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Journal of Hydrodynamics

Ser.B,2007,1 9(1):78-83 sdlj.chinajourna1.net.cn

CALCULATIoN oF FLOW FIELD AND ANALYSiS OF Sn WNING SITES

FoR CHINESE STURGEoN IN THE Do、ⅣNSTREAM oF GEZHoUBA

DAM

FU Xiao-li,LI Da-mei,JIN Guo-yu

School of Water Resource and Hydropower,Wuhan University,Wuhan 430072,China,

E-mail:fuxiaoli 1 979@yahoo.corn

(Received October 25,2005;Revised April 1 9,2006)

ABSTRACT:The Chinese sturgeon(Acipenser Sinensis)is

one of the unique and important fishery resources in China.

Since the construction of the Gezhouba Dan3,the traditional

migration route of the sturgeon has been blocked;consequently,

the len础of natural spawning sites is reduced from 800 km in

thepasttolessthan 5 km atpresent.As an endangered species,

the Chinese sturgeon has become one of the most conserved

aquatic species.In this article,the flow field of its spawning

states in the downstream ofGezhouba Dam was simulated and

analyzed using N.S equations and k一8 turbulence mode1.

Volume Of Fluid(VOF、method with the Finite Volume

Method(FVM)was used to simulate the water-air two-phase

flow to examine the computed area.On the basis of the

ecologica1.hydraulic characteristics of Chinese sturgeon,the

features of the flow field were investigated to provide

theoretical support for the proper managemeut of the Three

Gorges Reservoir.

KEYWORDS:Chinese sturgeon(Acipenser Sinensis),Finite

Volume Method(FVM),Volume Of Fluid(VOF),natural

spawning site,three—dimensional river channel

1.1NTRoDUCTloN

1.1 Researchproblem

The Chinese sturgeon(Acipenser Sinensis)

belongs to the sturgeon family ’ .They ale a type of

anadromous,bosom-feeding fish.Between October

and November each year in natural spawning sites in

the eight-hundred-kilometer river area between

Pingshan and Mudong in the upper reaches of the

Yangtze River.The fish typically lay eggs in deep

waters and rock heaps in the riverbed.The

construction of the Gezhouba Dam in 1 98 l blocked

the migration route of tllis fish.and this raised a

significant threat against the reproduction and survival

of the fish and substantially reduced this fishery

resource.Despite the fact that Chinese sturgeons can

travel only 21 0 km ups ̄eam.because of their

strong viability, sensitivity, selectivity, and

adaptability with regard to the changes in the

conditions of flow field. they have found new

spawning sites in the river area 5 km downstream of

the Gezhouba Dam.However,their spawning rate is

less than 20%of the normal spawning rate.Therefore.

the Chinese sturgeon has been considered as an

endangered species. More seriously,the river

structures of the spawning sites are constantly

threatened by the flood discharge of the e

Georges Reservoir and dredging of the waterways.

The environment for the spawning and reproduction

of Chinese sturgeons is very fragile.

1.2ResearchontheChineseSturgeon

Some research institutions in China are devoted

to the protection of Chinese sturgeons.For example。

the I中秋月饼图片大全 nstitute of Hydrobiology of the Chinese Academy

of Sciences has been involved in the biological studies

of Chinese sturgeons.The Yangtze River Institute of

Aquatic Products of the Chinese Academy of Aquatic

Sciences has produced Chinese sturgeons through

artificial incubation.Each year a number of Chinese

★Project supported by the Three Georges Construction Commission and the National Natur童孙未解供耕织下一句 al Science Foundation of China

(Grant No.30490231).

Biography:FU Xiao—li(1979一),Female,Ph.D.

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sturgeon fry and breeding sturgeon with 0.2 m size are

putintotheYangtzeRiver.

1_3 D/stribution ofthe spawning sites ofChinese

sturgeon

The records on the spawning sites of Chinese

sturgeons collected since 1 983 indicate that these sites

have been concentrated in the 1 0 km river area

betweenthe Gezhouba Dam and the Yanzhiba Dalil.L

Figure l shows the diferent districts of the river aFea.

The results obtained by tracking the spawning

sturgeons with ultrasonic telemetering devices and

directly gathering the zygotes of the fish from the

riverbed indicate that the fish’s eggs are mainly found

in the districts III and IV.with small distributions in

the districts I.B,II.B,II.C,and V.B.Dislributions of

eggs in other districts are extremely rare.To

understand the patterns of the fish’s spawning,this

article aims to simulate the features of the river

channel and the f1ow velocity distributions.Because

the natural fiver channel is winding.it is dif行cult to

present it exactly as it is in the three.dimensional

mathematical mode1.Therefore, some

conceptualization is necessary.With the topographic

map(see Fig.2)ofthe spawning sites for sturgeons,a

computational diagram is given in Fig.3.

Fig.1 Layout of spawning sites of Acipenser Sinensis

Fig.2 Map of spawning sites ofAcipenser Sinensis

2. NUMERICAL SIMULATIoN AND

CoMPUTATIoNAL MIETHoDS

The natural fiver channel鹊桥仙表达了怎样的情感 has several

uncertainties such as the complex boundaries and

turbulentflow.Therefore,the computation at the

79

Fig.3 Sketch of the boundaries of the spawning site of

Acipenser Sinensis

boundaries of river channels has been a hot but

dimcult subject.Since Launder and Spalding L)J

established the k一 mode1.it has become the most

widely used model of turbulent flow and has been

successfully used to simulate several complex flow

prOblems.Although the Reynolds stress model or the

algebraic stress model is more accurate than the

k一 model for the simulation ofnonuniform flows.

with the introduction of the two.phase flow Volume

Of Fluid(VOF)method for the computation of river

channe1.the k一 model provide results that are

more similar to the on-site measu

,…

red values compared

with the Reynolds stress model,t Therefore

.in this

study.the k一 turbulent flow model is employed

for the nUlTlerical simulation of the whole flow field.

The obvious dividing interface between water flow

and air in the river channel makes simulation possible

by using the two.phase flow model in water.air

two-phase flow.At present,the method of volume of

fluid created bv Hirt and Nichols 】is considered as

an ideal method for dealing with the problems related

to free surface flow.Using this method,two or three

immiscible flows can be simulated via the solutions of

individual momentum equations and the examination

ofthe volume ratio of each flow passing through the

area.This method is suitable for the simulation of

flows in natural river channels.Given the fact that two

or more flows(or phases)are not mixed,the VOF

formulae considers the new variable of each phase

mat is added to the model to compute the volume ratio

of the phase in the element.Wimin each controlled

volume.the sumofthevolume ratiosofallphasesis 1.

A11 variables and their a衔liated areas are shared by

every phase.They represent the mean volumes as long

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as the volume ratio of every phase at each position is

nown.Hence,a volume ratio equation in addition to

the continuity equation,the momentum equation,and

the k, equations are used to solve the free surface

problems,as follows.

Volume ratio equation:

The interface between tracking phases is

established by the solutions of single—phase or

multiphase continuous volume ratio equations.For the

phase q,the equation is expressed as

at (1)

Generally,the volume ratio equation is not used for

the solution of the primary phase.The computation of

the volume ratio of the primary phase is based on the

following constraint:

∑ =1

q=l

Continuity equation:

+ ( ):o a

t a)C:、。

Momentum equation:

OP ui

+考 一筹+毒 +

k equation:

O(pk)

equation:

(2)

(3)

(4)

:( + )当+G一 ax

i ok a)ci

(5)

o(pe)+

: ( + +O t

f f o Oxf

Cl 丢G (6)

where f is the time,uf and xi are the velocity

components and the coordinate components,

respectively,P is the density, is the molecular

viscosity coefficient,and P is the moderated stress.

is the turbulence viscosity represented as:

p乙u一

where C is an empirical constant( 0.09),o- and

a are the Prandtl turbulence constants for

k andE(o- =1.0, =1.3),Cl and C2 are the

constants for (C1 =1.44,C2 =1.92),G is the

turbulence momentum product caused by the average

velocity scale as defined below:

G -O uy]

Oui

Boundary conditions:

Atinlet

The boundary conditions at the inlet for the case

isthatonlytheErjiangPowerPlantisin operationand

the Dajiang Power Plant and the ship lock are closed.

These conditions,as shown in Figs.1 and 2,are

identical with the case that the Gezhouba Dam

operates during the spawning period of Chinese

sturgeons.On the basis of the information collected

and those provided by the Institute of Hydrobiology of

the Chinese Academy of Sciences,the inlet of the

model is placed in front of the outlet of the Gezhouba

Power Station.and it is the furthest possible place

where the surveying ship can reach.The inlet flow

velocity at the Erjiang Power Plant is 2.55 m/s.

whereas the flow velocity at the Dajiang Power Plant

and at the ship lock is 0.32 rn/s.The depth of the

water at the inlet ofthe model is 8 meters and the rest

is all air.k and at the inlet are given using the

empirical formula.

At outlet:

The normal derivatives of all variables are 0.tl1at

is,the second boundary condition is:

:o

On

Atfree surface:

The free surface is treated as a pressure boundary

atwhich the pressure valuep=0.

Atwall:

Use the standard wall function.

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Construction of mesh:

In this article,the nonstructural mesh

.which iS

well suited for complex computed areas

.iS combined

with the finite volume method to divid却看妻子愁何在翻译 e the computed

area.Similar to a fmite element。the nonstructural

mesh relies on the relationship between nodes and

elements to mark their positions and the connections

between adjacent elements[13-15].For three—

dimensional problems,tetrahedron,prism,cube and

other flexible spatial shapes Can be used to divide the

computed area.A tetrahedral or prismatic element can

be used in the irregular areas,whereas a cubic element

Can be used In the regular areas.Figure 4 shows the

construction of surface mesh for the computed area

Fig.4 Computation mesh

3.ANALYSIS oF THE COMPUTATIONAL

RESULTS

The th感恩母亲的诗歌 ree—dimensional flow field iS unique for

analyzing the model at diferent sections

.The

lnformation with regard to the distribution of flow

velocity can be obtained by the examination of the

diferent sections of the fiver channe1

.Figures 5一ll

present the flow fields and streamlines of different

sections.

一20

Fig.5 Velocity at section x=85m

The topographical m印shows a big,deep‘'hole”

at the river bend resulting from water discharging and

scounng for years by the discharge from the Dajiang

Power Plant and the Erjiang Power Plant since the

construction of the Gezhouba Dam.It iS around this

sturgeons are concentrated.Therefore,the flow field

8l

around the deep hole iS the focus ofthe computation

. The horizontal flow direction of the river channel is

given in Figs.9’10.For the case that only the Erjiang

Power Plant IS in opermion,a strong backflow area is

formed near the Dajiang Power Plant and the ship

lockgate.Additionally.there iS a small backflow area

at the riverbend.The backflow becomes weaker and

the flow tUI ̄s to be more stable near the boRom ofthe

river.Down In the hole there印pears a vo ̄ex that

exhibits a complicated flow behavior

lO

l5

Fig.6 Underwater velocity distribution at measured section

。lO

一20

Fig.7 Velocity at section y=3m

95

9o

85

8O

75

Fig.8 Streamline at section .1

.5m

Figure 7 shows the flow velocity at the vertical

section of the deep hole

.When the main flow passes

through the deep hole of the simulated river channel-

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82

vortices with opposite directions are formed at the

bottom ofthe hole and at the upper and lower parts of

the main flow(clockwise atthe bottom ofthe hole and

counterclockwise in the upper part of the flow).11le

air atthe upperpart ofthe flow is irregularbecause of

the influence of the water flow.Figure 5 shows the

flow velocity of the passing water section at the center

of the deep hole.A demarcation line between the air

and the water can be easily seen.The flow is turbulent.

Small vortices near the wall and a huge vortex in the

whole flow area are found.Figure 6 represents the

distribution offlow velocity ofunderwater at the river

section measured with the Acoustic Doppler Current

Profiler(ADCP).It is obvious that the velocity

distributions in Figs.5 and 6 are similar.Figure 8 is

also obtained by sectioning at the bottom ofthe hole

the water plane at the center of which vortices are

spotted.Finally.Fig.1l shows the general similarities

between the computed results and the on.site

measurements of the flow velocity distribution at the

underwater sections.

0 50 lo0

Fig.9 Streamline at section z=-8m

4o

20

-20

0 50 lo0

Fig.10 Streamline at section z=-4m

4.CoNCLUSIoNS

(1)The numerical simulation ofthe flow field in

the spawning sites for sturgeons in the downstream of

the Gezhouba Dam shows very complex

characteristics. en only the Erjian Power Plant is in

operation,the velocity of the main surface flow is

high,and a deep hole i泊秦淮 杜牧 n the river area is formed.

enthewaterflowpassesthroughthe deephole,the

flow field ofthe vortices at the bottom of the hole is

extremely beneficial for the sedimentation ofthe fish

eggs.In addition,the strong viscosity of the fish eggs

enables them to stick to the crevices ofpiled rocks at

the bottom ofthe river without being washed away or

devoured by other fishes.thus effectively protecting

theincubationofthe eggs.

40

20

_20

Fig.1 1 Calculated velocity

(2)The on.site measurements and computational

results indicate that Chinese sturgeons tend tO lav eggs

among piled rocks ofthe deep hole,where the surface

flow velocity is high,the flow velocity at the bottom

is low.and the flow is relatively stable.This result is

in accordance with the hydrodynamic characteristics

of spawning sites for Chinese sturgeon.

(3)The spawning sites for Chinese sturgeons in

the downstream ofthe Gezhouba Dam are very shaky,

therefore,Chinese sturgeons can become extinct at

any time,and this is attributed to the water discharge

fromthedamandthedredgingofthewaterways.

REFERENCES

SICHUAN INVESTIGATION GROUP FOR THE

YANGTZE RIVER AQUATIC RESOURCES.

Sturgeons and Chinese Sturgeon[M】.Sichuan

Science and Technology Press,1988(in Chinese).

LI Da-mei.Study of water intakes for oncemelania

control based on information of oncemelania behavior

and CFD results『J1. Science in China,Ser.E,

200 l,44(5):522.530.

WANG Yu.tang.The status of the sturgeon resources

[J】.China’s Aquatic Products,1999,(9):16-19(in

Chinese).

1(J三Fu.en,WEI Oi-wei et a1.On the protection and

saivation of rare aquatic and wild animals on the

Yangtze River[M】.Beijing:Environmental Science

Press,1994(in Chinese).

维普资讯

[5】

[6】

[7】

[8】

[9】

[1O】

LAU拒组词语 NDER B.E—SPALDING D.B.Lectures in

mathematics models of turbulent『M1.London,

England:Academics Press,1 972.

WANG Fu-jun.Computational fluid dynamics and

analysis[M】.Beijing:Tsinghua University Press,2004

(in Chinese).

FU Xiao-li and Li Da-mei.Analysis of ecological flow

field in an oncemelania.free water intake device[J1.

Journal of Hydrodynamics,Ser.B,2005,17(3):

301.305.

XU Wei一1in and L O Hua-sheng. Numerical

simulation of flOW field of a river with complicated

boundaries[J].Journal of Hydrodynamics,Ser.B,

1996,8(3):75-8O.

mI C.W..NICHOLS B.D.Volume offluid(VOF)

method for the dynamics of free boundaries[J].Journal

ofComputational Physics,1981,39(1):201.225.

RUDMAN M. A volume-tracking method for

incompressible muRiplied flows with large density

variations[J].Int.J.Number.Method in Fluids,1998,

(28):357.378.

[12】

[13】

[14】

[15】

83

VANDOORMAAI J.P. and RAITHBY G. D.

Enhancements of the SIMPLE method for predicting

incompressible fluid flows[J].Heat Transfer,1984,

7(11:147-163.

PATANKAR S.V.and SPALDING D.B.The

numerical computation of turbulent flows 『J1.

Computer methods in AppHed Mechanics and

Engineering,1974,3(2):269-289.

TAN Wei.yan. Shallow-water computational

dynamics[M],Beijing:Tsinghua University Press,1998

(inChinese).

JIN Zhong-qing.Numerical solutions to N—S

equations and turbulent flow models[M1.Naniin2:

Hohai University Press,1 989(in Chinese).

TAO Wen-quan.Numerical heat transfer[M1.)(i’an:

Xi’an Jiaotong University Press.1989(in Chinese).

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