京都大学防災研究所年報 第 55 号 B 平成 24 年 6 月
Annuals of Disas. Prev. Res. Inst., Kyoto Univ., No. 55 B, 2012

The Effect of End-sill Geometry on Functionality of In-ground Stilling Basin
M. MESHKATI SHAHMIRZADI(1), Tetsuya SUMI and Sameh KANTOUSH(2)(1) Graduate School of Engineering(2) German University in Cairo, Egypt
Synopsis
In practice, design of stilling basin downstream of Flood Mitigation Dams
(FMDs) is still facing several problems such as blockage of sediment passage and fish
migration; and thus, it is necessary to improve its design. In this paper a new concept ofstilling basin for FMDs is introduced; called In-ground Stilling Basin (ISB). Present
study mainly focuses on experimental investigation on end-sill geometry at the end
downstream of ISB. As results, several unique outcomes of experimental investigations
have been obtained to improve the performances of FMDs as well as facilitate the fishand sediment passage.
Keywords: flood mitigation dam, stilling basin, bottom outlet, end-sill.

1.

Introduction

Recently, huge floods have been experienced
worldwide more often than the past and it causes
severe losses and damages for human being
properties and civilization. Thus, developing
innovative strategies is vital for protection of urban
area against the massive floods. One of thewell-known constructive flood control measures is
Flood Mitigation Dam (FMD) which attracted muchattention over past decades. FMD is defined as adam devoted only to flood retention and retardation
which its storage volume is completely dry except
for a few weeks per century, while in case of flood
events the flood flow can be stored temporary its
inside and gradually discharge out through its
gateless bottom outlet (Lempérière, 2006).
In practice, FMD’s design is still facing toseveral problems; and need more investigation inorder to improve its design. In particular, design ofstilling basin at the downstream of FMDs required
to be modified. Stilling basin (SB) is a hydraulicstructure aimed to dissipate the excess energy offlow and prevent the undesirable scouring at its
downstream area by inducing hydraulic jump.
Truncate of hydraulic jump within a limited area is
notsimplyachievable,
unlessutilizing
appurtenances such as fully width (continuous)
end-sill with an adequate height to compact thejump, resulting in reduction of SB length and an
economical design. But it should take in to accountthat, a fully width end-sill can negatively disrupt
the fish migration and sediment transport in river
system. Then, presence of fully width end-sillcreates the contradictory goals for SBs.
In this paper, a new concept of SB for FMDs is
introduced; called In-ground Stilling Basin (ISB).
ISB can be defined as a non-prismatic SB with asudden transversal enlargement combined with avertical abrupt drop at its upstream end where thebottom outlet of FMD is located. A positive step
(an abrupt rise) at ISB’s downstream end, also, hasbeen added to its geometry. The height of positive
step is exactly equal to abrupt drop, so that it― 561 ―

End-sill

Negative
stepa)Side viewb)

Plan vieew

Positive
step
Free spaces

End-sill

matic side andd plan view ofo ISB downsttream of FMD
D.
Figg. 1 The schem
Creates aan empty droop box below FMD, similaar tothe shapee of an elongated pool. A slit-type end -sill,
optionallly, can also be added abbove the possitive
step as mmeans of insurring the formaation of jumpp andcontrol its position within ISB
B. The slit--type
end-sill is similar tot fully wid
dth (continuuous)
end-sill w
with a tiny difference ass it has two freespaces aat the lateral sides which
h may positiively
facilitates the fish migration and sedimentspasssing.
The scheematic view of the ISB anda the hydraaulicparameteers tested arre shown inn Fig. 1. Eiither
consideriing only possitive step at the downstrreamend of IS
SB or its combbination withh slit-type endd-sillare intennded to force the hydrau
ulic jump wiithin
ISB’s appron withoutt the assistan
nce of tail-w
water
depth doownstream. PresentP
researrch, thus, cann beconsidereed as a subsset of forced
d hydraulic j ump
studies.
2.

Back
kground

Extenssive experim
mental studies have bbeen
devoted to the stuudy of hydrraulic jumpss in
non-prism
matic stilling basin which can be classiified
into threee main categories as: hy
ydraulic jum
mp incase of oonly sudden ennlargement in
n the flume w
width(Rajaratnnam and Subbramanya, 19968; Bremen andHager, 19994; Ohtsu et al., 1999; ZareZ
and Doerring,2011), onnly abrupt droop at the bed (Rajaratnamm andOrtiiz, 1977; Hag
ger and Bretz,, 1986; Kawaagushi andHagger, 1990; Oh
htsu and Yassuda, 1991; Hotchkiss
Hand Larson, 20055), and combbination of both sudden
enlaargement andd abrupt dropp (Katakam and Rama,
199
96; Frerri andd Nasello, 20002) whose commonlycusedd in the reality.
The majo
ority ofabove-mentioned
d studies hahave focusedd on thedetaails descriptio
on on hydrau
aulic characteeristics ofjum
mp as well as predictioon of sequennt depth.
Liteerature review
w evince thhat a few nu
umber ofpapers concern the
t combinatiion of abrupt drop andsudd
den enlargem
ment simultanneously. Kataakam andRamma (1996), expand an analytical andexperimental study of the hyddraulic jump in stillingbasiin with abru
upt drop andd sudden enlargement.
Theey found thaat the requireed tail-waterr level toensu
ure the hydraaulic jump wiithin stilling basin canbe reducedrby combiningcthhe sudden enllargement
and abrupt drop.. They introdduce the mostt common
featture of hydrau
ulic jump in ccase of simulltaneously
abru
upt drop and sudden enlarrgement; called spatial
B-ju
ump which has relatively
ly higher energy losscom
mpared to eitther the speccial jump orr B-jump.
Frerrri and Nassello (2002),, provide qualitativeqphyysical explan
nations on ssequence of different
hyddraulic jumps below abruppt drop comb
bined withsudd
den enlargem
ment as tail-w
water depth increases.
Theey stated thhat, hydrauliic jumps att a dropcom
mbined with sudden enlaargement present very

― 562 ―

discharge and bottom outlet dimension. Proposing a
new design procedure by using the successful test
outcomes is the ultimate goal of this experimental
investigation which it should be valuable forpracticing engineers.

different and complex characteristics whose overallcharacteristics at time are mainly referable to thoseof drop only, at other times to those of enlargement
only, while yet other times the jumps just haveautonomous characteristics. Additionally, theyemphasize on necessity of specific experimental
investigation for each type of hydraulic jump thatcan occur in order to design of structure.
There are some differences between the present
study and exist studies in the literature. First, theapproach supercritical flow after discharging out
through the bottom outlet was plunged into the ISB
pool (drop box) and then was encountered to a
positive step as well as an end-sill at thedownstream end. Second, there was no adjustment
for tail-water depth at further downstream of ISB.
Third, the combination of positive step and theslit-type end-sill have not been examined yet.
Present study experimentally evaluates thefunctionality of in-ground stilling basin (ISB) as analternative of conventional stilling basin on energy
dissipation of high velocity flow exiting from the
FMD’s bottom outlet. Particular motivation during
study was to solve the problem of fish and sedimentpassages disruption in conventional stilling basin
design. Additionally, functionality assessment of
ISB for residency of aquatic animals as a desire
habitat was one of the other interest point in current
research. Thus, an extended series of experiments
were carried out to obtain the optimum ISB
geometry (length and depth) as well as thenecessary end-sill geometry (height and width) thatwould force and stabilize hydraulic jump for given

3.

Experimental investigation

3.1 Definition of main governing parameters
Fig. 2 shows the schematic side and plan viewsof the constructed model at Disaster Prevention
Research Institute of Kyoto University (Japan)
including the main hydraulic parameters involvedin this study. Functionality of an ISB can be
discussed in two different aspects, hydraulicfunctionality (HF) and ecological functionality(EF). To evaluate the hydraulic functionality of an
ISB different hydraulic criterion can be utilized i.e.
velocity reduction along the ISB, energy dissipation
within ISB, water level fluctuation inside the ISB
and flow condition downstream of ISB. Based on
the literature review and preliminary experiments, it
was found that the hydraulic functionality (HF) of
ISB may depend on the following parameters: theoutlet velocity at the bottom outlet exit (U0), thebottom outlet width (b), the bottom outlet height(h1), the drop height or in other words, step depth(s), the ISB width (B), the ISB length (L), thesequent depth (h4), the end-sill height (he), theend-sill width (be), the water density ( ) and thegravitational acceleration (g):, ,, , , ,

,

,

,

,

(1)

Main reservoir
Water Surface

1.50 mHR

Pierced sheets

Bottom outlet
U0

h1

h3

h4

s

s

End-sill

50 cm
heighthe
Side view of model

In-ground SB
L

2.5 m

9 m LengthEnd-sill width
Pierced sheets V0

Main reservoir

U0

b1

bB

be

In-ground SB

50 cm widthPlan view of modelFig. 2 The schematic side and plan view (not to scale) of experimental setup.

― 563 ―

The relattive hydraulic functionality (RHF) cann be
written as a functiion of eighht dimensionnlessparameteers as below:, ,, , , , ,Bottommoutlett(2)

where Frr is the Froudde number at the bottom ouutlet
exit, Y iss the ratio off sequent dep
pth to the botttom
outlet height h4/h1, Y3 is the degreee of submergeence
or in otheer words the ratiorof waterr depth at the faceof bottom
m outlet to thee bottom outlet height h3/hh1,
is the reelative end-siill width be/B
B,
is the ddrop
number ((s+he)/h1, δ iss the ratio of end-sill heighht tothe end-ssill position (s+he)/L, α is the expannsion
ratio B/b and β is the aspect ratio L/B. It shoulld betake into account that,, the sequent depth (h4) caan be
defined iin Eq. (3) wherew
hc is thhe critical w
water
depth oveer the end silll (Fr =1).
(3)
3.2 Exp
perimental condition andd limitations
The exxperiments were carried ou
ut under diffeerent
ISB geom
metries as follow: ISB len
ngth (L= 75, 100
and 125 cm), step depthd(s= 5, 10 and 15 ccm),
however,, the width of ISB for all experiments was
the same B= 50 cm eqqual to the wiidth of flume.. For
each ISSB geometrry configurration, diffeerent
geometryy of end-sill withw various heightsh(he= 00, 4,
8 and 12 cm) and widdth (be= 50, 40 and 30 cm)) has
been syystematically examined to obtain the
optimumm case. The ennd-sills used ini this study w
were
made by plywood andd were uniforrm in both heeight
and thickkness. The ennd-sills were placed verticcallyabove thhe positive sttep and perp
pendicular too thelongitudiinal axis of flume.
f
The end-sillewith two
free spacces located att the downstrream end of ISB
was shown in Fig. 3. In additiion to the tthreedifferent Froude numbber of supercrritical flow att thebottom ooutlet exist (nnamely Fr= 3,, 4.3 and 5), only
one dimeension of botttom outlet (hh1= 5 cm andd b1=
10 cm) w
was examined, thus, creates an expannsion
ratio of 55.
3.3 Exp
perimental setup
The exxperiments werew
conducteed in a horizoontal
rectangullar flume, 0.55 m width, 0.5
5 m deep and 9m

Free spaceEnd-silll

Fig.. 3 The front viewvof end-ssill with two freespacces at its bothh sides.
Lonng. This flu
ume had a transparent Plexiglas
sideewall which facilitates tthe visual access.
aA
centtrifugal pum
mp was emplloyed to suppport thereciirculating water system in this sttudy; bypum
mping up the waterw
into thee supply tankk from theundderground sum
mp. Volumee rates of fllow wereregu
ulated by a valve loocated betw
ween theundderground sum
mp and the suupply tank. The supply
tankk was locatedd at the upstrream of the flumefandequipped by a caalibrated 90 ddegree V-notch weir.
To measuremthe waterw
head abbove the V-nnotch weira point
pgage was used, and then average
timee-volume meethod was utiilized for five readingfor each flow rates to obbtain the rellationshipbetw
ween water headhand thee pertinent discharge.
dThee water over thhe V-notch w
weir, then, waas fall intoa hexahedralhshape tank constructed
d at thebeginning and insideiof thee flume; nam
med mainreseervoir. The mainmreservoirr was representative of
FMD and it wass equipped bby a low leveel verticalgatee at its downstream end. T
The opening height ofdisccussed low leevel gate couuld be simply
y adjusted
by slidingsthe veertical gate upp or down. The exit of
the low level gatte was faced tto the ISB, whereasw
its
entrrance was lo
ocated 50 cm
m inside of the mainreseervoir to guaarantee the sstraight stream
mlines offlow
w approaches to the exit. Since the fu
unction oflow
w level gate inn this study w
was exactly similar tothe concept off bottom ouutlet in FM
MDs; thetermminology of bottomboutlet was selected for that.

― 564 ―

Suppply tank

Bottom outlet

End-sill

8.5 cm
15 cm
15 cm

Mainn reservoir

8.5 cmx/L
L=0

x/L=0.225

x/L=0.5

x/L=0.75

x/L≃1

Flume

Fig.. 5 The pointss in which waater level weremeaasured throughout ISB.

Fig. 4 Thhe model setuup used in thiss study.
Additionally, two pierced platees were instaalledinside off the main reeservoir to attain the lam
minar
outflow discharge innto the ISB
B; so a unifformsupercritiical flow wiith a thickneess equal to thebottom outlet was fall into the ISB. The
photograaphy of constrructed model setup was shhown
in Fig 4.
3.4 Expeerimental meeasurements
The mmeasurements in all experim
ments were taaken
15 minuttes after the pumppstartedd to re-circulaatingwater thrroughout the model. Wateer head in sup
upply
tank (hw) and water deepth in the mainmreservoirr (hr)were meaasured and coontrolled several times duuring
the experriment, usingg respectively
y point gauge andpiezometter tube, to ennsure a constaant dischargee andupstreamm water depthh for steady statescompliaance.
The basiic data collecction procedu
ure was the ssame
for all off the experimeents run.

to 50
5 HZ and the number of sample takenn for eachrun was around 35000 to coppe with the ap
pplicationof Fast Fourieer Transformm (FTT) inn energy
specctrum calculaation.
(3) Velocity mea
asurements
UsingU
an electro-magnnetic curren
nt meter(AC
CM-3RS prod
duced by JFFE_ADVANT
TEC) thestream-wise innstantaneous 3D veloccity wasmeaasured in fou
ur different crross sectionss for eachtest run. At every
y section the vvelocity was measured
at 3 cm interval. The samplinng frequency was
w set to50 HZ.
H The red dots
d in Fig 6 show the points where
were measured. Fig. 7
velo
ocity profile distributionsdshow
ws the waterr level meterr and electro--magnetic
currrent meter in a position cloose to the end
d-sill.
Bottom outlett

End-ssill

8.5 cm
15 cm(1) Hydraulic jump properties
For eaach test digital photograaphs were taakenfrom botth side and planpview off ISB and viisualobservatiions were recorded using
g high resoluution
digital camera. Thus, the main characteristicc
cs ofhydraulicc jump were acquired through the immagetreatmentt.
(2) Wateer depth and fluctuation
The water level meeter (ACH-300RS produce d by
JFE_ADVVANTEC) was
w used to measure
m
the m
mean
water deppth and its fluuctuation throoughout ISB. The
red dots in Fig 5 indiccate the pointts in which w
waterlevel werre measured. A sampling frequencyfwass set

x/L=0
x

x/L=0
0.25

x/L=0.5

x/L=0.75

x/L≃1

Fig.. 6 The pointss in which vellocity profile weremeaasured throughout ISB.
(4) Flow conditiion downstreeam of ISB
The
Tmean velocity andd the wateer depth
disttribution at a specific crosss section downstreamof ISBI
were taken (4 meter ffarther downstream ofbotttom outlet section) wheree uniformly distributeddflow
w was re-estab
blished in chaannel. These data wereusefful in determiining the enerrgy loss in ISB.

― 565 ―

end-sill. It shou
uld be noted that precisee velocity
disttribution measurements have been done inseveeral longitudiinal and transsversal cross sections.
This kind of measuremeent is neeeded forenvironmental analysisaof IISB design. Velocity
vecttors and mag
gnitude, and its variationn in eachpoinnt over timee are three rrequired indiicators to
answ
wer the question of whicch geometry of ISB ismorre acceptable from the vieew point of habitat
hforaquatic animals.
Moreover,M
totaal wetted periimeter and tottal wetted
areaa of ISB was considered aas two main indicatorsifor selecting the economical geometries. Then, theoptiimal geometrry was selectted between the cases
thatt could satissfy all threee terms of hydraulic,hecon
nomic and en
nvironmental requirementss.

Water leveel
meterElectro-maagnitude
current meter

Fig. 7 Thhe water levell meter and ellectro-magnettic
current mmeter used in this study.
3.5 Expeeriments proogram
As preeviously menttioned, presen
nt study aimeed toultimatelly propose a new desig
gn guideline forstilling bbasin downstream of FM
MDs how too be
hydrauliccally, econom
mically and environmenttally
acceptablle. To achievve this final purposepand tto beable to prropose a robuust and usefull design guideeline,
it is neccessary to put
p efforts inn organized andsystematiical manner. Here in, th
he details off theexperimeents program was described.
The 50 experimentts were carriied out in “cclear
water” ccondition to select optim
mum geometryy of
ISB in w
which dissipatiion of energy
y and stabilizaationof hydraaulic jump werew
significaantly higher thanothers. T
The hydraulicc criteria used
d to evaluatee theoverall efficiency ofo ISB geom
metry (from thehydraulicc point of view) includees: dissipationn ofenergy b etween bottom outlet secttion and a secction
at the doownstream ofo end-sill, momentumm
att thedownstreeam of endd-sill, type, symmetry andstabilizattion of hydraulic jum
mp within IISB,
fluctuatioon of water surface withinw
ISB, themaximumm height of sttanding wave over the end--sill,
stream-w
wise velocity reductionr
alo
ong the centerrline
of ISB, aand tail wateer depth at th
he downstream
m of4

Results

4.1 The effect of end-sill height on hydraulichfunctionality of ISB
To
T identify theteffect oof end-sill heighthonhyddraulic functiionality of IISB, four teests weredesiigned in whicch all parameeters were con
nstant andonly
y the end-silll height varieed. Table 1 showssthegeometric and hy
ydraulic variaables of desig
gned tests
for this section. In orderr to investiigate theeffeectiveness off different ISSB geometry
y in flowvelo
ocity reductioon, the normaal stream-wisee velocity(Uavve/U0) along the centerlinne of ISB isi plotted
agaiinst the norm
mal distance ffrom the bottom outlet
secttion (x/L). Fiig. 8 plots thhe normal strream-wisevelo
ocity (Uave/U0) distributionn along the centerline
cof ISB for different end-sill hheights. As caan be seen,
in casecof expeeriment withoout end-sill (E1), theUavee/U0 was rem
mained considderably high until theend of ISB. WhileW
for thee cases E3 and E4,
resp
pectively 8 an
nd 12 cm endd-sill height the lowest
mag
gnitude of Uave/U0 was obbserved at thhe end of
ISB
B.

Table 1: The desig
gned geometrric and hydrau
ulic variabless for section 44.1.
Case

Q(lit/sec)Frh1(cm))b1(cm)

L(cm)

s(cm
m)

he(cm)

be(cm)

E1

15

4.3

5

10

100

15
5

0

50

E2

15

4.3

5

10

100

15
5

4

50

E3

15

4.3

5

10

100

15
5

8

50

E4

15

4.3

5

10

100

15
5

12

50

― 566 ―

1.2
1

Flow dirrection

End-sill
E

Umax/Uo

0.8
E
E1
E
E2
E
E3
E
E4

0.6
0.4
0.2
0
0

0.5 x/LL

1

Fig. 8 Thhe normal streeam-wise velo
ocity (Uave/UU0 )reductionn along the ceenterline of ISSB.

w pattern withiin ISB for case E3.
Fig.. 10 The flow(Fr== 4.3, Q=15 lit/sec,lL=1000 cm, s= 15 cm
m, h1=5
cm, b1= 10 cm, be= 50 cm, he= 8 cm).

Additionally, this figurefindicatees that increaasing
the heighht of end-sill from 8 to 12 cm (E3 to E4)
has not aany significannt effect on velocityv
reducction
along thhe ISB. The laboratory observation also
proves tthe results obtained byy flow veloocity
measuremments. In casse of the exp
periment withthout
end-sill, E1, the jet skkims on the su
urface of staggnant
water wwithin ISB and a supeercritical currrent
observedd which enlaarges to the whole widthh of
flume in the second half
h of the IS
SB. Then, a hhuge
number of minor juumps were observed at thesecond ddownstream halfhof ISB anda consequeently
consideraable amount of air was entrainedeintoo thewater body that is draagged far dow
wnstream of ISB(Fig. 9). It means thaat the ISB len
ngth and endd-sillheight w
was not suffficient to forrce the jumpp to
occupy w
within ISB. Whereas, byy increasing theend-sill hheight to 8 cm, the toe off the jump drraws
back tow
ward the bottoom outlet secttion and the juump
stabilize within limiteed area of ISB
B (Fig. 10).

As
A can be seeen in Fig. 111, by increasing theend-sill height frrom 0 (case E
E1) to 8 cm (case E3)
the energy loss withinw
ISB coontinuously increased.
i
While further increase of endd-sill height, adversely
decrreases the energy dissippation (case E4). The
following equattion was ussed to calcu
ulate therelaative energy loss below
w the FMD
D due tosubm
merged jump:∆(4)

wheere ∆ is thee differential of head losss between
botttom outlet section and a ssection 4 metter further
dow
wnstream of FMD,
F
calledd section 5, where
w
the
flow
w velocity disstribution is hhomogenous there.
andare resp
pectively the average velo
ocity andthe average wateer depth in secction 5.
iss the totalhead
d at the toe ofo submergedd jump at the upstream
end of ISB.
0.92
0.9
△H/H1

Flow
w
directiion

0.88
0.86
0.84
0.82
E1
E

Fig. 9 Thhe flow patterrn within ISB for case E1.
(Fr= 4.3,, Q=15 lit/secc, L=100 cm, s= 15 cm, h1==5cm, b1= 110 cm, be= 500 cm, he= 0).

E2
E3
Cases

E4

Fig.. 11 The variaation of relatiive energy losss
verssusthe different end-sill heeight. (E1 : =0 cm,
E2 : =4 cm, E3
3:=8 cm, E4 :=12 cm).
c― 567 ―

1.2
1
Umax/Uin

0.8

E2
E5
E6
E3
E8
E9

0.6
0.4
0.2
0

0.55 x/L

01

mal stream-wisse velocity (UUave/U0)
Fig..12 The norm
redu
uction along thet centerlinee of ISB.

0.92
/ 1
△H/H

4.2 The effect of end-sillewidtth on hydraaulicfunctionality of ISB
To cllarify the effect of ennd-sill width on
hydraulicc functionaliity of ISB, six tests w
were
designedd in which all parameters werew
constantt andonly thee end-sill heeight and wiidth varied. The
designedd geometric annd hydraulic variables of ttests
for this section are tabulatedtin Table 2. Figg. 12
illustrates the norrmal stream
m-wise veloocity(Uave/U0) reduction aggainst the norrmalized distaancefrom thee bottom ouutlet sectionn (x/L) for two
different end-sill heights, (E2, E5 anda E6 with 4 cm
end-sill height and E3, E8 and E9 with 8 cm
end-sill hheight).
As cann be seen, in casecof experriment with loower
end-sill hheight (E2, E5
E and E6), the less veloocity
withreductionn occurred compare to the cases w
higher ennd-sill height (E3, E8 and E9).
E Additionnally,
consideriing two freee spaces at thetboth sidee ofend-sill sslightly reduced the functio
onality of ISB
B forvelocity reduction, however thee magnitudee of
Uave/U0 hhas not been changed con
nsiderably att thedownstreeam end. Thuus, free spacees at both sidde ofend-sill can effectivvely facilitatte the fish andsedimentt passage while it has not significant
s
im
mpact
on functiion of ISB.
Fig. 122 also shows that the low
wer end-sillss are
more sennsitive againsst the free sp
pace width raather
than higgher end-sillss. The resultt of energy loss
calculatioon for designed test in this section wasshown inn Fig. 13. As can be seen, the reesult
withobtained by Eq. (4) is in good agreement w
velocity reduction anaalysis along thet ISB. Hi gher
end-sill ccould dissipatte more energ
gy than the loower
one and decreasing thhe end-sill width
wreducedd thefunction of ISB.

0.87
0.82
E2

E5

E6 E
E3
Cases

E8

E9
9

Fig.. 13 The variaation of relatiive energy losss versus
the different end-sill height. (E
E2:
=4 cm
m, =50cm ;E5: =4 cm
m, =40 cm ;E
E6:
=4 cm
m, =30cm ;E3:=8 cm
m, =50 cm ;;E8:=8 cmm, =40cm ;E9:=8 cm
m, =30 cm )).

Table 2: The desig
gned geometrric and hydrau
ulic variabless for section 44.2.
Case

Q(lit/sec)

Fr

h1(cm
m)

b1(cm)L(cm)s((cm)he(cmm)

be(cm)

E2

15

4.3

5

10

100

15

4

50

E5

15

4.3

5

10

100

15

4

40

E6

15

4.3

5

10

100

15

4

30

E3

15

4.3

5

10

100

15

8

50

E8

15

4.3

5

10

100

15

8

40

E9

15

4.3

5

10

100

15

8

30

― 568 ―

5

Conclusions

The new concept of stilling basin as well as
end-sill for FMDs has been proposed in this study,
which could be environmentally acceptable fromthe point views of fish and sediment passages. The
velocity reduction of stream-wise flow affected bydifferent end-sill heights and width was
experimentally investigated. On the basis of present
study following conclusions are arrived at:(1) The presence of end-sill at the end downstreamof ISB could stabilize the hydraulic jumpsymmetrically.
(2) The taller fully end-sill can effectively reducethe magnitude of velocity within ISB compare to
the shorter one.
(3) Considering two free spaces at the lateral side ofend-sill (slit-type) shows the almost equal function
for velocity reduction with fully end-sill andpositively provides additional effects for fish andsediment passing.
References
Bremen, R., Hager, W.H. (1994):Expanding stillingbasin, Proc. ICE, Water, Maritime and Energy,Vol. 106, pp, 215-228.
Ferreri, G.B. and Nasello C. (2002): Hydraulicjumps at drop and abrupt enlargement inrectangular channel. Journal of hydraulic research,
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Hager, W.H. and Bretz V.N. (1986): Hydraulicjumps at positive and negative steps, Journal of
Hydraulic Research, Vol. 24, No. 4, pp. 237-253.
Hotchkiss, R. and E. Larson. (2005): Simple
methods for Energy Dissipation at Culvert Outlets.
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Katakam, V.S.R. and Rama P. (1998): Spatial
B-jump at sudden channel enlargements withabrupt drop. Journal of hydraulic engineering,
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Kavagoshi, N. and Hager, W.H. (1990): Wave typeFow at abrupt drops, Journal of HydraulicResearch, Vol. 28, No. 2, pp. 235-252.
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on Master of Science in civil engineering,
Washington state University.
Ohtsu, I. and Yasuda, Y. (1991): Transition fromsupercritical to subcritical fow at an abrupt drop,
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Rajaratnam, N. and Ortiz, V. (1977): Hydraulicjumps and waves at abrupt drops, Proc. ASCE,
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HY4, pp. 381-394
Rajaratnam, N. and Subramanya, K. (1968):
Hydraulic jumps below abrupt symmetricalexpansions, Proc. ASCE, Journal of theHydraulics Division, Vol. 94, No. HY2, paper
5860, pp. 481-503.
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825-835.

― 569 ―

(Received June 8, 2012)潜り跳水式減勢工の減勢効果に及ぼすエンドシル形状の影響

Mohammad MESHKATI
(1)
(2)

(1)

・角

哲也・Sameh KANTOUSH(2)

京都大学工学研究科

エジプト・カイロドイツ大学

要

旨

流水型ダム下流に設置される減勢工の設計には，土砂や魚類の安全な通過のための課題が残されており，改善が求められている。本研究では，河川環境に対する適合性を高めるために，ダム直下を潜り跳水式とした新
しい減勢工形式について，その考え方と水理設計上の課題について検討を行った。ここでは，減勢工下流に設置されるエンドシル高さと形状に着目して水理実験を行った。その結果，減勢機能を満足しつつ，土砂や魚類の通過機能も満たすことが可能な減勢工形状を結果を得ることができた。

キーワード: 流水型ダム，減勢工，底部洪水吐，エンドシル― 570 ―