3D layer-integrated modelling of flow and sediment transport through a river regulated reservoir

Transcription

1 River Flow 00 - Dittrih, Koll, Aberle & Geisenhainer (eds) - 00 Bundesanstalt ür Wasserbau IBN D laer-integrated odelling o low and sedient transport through a river regulated reservoir Faghihirad, B Lin & R A Faloner hool o Engineering, Cardi niversit, Cardi, K ABTRACT: Details are given o the reineent o a three-diensional laer integrated turbulene odel and its appliation to a saled phsial odel o a river regulated reservoir, naed Haidieh Reservoir The strong turbulent lows generated in the regulated reservoir are due to the high volues o low diversion with low head dierenes In this paper, the nuerial odel is applied to a regulated da, assoiated with water intaes and sluie gates, with the ai being to investigate the low patterns and sedient transport proesses in the viinit o these hdrauli strutures The alibration o the odel is undertaen using easureents ade ro a saled phsial odel The nuerial odel is able to test various senarios whih are diiult to test in the phsial odel In this ontet dierent senarios are introdued to investigate the eets o dierent intae and sluie gate onigurations, as well as their operation shees on the low and sedient transport proesses in Haidieh Reservoir The results have shown that a non-unior veloit distribution one eists upstrea o one o the intaes Also, the sluie gates do not appear to have an onsiderable eet on the suspended sedients onentrations oving through the intaes Kewords: Nuerial odels; odel; Regulated reservoir; 3D low; Laborator tests INTRODCTION In reservoirs and rivers, in order to understand the ipat o hdrauli strutures on the hdrodnai and sedient transport proesses it is oten neessar to investigate these proesses in three diensions Currentl, phsial odels are still widel used as an essential tool to obtain inoration about these proesses Generall speaing, phsial odels need a long tie to onstrut and are epensive to run, partiularl i large sales are involved In the projet presented in this paper a detailed nuerial odelling investigation has been undertaen to siulate water lows through hdrauli strutures and their interation with sedients sing a nuerial odel it is possible to eaine various senarios that are diiult to test in phsial odels These senarios are useul or hdrauli struture design and operation shees and uture aintenane River regulated reservoirs are oten onstruted downstrea o das, with relativel low elevations, to enable water to be distributed or water suppl purposes However, there are ajor dierenes between the low head regulator reservoirs and those reservoirs that are assoiated with noral high das, in that strong turbulene lows generated in the regulated reservoir are priaril due to high low disharges The turbulene a introdue ople low patterns, whih an be diiult to predit In reent ears, a nuber o studies have been undertaen using two- and three- diensional hdrodnai odels to ahieve iproved understanding o the role o hdrauli strutures Dierent tpes o nuerial odels, suh as MIKE, MIKE_3 and Delt3D, have been used to predit the ipat o hdrauli strutures on the hdrodnai, sedient transport and orphologial proesses For the odel siulations reported herein, preditions were obtained using a laer integrated three-diensional hdrodnai and sedient transport odel In this odel a two-equation turbulene odel was used, with details o the governing equations and boundar onditions being given The original atheatial odel was developed b Haiadeh and Faloner (007) 573

2 or siulating re-irulating lows in tidal basins oe iproveents were ade in the odel in order to prediting the low, sedient transport and orphologial proesses in a river low regulated reservoir These iproveents enhane the apabilities o the eist odel The reined odel was applied to the saled phsial odel o Haidieh regulated reservoir to obtain better understanding o the low and sedient transport regie within the reservoir NMERICAL MODEL In this stud, the nuerial odel used to predit the low and sedient transport through a river regulated reservoir oprises two odules: a hdrodnai odule and a sedient transport odule The hdrodnai governing equations are solved using a obined laer-integrated and depth-integrated shee (Lin & Faloner, 997), with the two-equation - odel being used or turbulene losure (Haiadeh & Faloner, 007)) In the sedient transport odule, the suspended sedient transport equation is solved using an operator splitting algorith (Lin & Faloner, 996) Laer integrated hdrodnai odel The governing equations used to desribe lows in reservoirs are generall based on 3-D Renolds equations or inopressible and unstead turbulent lows I the vertial aeleration o the low is negligible in oparison with the gravit and the vertial pressure gradient ters, then the hdrostati pressure distribution assuption an be ade As a irst attept, the densit o the water has also been assued onstant throughout the oputational doain In appling these approiations, the three-diensional governing equations o ass and oentu an be written respetivel in their onservative or as ollows: u v w 0 u uu uv uw p v t ρ ( u v ) ( u w ) ( u u ) () () u vu vv vw p u t ρ ( v u ) ( v v ) ( v w ) (3) p ρ g 0 (4) where t tie,,, Cartesian o-ordinates, uvw,, oponents o veloit in the,, diretion, respetivel, p pressure, ρ densit o water, Coriolis paraeter, g gravitational aeleration and u u, u v, u w, v u, v v, v w Renolds stresses in the, plain, respetivel A seth o the 3D grid and relative positions o the governing variables in the plane are illustrated in Figure As an bee seen ro Figure that there are three laer tpes inluding: the top, iddle, and botto laers The ree surae and bed topograph are presribed within the top and botto laers, respetivel, with both varing in thiness with the, oordinates so that the onl inlude water ( the nuber o laers) Figure Coordinate sste or laer integrated equations Turbulene odel In the nuerial odel reported herein the edd visosit onept has been used to represent the Renolds stresses The horiontal edd visosit was equated to the depth averaged edd visosit, based on the horiontal veloit distribution derived ro integrating the odel predited vertial veloit distributions For the two-equation turbulene odel, the horiontal edd visosit was deterined using the depth integrated turbulene odel, given as (Faloner and Li, 994): H H VH t th H H i, - i-, i, v i, th H th H Horiontal veloit Vertial veloit Turbulene odel 574

3 H V 3 * (5) th H th H VH H t H V H H H V 4 * (6) where depth average turbulent ineti energ; V, depth average veloit oponents in the, diretion, respetivel; and depth average dissipation rate o ineti energ The e oeiients are given as: ( ), / ( ), / / th where,,,, onstant oeiient; with Dar rition ator B assuing that ( ), (var) var d where ± reer to the vertial elevations o the laer interae between the, and - laers respetivel suh as ( ), d then the vertial edd visosit an be evaluated using the laer integrated or o the equations, as derived in Haiadeh (997), giving w w q q t p (7) w w q q t δ p (8) where v u p (9) ˆ (0) For the turbulene odel equations the ollowing boundar onditions were used: (i) inlet: distribution o and were given Deunren & Rodi (983) suggested two orulae or ull developed hannel lows: d d u () b d d / 4 3 / () where d u inlow veloit, and b inlet width (ii) outlet: 0 n and 0 n (iii) ree surae: and ust be given Krishnappan & Lau (986) suggested or the ollowing ondition should be used: κ 3 / (3) where distane ro the ree surae to the grid entre, and the orresponding value or the turbulent energ The value o used in equation (3) is 064, 009 and κ 04 is the von Karan onstant 3 edient transport equation Depending upon the sie and densit o the bed aterial and the low onditions, sedient partiles an be transported b the low in the or o bed load and suspended load The 3-D ass equation or sedient in suspension is written as: ( ) ( ) ( ) [ ] W w v u t s (4) where sedient onentration, s W partile settling veloit,, and sedient iing oeiient in,, diretion, respetivel For suspended sand partiles in the range o , the ollowing equation was used to deterine s W (van Rijn, 984): 575

4 3 00( s ) gd s W 0 (5) s Ds 05 where ineati visosit or lear water, s speii densit o suspended sedient, and D s representative partile diaeter o the suspended sedient partiles The iing oeiients were related to the turbulent edd visosit through the equations: th, h th and h (6) v where h, v hidt nubers is the horiontal and vertial diretions respetivel, with values ranging ro 05 to 0 In solving Eq (4), our tpe o boundaries (inlow, outlow, water surae and sedient bed boundar) need to speiied For ore stud, those reer to Lin and Faloner (997) The iportant assuption or a oveable bed ontains that in ones where the luid low is varing rapidl or in (irulation) ones where the veloities are too sall to initiate sedient otion, the appliation o an instantaneousl adjusted equilibriu bed onentration a result in a positive onentration gradient near the bed In the urrent odel the ain ous is the sedient transport A ied bed was assued, but ass o bed sedient hanges due to erosion and deposition was reovered 3 PROJECT BACKGROND 576 Haidieh regulated reservoir is loated awa ro Haidieh Town It is loated on the Karhe River, downstrea o Karhe reservoir da There are two water intaes, naed Ghods and Vosaileh intaes Currentl, the Vosaileh water intae hannel is 08 long with a aiu disharge o 60 3 / s while Ghods operates with a 5 long hannel with a aiu disharge apait o 3 3 / s Due to the developent in irrigation and drainage networ o Aadegan and Charan regions, the present onditions o the water intaes are not able to eet the water deand Hene, it is neessar to inrease the low rate ro these intaes b building new water intae strutures Haidieh reservoir da is 9 long, 45 high with 9 spillwa bas and 0 sluie gates Aadegan is to replae Ghods water intae with an inlet width o 56, 8 opening bas and 4 under sluie gates It is intended to inrease the disharge apait ro 3 3 / s to 75 3 / s Vosaileh water intae is also to be replaed b Charan with an inlet width o 866, 6 opening bas and 3 trash ras opening to inrease the disharge apait ro 60 3 / s to 90 3 / s Figure shows a plan view o Haidieh regulated reservoir and assoiated strutures An undistorted 0-sale phsial odel o Haidieh regulated reservoir and its relevant strutures was onstruted in 00 The ai o projet is to investigate the operation o the entire sste and to iprove the understanding o low and sedient behaviors near the strutures Right luie Gates Aadegan Intae Let luie Gates Haidieh diversion da Charan Intae Figure Plan o Haidieh regulated da 4 NMERICAL IMLATION Flow diretion 4 Part one: hdrodnais Details are irst given below o the nuerial odelling stud o the hdrodnai proesses in the Haidieh regulated reservoir The odel siulation was based on ield surveed data and easureent data obtained ro the phsial odel or various operation onditions o the intaes and sluie gates The results inlude the general low patterns and ore detailed veloit distributions within the reservoir and in the viinit o hdrauli strutures The bathetr data and hdrodnai senarios were deined b using ield surveed data and laborator data Figure 3 shows the bathetr o the reservoir and the intaes based on the phsial odel sale One dredging one in ront o Aadegan intae lose to the right ban has been reoended in order to ae stable diversion low into the intae or the long ter water suppl operation Nuerial and phsial odel siulations have been undertaen to investigate the easibilit o this easure in iproving the ondition or suppling water Table lists the hdrauli paraeters used to set-up the nuerial odel or testing hdrodnai odel senarios These paraeters were hosen on the basis o the data obtained ro the phsial odel eperients, in whih the veloit

5 distribution was easured in ront o the two intaes The loations o these points are shown in the Figures 4 and 5 on veloit logarithi proile assuption or easuring ean veloit Figure 3 Bathetr o Haidieh, phsial odel sale Table The harateristi or the hdrodnai senario Reservoir A Intae Ch Intae Hdrauli Boundar Condition Disharge 8 liter/s Disharge 49 liter/s Water Level Turbulene Boundar Condition urae and Inlet Outlet Outlet Operation Water level (0 ) ( ) L Closed - R Closed - A Intae Aadegan Intae, Ch Intae Charan Intae, L Let sluie gate and R Right sluie gate The investigation o veloit distribution in the reservoir and the viinit o the intaes presented a plator or studing the hdrodnai behavior In the phsial odel stud the veloit was easured in ront o the intaes at several points b urrent-eters The loation o these points is shown in the Figures 4 & 5 In this stud, the veloit easureents at these points, together with the observed water surae levels were used or alibrating the hdrodnai odel Figure 4 Loation o veloit easuring points in viinit o Aadegan intae In the phsial odel stud, the veloit was easured b a urrent-eter at 0 6D ( D water depth) ro the water surae and itted to the phsial sale This depth had been hosen based Figure 5 The loation o veloit easuring points in the viinit o Charan intae In appling the 3D laer integrated odel to this ase stud the water depth was divided into 5 laers The thiness o eah laer was set to 0057, eept or the top laer whih was 005 in the ain hannel The grid sie was seleted 05 The water surae level was alibrated with the dierenes between the observed water surae levels obtained ro the phsial odel and alulated b the nuerial odel being between 000 and (Roughness paraeter is used or alibrating water level regard to the phsial tests) Table indiates the veloit values or dierent loations that were pointed in Figures 4 and 5 or both the phsial and the nuerial odels Table Coparison between veloit values obtained ro nuerial and phsial odels Loation Points Measured (/s) Calulated (/s) Charan A B M C D E F N G H Aadegan A B C E F D The phsial odel stud and the nuerial odel siulation were not arried out siultaneousl In this researh, eorts have been ade to use the easured data or better alibration but it was not possible to test and easure hdrauli paraeters or ore senarios and loations Despite these liitations, the oparisons ade using the available data in table shows that the trend and quantities o veloit values obtained ro the nueri- 577

6 al and phsial odels are in an aeptable level o agreeent or this opliated situation In this hdrodnai senario 4 gates operated siultaneousl and with a real bathetr being used The nuerial results show that the agnitude o the vertial edd visosit is ro 0 up to 500 ties larger than the orresponding horiontal edd visosit in dierent areas The results obtained ro both phsial and nuerial odels are presented or the undistorted :0-sale odel o Haidieh regulated reservoir The low pattern and veloit ontours in the reservoir were alulated b the nuerial odel and illustrated in Figure 6 The speed proiles along the depth predited b the nuerial odel at 4 points near o the intaes (B&F or Aadegan and M&N or Charan) were shown in igure 7 The easured veloit at 06 D ro the water surae in the phsial odel is also shown in this diagra Figure 6 Nuerial odel predited low pattern and speed ontours Depth() Veloit(/s) ANu Point B(TD) APh Point B(06D) ANu Point F(TD) APh Point F(06D) ChNu Point M(TD) ChPh Point M(06D) ChNu Point N(TD) ChPh Point N(06D) Figure 7 Model predited veloit distributions and easured veloities at 06D ro water surae (AAadegan Intae, ChCharan Intae, NuNuerial, PhPhsial and TDTotal Depth) Fro Figure 7 it an be seen that the atheatial odel predited veloit values agree reasonabl well with easured ones ro the phsial odel although soe variations an be observed An analsis o the hdrodnai results identiies two ain issues: - Aording to the observation o the low diretion, it is notied that a non-unior veloit distribution one eists upstrea o Charan intae on the let ban side This is thought to be related to the loation o the intae - The veloit pattern or the regulator ondition at the artiiial dredging one (in ront o Aadegan intae) suggests that this is a loation or high potential sedientation 4 Part two: sedient transport For siulating sedient transport in hdrauli sstes inoration suh as partile sie distribution, inlow disharge and assoiated sedient disharge, tpe o sedients (ohesive or nonohesive) and understanding the doinant proess o sedient transport (suspended load or bed load) in the nature are required Previous studies have showed that the suspended transport is the doinant proess or this ase The ajorit o sedient ound in this region belongs to nonohesive tpe One o the ost iportant tass is to prevent sedients ro entering the intaes An sedient partiles deposited into the irrigation anals would ause a derease in the low rate Currentl, the staeholders o the irrigation networ have to dredge the anals periodiall In designing the new sste o Haidieh da a great eort has been ade to itigate the sedientation proble in anals In this researh, dierent senarios were onsidered in order to deterine the aount o sedients entering the intaes Details are given below o the nuerial stud o sedient transport proess The nuerial odel preditions were opared to the phsial odel results at three sites The plan o these sites is shown in Figure 8 In the nuerial odel, the senarios were seleted on the basis o the laborator tests van Rijn s (984) orula was used to alulate the sedient transport rate The patterns o the suspended sedients onentrations are shown in Figures 9, 0 or senarios and 3, respetivel The suspended sedient onentrations oputed b the nuerial odel have deonstrated a good agreeent with the ones easured ro the phsial ode (A aiu error is less than 3% and an averaged error is less than 7% that sees aeptable onsidering the overall opleit o the sedient transport) The sapling o suspended sedient onentration in the phsial odel was taen on the whole depth and alulated using a depth integrated orula Table 4 shows a oparison between the easured and alulated suspended sedients onentrations in dierent points shown in Figure 8 The results e- 578

7 press the oveent o suspended sedient in the reservoir and over the intaes Figure 8 Loation o easured sedient onentration points (CAZConentration in Aadegan Intae, CCHConentration in Charan Intae and CRR, CRM & CRLConentration in the reservoir) - High low ondition with sluie gates in both sides o the da in operation (3) The attributes o the senarios are presented in table 3 The results showed that the suspended load has an iportant role in the sedient transport proess and is losel related to partile sie A good agreeent has been observed between the Cs obtained ro nuerial and the phsial odels The analsis o the sedient transport results identiies that: (i) The suspended sedient onentration in Charan intae is higher than the one in Aadegan intae The ain reason is thought to be the loation o the intaes Charan intae is loated in the internal urve position when onsidering the laout o the sste Table 3 Main paraeters or sedient senarios No Operation Boundar Condition Conentration gr/liter Reservoir Water level Disharge liter/s 0474 A Intae - Disharge - 49liter/s Ch Intae - Water level - L R Reservoir Water level Disharge liter/s A Intae - Disharge - 49 liter/s Ch Intae - Water level - L - Disharge 56 - liter/s R Reservoir Water level Disharge liter/s A Intae - Disharge - 49 liter/s 3 Ch Intae - Water level - L - Disharge - 5 liter/s R - Disharge - 5 liter/s General d6, d50, d84 & d ,00076,0066 & data epeiig ravit 67, Grid sie 05 and Coputational tie360 in with Intel(R) Core(TM) Quad CP 66 GH A Intae Aadegan Intae, Ch Intae Charan Intae, L Let sluie gate and R Right sluie gate Details are given o the odel senarios or siulating sedient transport in the ase stud The senarios are designed in three ategories The harateristis o these senarios are: - Low low ondition without sluie gates () - Low low ondition with one sluie gate () Figure 9 Pattern o suspended sedients onentrations (C), senario Figure 0 Pattern o suspended sedients onentrations (C), senario 3 (ii) The pattern o the suspended sedient oveent in the reservoir has showed that the sedient entering rate to Charan intae is aeted ver little b the sluie gate operation shees It eans that the sluie gates on the let side do not have a onsiderable eet on reduing the suspended sedient onentration oving through Charan intae 579

8 (iii) It sees that the proble o sedient entering the intaes is reained The laout o these hdrauli strutures is onl part o the reason or this proble The natural sste o sedient transport and the sie o the sedients have an iportant role or this situation 5 CONCLION Details are given o the appliation o a threediensional nuerial odel to predit the low and sedient transport through a river regulated reservoir The ai o the stud was to iprove the understanding o the abilities o suh nuerial odels in siulating these ople proesses in a real ase An enhaned odel was used to represent the ople low pattern in the viinit o hdrauli strutures Table 4 C easured and predited at sapling points enarios Points C (Measured) gr/liter C (Calulated) gr/liter enario CRL CRM CRR CAZ CCH enario CRL CRM CRR CAZ CCH enario 3 CRL 8 3 CRM 38 3 CRR 3 CAZ CCH 5 C edient suspended sedient A series o senario runs o the operation shees or Haidieh regulated reservoir have revealed the governing phenoena in the sste to a ertain etent The results obtained ro the nuerial odel runs onir that: (i) A non-unior veloit distribution one eists upstrea o Charan intae on the let ban side (ii) The reoended artiiial dredging one, loated in the ront o Aadegan intae, will not aet the hdrauli behavior signiiantl (iii) The loation o Charan intae has a onsiderable ipat on the suspended sedient onentration oving through the intae (iv) The sluie gates operation shee has ver sall ipat on the suspended sedient lu entering into Charan intae (v) The alibrated nuerial odel has been used to predit the water low and sedient lues everal senarios were onsidered, with the nuerial odel results being used jointl with the eperiental results to assist in the hdrauli design o the reservoir ACKNOWLEDGMENT The writers wish to than the Water Researh Institute in Iran or assisting in the laborator phsial odel tests REFERENCE Deuren, AO, Rodi, W 983 ide disharges into open hannels: Matheatial Model Journal o Hdrauli Engineering, v 09, n, p Atinson, E, Lawson, JD, Tosswell, P 994 Coparison o phsial and oputer odelling o the Kapunga intae with perorane o the prototpe Hdrauli Researh Walingord, K, Reprot no ODP Faloner, R A, Li, G 994 Nuerial Modelling o tidal eddies in oastal basins with narrow entrane using turbulene odel Miing and transport in the environent, K J Beven et al, eds, Wile, London, Haiadeh, H 997 Turbulene odelling o tidal urrents in retangular harbors PhD thesis, niv o Bradord, Bradord, K Haiadeh, H, Faloner, R A 007 Laer integrated odelling o three-dinesional reirulating lows in odel tidal basins Journal o water, port, oastal and oean engineering; DOI: 006(ACE) X Krishnappan, B G, Lau, Y L 986 Turbulene odelling o lood plain lows Journal o hdrauli engineering, v, n 4, p 5-66 Lin, B, Faloner, R A 996 Nuerial odelling o three diensional suspended sedient or estuarine and oastal waters Journal o hdrauli researh 34(4), Lin, B, Faloner, R A 997 Three-diensional laer integrated odelling o estuarine lows with looding and dring Estuarine, oastal and shel siene, 44, Water and Eletriit Organiation o Khuestan Provine (WEOKP) 00 Karhe irrigation networ operation opan, Bulletin No 3, p 3-3 Water Researh Institute 00 Phsial odel o Haidieh regulated reservoir Report No 3-76, 48p Van Rijn, L C 984 edient transport, part II: suspended load transport J Hdrauli Eng (ACE), 0(), Van Rijn, L C 986 Matheatial odelling o suspended sedient in non-unior lows J Hdrauli Eng (ACE), (6),