2D Visualization of flow phenomenon over individual inlet and outlet keys of piano key weir by CFD modeling (original) (raw)
Related papers
2021
Piano key weirs are being increasingly used for better flood passage downstream, both as a new structure or on top of hydraulic structures like a dam, to increase their discharging capacity as well as reservoir storage. Much research has been done on rectangular plan-form, while other plan-forms warrant attention. The present study focuses on two different plan geometries of PKW, i.e., rectangular (RPKW) and trapezoidal with angle α equal to 9 degrees (TPKW9) for their head-discharge relation in a wide channel of 0.984 m width under free-flow condition. Since the role of CFD is increasingly becoming prominent in present times, a numerical study using ANSYS-FLUENT was also carried out to ascertain its relevance in predicting flows around complex structures like PKW. Further, the tailgate was closed to render the PKW’s outlet from partial to fully submerged conditions. The effect of these submerged outlets was studied for any changes in the discharging capacity of the PKW. The study s...
Hydrodynamics and Free-Flow Characteristics of Piano Key Weirs with Different Plan Shapes
Water, 2021
This paper focuses on Piano Key Weirs (PKWs) as an effective solution for improving the discharge capacity of spillway systems. The flow behavior in inlet and outlet keys is experimentally studied to analyze the discharge capacity of PKWs with different plan shapes (i.e., rectangular, trapezoidal, and triangular). The results show that in outlet keys, the flow aeration regimes extend to higher values of headwater ratios (Ho/P) by increasing the length magnification ratio (B/w) and apex width ratio (A/w). In addition, the local submergence length is a decreasing function of A/w, especially in high flow heads. While the total interference length enlarges by reducing A/w in lower Ho/P values (Ho/P < 0.5), a reverse trend is observed in higher headwater ratios. PKW performance may also be impacted by the flow contraction and recirculation zone in inlet keys, which intensify in higher values of Ho/P, B/w, and A/w. According to the obtained results, while the discharge coefficient is a...
Water Practice and Technology
A piano key weir (PKW) is a modified version of non-linear weirs and it can be obtained via amending the centerline length of the weir by a small footprint. It is developed to increase the hydraulic performance of the linear weirs via increasing the pass discharge and the energy dissipation. A laboratory investigation is conducted on five physical PKW (Type A) models to investigate the effect of inlet to outlet width ratio (Wi/Wo) on the hydraulic performance of PKWs. The results showed that the (Wi/Wo) ratio has a predominant influence on the hydraulic performance of PKW. It was found out that the best hydraulic performance was obtained with Wi/Wo ratio equal to 1.25 among other investigated Wi/Wo ratios because the discharge coefficient was the highest for the given discharge and head. Further, the results revealed that the variation of Wi/Wo ratio from 1.25 had a negative impact on both discharge coefficient and efficiency. It was found out that the percentages of reduction in di...
Hydraulic Behavior Of Piano Key Weir Type B Under Free Flow Conditions
2016
In this study, laboratory experiments were performed to evaluate the effects of the weir geometry of a Piano Key Weir (PKW) type B on the discharge coefficient under free flow conditions. Experiments were conducted in a 15m long, 0.3m wide and 0.45m deep rectangular glass-walled flume. The experimental work includes testing of fourteen PKW models which results 290 tests to cover the effects of weir length and height, up-and downstream key widths, upstream apex overhangs length, dam height and noses length on the weir flow discharge coefficient as well PKW with outlet stepped key were considered in the analysis. Considering the experimental data, the dimensional analysis allowed the development of relations between discharge coefficient and the shape of the PKW and gave a good agreement. Experimental results showed that the most influential parameters for the tested PKW models are the Relative length L/W, Key widths W W ⁄ , PKW Height B/P, and Overhangs length B B ⁄ . The effectivene...
Applied Water Science
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. Further...
Experimental and numerical study of a piano key side weir with oblique keys
Water and Environment Journal, 2019
Side weirs deflect the approaching flow to the side channel with a specific angle. Considering this angled flow, the oblique shape of side weirs would improve the flow discharge efficiency. In this paper, a Piano Key Side Weir (PKSW) with oblique keys is proposed. Sixteen PKSWs with different key angles were studied in the laboratory, as well as two PKSWs by using CFD modelling. Flow characteristics and discharge coefficients of the proposed side weirs were investigated. Results show that a PKSW with positive key angles can decrease the flow disturbance (a phenomenon usually occurs in symmetric PKSWs), which results in higher discharge coefficients especially in high Froude numbers (F 1 > 0.35). Among the studied PKSWs with oblique keys, the best performance was achieved with a PKSW with 30° key angle. The findings of this study can be used for a better design of PKSWs.
Evaluation of discharge equations of the piano key weirs
Flow Measurement and Instrumentation, 2019
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 to 0.8.
Study of hydraulic characteristics of trapezoidal piano key side weir using different approaches
Water Science & Technology: Water Supply, 2022
Side weirs are widely used in hydraulic engineering applications. The studies on the subject have been generally focused on classical and labyrinth side weirs. However, the same is not true for piano key side weirs (PKSW) in a straight channel. The piano key weir (PKW) has high discharge capacity compared with classical weirs. In this study, the hydraulic characteristics of a trapezoidal piano key side weir (TPKSW) in straight channels were investigated experimentally. In all experiments, the hydraulic characteristics of nine TPKSW models were studied extensively using the De Marchi, Domínguez and Schmidt approaches in the subcritical flow regime, with Froude number range 0.12 , F 1 , 0.87. The results show that a TPKSW provides better performance compared to traditional rectangular and triangular labyrinth side weirs. Specifically, for the 0.12 , F 1 , 0.4 condition, the efficiencies of a TPKSW and trapezoidal labyrinth side weir are close to each other. A trapezoidal labyrinth side weir is more efficient than a TPKSW at larger Froude numbers. The discharge capacity of the TPKSW is 2.9 to 12 times higher than that of the rectangular side weir. Scatter diagrams were obtained for C PW and F 1 numbers using various approaches available in the literature. The diagram generated by the De Marchi approach has much less scattering, compared to the diagrams generated by the Domínguez and Schmidt approaches. It has been determined that TPKSWs are an effective type of side weir in lateral flows. Lastly, an empirical equation was obtained for the discharge coefficient, which is in good agreement with the experimental data.
performance evaluation of a piano key weir and a rectangular weir
The Piano Key Weir (PKW) is a particular shape of labyrinth weir, using up- and/or downstream overhangs. The horizontal rectangular labyrinth shape allows to multiply the crest length for a given weir width. With the increasing demand of power, it is becoming greatly essential to increase the storage capacity of existing dams without neglecting their safety. The present aims at comparing the performance of piano key weirs in respect to the normal sharp-crested weirs. The discharge v/s head data for the piano key weir and normal sharp-crested weir obtained from the experimental study were compared and analysed using regression analysis. Piano key weir was found to perform doubly w.r.t a normal weir. The flow profiles show the parabolic nature of flow and the nappe interference in the inlet keys.
Numerical simulation of Piano Key weir type-B
3RD INTERNATIONAL CONFERENCE ON ENERGY AND POWER, ICEP2021
In this research, five geometric parameters had been tested in order to investigating chief geometric parameters influence the weir of hydraulic efficient and for define their optimum values in numerical way by software program (Flow-3D). The study consists of 16 models which by the program lithographic (Standard Triangle Language (stl)), the geometric shapes are provided, or has been drawing in AutoCAD and exported in the (stl) format. The (stl) file is then right inserted to Flow-3D and every model had been tested by at least 15 rans. All the tests were 400 ran. The geometric parameters are :(Influence of the upstream head above the weir crest, Influence of relative length, Influence of Key width, Influence of Height and Influence of difference height of upstream and downstream). This research is based on theoretical experiments which aim to determine the Piano Key Weir discharge coefficient for different geometrical configurations under free flow conditions for type B. An empirical equation was developed using theoretical data, based on the technique dimensional analysis and the statistical program SPSS. The developed formula finds the discharge coefficient and related with seven parameters; the coefficient of determination is (R 2 =0.964). By comparing the developed formula with previous formula on PKW, the results showed a good agreement.