EFFECT OF DIFFERENCE IN SHAPE OF STEPPED FISHWAY ON FLOW STRUCTURE
TAKAYUKI TANAKA (National Institute of Technology, Toyota College, Toyota, Japan)
KEIGO AOKI （National Institute of Technology, Toyota College, Toyota, Japan)

VELOCITY VECTOR DISTRIBUTION IN HORIZONTAL PLANEINTRODUCTION
There are various structures such as the step type and the ice harbor type in the fishway, and the flow situation
changes greatly depending on the structure, and it has a great influence on the habitat of fish. In this study, wefocus on stepped fishways existing in the middle and downstream of real rivers, and examine how thedifference in the structure of the fishway affects the turbulent structure.

z/H =0.5z/H =0.5

flow

flow

CCD Camera

APPARATUS AND EXPERIMENTAL METHODFlow〈APPARATUS〉
A model of the existing stairway type Fishway A and Fishway B is
installed in an open channel in a room. The Fishway B has a latent holeat the bottom of the partition wall.

Fishway A
Computer
Laser light sheet

PIV sistemsLzy

23.3cm

6.6cm

x

7.8cm
40.0cm40.1cmFishway Aflow

L5.4cmzyx

57.0cm〈EXPERIMENTAL METHOD〉
・Point measurement of flow velocity:
Electromagnetic current meter・ Simultaneous measurement of flow velocity:
PIV (particle image velocimetry) method

20.9cm

Case

2.8cm
2.8cm

Experimental Conditions

8.8cm
13.6cm
40.0cmFishway B

Fishway model used for hydraulic experiments

Fishway A
Fishway B

Flowdischarge
Q (l/s)6

Fishway B

Velocity vector distribution in horizontal planeflow
40.0cmFishway A
Circulating flow is occurring on the left bankside of the pool.
Fishway B
Two circulating flows are observed downstreamof the left bank, and the velocity vector shows alarge value on the right bank.

Bed slopeI
1/40

Downstream
length of pool Model scale
L (cm)
40

1/2.6

56

1/7.4

MAIN FLOW VELOCITY CONTOURS IN CROSS SECTION
Fishway A
In each case, the main flow velocity is small near thebottom, which is considered to be a rest space for fishes.
Fishway B
At the downstream point, it can be seen that theinfluence of the submerged mouth is on the right bankside, and the effect of the upstream notch remains
near the water depth.
Compared with the Fishway A, it was clarified that
there was no clear space for the fish to take a breakbecause the sections where the flow velocity was small
were different in each section.

Downstream point

Midstream point

Downstream point

Midstream point

Upstream point

Fishway A
Upstream point

Fishway B

Main flow velocity U/Um contours in cross section

TRANSVERSE REYNOLDS STRESS DISTRIBUTION IN CROSS SECTION
Downstream point

Upstream point

Midstream point
22

Fishway A
NUMBER OF RUN-UPS IN ACTUAL RIVERS IN EACH FISHWAY
At midstream point, the Reynolds stress shows a
Number of run-ups
Fishway A is 4 km upstream from positive extreme value below the half water depth
8×106
FishwayA
Fishway B. The run-up number of on the left bank side from the center of the channel,
FishwayB
sweetfish changes every year, and the and it can be confirmed that the three-dimensionality
6×106change is similar in both fishways. of the flow is strong.
4×106
However, the number of Fishway B Fishway B
was large in all years, especially in At the midstream point, it can be confirmed that the6
2×102007, Fishway B showed 6.4 times right bank shows negative values in the verticalthe number of Fishway A.
19962000
2004 2008
2012
2016
Step type in the fishway
direction due to the effects of the notch on theYear
Ayu (sweetfish) run-up number per year
upstream side and the submergence on the downstreamside.

Fishway A
Downstream point

2

Upstream point

Midstream point2

Fishway B

Transverse Reynolds stress distribution in cross section

CONCLUSIONS・It was found that a complicated flow occurred especially in the horizontal plane in the fishway with a structure with a submerged hole, and there was no clear place to rest for the fish going up.
・Due to the flow velocity distribution in the cross section, Fishway A showed a stronger three-dimensionality of the flow than Fishway B, especially at the center of the pool. Furthermore, it became clear that thedistribution tendency of the turbulent structure differs greatly depending on the installation position of the notch.
As a result, it became clear that it was important to carefully consider not only the presence or absence of a submerged opening but also the location of the notch.