Fig 2 - uploaded by Serife Yurdagul Kumcu

Content may be subject to copyright.

# Flow Velocity Measurements at the Approach Belonging to Theoretical Project Design and the Design which is Observed after the Experimental Modifications

Source publication

As a part of design process for hydro-electric generating stations, hydraulic engineers typically conduct some form of model testing. The desired outcome from the testing can vary considerably depending on the specific situation, but often characteristics such as velocity patterns, discharge rating curves, water surface profiles, and pressures at v...

## Contexts in source publication

**Context 1**

... extended longitudinally in vertical direction up to mixing with the dam body (290 m above the talweg) for stability issues. Flow measurement sections and modifications which were done after experimental investigations are given in Fig. 1. Flow velocity measurements belonging to original project and experimentally modificated project are given in Fig. 2. It is clear from the Fig. 2 that, approach flow velocities are decreasing after doing modifications. In the theoretical study of the project, the discharge capacity of the spillway was computed considering that all gates would be completely open for all reservoir water levels. Discharge rating curve varies with S ç 1977). Each of the ...

**Context 2**

... direction up to mixing with the dam body (290 m above the talweg) for stability issues. Flow measurement sections and modifications which were done after experimental investigations are given in Fig. 1. Flow velocity measurements belonging to original project and experimentally modificated project are given in Fig. 2. It is clear from the Fig. 2 that, approach flow velocities are decreasing after doing modifications. In the theoretical study of the project, the discharge capacity of the spillway was computed considering that all gates would be completely open for all reservoir water levels. Discharge rating curve varies with S ç 1977). Each of the conditions has ranges and ...

## Similar publications

The paper summarizes technical results and first highlights of the cooperation between DLR and Airbus Defence and Space (DS) within the work package “CFD Modeling of Combustion Chamber Processes” conducted in the frame of the Propulsion 2020 Project. Within the addressed work package, DLR Göttingen and Airbus DS Ottobrunn have identified several te...

Increase in computational power has resulted in employing RANS/CFD codes for research and development of marine and offshore units. These applications also include the fluid-structure interactions of large ocean going vessels which require the hydroelastic effects and their associated nonlinearities to be modelled accurately. This paper investigate...

In this paper a CFD investigation on the interaction between an offset jet and an oblique wall jet using two-dimensional steady RANS equations is performed. This combination is denoted WOJ (Wall Offset jets). Several turbulence models such as the standard k-ω, SST k-ω, standard k-ε, RNG k-ε and realizable k-ε models are tested in the present study....

The present paper presents the numerical analysis for a transonic centrifugal compressor using steady state CFD. The blade tip clearance effect over the position of shock waves, tip losses and the performances of the impeller are studied. Numerical simulations have been performed using RANS modelling, with the k-omega SST turbulence model (Shear St...

The region of the tip in the blades of a wind rotor presents the phenomenon of induced drag, which decreases the aerodynamic efficiency of the turbine and increases the stresses on the structure. In this work, different tip devices are computationally analyzed (CFD), based on similar applications as Winglets, Split-Tips, Tip-Tanks, as an alternativ...

## Citations

... Analisis hidrolik aliran dilakukan dengan bangunan model uji, yaitu dengan menirukan desain prototipe bangunan yang dibangun dengan skala tertentu dengan prinsip-prinsip kesebangunan (geometris, dinamis, dan kinematis). Pemodelan skala fisik telah digunakan pada investigasi desain dari suatu struktur hidrolik selama lebih dari 100 tahun [6]. Dan yang terutama, dengan pertimbangan bahwa untuk pelaksanaan konstruksi dari suatu bangunan air yang mempunyai fungsi strategis dan bernilai ekonomi tinggi, Pemerintah mengeluarkan peraturan perlunya sertifikasi keamanan terhadap suatu desain, salah satu diantaranya adalah melalui uji laboratorium model tes hidrolika. ...

Bendungan Sidan Provinsi Bali direncanakan menggunakan pelimpah samping tipe gergaji untuk mengalirkan debit banjir. Pelimpah samping memiliki kondisi hidrolik aliran yang kompleks yang sering kali belum teridentifikasi secara jelas. Perhitungan teoritis serta pemodelan fisik dimaksudkan untuk memvisualisasikan dan menguji kondisi aliran berdasarkan kaidah-kaidah hidrolik yang berlaku. Analisis hidrolik aliran dilakukan menggunakan persamaan momentum dan energi, dan metode tahapan standar pada saluran peluncur. Pengujian model dilakukan dengan mengukur tinggi muka air dan kecepatan aliran pada bagian saluran yang ditinjau untuk setiap debit banjir rancangan. Sehingga dapat diketahui alternatif desain terbaik dalam upaya menyempurnakan kinerja hidrolik aliran pada pelimpah samping secara menyeluruh. Hasil pengujian pada model fisik seri ke-2 menunjukan kondisi aliran yang sudah memenuhi kaidah-kaidah hidrolika yang berlaku. Saluran pengarah dapat mengalirkan debit banjir tanpa terjadi aliran balik dengan V < 4m/s dan Fr < 0,4. Efektifitas pelimpah gergaji sudah memuaskan. Saluran samping senantiasa dalam kondisi aliran subkritis. Kondisi aliran pada terowongan peluncur adalah superkritis (Fr > 1) tanpa terjadi transisi aliran subkritis. Efisiensi peredam energi tipe loncatan berkisar antara 73% - 75%.

... Over the past twenty years, several numerical simulation models using computational fluid dynamics (CFD) were developed. Compared with the results of the physical or experimental models, broadly good agreement was achieved with the results of the numerical simulation techniques [3,4,5,6]. ...

... Due to their importance, spillways are carefully studied in their project design and their calculations are supported by modelling when necessary. Although physical model experiments are the commonly used method in this regard, numerical models using advanced techniques have also been widely used today (Aydin et al., 2020;Kumcu, 2017). Since numerical models are more advantageous than experimental models in terms of time and cost, only numerical models can be used in some cases. ...

Examining the Change in Pressure Parameters in the Chute Spillway with a Numerical Model. Knowing hydraulic parameters is very important in the design of spillways, which are the safety structures of dams. While obtaining these parameters, traditionally theoretical and empirical approaches are used and scale model experiments are performed. Today, with the increase in computer processing capacity, numerical modeling techniques are used as an alternative to long and costly experimental studies. In this study, the pressure parameter changing along the longitudinal section in the chute spillway was examined using computational fluid dynamics (CFD). In the 3D CFD model of the spillway, the VOF method and the standard k-e turbulence model, which can solve two-phase flows, were used for the design discharge. The obtained pressure parameter results were examined and interpreted along the spillway section. According to the pressure results obtained as a result of numerical analysis, points along the spillway where cavitation may occur have been determined.

... Due to their importance, spillways are carefully studied in their project design and their calculations are supported by modelling when necessary. Although physical model experiments are the commonly used method in this regard, numerical models using advanced techniques have also been widely used today (Aydin et al., 2020;Kumcu, 2017). Since numerical models are more advantageous than experimental models in terms of time and cost, only numerical models can be used in some cases. ...

Across the world best practice, the flood hazard and risk maps are core instruments used for the development and implementation of flood management policies. These maps sit as base information for developing flood management strategies and plans, designing of new flood defence schemes and assessment of the existing flood scheme performance, elaboration of emergency and action plans, territorial planning (zoning and permissions), land use control, climate changes impacts evaluation, insurance industry etc. Romania did remarkable steps in developing high quality flood hazard and risk maps as core action for an integrated flood risk management. In the second cycle of Floods Directive 2007/60/EC implementation, Romania developed and reported to European Commission (EC) the hazard and risk maps for 526 APSFRs (Areas with Potential Significant Flood Risk). The hazard maps built in second cycle are the result of detailed models developed based on high resolution Lidar (0.5m), calibrated hydrological data and advanced modelling technics. Crasna River is one of the watercourses from the Somes-Tisa Basin which benefited from advanced 2D hydraulic modelling having in-place all the existing infrastructure and which has been well - calibrated on the flood event recorded in 2015. The calibration of the model on 2015 flood event was performed both for flows and levels. The article aims to explicitly present the performance of the existing defence system of Crasna river during extreme flood events with different magnitudes having in hand these high-quality hydraulic model and hazard maps.

... This multiphase model was applied for this simulation because, contingent on the volume fractions of relative phases in the cell, some variables and components in a given cell reflect group of individual phases or a mixture of phases. Topological changes are automatically taken into account by the level-set concept in VOF [19,20]. Furthermore, because water surface is the point of contact between air and water, implementing boundary conditions here on surface has been disregarded. ...

By recording parameters such as velocity and volume fraction by contour plots or plane, a CFD model enables to analyse flow patterns in the model, such as free-surface vortices A free-surface vortex, a common problem may indeed be observed in a variety of submerged water intakes, notably shallow basins and low head intakes. These FSVs are likely to form an air-core vortex, eventually entrapping detritus and air pockets in the water intake system and causing further vibration and damage to the downstream turbine. When paired with a high velocity, the formation of vortices in the system been known to produce hydraulic transients, which cause unwanted operation or pressure changes. The model of the 1:100 scale dam reservoir was generated, computationally meshed, and modelled in FLUENT under ANSYS 2019 R3 at two different water levels to observe the FSV formations. To mitigate those FSV formations, anti-vortex plates with two distinct plates—square and wedge—were used. From the findings square plates outperform wedge plates because square it lowers the speed of a fast-flowing fluid and reduces it into a laminar flow rather of a turbulent flow, which benefits vortex class deterioration. Data from the simulation and experimental shows a strong agreement in terms of velocity at outlet 1 from both water levels with relative errors of 3.0% and 14.1% respectively

... The review concludes that CFD modelling is a cheaper way to obtain a rating curve. The application of CFD models for rating curve investigation is cover by various publications [18]- [20]. In contrast, the physical models are still more reliable in identifying complicated and unexpected problems (especially unsteady flow patterns). ...

... Numerous works published in professional journals [16], [20], [23], [24] and experience from our applied research show that the rating curve determined by the CFD model corresponds with the values measured on the physical model. The relative percent difference between values from CFD and physical model is below 5 %. ...

Discharge measurement is the base of proper water management. The effective design and operation of hydraulic structures under both normal and extreme flow conditions depend on the quality of hydrological data. Understanding the water system requires consistent and long-term measurement. Despite that, the gauging station network is sparse, and its numbers are declining worldwide. This article aims to draw attention to the possibility of accurate flow measurement using existing hydraulic structures. Flow over a hydraulic structure profile is a physically well-defined phenomenon as the construction shape is fixed and simple compared to river profiles. The discharge can be derived from rating curves, turbine characteristics, and several easily measured variables. That allows continuous discharge measurement. The accuracy is compared with the gauging station on the river. Suitable technical solutions for ensuring and monitoring ecological flow are discussed.

... BC Hydro has been using FLOW-3D to investigate a wide range of challenging hydraulics problems for different types of water conveyance structures, leading to a greatly improved understanding of flow patterns and performance (BC Hydro 2022). Numerical results including velocity, flow depth, and pressure simulated by Flow 3D software are well matched with observation ones (Parsaie et al. , 2016Kumcu 2017). However, the improvement of the confidence in the numerical model results is not able to use for which constructions are lacking measured data on prototype model (BC Hydro 2022). ...

Hydraulic safety assessments on existingconveyance structurers, such as spillway and outlet work, are urgent tasks in water resources
management. 3D numerical model has been considered an efficient tool to evaluate hydraulics characteristics of the flow over these works. Flow
3D model involvingturbulence and air entrainment modules is used to assess flow rate, velocity, pressure, and air entrainment rate alongTa
Trach spillway (Thua Thien Hue, Vietnam). Computed discharges released fromspillway and bottomoutlet are well matched with analytical
results. Besides, two standards of concrete erosion are used to assess hydraulic safety level under different workingconditions. In the group of
extreme cases includingInflow design flood (IDF) and Exceeded flood (EF) cases, spillway is more likely to damage fromcavitation than the
culvert with the cavitation indexrangingfrom0.45 to 1.0. While groups of control gate of spillway and culvert are likely to suffer fromabrasion
when the high-speed flow appears. The concrete grade of the bottomof culvert is not guaranteed when velocity in culvert is greater than
threshold value of 9 m/s, which may cause the surface damage of the construction

... A dam is a water storage structure that does not permit overtopping. It is equipped with a spillway to avoid its collapse due to large hydrostatic pressure caused by overflows [KUMCU 2016]. Dams cause water levels to rise, which leads to an energy (head) difference between the upstream and downstream of the spillway. ...

Potentially hazardous side-channels of complex geometry need to be investigated using detailed hydraulic physical models. This study aims to analyse the cross-waves pattern and pulsating flow using a side-channel spillway physical model. This study compares the cross-waves pattern were measured using an experimental installation set to generate cross-waves on the surface (original series) with another structure that did not produce cross-waves (modified series). The results showed that the geometry of the left wall caused instability in flow patterns and secondary flows. The starting point of Q 2 discharge was detected by minor turbulence on the water surface near the left wall at a water depth of 3.3 m at the starting point of the wall, but with no overtopping. Cross-waves formed downstream at the right wall crosswise, lower than at the left wall. The height of the cross-wave increased substantially from Q 100 to Q 1000 discharges leading to overtoppings near the left wall at a water depths of 4.2 and 5.0 m at the starting point of the wall, and near the right wall at a water depths of 3.8 and 4.0 m at the upstream point of the wall. The modifications provided optimal hydraulic conditions, i.e. elimination of cross-waves and non-uniform flows. The Vedernikov and Montouri numbers showed that both original and modified series did not enter the area where the pulsating flow occurred. This indicated that both series were free from the pulsating flow.

... The application of CFD modeling for hydraulic analysis of spillway flows and performance evaluation of aerators is quite recent (Aydin 2018;Gadge et al. , 2019Gurav 2015;Jothiprakash et al. 2015;. Some other researchers like Bennett et al., (2018), Kumcu, (2017), and Yang et al., (2019 have also used CFD models to analyze the flows of different spillway projects. Another branch of CFD, i.e., particle methods in specific SPH (Shadloo et al. 2016;Ye et al. 2019;Luo et al. 2021), is also being applied for simulation of spillway flows (Saunders et al. 2014;Gu et al. 2017;Moreira et al. 2019Moreira et al. , 2020. ...

Submerged spillways with large capacity outlets are generally provided below the dam crest to perform the dual functions of flood disposal and sediment flushing. Flood water passing through these spillways exhibits turbulent behavior. Moreover; hydraulic analysis of such turbulent flows is a challenging task. Therefore, the present study aims to use numerical simulations to examine the hydraulic behavior of submerged spillways constructed at Mangla Dam, Pakistan. Besides, the hydraulic performance of aerator was also evaluated at different operating conditions. Computational fluid dynamics code FLOW 3D was used to numerically model the flows of Mangla Spillway. Reynolds-averaged Navier–Stokes equations are used in FLOW 3D to numerically model the turbulent flows. The study results indicated that the developed model can simulate the submerged spillway flows as it computed the flow parameters with an acceptable error of up to 6%. Moreover, air concentration computed by model near spillway chute bed was 3% which raised to more than 6% after the installation of ramp on aerator which showed that developed model is also capable of evaluating the performance of submerged spillway aerator.

... Kumcu [15] comparing experimental data and CFD analysis for flow over the spillway for under construction Kavsak Dam in Turkey. She investigated experimentally by a physical model using a 1/50 scale to conducting experiments, and Flow depth, discharge, pressure data were recorded for different flow conditions. ...

Spillways are designing to release surplus water over a volume of storage. The excess water flows from the top of the reservoir and is carried back to the river by a spillway. Many radial gates were destroyed under hydrodynamic load. Radial gate connectors are susceptible to fatigue failure due to excessive vibration; therefore, gate vibration during operation must be investigated to confirm safe operation at the design water pressure. Several studies were carried out to analyse and simulation of flow over the spillway. In this article, the flow pattern over the Haditha dam spillway has been simulated using computational fluid dynamics (CFD). The numerical model was performed using Ansys Fluent 2020 R1 to simulate the flow properties; determination of cavitation damage at three discharges corresponding in the design of Haditha dam are 4700, 7140, and 7900 m3/s. In addition to finding the effect of gate vibration under dynamic water loads. The Realisable k-ɛ turbulence model was utilised with the volume of fluid (VOF) model to simulate the interaction between air and water phases. The validation of the numerical model was achieved by comparing it with a physical model. The physical model of the Haditha Dam spillway was made from iron with a scale of 1:110. It has been designed and constructed in a hydraulic laboratory according to the modelling principle of the hydraulic structure. The results showed that a high agreement between the physical and numerical model and the k-ɛ turbulence model could simulate the Haditha dam spillway with low cost and few times. The cavitation damage may occur at the region start at the end of the arching spillway to stretches downstream, and there is no damage of gate vibration under dynamic water load.