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

Numerical Study on Hydraulic Characteristics and Discharge Capacity of Modified Piano Key Weir with Various Inlet/Outlet Width Ratio

“…Although with the increase of water heads (Figure 17(b) and Figure 17(c)), the flow direction of the inlet key flow to the outlet key decreases and flows straightly downstream. In this study, it can be observed that the separation bubbles do not occur in the front of the inlet key compared to the previous study by Li, et al [31]. The finding of this study confirmed that installing parapet walls and noses beneath the upstream apex overhangs of the PKW produced a hydraulically more efficient inlet (reduced flow contraction, reduced energy loss, reduced separation bubbles, and their transverse width, and potentially modified critical flow section location) and increased discharge efficiency.…”

“…Consequently, the finding of this study confirmed that adding a rounded nose and a parapet wall weir can improve the upstream flow pattern, as well as the hydraulic efficiency of the PKW and that a higher weir height (P) allows the benefits of increasing Wi/Wo ratio to be more significant. In addition to reducing inlet energy losses and separation bubbles (backflow) that occur in the front of the inlet key, Machiels, et al [20] and Li, et al [31] suggest that reducing the inlet key inlet flow velocity by adding noses to the PKW upstream apexes may improve PKW discharge capacity by modifying the nature of the critical section in the inlet key and improving the discharge efficiency of the lateral PKW walls.…”

“…The Renormalization Group (RNG) k-ε turbulence model has been successfully applied in many numerical simulations of labyrinth weirs and piano key weirs by numerous researchers, with good accuracy based on the results of the numerical investigation, such as Sangsefidi, et al [27], Safarzadeh and Noroozi [28], Crookston,et al [8], Chahartaghi, et al [29], Ghanbari and Heidarnejad [30] and Li, et al [31]. Moreover, a small number of encrypted grids and high calculation efficiency are required on the wall.…”

Hydrodynamics and Free-Flow Characteristics of Piano Key Weirs with Different Plan Shapes

“…Based on the results of previous studies [17,25,27], the C d of a rectangular PKW increases by~10% by increasing the inlet-to-outlet width ratio from A/D = 1 to~1.25, leading to a reduction in the inlet key velocity. On the other hand, C d decreases in lower w/P values due to an increase in the nappe interference ratio [53], which can be seen by comparing the data of Anderson and Tullis (2013) and Li et al (2020) [17,32]. This point can be validated by comparing the Rec-B2 model to the mentioned geometry of Machiels (2012) [40], which has a smaller C d regardless of having a lower B/w value (the decreasing trend of C d with B/w is subsequently presented in the current section).…”

“…The experiments by Machiels et al (2011) on a large-scale rectangular PKW (P = 52.5 cm) revealed that due to the sharp-corner entrance, a recirculation zone may form in the inlet key of a rectangular PKW [31]. The simulations of Li et al (2020) and Safarzadeh and Noroozi (2017) confirmed the recirculation zone formation in a rectangular PKW, which enlarges and results in higher heads, leading to a reduction in the inlet key effective area [28,32]. Denys et al (2017) and Denys (2019) investigated the specifications of the recirculation zone in more detail [33,34].…”