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

... 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

... 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.

... Stepped spillways are widely used in hydropower engineering because of their simple structures and high energy dissipation (Boes and Hager, 2003a;Zhang et al., 2020). Generally, three distinct flow patterns for a stepped spillway occur successively with the increase in the unit discharge: nappe flow, transition flow, and skimming flow (Kumcu, 2017;Zhang and Chanson, 2018). In the skimming flow, air is entrained into the flow when the turbulent boundary reaches the free surface (Pfister and Hager, 2011;Hunt and Kadavy, 2021). ...

For a traditional stepped spillway, low energy dissipation and cavitation damage may occur when the unit discharge is larger than a limit due to reduced air entrainment in the flow. In the present work, a new type of stepped spillway called hydraulic-jump-stepped spillway (HJSS) was developed, and the air was efficiently entrained into the flow by means of a hydraulic jump in the aeration basin, which was an aeration element of this stepped spillway. Compared with the traditional stepped spillway, various aspects of the hydraulic performance of the HJSS were experimentally investigated, including the flow pattern, energy dissipation, air entrainment characteristics and time-averaged pressure. Physical model results demonstrated that the HJSS achieved a higher energy dissipation, a more favorable air entrainment performance, and a more reasonable pressure distribution. The HJSS successfully increased the unit discharge from 50–60m2/s for a traditional stepped spillway to 101.47 m2/s.

... Measurement of smallscale fluctuations of water levels are also important in numerous cases. Examples of these are the measurements on hydraulic structures such as flumes and weirs, e.g., [1], evaporation pans and ring infiltrometers, e.g., [2], controlled laboratory experiments on fluid dynamics, e.g., [3]. Further, measurements with high-frequency are needed in many cases, such as roll-waves, transient flows, surface wave propagation, or dam-break analysis. ...

Measuring and monitoring the water depth/level is a key issue when studying free-surface flows. These tasks are usually expensive in terms of time and money; however, even that expenditure is sometimes not enough to assure reliable and/or accurate results. Free-surface flows are complicated to deal with, as the instability caused by e.g., turbulence, wind, or air-entrainment, can cause important spatial and temporal fluctuations at the surface level. This work presents a non-intrusive, computer vision-based image treatment and segmentation technique that assures the detection and measurement of the free-surface water fluctuations along space and time. The laboratory physically based tests under steady flow conditions, and different channel bed roughness and slopes, showed a very good fit with manually direct measurements carried out with a point-gauge micrometre. Under unsteady flow conditions this technique also showed to successfully deal with applications requiring high spatiotemporal resolution of water depth/level measurements.

... This software provides various modules, such as viscosity and turbulence, air entrainment, shallow water and granular flow, to solve complicated hydraulic problems including supercritical flow, shock wave due to dam break flow, hydraulic jump in stilling basin, etc. Studies on the hydraulic characteristics of stepped spillways have been widely researched [3][4][5][6][7][8][9][10]. "White flow" can be observed when a rapid velocity flow occurs on a channel chute and stilling basin due to self-aeration and turbulent features. ...

... When modeling turbulent flows, Flow 3D recommends using Reynolds-averaged Navier-Stokes (RANS) with the two equations k-ε (RNG), or the two equations k-ω. Previous studies [6,9] suggest that the RNG turbulence model is the most accurate when simulating turbulent rapid flow on a group of structures, so we selected it to compute all flow characteristics in this research. ...

Spillways and channel chutes are widely used in hydraulic works. Two kinds of abutment-walls and steps-are usually constructed to dissipate energy; however, they may also cause cavitation at the abutment position. In this study, we used Flow 3D with the Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) turbulent models which included air entrainment to simulate the free surface flow through the spillway, channel chute and stilling basin of the Ngan Truoi construction to optimize the configuration of walls and dams. We measured the water level, velocity and pressure to estimate the influence of grid size and the turbulent model type used. Our results highlight the need to include air entrainment in the model simulating rapid flow over a hydraulic construction. With adjustments for energy loss, this study shows that walls provide the best results and the optimal distance between two walls is 2.8 m.

... Fadaei Kermani et al. [16] proposed a method to predict cavitation damage on spillways. Serife Yurdagul Kumcu [17] investigated of flow over spillway modeling through the 1/50-scaled physical model. In his study Flow depth, discharge, and pressure data were recorded for different flow conditions. ...

... Consequently, a solid surface receives a hole, so-called cavitation pitting. Several cases of cavitation damage in a chute of spillways documented [17,28,29]. The flow pressure and velocity are the main parameters to evaluate the cavitation potential as shown in the following equation [28,30]: ...

Maintaining the reservoir safety of large dams has considerable importance for the public where they are constructed in heavily populated and industrialized areas. The extreme hydrodynamic force caused by ground acceleration, cavitation damage, and vibration are among concerns that threaten the safety of the spillway and its conveyance structures when subjected to a natural disaster, such as earthquakes and severe floods. Current research investigates the hydrostatic and hydrodynamic performance of the Karkheh Dam spillway radial gate through 3-D finite element (FE) models using ABAQUS/Explicit. The common loads applied on the radial gate were reviewed and stress-strain in the skin plate and trunnion were investigated as a result of developed hydrodynamic pressures. The performance of conveyance structures subjected to significant discharge was also investigated through a small-scale model to evaluate the cavitation damage index. The results of this research will help researchers in the field of civil and hydraulic engineering for the risk analysis of the radial gates and conveyance structures.

... Withrecent advances in computational modelling and computer processing that have facilitated solving governing fluid flow equations, numerical models are becoming desirable for hydrodynamic processes, including flow over spillways. A comparison of numerical outcomes with related experiments is important to calibrate and verify these advancements (Kumcu, 2017). ...

A study was conducted to compare flow characteristics, such as water surface profile, vertical velocity distribution and crest pressure distribution, for standard ogee spillways. Various methods, such as (physical and numerical models and Waterways Experiment Station, WES, design nomographs) were used. The experimental models were made of rigid foam and installed in a testing flume. Pressure taps were fixed along the centrelines of spillways. The water surface profile, piezometric head, and flow velocity were recorded for 10 models with different design heads. Particle image velocimetry (PIV) was used to record the velocity of the flow. Vertical velocity distribution was obtained by analyzing the series of captured images using MATLAB codes. Commercially available computational fluid dynamics (CFD) software was used to design the physical model setup that solves the Reynolds-Average Navier-Stokes formulas. The maximum absolute difference between the measured and computed results of the water surface profile was 2.62%, that of the pressure distribution results was 4.8%, and that of the vertical distribution of velocity was 2.87%. The numerical results for the flow characteristics showed good agreement with the physical model results. Interpolated data from the U.S. Army Corps of Engineers (USACE), Waterways Experiment Station (WES), and design nomographs were used for additional comparison.