A study of hydraulic intake entrainment envelope delineation methods

Surface water has been a reliable source of providing municipal drinking water over the years by drawing water through hydraulic intake pipe. In this study, an effort is made to establish the entrainment envelope for the hydraulic intake pipe in a uniform cross-flow. The envelope is essential in defining the proportion of passing contaminants and flow ingested by the intake. An analytical delineation method--potential flow theory investigated the two and three dimensional flow solutions. The results were validated by numerical modeling of inviscid and laminar flow conditions; and velocity measurements obtained with laser Doppler anemometer confirmed the intake entrainment envelope as the immediate zone from which the water intake withdraws water. Comparison of the flow pattern, stagnation streamlines and velocity field plots show that intake entrainment envelope is characterized by a symmetrical half-body which increase in size with increasing intake discharge irrespective of the flow conditions. The entrainment envelope for viscous flow exceeded the inviscid radial flow in width and depth by distorting the entrainment envelope as a result of clockwise vortices found in the vicinity of the hydraulic intake for high intake withdrawal rates. The three-dimensional study confirmed these deductions and inferred the validity range for the potential theory and inviscid flow assumption

Full Proceedings: IJREWHS 2019

Full proceedings for the 7th International Junior Researcher and Engineer Workshop on Hydraulic Structures

Free surface vortices at hydropower intakes: – A state-of-the-art review

This is the final version. Available on open access from Elsevier via the DOI in this recordFor years, the study of free surface vortices at hydropower plant intakes has been a topical and intriguing subject among engineers and researchers. This subject will continue to attract attention especially as the world strives to meet the ever-increasing demand for energy. Despite the numerous benefits associated with hydropower, the sustainability of some hydropower plants is being threatened due to low inflows often associated with climate change. Free surface vortices associated with low water levels or submergence at plant intakes can have very detrimental consequences on the operation of hydropower plants if not addressed. Notwithstanding this, free surface vortex flows have also been found to be very relevant in emerging technologies such as the water vortex hydropower plant system. This paper, therefore, presents a state-of-the-art review of the subject including summarised historical findings, but with an emphasis on current developments, findings and research gaps to guide practitioners and researchers. In response to the research gaps identified, the authors make a number of recommendations for further studies which include establishing relationships between free surface vortices formation and turbine efficiency, development of more accurate models for critical submergence and free surface vortices, assessment of free surface vortices at multiple and multi-level intakes, establishing the relationship between free surface vortices and sediment transport at intakes, application of Computational Fluid Dynamics (CFD) shape optimization tools for intake and anti-vortex device optimisation, as well as the continuing development of CFD tools to simulate air-entrained vortices at hydropower intakes

Determination Of Vortex Formation At Temenggor Tnb Hydropower Station

The power generated by Temenggor Hydropower station is only 80% of the station’s full capacity. The reason behind this reduced power generation, is due to the formation of free surface vortices at the hydraulic intake. This study is focuses on numerical simulation using ANSYS fluent software. The model was built using SolidWorks and the data were obtained from the dam’s blueprints and LIDAR scanner (Light Detection and Ranging) for the intake topology. The mesh sensitivity analysis was then carried out by testing different element sizes. This study was carried out by simulating the dam water flow using k-epsilon turbulence model and volume of fraction (VOF) at different water level in order to observe the vortices formation at hydraulic intake. The results validation is then carried out by comparing the simulation outlet discharge with the real discharge. The analysis was carried out by comparing the energy level, outlet flow rate and total loss in penstock with respects to different water level. The findings from the simulations and results are, the vortices disrupt the intake flow but with increasing water level the effect reduced. Penstock 4 are affected the most due to vortices consistently form at any water level

Numerical Analysis of Vortices Behavior in a Pump Sump

Recently, designers and engineers of pump stations realized that the efficiency and performance of a pumping station does not depend only on the performance of selected pumps, but also on proper design of intake structure. Most recurring problems faced in a pumping station are related to the sump or intake design rather than pump design. International design standards for a pump sump restrict undesirable flow patterns up to a certain extent implication of which does not guarantee a problem free sump but provides a basis for initial design. A faulty design of pump sump can lead to form of swirl and vortex, which reduce the pump efficiency and induce vibration, noise, and cavitation. To reduce these problems and for the advanced pump sump design with high performance, it is essential to know the detailed flow behavior in sump system. Swirl angle parameter and vortices formation are important parameters that determine the quality of flow ingested by sump. According to the swirl angle parameter, the hydraulic institute prescribes the method that needs to be employed for estimating this parameter. In this study, numerical analysis and experimental test of pump sump were carried out to predict vortex formation (free surface vortex, side wall and submerged vortex) occurrence, location, and air entrance in details. A four blade zero-pitch traditional swirl meter was installed at the suction pipe to measure the flow intensity by swirl angle calculations; the key point is to obtain the average tangential velocity at different suction pipe diameter. The other part of this study is overall numerical analysis for sump model with a mixed flow pump installed. Hydraulic performance of the mixed flow pump for head rise, shaft power, and pump efficiencies versus flow rate changed from 50% up to 150% of the design flow rate were studied by performances curves. In addition, a basic numerical simulation of cavitation phenomenon in the mixed flow pump has been performed by calculating the full cavitation model with k-ε turbulence model. Swirl angle and average tangential velocity estimated by CFD simulation was in agreement with experimental results obtained. The results also show that submerged vortex strength was almost proportional to the flow rate in the sump. The free surface vortex had an unsteady behavior as its location and duration drastically varied. In addition, post processing results showed the tangential velocity behavior and the four types of free surface vortex (Surface swirl, Surface simple, air bubbles and full air core to intake) by changing the air volume fraction values. In the mixed flow pump performance study, the efficiency without and with sump model was 83.4% and 80.1% respectively at the design flow rate.Chapter 1 Introduction 1 1.1 Background 1 1.2 Previous study 2 1.3 Study methodology 3 Chapter 2 Pump Intake Design Theory and Vortices Formation 4 2.1 Introduction 4 2.2 Importance of pump intake design 4 2.3 Standard for pump intake design ANSI/HI 9.8. 5 2.3.1 Recommended dimensions for a rectangular sump 6 2.3.2 Inlet bell design diameter 9 2.4 Model test of intake structure 12 2.5 Similarity condition and scale effects 12 2.5.1 Similarity condition 12 2.5.2 Scale effects 13 2.6 Vortices formation around pump intake 15 2.6.1 Overview 15 2.6.2 Vortices formation in pump sump 15 2.6.3 Classification of vortex type 17 2.6.4 Acceptance criteria 19 2.6.5 Preventive measures for vortex problem in pump sump 20 2.6.6 Approach flow patterns 21 2.7 Cavitation phenomena 23 2.7.1 Overview 23 2.7.2 Bubbles implosion 24 2.7.3 Net positive section head (NPSH) 25 Chapter 3 Computational Fluid Dynamics (CFD) Analysis and Experimental setup 27 3.1 Introduction to CFD 27 3.2 Governing equation 28 3.3 Turbulence models 29 3.3.1 k – turbulence model 30 3.3.2 Shear stress transport model 31 3.4 Cavitation models 32 3.5 Description of model cases 35 3.5.1 Creating the geometry 35 3.5.2 Geometry of scaled sump model 36 3.5.3 Design of mixed flow pump 38 3.6 Mesh generation 42 3.7 Numerical approach 46 3.8 Experimental setup 48 Chapter 4 Swirl Angle Analysis 52 4.1 Swirl meter rotation 52 4.2 Swirl angle method 54 4.3 Rigid body motion 56 4.4 Swirl angle result 58 Chapter 5 Results and Discussion 61 5.1 Vortices results 61 5.1.1 Free surface vortex 61 5.1.2 Submerged and sidewall vorticity 66 5.2 Results of mixed flow pump sump model 69 5.3 Cavitation phenomena analysis 72 Chapter 6 Conclusions 75 Acknowledgement 77 References 78Maste

Flow measurement in open channels

CER62ARR-ARC4.Paper to be presented at National Meeting, American Society of civil Engineers, Houston, Texas, Feb. 19-23, 1962.Joint contribution from Colorado State University and the Soil and Water Conservation Research Division, Agricultural Research Service, U.S. Dept. of Agriculture, Fort Collins, Colorado

Diversion of flow and sediment towards a side channel separated from a river by a longitudinal training dam

A human‐made entrance to a side channel separated from the river by a longitudinal training dam can be considered a new, emergent type of river bifurcation. To understand the processes controlling the diversion of flow and sediment towards the side channel at such bifurcations, a comprehensive field‐monitoring programme was performed in the Waal River, which is the main branch of the Rhine River in the Netherlands. Local processes govern the flow field in the bifurcation region. The angle between the main river flow and the flow into the side channel increases with decreasing lateral and longitudinal distance to the bifurcation point, which corresponds to the head of the training dam. The general flow pattern can be well reproduced with a uniform depth, potential flow model consisting of a superposition of main channel flow and lateral outflow. For submerged flow conditions over the sill, the side channel hydraulic conditions influence the exchange processes, yet free flow side weir theory describes the flow field at this bifurcation type qualitatively well. The vertical flow structure in the side channel, which governs the sediment exchange between the main channel and the side channel, is steered by the geometrical details of the sill. The presence of the sill structure is key to controlling the morphological stability of this type of bifurcation given its primary influence on bed load sediment import and exerts an indirect impact on suspended sediment exchange