Turbulence Measurement in Nonuniform Open-Channel Flow Using Acoustic Doppler Velocimeter (ADV)

Dominant features in three-dimensional turbulence structure: comparison of non-uniform accelerating and decelerating flows

“…The employed non-uniform flows measured a set of j, B r and G. j and B r for the non-uniform flows remained almost constant; while G was found to change in a linear relationship with the pressure gradient parameter b. Both j and B r constants found from this study corresponded to previous studies suggested range, in which j fell within the suggested range in Auel et al [2] and B r showed similarity with the proposed values in rough bed flow studies by Kironoto and Graf [14] and Song and Chiew [28]. The B r finding further suggested its universality in different bed roughness conditions.…”

“…9b, this study's B r remains constant at around B r = 8.1 with regression coefficient R 2 of 0.84 compared to measured data. When compared to rough bed non-uniform flow B r , such as 8.5 proposed by Kironoto and Graf [14] and 8.21-8.61 proposed by Song and Chiew [28], B r proposed in this study agrees well with them. In their rough bed flow's log-wake law, their utilised parameter z ?…”

“…(7)] was utilised to calculate the change of velocity and turbulence structure for nonuniform flow in Song et al [30], Kironoto and Graf [14] and Song and Chiew [28]. For It is found by depth averaging of the time-averaged u-velocity uniform flow, b has a constant value of -1; whereas for the non-uniform flow, b is nonconstant (as suggested by [2,14,28]). As both B r and G of the non-uniform flow are in the function of b, the non-uniform flow's log-wake law should therefore be expressed as…”

“…There are several ways to determine the shear velocity [27], in which two common approaches are: (1) the extrapolation method from the measured Reynolds stress profile, and (2) the energy gradient method. These methods have been shown to give reasonable estimation of the wall shear velocity [7,28] providing that the wall boundary is relatively uniform through longitudinal space, i.e. particularly suitable for smooth bed flows.…”

“…According to their study, due to the existence of the pressure gradient in the non-uniform flows, the velocity distribution should be characterised by non-constant wake parameter P and log-law integration constant B r . Kironoto and Graf [14] and Song and Chiew [28] further detailed the change of B r and P values using a pressure gradient parameter b, which is defined by…”