head, the greater amounts of discharge have been measured for circular piano key inlet with an angle of 90 degrees. Comparison between discharge coefficients of three circular piano key inlet models showed that for a constant amount of H/D (Head/Diameter), circular piano key inlet with an angle of 90, 60 and 45 degrees have the greater amount of discharge coefficients, respectively. Experiment results indicated that circular piano-key spillway (with an angle of 90 degrees) increases overflow discharge capacity about 15.16% compared with shaft spillway. Among circular piano key inlets, the model with an angle of 90 degrees has the best hydraulic performance.

Laboratory Investigation on Discharge Coefficient of Trapezoidal Piano Key Side Weirs

A spillway is a hydraulic structure used to provide the controlled release of surplus waters and floods from a dam into a downstream area. A side weir is a multipurpose hydraulic structure which is constructed in water conveyance systems with a height lower than that of the canal wall. When the water surface level goes up, the side weir regulates the discharge and controls the water surface in the main canal. Besides, the side weir controls and diverts floods in dam reservoirs, diverts the flow and protects the structure against the river inundations. In this research, a laboratory investigation is performed with 16 Type-A piano key weirs and three different pier heights of 10, 15 and 20cm. These weirs are studied for two cases of 1 and 2. The results show that the weirs with 15cm and 20cm heights in both cases 1 and 2 have the highest discharge coefficient in dimensionless ratios of 0.2> H/P> 0.4 and H/P>0.5 respectively. Having reviewed previous studies, it could be concluded that the trapezoidal piano key side weir is capable of releasing a flow 1.2 times more than that of the linear trapezoidal labyrinth weir with 12 degrees angle and 1.87 times more than the one with 6 degrees angle, and 1.5 times more than that of the triangular labyrinth weir.

Evaluation of discharge equations of the piano key weirs

In present scenario, Piano key weir has played a vital role in increasing the discharge capacity of the available dams. This modified weir is the replacement of creaky and conventional labyrinth weir and it is best suited for the low head dams. This new labyrinth type weir is utmost solution for the rehabilitation of the spillways all across the globe. There are various equations available for the estimation of coefficient of discharge of Piano key weir. The present study encapsulates about the observable fact of coefficient of discharge for the Piano key weir and assigns different procedure for its evaluation. The validation of the four existing equations given by the investigators for the coefficient of discharge is monitored in the study. The graphical representation and statistical perusal of the equations given by the investigators show that the relationship proposed by Crookston et al.; Cicero and Delisle predict coefficient of discharge better than other equations for the data sets used in this present study. For these two equations 97% results lie within ±20% error lines. The present experimental study is also compared with the relationships given by the previous investigators. The equation suggested by Crookston et al. estimates coefficient of discharge effectively for all ranges of H/P, whereas the equation proposed by Cicero and Delisle is slightly more efficient for H/P between 0.2 and 0.8.

Experimental and numerical simulation of arced trapezoidal piano key weirs

Piano key weirs are high performance labyrinth weirs particularly at lower heads (water height over the weir). These weirs are considered a recent development in terms of application and research. This study was conducted to numerically and experimentally investigate the hydraulic performance of arced trapezoidal piano key weirs ATPKW under different hydraulic and geometric conditions. The main purpose was to investigate the effect of the planform arc angle on the weir's hydraulic performance. To this end, four LRPKW models as well as four ATPKW models were studied. Due to the complexities associated with flow over piano key weirs, numerical models were used to simulate the flow pattern over the weir. Comparison of the results obtained for the ATPKW and LRPKW models indicated that, at upper heads, the ATPKW models offered a higher hydraulic performance than the LRPKW models. On the other hand, LRPKW model indicated better performance at lower heads. In addition, it was found that reducing the planform arc angle from 90° to 45° caused an initial reduction in the discharge coefficient, after which it dramatically increased. Also, LRPKW models indicated a more effective length and a more appropriate performance.

Upstream Erosion and Sediment Passage at Piano Key Weirs

AbstractPiano key weirs (PKWs) are a weir type characterized by an effective rating curve. Accordingly, this control structure is primarily applied at dams to increase the spillway capacity. In rec...

Laboratorijska analiza hidrauličkog koeficijenta labirintskog preljeva zakrivljenog tlocrta i tipkastog preljeva

Laboratorijska analiza hidrauličkog koeficijenta labirintskog preljeva zakrivljenog tlocrta i tipkastog preljeva

Investigating the effect of a parapet wall on the hydraulic performance of an arced piano key weir

ABSTRACT Piano key weirs (PKWs) are classified as broad-crested weirs offering a high hydraulic performance. In this experimental study, the hydraulic performance of PKWs (of curved plan-form) under different hydraulic and geometric conditions was studied. A total of 16 experimental models with four different arc radii (35, 49, 70 and 90 cm) and central angles (90°, 65°, 50°, 45°) with a parapet wall of 4.5 cm height were considered. The results showed that by increasing the angle of the curved plan-form, the hydraulic performance of the weir was further affected by the parapet wall. Moreover, the parapet wall increased the hydraulic performance by 10% at most. In addition, the arced PKW with a parapet wall increased the performance by 2.98 and 3.82 times compared to the arced sharp-crested weir and the linear sharp-crested weir, respectively.

Hybrid meta-heuristics artificial intelligence models in simulating discharge passing the piano key weirs

Piano key weirs (PKWs) are acquired and developed for free surface control structures which improve their performance by increasing the storage capacity and flood evacuation. In this study, the potential combinations of two popular artificial intelligence data-driven models (AI-DDMs) of multi-layer perceptron neural network (MLPNN) and adaptive neuro-fuzzy inference system (ANFIS) with four meta-heuristic optimization algorithms (particle swarm optimization, genetic algorithm, firefly algorithm & moth-flame optimization) are assessed for predicting the PKW’s flow rate. Comparing the outcomes of the ten standard and hybrid AI-DDMs with three empirical relations based on several statistics and diagnostic analysis (such as the Taylor diagram) for estimating the flow rate shows that the AI-DDMs can predict the passing flow more accurately. In addition, the particle swarm optimization and firefly algorithm meta-heuristic algorithms improve the performance of ANFIS and MLPNN, respectively. The Mann-Whitney test for investigating the differences between two independent applied models indicates a significant difference between the AI-DDMs and two of the empirical relations at the 95% confidence level.

Discharge capacity evaluation and hydraulic design of a piano key weir

Abstract A piano key weir (PKW) is a new type of labyrinth weir that increases the unit discharge at the unregulated spillway inlet of the weir. It is considered to be an important structure in water supply and drainage systems. However, its complex geometry makes it difficult to achieve an optimal hydraulic design, and only a few design equations and criteria are available. This study investigates the discharge capacity of a PKW and evaluates the characteristics of its discharge using various sources of experimental data from a database. First, previously proposed discharge capacity formulas are summarized and analyzed. Then, a new formula that integrates the existing test data with the results of dimensional analysis and multiparameter optimization is proposed. The weir characteristics are evaluated using the proposed formula and a mathematical model. The results show that both the proposed formula and numerical model are promising approaches to evaluate the discharge capacity of an A-type PKW and can guide its design.

Numerical study of characteristics and discharge capacity of piano key weirs

A comprehensive numerical investigation was performed to better understand the flow patterns of Piano Key weirs (PKW) for different upstream heads, based on the volume-of-fluid model. The results of numerical simulation indicate that, the efficiency of side crests are limited by following factors: the change of side crest flow direction caused by the effect of the longitudinal flow velocity along the inlet keys, submerged flow regime in outlet keys, interference between nappes, and the head loss along the inlet keys, under the conditions of high upstream head, which eventually leads to the decrease in discharge efficiency with an increase in the upstream head. An orthogonal analysis revealed that, the weir height, inlet/outlet key width ratio, significantly affect the piano key weir discharge efficiency. New formulas with obvious physical significance and high accuracy for the piano key weir discharge were then derived and verified, which improve the accuracy of the design and structural optimization of the piano key weir.