Introduction Piano key weirs (PKW) is the newest type of long crest weirs, which achieve more crest length in the same width as congress weirs, and therefore, the capacity of the void is higher than that of the mounted piano key weirs, with the aim of increasing the amount of energy dissipation in them. It was noticed that the piano key weir oscilloscopes are used in the crest of reservoir dams and in irrigation and drainage networks. This has been implemented due to the importance of the issue of energy dissipation in these types of instruments. So far, many studies have been done on the discharge coefficient of the piano key weir, but no research has been done on the relative energy dissipation of the triangular Piano key weir.MethodologyThis research is a continuation of previous research on PK weirs. Figure 1 shows the rotating flume environment, which experiments were performed in that laboratory at the Tarbiat Modares University of Tehran (Dimensions: 10 meters long, 2 meters wide, and 0.9 meters high). Experiments have been performed on a triangular weir with a zero slope (i.e., Tri-Base model) (Fig. 2 and 3) and 10 degrees in the flow direction (Fig. 2 and 4). In this article, PK weir with horizontal and sloped crest is called Tri-Base and Tri-B1 models. The weir characters used in the laboratory are provided in Table1. Eq (3).The upstream depth (ho = P+h) and downstream (h1) was measured with an accuracy of ± 0.1 mm at a distance of 4P for the upstream depth (Crookston, 2010) and 10P for the downstream of the overflow (Eslinger & Crookston, 2020).Results and DiscussionFor the ∆E/E0 curves, firstly, the relative energy dissipation curves for triangle PK weir with horizontal crest have been plotted (Fig 5) and compared with the present study and other researchers' results. The differences between results are because of the differences in geometric characteristics. Because the head and weir height changes for every discharge, Fig 6 has been plotted curves of (q - E1/E0).The trend of the relative energy dissipation curve of nonlinear weir may be according to a logarithmic curve (Lopes et al., 2011). Figure 5 shows the changes in energy consumption for the Tri-Base and Tri-B1 models and their comparison with the results of other researchers. According to Figure 5, the highest relative consumption of energy is for the Tri-Base model. In other words, at the same flow rate, the highest relative amount of energy dissipation is related to the weir model with a horizontal crest. It is also clear that the highest relative energy loss in all samples occurred at the lowest flow rates.As the flow rate increases, the relative dissipation of energy decreases in both models. The reason for this is that with the increase in flow rate and flow speed, the amount of flow friction is reduced, and as a result, the dissipation of the flow is reduced.With the increase of Froude Number, the acceleration increases, and the flow travels a longer path towards the separation, which causes the separation area to decrease and the Drag force to decrease. Because of the slope of the weir walls, the flow speed in the Tri-B1 model is higher than the Tri-Base model (the flow moves like a slide from the spillway to the downstream side), so the separation area in the Tri-B1 model is reduced, and the Drag force and consequently the relative depreciation The energy in the Tri-B1 model (about 24%) is lower than the Tri-Base model.Figure 6 shows the residual energy curve of the piano key weir in relation to the flow rate per unit of the overflow width. According to Figure 6, the E1/E2 ratio increases with the increase of flow per unit width. In other words, the relative residual energy in both models occurs at high flow rates. Also, in both models, at low flow rates, the increase in E1/E2 ratio is higher than at high flow rates. The reason for this is the local sinking upstream of the weir in high discharges; so that in high heads, the aeration on the weir is reduced.Finally, Fig 7 shows the comparison of measured and calculated values of triangular PK weir.ConclusionIn the triangular piano key weir, by increasing the slope of the side walls (θ) from zero to 10 degrees in the flow direction, the relative dissipation of energy has decreased by 24%. Also, the highest dissipation of energy in the weir with a horizontal crest occurred in the lower heads, and this value decreases with the increase of the head.The highest amount of energy dissipation for Tri-Base and Tri-B1 models is 0.74 and 0.85, respectively, in this case. Finally, relationships (9) and (10) are proposed to calculate the relative energy consumption of the overflow of the piano key with horizontal and sloping crest, respectively.

Stepped spillways are an accessory of reservoirs and water conveyance system, which dissipate flow energy and reduce the size and costs of stilling basins (SBs). As the reverse inclination of each step helps form a small SB, therefore, energy dissipation becomes more efficient. In this study, using a Plexiglas spillway (height: 72 em), which was installed in an experimental flume (width: 50 em), various arrangements of numbers and inclination steps of spillway were investigated installing 12 set-ups. The first experiment was conducted on the weir itself without any steps; another set-up was with one step without inclination and one step with reverse inclination. This procedure was continued asymmetrically with the array of 8 steps. As expected to efficiently dissipate the energy, more steps are required as the flow increases. It was observed that one inclined plus two horizontal steps provide the best energy dissipater array. Furthermore, it was revealed that there was a limit to increase the number of steps and their inclination in energy dissipation, i.e., efficiency may not be enhanced by increasing the number of inclined steps.

Shear walls are a type of structural system that provides lateral resistance to a building or structure and have relatively high stiffness and strength. However, since the energy dissipation is made within a limited part of the shear walls, they do not exhibit ductile behavior. Shear walls may be considered as an obstacle to make openings in the buildings. Coupled shear wall is one of the types of shear walls that has removed some of the problems encountered with shear walls. Yielding of link beams in the coupled shear walls may cause increase in energy dissipation and development of damage. Regular and uniform openings in the coupled shear walls reduce the architectural design limitations. As well as coupled shear walls, two other types of shear walls, namely slit shear walls and shear wall with upper connection have been investigated in this paper to develop energy dissipation along with the wall height. Such shear walls concerning the architectural design limitations are lower than the normal shear walls. In this research, the above-mentioned shear walls have been examined under the same conditions and a comparative study has been carried out concerning some parameters such as strength, stiffness, lateral displacement, cracking development and steel weight. Moreover, shear walls have been compared through considering the ratio of strength to steel weight and their ductility and the results revealed that slit and coupled shear walls showed more favorable performance.

One of the most efficient energy dissipatoion structures in open channel flow are block ramps; which have been considered and used most often recently because of the simple performance. This kind of energy dissipators can be assumed as a particular type of baffle block chutes, but with natural base materials like sands and gravels and without cement. In laboratories, several physical models have been built and examined regarding their efficiencies to dissipate energy of flow. These experimental studies are not only too expensive and time consuming, but also some of the hydraulic conditions like higher velocities could not be obtained in controlled conditions of laboratories. Moreover, there are always problems with changing scales in laboratory studies. Hence, using computational fluid dynamics (CFD) codes are to some extent more favorable to engineers with which fluid hydraulic behavior is more widely examined. This paper at first, reviews the classifications of these structures regarding their fabrication and roughness from various point of views, and then deals with the formation of some types of flow regimes with different volume flow rates on them. In continuation, to study the three dimensional flow field around block ramps, Flow-3D software is utilized and hence, the mechanism of energy dissipation on various flow regimes on these structures has been surveyed. In this research, incompressible fluid assumption is made and Large Eddy Simulation (LES) turbulence model is used. Since it was a shallow water condition, Volume of Fluid (VOF) method is used to calculate the free surface elevation. The numerical results showed the more energy dissipation with more turbulence and more turbulence with forming the recirculating flow and extending the distance of the reattachment point from the boulders. Consequently, energy dissipation is maximum for lower volume flow rate and higher slope of the ramp. Since in these two conditions, the flow involves with roughness of the ramp more and more; hence it gets easier for turbulent flow to happen. In other words, energy dissipation is also maximum for the non-submerged boulders. Flows for the cases in which boulders are submerged have different mechanism of energy dissipation. In these types of flows, energy dissipation is maximum for the wake-interface flow condition and isolated roughness flow condition, respevtively. Therefore, in order to enhance the energy dissipation in flow over block ramps, it is advised to reduce the effective cross section or reduce the submergence of scale roughness while maintaing the same effective cross section and the volume of fluid flowing over the structure. Changing the boulder ordering from rows to staggered would be another way to increase the energy dissipation.

Drops are the most important and common hydraulic structures used as energy dissipators in irrigation networks and erodible waterways. Dissipation of energy occurs in two different ways. One portion belongs to the geometric form of the structure (briefly called loss due to structure), whereas the other occurs due to happening of hydraulic jump downstream of the structure. The dimensions of drop structure and downstream stilling basin can be optimized if geometric and hydraulic characteristics are recognized properly. In this research, the effects of drop geometry and hydraulic characteristics on the loss due to structure were investigated. At first, the effective dimensionless parameters were specified. 14 physical models of more common drops including straight, inclined and stepped drops were then built in 2 heights of 51.5 & 25.5 centimeters and 2 bed slopes of 26.6 & 33.7 degrees. The number of steps in stepped models was chosen equal to 3 and 7. With establishment of 90 flow rate, the energy losses were compared. The results showed that in the range of variable parameters, the straight drop has the maximum amount of energy dissipation.

Contact interfaces are known as the main source of energy dissipation in the structural joints. Therefore it is important in structural dynamic analysis to use predictive joint models which are capable to simulate the structural response and energy dissipation with an acceptable accuracy. In this paper an analytical model is proposed for energy dissipation evaluation due to micro slip mechanism in a beam structure with frictional-free boundary condition. The bending response governing equations are derived under harmonic external excitation and are solved in order to detect transition from stick to slip at the contact interface. The resultant hysteresis loops are obtained and parametric study is done for a numerical case study.

Introduction: Drop manholes are widely used in sewer and drainage systems in steep urban catchments. Those are often employed to provide energy dissipation in order to control high flow velocity and minimize structural damage. Under Regime R2 insufficient energy dissipation and excessive air entrainment could lead to hydraulic problems in the downstream system. Therefore, the plane jet-breaker device was recommended by Granata et al. (2014) to improve drop manhole performance. It would have some positive impacts on hydraulic features of the drop manhole if is properly designed. Methodology: In the present study, the effects of the jet-breaker length, width, sagitta, and angle, on drop manhole energy dissipation (as response variable) have been analysed under various inlet pipe filling ratios. Dimensional analysis and modern statistical Design of Experiment (DoE) have been brought together and experiments have been designed according to the 2 5 full factorial design with four replications at the center point. Seventeen jet-breakers have been examined and about 350 tests have been performed on a physical model of drop manhole at the Hydraulic Structures Laboratory of Shahid Bahonar University of Kerman, Kerman, Iran. Results and discussion: Energy dissipation is closely related to the flow regimes. The variation of Ed/Eo versus the impact number (I) showed that some jet-breakers effectively leveled Ed/Eo at one (1) over different flow regimes, which is the optimum condition. Moreover, reduction of the filling ratio from 80% to 40% causes obvious deviation from manhole optimum energy dissipation operation. Significant main and interaction effects were distinguished from the full model Analysis of Variance (ANOVA). This analysis revealed that inlet pipe filling ratio (factor A) effect was significant at 0. 01 significance level (α = 0. 01), whilst AD (inlet pipe filling ratio and jet-breaker sagitta ratio interaction) and AE (inlet pipe filling ratio and jet-breaker angle interaction) effects were significant at α = 0. 05. The significant effects of the full model ANOVA (i. e. A, AD, and AE), together with factors D and E, were used to perform reduced model ANOVA and fit a regression model to the response variable. The former factors were considered to maintain the model hierarchy. The result shows that all considered effects are statistically significant at α = 0. 01, apart from factor E effect which is significant at α = 0. 05. The statistical significance is determined by using pvalue, which shows the probability value and is associated with the test statistic F0 value; smaller p-value (or larger F0 value) leads to a more significant effect. The ANOVA indicates that there is no evidence of second-order curvature in the response over the region of exploration at 0. 01 significance level. Additionally, the lack of fit (LOF), which is defined as the deviation of the data from the fitted model, is not significant. It means that there is a strong indication that the regression function is linear and the model fitted to the data well. Moreover, a regression model was intudeced regarding the result of the reduced model ANOVA. Conclusion: The statistical analysis of the results revealed that the response variable was significantly improved when the inlet pipe filling ratio was 80% and jet-breaker sagitta was equal to zero, and its angle was at 70 ˚ . Jet-breaker length ratio and width ratio had neither significant main nor significant interaction effects on the response variable. Even though with reference to practical considerations and previous investigations, jet-breaker length equals manhole diameter and jet-breaker width of 140% larger than inlet pipe diameter, were suggested. Moreover, the use of DoE resulted in straightforward data analysis and unbiased concluding.