## 3 Results
For the VS fishway, RSS values are uniform across the entire flow depth, with values of 32 N/m\({}^{2}\), 17 N/m\({}^{2}\) and 18 N/m\({}^{2}\) for \(\tau_{uw}\), \(\tau_{uw}\) and \(\tau_{vw}\), respectively. All fishway configurations are characterized with the highest RSS values for o12 or o12 orifices, and the lowest for the o8 orifice, with VS fishway values comparable to the ones from the PO fishway with an o12 orifice. A fishway with the increased pool length and the same bottom slope (i125I60, Figure 6) is characterized by a larger variation in the RSS data across all RSS planes. The same pattern of prevailing streamwise RSS components, in comparison to horizontal and vertical,is determined: \(\tau_{uw}\) is higher by +69% and +90% on average, respectively. Differences between the RSS components in corresponding VS fishways are more notable, with \(\tau_{uw}\) twice to concurrent \(\tau_{uw}\) and \(\tau_{uw}\), +102% and +105% on average. In both PO and VS fishways, values of RSS for the C plane prevail amongst those deviating from the established correlation. Concurrent values of \(\tau_{uw}\) and \(\tau_{uw}\) are approximately of the same stress range, with differences between them ranging from +1% to +44% in the PO fishway (\(\tau_{uw}>\tau_{uw}\)) and \(-1\%\) in the VS fishway (\(\tau_{uw}<\tau_{uw}\)). There is no visible pattern of values for which \(\tau_{uw}\) and \(\tau_{uw}\) are higher than \(\tau_{uw}\) across the measured range, other than, in the pool-orifice fishway, values in the C plane prevail amongst those deviating from the established correlation, as observed for the previous configuration. The lowest RSS values are concentrated in the A plane for all PO fishways, not exceeding 23 N/m\({}^{2}\) on average, while the largest RSS values are concentrated in the C plane for all PO fishways, above 16 N/m\({}^{2}\) on average for all orifices, with a maximum value of 53 N/m\({}^{2}\) for the \(\tau_{uw}\) under the largest orifice. For the VS fishway, RSS values are uniform across the entire flow depth, with values of 49 N/m\({}^{2}\), 24 N/m\({}^{2}\) and 24 N/m\({}^{2}\) for \(\tau_{uw}\), \(\tau_{uw}\) and \(\tau_{uw}\), respectively. All fishway configurations are characterized with the highest RSS values for o12 orifices, and the lowest for the o8 orifice, with VS fishway values comparable to the ones from the PO fishway with an o10 orifice. A fishway that combines the steepest bottom slope and the longest pool length (i125l90, Figure 7) has an advantage over the previous configurations in the large pool area which has the potential to accommodate the resting area for passing fish. In contrast, a steep bottom slope over a longer pool length results in a relatively large height difference between the upstream and downstream pool bottom elevation that must be compensated for with a higher flow depth at the downstream boundary condition in order to sustain the design flow depth at the upper side of the pool. A longer pool has resulted in a larger recirculation area of lower velocities, which contributes to a decrease in the Reynold's shear stress across all configurations. On average, the RSS for an orifice size of o10 is lower than i125l45 and i125l60 by \(-7\%\) and \(-19\%\), respectively, and for o12 orifices, \(-1\%\) and \(-9\%\), respectively. For the smallest orifices there is no distinct reduction in RSS with pool length increase. The same pattern of prevailing streamwise RSS components, in comparison to the horizontal and vertical components, is determined in the same way as for the shorter pool length, with \(\tau_{uw}\) higher by +73% and +59% on average, respectively. Differences between RSS components in corresponding VS fishways are almost identical, at +79% and +62% on average. Concurrent values of \(\tau_{uw}\) and \(\tau_{uw}\) are approximately of the same stress range, with differences between them ranging from \(-2\%\) to \(-20\%\) in PO fishways and \(-9\%\) in VS fishways (\(\tau_{uw}<\tau_{uw}\)).