Vortex Drop Research Articles

Effect of the flow regime on the hydraulic features governing the operation of vortex drop shafts with spiral inlets.

If the operation of existing vortex drop shafts should be verified, then it is essential to know the hydraulic performance of these special structures under both subcritical and supercritical flow regimes. The purpose of the present research consisted of providing practical guidelines and recommendations for managing the hydraulic design and verification of subcritical and supercritical vortex drop shafts. The examination of various experimental results from physical model investigations allowed to show that the inlet channel and the spiral inlet behaved differently depending on the energy approach flow content. The main dissimilarity lay, however, in the functioning of the vertical shaft and the dissipation chamber. The rotation of the falling flow along the vertical shaft was more evident for approaching supercritical flows. Severe flow conditions in terms of water depths and bottom pressures could be observed in the dissipation chamber under a supercritical flow regime. The design of this special component must be carried with prudence compared with the subcritical flow regime because failure events as the chamber submergence and the crash of the bottom surface just under the shaft outlet may occur for approaching supercritical flows.

Experimental Study of Flow Characteristics in Vortex Drop Shaft

AbstractVortex drop shafts are utilized to dissipate and transport the energy of flows in sewerage networks. A vortex drop shaft is composed of three parts: the inlet structure, the vertical shaft,...

Three-Dimensional Flow of a Vortex Drop Shaft Spillway with an Elliptical Tangential Inlet

Vortex drop shaft (VDS) spillways are eco-friendly hydraulic structures used for safely releasing flood. However, due to the complexity of the three-dimensional rotational flow and the lack of suitable measuring devices, current experimental work cannot interpret the flow behavior reliably inside the VDS spillway, consequently experimental and CFD study on a VDS spillway with an elliptical tangential inlet was conducted to further discern the interior three-dimensional flow behavior. Hydraulic characteristics such as wall pressure, swirl angle, annular hydraulic height and Froude number of the tapering section are experimentally obtained and acceptably agreed with the numerical prediction. Results indicated that the relative dimensionless maximum height of the standing wave falls off nearly linearly with the increasing Froude number. Nonlinear regression was established to give an estimation of the minimum air-core rate. The normalized height of the hydraulic jump depends on the flow phenomena of pressure slope. Simulated results sufficiently reveal the three-dimensional velocity field (resultant velocity, axial velocity, tangential velocity and radial velocity) with obvious regional and cross-sectional variations inside the vortex drop shaft. It is found that cross-sectional tangential velocity varies, resembling the near-cavity forced vortex and near-wall free vortex behavior. Analytic calculations for the cross-sectional pressure were developed and correlated well with simulated results.

Energy Head Dissipation and Flow Pressures in Vortex Drop Shafts

Vortex drop shafts are special manholes designed to link sewer channels at different elevations. Significant energy head dissipation occurs across these structures, mainly due to vertical shaft wall friction and turbulence in the dissipation chamber at the toe of the shaft. In the present study two aspects, sometimes neglected in the standard hydraulic design, are considered, namely the energy head dissipation efficiency and the maximum pressure force in the dissipation chamber. Different physical model results derived from the pertinent literature are analyzed. It is demonstrated that the energy head dissipation efficiency is mostly related to the flow impact and turbulence occurring in the chamber. Similarly to the drop manholes, a relation derived from a simple theoretical model is proposed for the estimation of the energy head loss coefficient. The analysis of the pressures measured on the chamber bottom allows to provide a useful equation to estimate the pressure peak in the chamber as a function of the approach flow energy head.

Experimental flow characterization in a spiral vortex drop shaft.

Connecting storm-sewers located at rather different elevations may be made with vortex drop shafts in which the energy dissipation is made by the friction between the vertical shaft and the flow and downstream by the impinging jet in a dissipation chamber. Following the first model design in the 1940s, different types of vortex drop shafts have been developed. One of the most used type is the so-called spiral vortex drop shaft developed to work in supercritical flow with good performance in both energy dissipation and space constrains. In this paper, an experimental flow characterization in a spiral vortex drop shaft is conducted covering the three main components of these structures, namely the inlet channel, the vertical shaft and the dissipation chamber. The results include measurement of water depths, pressure and velocity.

Hydrodynamic modelling approaches to assess mechanisms affecting the structural performance and maintenance of vortex drops shaft structures

ABSTRACTVortex drop shafts, a key hydraulic structure within modern day deep sewer conveyance systems, must be designed structurally to sustain performance and longevity of operating life under very energetic loading conditions. This has significant cost implications but to date little research has been undertaken to investigate the loading conditions with a view to optimising the shaft designs and thus lowering costs. In this study, several modelling methods were adopted to simulate hydrodynamic conditions within a vortex drop shaft to assess hydrodynamic mechanisms that impact a drop shaft liners structural performance and maintenance. A 1/10 scaled physical hydraulic model of a tangential inlet vortex drop shaft structure is tested and used to validate a three-dimensional multiphase numerical model. Collectively, the study presents methods on identifying hydrodynamic phenomena such as pressures, velocities, erosion and abrasion mechanisms, debris impact locations and blocking mechanisms. The study highlighted that the hydrodynamic forces that threaten structural integrity reside in the vortex generator and a short length of the drop shaft downstream. This is shown through a new model developed by the authors to predict centrifugal forces along the length of the drop. Through these methods, the study proposes that drop shaft liners can be designed more efficiently.

Hydraulic design aspects for supercritical flow in vortex drop shafts

ABSTRACTVortex drop shafts, as special sewer manholes, operate optimally if an adequate energy dissipation is guaranteed and the integrity of the structural components is safeguarded. The results of an experimental study on a vortex drop shaft with supercritical inflow are discussed herein. The hydraulic behaviour of the spiral inlet, the vertical shaft and the dissipation chamber is described. Based on detailed flow observations, useful recommendations for designing these structures are provided. It is demonstrated that a relation adopted for supercritical bend flows provides a reliable estimation of the maximum wave height along the inlet. A procedure for predicting the rotational flow angles and the velocity distribution along vertical shafts with swirling flows is developed. Water levels and pressure measurements in the dissipation chamber are further analysed to identify maximum forces acting on the chamber invert and to derive preliminary design equations.

A VORTEX DROP STRUCTURE AS DEAERATION SYSTEM FOR A SUBMARINE OUTFALL PIPELINE

Use of submarine outfall pipelines became more common since World Bank Group issued a new guideline for maximum emissions levels for thermal power plants in 1998 (van Dijk, 2005). The more restrictive levels for temperature increase at the receiving water, requires outfall systems to conduct the water down to greater depths to achieve the required dilution standard. However, air entrainment control into outfall pipes could be challenging, especially for discharges with high flowrates for which conventional deaeration chambers become too large. The problem could turn more difficult in coastal shelf areas at seismic zones, where the hydraulic height of the incoming flow must be effectively controlled and the design not only has to pursue hydraulic objectives but also stability requirements for these massive structures subjected to relevant seismic thrusts. A vortex drop structure was designed for the cooling water discharge system of a thermal power plant in Mejillones Bay, Chile. The structure addresses the elevation difference between the return flow pipe and the ocean outfall pipelines while adhering to the spatial restrictions at the project site. Energy dissipation as well as limitation of air entrainment into the outfall pipelines were critical design considerations. Tests where done on a 1:12.5 scale (Froude) physical model. Prototype structure is under construction. Operation is planned to start on mid-2018.

Numerical Simulation of Hydraulic Characteristics in A Vortex Drop Shaft

A new type of vortex drop shaft without ventilation holes is proposed to resolve the problems associated with insufficient aeration, negative pressure (Unless otherwise specified, the pressure in this text is gauge pressure and time-averaged pressure) on the shaft wall and cavitation erosion. The height of the intake tunnel is adjusted to facilitate aeration and convert the water in the intake tunnel to a non-pressurized flow. The hydraulic characteristics, including the velocity (Unless otherwise specified, the velocity in this text is time-averaged velocity), pressure and aeration concentration, are investigated through model experiment and numerical simulation. The results revealed that the RNG k-ε turbulence model can effectively simulate the flow characteristics of the vortex drop shaft. By changing the inflow conditions, water flowed into the vertical shaft through the intake tunnel with a large amount of air to form a stable mixing cavity. Frictional shearing along the vertical shaft wall and the collisions of rotating water molecules caused the turbulence of the flow to increase; the aeration concentration was sufficient, and the energy dissipation effect was excellent. The cavitation number indicated that the possibility of cavitation erosion was small. The results of this study provide a reference for the analysis of similar spillways.

Effects of the bottom slope and guiding wall length on the performance of a vortex drop inlet.

Laboratory experiments were conducted to assess the performance of a vortex drop inlet with a spiral intake in subcritical and supercritical flow conditions. The water surface elevation at multiple locations was measured for different flowrates by varying the extent of the guiding wall and the longitudinal and radial bottom slopes. The measurements show that a steeper longitudinal bottom slope decreases the water surface elevation at the beginning of the intake, resulting in a transcritical flow in the intake structure. However, a steeper longitudinal bottom slope also causes the maximum water surface elevation to occur within the spiral intake. For an effective vortex drop inlet design, achieving a low water surface elevation throughout the entire spiral intake structure is required. Experimental results show that the two seemingly conflicting design criteria, namely, achieving a low water surface elevation in the approach channel and reducing the maximum water surface elevation in the intake structure, can be simultaneously achieved by adding a radial bottom slope.

Experimental and Numerical Investigation of Flow in a Newly Developed Vortex Drop Shaft Spillway

AbstractA new shaft spillway composed of an inlet structure that includes inlet swirling-flow-generating piers, an annular weir, a vertical shaft, and an outlet structure is presented. Major factor...

Vortex Drop – Field Study and Design Considerations

Vortex Drop – Field Study and Design Considerations

Numerical and Physical Model Study of Tangential Vortex Dropshaft

Drop shafts, especially the vortex drop structure, are vertical conveyance conduits used in hydraulic engineering, water supply and drainage engineering, and so on. Because of complex flow properties and safety requirement, the system running security and reinforcement measure should be verified before it was built. In this paper, numerical and physical simulation methods were employed to verify mutually and analyze the hydraulic characteristics in a tangential vortex dropshaft. It is shown that the water carrying capacity of the dropshaft could be increased suitably and the safety freeboard of the conduit is the limiting factor. The air-water mixing at the junction may reduce the energy dissipation and reinforcement measure for the whole wall is necessary.

Numerical Simulation of Hydraulic Characteristics in a Tangential Vortex Dropshaft

Drop structures are commonly used to convey water from a higher to a lower elevation in different engineering domains, especially the vortex drop structure. Because of complex flow properties and construction technology, the system running security should be verified before it was built. In this paper, numerical simulation method was employed to analyze the hydraulic characteristics in a tangential vortex dropshaft. It is shown that there is a control section in dropshaft, and inhaled water at the control section should be avoided during the running and designing process. The numerical model is able to provide an insight into the hydraulic behavior at different flow size, and can be extended for other design verification in engineering.

Theoretical and Experimental Studies of Hydraulic Characteristics of Discharge Tunnel with Vortex Drop

The velocities at given points in the volute chamber, the contracted section and the vertical dropshaft of a discharge tunnel with vortex drop were measured by a small specially designed L-shaped tube, as Laser Doppler Velocimetry (LDV) or Particle Image Velocimetry (PIV) would not work there due to the special structure of the discharge tunnel with vortex drop. Hydraulic empirical formulas were proposed to predict the velocities and the angles of the velocities made with the vertical direction θ. The theoretical analysis results were in good agreement with experimental data. Therefore, the method proposed in this paper can be used to analyze related characteristics of discharge tunnels with vortex drop. Additionally, different model scales were considered to predict the cavitation characteristics on the wall of a dropshaft in practical engineering.

Design of a Scroll Vortex Inlet for Supercritical Approach Flow

Vortex drop shafts are used in urban drainage systems to connect two sewers located at considerably different elevations. After their introduction in 1947, these were studied with particular reference to subcritical approach flow. Vortex shafts for supercritical approach flow can also be used, but the intake structure may have relatively high cost due to the complex geometry. The present study includes experimental results of a specific investigation on the changes to be made in the supercritical approach channel if a subcritical vortex intake is used. The experimental investigation analyzes the effect of a hydraulic jump on the performance of vortex intake structure to define appropriate technical solutions, essentially consisting in a negative step to be located along the supercritical approach channel. Design criteria are finally presented for the evaluation of the step height and its distance from the vortex intake structure.

On the physical modelling of large vortex drop structures in municipal sewerage systems

Classically, dimensional analysis is used to establish the fundamental scaling laws to predict prototype behaviour from observed model results. However, the same dimensional analysis demonstrates that it is not possible to avoid scale effects if the prototype fluid - normally water - is used in the model studies. Flow through hydraulic structures is typically gravity-driven, and equality of Froude Numbers at homologous points in model and prototype leads to the determination of fundamental scaling laws. However, it is well known that, as a consequence, homologous values of other non-dimensional parameters, such as Reynolds Number and Weber Number, are not equivalent and this leads to scale effects due to the imperfect replication in the model of (for example) friction and surface tension effects. In such cases, it is necessary to use process functions to determine the magnitude of the scale effects and to inform the adjustment of measured flow properties in the model to reflect the true value of the flow properties in the prototype. The present paper extends the use of process functions to annular flows, such as those that occur in vortex drop structures and plunge pools. Within the vortex drop, it is shown that the process functions cannot be used to evaluate scale effects directly, but, instead, must be used in conjunction with the model data to develop an analytical model for the prediction of corresponding prototype behaviour. Within the plunge pool, it is hypothesised that the momentum flux at the exit of the vortex pipe must be correctly modelled to ensure the proper replication of flow conditions within the plunge pool. The techniques are developed, and their use illustrated through application to a large physical model study of a vortex drop and plunge pool in a municipal sewerage system. It is shown, further, that ignoring the insight gained from the developed process functions would lead to large errors in the prediction of prototype flow behaviour from measured model results.

HYDRAULIC DESIGN ASPECTS FOR SWIRLING FLOW AT VERTICAL DROP SHAFT SPILLWAYS

ABSTRACT Vertical drop shaft spillways are generally provided on either banks of the reservoir. It is a hydraulically efficient way to convey water as a swirling flow down vertical drop shaft. The flow adheres to the shaft wall along its entire length and wall friction is effective in reducing the vertical fall of velocities. Generally, vortex drops are provided for sewers. However, in the recent times it is increasingly adopted for heights varying from a few metres up to 200 m and the total discharge of the order of 2000 cumec. Extensive aeration/de-aeration arrangements would be necessary along the vertical shaft as well as at the junction of vertical shaft and horizontal tunnel so that air-bursting phenomenon could be avoided. This paper discusses the hydraulics of the vortex drop shaft spillway and also the experience gained while evolving the hydraulic design including a horizontal air groove in the shaft.

ESTIMATING AND CONTROLLING ODORS IN COLLECTION SYSTEMS/TUNNELS WITH VORTEX DROP SHAFTS

ESTIMATING AND CONTROLLING ODORS IN COLLECTION SYSTEMS/TUNNELS WITH VORTEX DROP SHAFTSThe Western Regional Conveyance Tunnel Project (WRTP) is planned for construction in Western Boone County, Kentucky. The collection system upstream of the WRTP is under development, and flows from that system must be conveyed to the new Western Regional Treatment Plant. Northern Kentucky Sanitation District No. 1 (SD 1) is designing the WRTP for the conveyance and wet weather storage of flow to...Author(s)Bill DesingBrandon VatterJohn SiczkaChris QuigleySourceProceedings of the Water Environment FederationSubjectSession 60: Odor and Corrosion Control in Collection Systems: From the Pipes to the PlantDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2007ISSN1938-6478SICI1938-6478(20070101)2007:14L.4664;1-DOI10.2175/193864707787974210Volume / Issue2007 / 14Content sourceWEFTECFirst / last page(s)4664 - 4674Copyright2007Word count229

Experimental Study of Flow in a Vortex Drop Shaft

Model experiments were conducted to investigate the performance of a vortex drop structure with a relatively small height to diameter ratio. Detailed measurements of wall pressure and water thickness of annular jet flow were obtained along the vertical drop shaft, and the rate of air entrainment was measured. The results confirmed the high efficiency of energy dissipation in the vortex drop structure even for a relatively small drop height. The air entrainment rate was found to be significant, and good correlation was observed between the rate of air entrainment and the water jet velocity. The one-dimensional frictional free-vortex flow model was extended to include the effects of pressure forces. While the energy loss in the drop shaft can be simulated by correcting the friction factor, both the frictional model and the extended model significantly underpredict the wall pressure.