Prikaz modela linijskog tečenja u koritu za veliku vodu zasnovanog na razmeni količine kretanja između glavnog korita i plavnih površina

This paper aims at introducing a novel approach to 1D compound channel flow modelling to the Serbian hydraulic engineering community. To this aim an Exchange Discharge Model (EDM) is presented, first. The model can be used both for the estimation of a rating curve in a two-stage channel based on the recorded water level, and the slope of the energy grade-line for non-uniform flow calculations in a flooding river once the flood dis- charge is known. EDM is calibrated and tested against the benchmark data from the Flood Channel Facility at HR Wallingford, UK. An effect of two different controls on the rating curve is analysed the effect of a floodplain to main-channel width ratio (B / b) and that of the floodplain roughness. Moreover, the model is compared to traditional models that are still used in everyday engineering practice (single channel and divided channel methods, SCM and DCM), to an empirically based Ackers' method and one physically based method proposed by Radojković. It is readily demonstrated that physically based models that account for momentum exchange between the main-channel and floodplains provide almost perfect fit to measurements, while the DCM method over predicts the discharge value.Cilj ovog rada je da se stručnoj javnosti prikaže model linijskog tečenja u koritu za veliku vodu koji do sada nije primenjivan u našoj inženjerskoj praksi. Reč je o modelu koji ima dvostruku namenu. Kada se raspolaže zabeleženim tragovima velikih voda, može se iskoristiti za definisanje krive protoka u domenu vodostaja koji prevazilaze granice osnovnog korita, ali je isto tako pogodan i za procenu nagiba linije energije u proračunima linijskog tečenja za protoke pri kojima se voda izliva iz osnovnog korita. Model je proveren korišćenjem rezultata merenja u pravolinijskom prizmatičnom laboratorijskom kanalu Hidrauličke laboratorije u Volingfordu namenjenom ispitivanju tečenja u koritu za veliku vodu. Razmotren je uticaj dva činioca na krivu protoka - širine plavnih površina i različite rapavosti dna glavnog korita i plavnih površina. Rezultati modela upoređeni su i sa rezultatima tradicionalnih modela koji se standardno koriste u inženjerskoj praksi. Poređenje ukazuje na to da se najbolja slaganja sa merenjima postižu upravo primenom modela razmene količine kretanja između glavnog korita i plavnih površina, dok se tradicionalnim modelom zasnovanim na podeli preseka na hidraulički homogene segmente vrednosti protoka značajno precenjuju

Primena modela razmene količine kretanja u analizi uticaja geometrije i hidrauličkih otpora na osnovne odlike tečenja u koritu za veliku vodu

A series of numerical experiments is conducted to determine how compound channel geometry and floodplain roughness affect both a momentum transfer between main channel and floodplains and its contribution to the total energy 'loss'. To this aim, a 1D, exchange discharge model, which accounts for the momentum exchange between the main channel and floodplains, is used. It is found that the contribution of the momentum exchange to the total energy 'loss' reduces on floodplains with the flow depth regardless of the compound channel geometry and floodplain roughness and that both, the momentum exchange and its contribution to the total energy 'loss', are increased in the following cases: 1) when the main channel aspect ratio decreases, 2) when compound channel is asymmetrical and 3) when the roughness of the floodplain increases. In the main channel, the variation in the momentum exchange contribution with the flow depth depends only on the floodplain roughness.U radu je sproveden niz numeričkih ogleda sa ciljem da se utvrdi kako geometrija korita za veliku vodu (KVV) i rapavost plavnih površina utiču na razmenu količine kretanja (RKK) između glavnog korita i plavnih površina i njen udeo u ukupnom 'gubitku' mehaničke energije toka. U tu svrhu korišćen je model linijskog ustaljenog tečenja u KVV vodu koji je zasnovan na RKK između glavnog korita i plavnih površina. Ispitivanje je pokazalo da se na plavnim površinama, zbog ujednačavanja hidrauličkih uslova u poprečnom preseku KVV, udeo RKK u ukupnom 'gubitku' energije smanjuje sa povećanjem dubine nezavisno od geometrije korita i rapavosti plavnih površina i da razmena i otpora trenja i oblika, troši i na razmenu količine kretanja između glavnog korita i plavnih površina. Za razliku od tradicionalnih, savremeni modeli linijskog tečenja uzimaju u obzir ovu razmenu i, kao takvi, pružaju mogućnost da se proceni udeo razmene količine kretanja u ukupnom 'gubitku' mehaničke energije toka. U ovom radu se, pomoću jednog takvog modela, ispituje kako geometrija složenog korita i rapavost plavnih površina utiču na razmenu količine kretanja i njen udeo u ukupnom 'gubitku' energije pri različitim relativnim dubinama vode na plavnoj površini. Reč je o tzv. modelu razmene količine kretanja (MRKK) koji su krajem 1990-ih predložili Buzmar i Zek [2]. Model je prethodno njen udeo postaju veći u sledećim slučajevima: 1) kada je glavno korito dublje, 2) kada se isključi jedna plavna površina, i 3) kada se poveća hrapavost plavnih površina

Study of the influence of channel geometry and hydraulic resistance on flow characteristics in compound channels with the exchange discharge method

U radu je sproveden niz numeričkih ogleda sa ciljem da se utvrdi kako geometrija korita za veliku vodu (KVV) i rapavost plavnih površina utiču na razmenu količine kretanja (RKK) između glavnog korita i plavnih površina i njen udeo u ukupnom „gubitku” mehaničke energije toka. U tu svrhu korišćen je model linijskog ustaljenog tečenja u KVV vodu koji je zasnovan na RKK između glavnog korita i plavnih površina. Ispitivanje je pokazalo da se na plavnim površinama, zbog ujednačavanja hidrauličkih uslova u poprečnom preseku KVV, udeo RKK u ukupnom „gubitku” energije smanjuje sa povećanjem dubine nezavisno od geometrije korita i rapavosti plavnih površina i da razmena i njen udeo postaju veći u sledećim slučajevima: 1) kada je glavno korito dublje, 2) kada se isključi jedna plavna površina, i 3) kada se poveća rapavost plavnih površina. Promena udela RKK sa povećanjem dubine toka u glavnom koritu zavisi samo od rapavosti plavnih površina.A series of numerical experiments is conducted to determine how compound channel geometry and floodplain roughness affect both a momentum transfer between main channel and floodplains and its contribution to the total energy “loss”. To this aim, a 1D, exchange discharge model, which accounts for the momentum exchange between the main channel and floodplains, is used. It is found that the contribution of the momentum exchange to the total energy “loss” reduces on floodplains with the flow depth regardless of the compound channel geometry and floodplain roughness and that both, the momentum exchange and its contribution to the total energy “loss”, are increased in the following cases: 1) when the main channel aspect ratio decreases, 2) when compound channel is asymmetrical and 3) when the roughness of the floodplain increases. In the main channel, the variation in the momentum exchange contribution with the flow depth depends only on the floodplain roughness

Application of EDM and ISM methods in estimation of stage- discharge curve in a compound-channel

Овај рад се бави проблемима процене криве протока у кориту за велику воду (КВВ). Истраживања течења у КВВ током протеклих 25 година показала су да традиционалне методе не дају добру процену протока и да за те поребе треба користити моделе линијског течења који узимају у обзир размену количине кретања између главног корита и плавних површина. У овом раду користе се две рачунске методе којима се решавају једначине таквог модела линијског течења – метода размене количине кретања (МРКК) и метода независних сегмената (МНС). Успешност две методе оцењена је поређењем срачунатих протока са протоцима измереним у лабораторијском каналу за четири огледне поставке којима су обухваћени случајеви течења у симетричном и асиметричном праволинијском КВВ са глатким и рапавим плавним површинама. Показало се да су одступања за обе методе у границама грешке мерења (< 8%), као и то да обе методе добро процењују расподелу протока по сегментима.The paper addresses problems with a stage-discharge curve estimation in a compound channel. Investigations into flow in compound channels that have been conducting during last 25 years undoubtedly indicated that traditional methods could not be considered as a reliable tool for discharge estimations. Thus, new 1D models, which account for the momentum exchange between the main channel and the floodplain, have been developed. Two computational approaches to solving the model equations are used – namely, the exchange discharge method and the independent sections method. The quality of the two models is demonstrated through а comparison of the model results against measurements collected in four compound channel layouts that cover symmetrical and asymmetrical straight compound channels with smooth and rough floodplains. It is shown that discrepancies between the measured and calculated discharges are within the measurement error limit (< 8%), as well as that the discharge distribution between the main channel and floodplains is well predicted with both approaches

Introduction to an exchange discharge model for compound channel flow modelling

Cilj ovog rada je da se stručnoj javnosti prikaže model linijskog tečenja u koritu za veliku vodu koji do sada nije primenjivan u našoj inženjerskoj praksi. Reč je o modelu koji ima dvostruku namenu. Kada se raspolaže zabeleženim tragovima velikih voda, može se iskoristiti za definisanje krive protoka u domenu vodostaja koji prevazilaze granice osnovnog korita, ali je isto tako po-godan i za procenu nagiba linije energije u proračunima linijskog tečenja za protoke pri kojima se voda izliva iz osnovnog korita. Model je proveren korišćenjem rezul-tata merenja u pravolinijskom prizmatičnom laboratorij-skom kanalu Hidrauličke laboratorije u Volingfordu na-menjenom ispitivanju tečenja u koritu za veliku vodu. Razmotren je uticaj dva činioca na krivu protoka – širine plavnih površina i različite rapavosti dna glavnog korita i plavnih površina. Rezultati modela upoređeni su i sa rezultatima tradicionalnih modela koji se standardno koriste u inženjerskoj praksi. Poređenje ukazuje na to da se najbolja slaganja sa merenjima postižu upravo prime-nom modela razmene količine kretanja između glavnog korita i plavnih površina, dok se tradicionalnim mode-lom zasnovanim na podeli preseka na hidraulički homo-gene segmente vrednosti protoka značajno precenjuju.This paper aims at introducing a novel approach to 1D compound channel flow modelling to the Serbian hydraulic engineering community. To this aim an Exchange Discharge Model (EDM) is presented, first. The model can be used both for the estimation of a rating curve in a two-stage channel based on the recorded water level, and the slope of the energy grade-line for non-uniform flow calculations in a flooding river once the flood discharge is known. EDM is calibrated and tested against the benchmark data from the Flood Channel Facility at HR Wallingford, UK. An effect of two different controls on the rating curve is analysed – the effect of a floodplain to main-channel width ratio (B / b) and that of the floodplain roughness. Moreover, the model is compared to traditional models that are still used in everyday engineering practice (single channel and divided channel methods, SCM and DCM), to an empirically based Ackers’ method and one physically based method proposed by Radojković. It is readily demonstrated that physically based models that account for momentum exchange between the main-channel and floodplains provide almost perfect fit to measurements, while the DCM method over predicts the discharge value

Prikaz modela linijskog tečenja u koritu za veliku vodu zasnovanog na razmeni količine kretanja između glavnog korita i plavnih površina

This paper aims at introducing a novel approach to 1D compound channel flow modelling to the Serbian hydraulic engineering community. To this aim an Exchange Discharge Model (EDM) is presented, first. The model can be used both for the estimation of a rating curve in a two-stage channel based on the recorded water level, and the slope of the energy grade-line for non-uniform flow calculations in a flooding river once the flood dis- charge is known. EDM is calibrated and tested against the benchmark data from the Flood Channel Facility at HR Wallingford, UK. An effect of two different controls on the rating curve is analysed the effect of a floodplain to main-channel width ratio (B / b) and that of the floodplain roughness. Moreover, the model is compared to traditional models that are still used in everyday engineering practice (single channel and divided channel methods, SCM and DCM), to an empirically based Ackers' method and one physically based method proposed by Radojković. It is readily demonstrated that physically based models that account for momentum exchange between the main-channel and floodplains provide almost perfect fit to measurements, while the DCM method over predicts the discharge value.Cilj ovog rada je da se stručnoj javnosti prikaže model linijskog tečenja u koritu za veliku vodu koji do sada nije primenjivan u našoj inženjerskoj praksi. Reč je o modelu koji ima dvostruku namenu. Kada se raspolaže zabeleženim tragovima velikih voda, može se iskoristiti za definisanje krive protoka u domenu vodostaja koji prevazilaze granice osnovnog korita, ali je isto tako pogodan i za procenu nagiba linije energije u proračunima linijskog tečenja za protoke pri kojima se voda izliva iz osnovnog korita. Model je proveren korišćenjem rezultata merenja u pravolinijskom prizmatičnom laboratorijskom kanalu Hidrauličke laboratorije u Volingfordu namenjenom ispitivanju tečenja u koritu za veliku vodu. Razmotren je uticaj dva činioca na krivu protoka - širine plavnih površina i različite rapavosti dna glavnog korita i plavnih površina. Rezultati modela upoređeni su i sa rezultatima tradicionalnih modela koji se standardno koriste u inženjerskoj praksi. Poređenje ukazuje na to da se najbolja slaganja sa merenjima postižu upravo primenom modela razmene količine kretanja između glavnog korita i plavnih površina, dok se tradicionalnim modelom zasnovanim na podeli preseka na hidraulički homogene segmente vrednosti protoka značajno precenjuju

Study of the influence of channel geometry and hydraulic resistance on flow characteristics in compound channels

У раду је спроведен низ нумеричких огледа са циљем да се утврди како геометрија корита за велику воду (КВВ) и рапавост плавних површина утичу на размену количине кретања (РКК) између главног корита и плавних површина и њен удео у укупном „губитку” механичке енергије тока. У ту сврху коришћен је модел линијског устаљеног течења у КВВ воду који је заснован на РКК између главног корита и плавних површина. Испитивање је показало да се на плавним површинама, због уједначавања хидрауличких услова у попречном пресеку КВВ, удео РКК у укупном „губитку” енергије смањује са повећањем дубине независно од геометрије корита и рапавости плавних површина и да размена и њен удео постају већи у следећим случајевима: 1) када је главно корито дубље, 2) када се искључи једна плавна површина, и 3) када се повећа рапавост плавних површина. Промена удела РКК са повећањем дубине тока у главном кориту зависи само од рапавости плавних површина.A series of numerical experiments is conducted to determine how compound channel geometry and floodplain roughness affect both a momentum transfer between main channel and floodplains and its contribution to the total energy “loss”. To this aim, a 1D, exchange discharge model, which accounts for the momentum exchange between the main channel and floodplains, is used. It is found that the contribution of the momentum exchange to the total energy “loss” reduces on floodplains with the flow depth regardless of the compound channel geometry and floodplain roughness and that both, the momentum exchange and its contribution to the total energy “loss”, are increased in the following cases: 1) when the main channel aspect ratio decreases, 2) when compound channel is asymmetrical and 3) when the roughness of the floodplain increases. In the main channel, the variation in the momentum exchange contribution with the flow depth depends only on the floodplain roughness

Very High Spatial Resolution Soil Moisture Observation of Heterogeneous Subarctic Catchment Using Nonlocal Averaging and Multitemporal SAR Data

A soil moisture estimation method was developed for Sentinel-1 synthetic aperture radar (SAR) ground range detected high resolution (GRDH) data to analyze moisture conditions in a gently undulating and heterogeneous subarctic area containing forests, wetlands, and open orographic tundra. In order to preserve the original 10-m pixel spacing, PIMSAR (pixel-based multitemporal nonlocal averaging) nonlocal mean filtering was applied. It was guided by multitemporal statistics of SAR images in the area. The gradient boosted trees (GBT) machine learning method was used for the soil moisture algorithm development. Discrete and continuous in situ soil moisture values were used for training and validation of the algorithm. For surface soil moisture, the root mean square error (RMSE) of the method was 6.5% and 8.8% for morning and evening images, respectively. The corresponding maximum errors were 34.1% and 33.8%. The pixelwise sensitivity to the training set and method choice was estimated as the variance of the soil moisture values derived using the algorithms for the three best methods with respect to the criteria: the smallest maximum error, the smallest RMSE value, and the highest coefficient of determination (R-2) value. It was, on average, 6.3% with a standard deviation of 5.7%. Our approach successfully produced instantaneous high-resolution soil moisture estimates on daily basis for the subarctic landscape and can further be applied to various hydrological, biogeochemical, and management purposes.Peer reviewe

Very High Spatial Resolution Soil Moisture Observation of Heterogeneous Subarctic Catchment Using Nonlocal Averaging and Multitemporal SAR Data

A soil moisture estimation method was developed for Sentinel-1 synthetic aperture radar (SAR) ground range detected high resolution (GRDH) data to analyze moisture conditions in a gently undulating and heterogeneous subarctic area containing forests, wetlands, and open orographic tundra. In order to preserve the original 10-m pixel spacing, PIMSAR (pixel-based multitemporal nonlocal averaging) nonlocal mean filtering was applied. It was guided by multitemporal statistics of SAR images in the area. The gradient boosted trees (GBT) machine learning method was used for the soil moisture algorithm development. Discrete and continuous in situ soil moisture values were used for training and validation of the algorithm. For surface soil moisture, the root mean square error (RMSE) of the method was 6.5% and 8.8% for morning and evening images, respectively. The corresponding maximum errors were 34.1% and 33.8%. The pixelwise sensitivity to the training set and method choice was estimated as the variance of the soil moisture values derived using the algorithms for the three best methods with respect to the criteria: the smallest maximum error, the smallest RMSE value, and the highest coefficient of determination (R-2) value. It was, on average, 6.3% with a standard deviation of 5.7%. Our approach successfully produced instantaneous high-resolution soil moisture estimates on daily basis for the subarctic landscape and can further be applied to various hydrological, biogeochemical, and management purposes.Peer reviewe