Search Results: “” — Page 1
David Ho, Karen Riddette, Michael Hogg, Jayanta Sinha and John Roberts
Blowering Dam was constructed in 1968 by the Snowy Mountains Hydro-Electric Authority, on behalf of the Water Conservation and Irrigation Commission. It is a large earth and rockfill embankment dam, approximately 112m high and 808m long, with a concrete chute spillway at the right abutment. The reservoir holds about 1,628GL of water that is mainly for irrigation and supplying an 80MW hydro-electric power station. The dam is owned and operated by State Water Corporation, NSW.
Revisions to the design flood estimate have highlighted the dam requiring an upgrade to cope with increased discharge rates. The NSW Department of Commerce has carried out feasibility studies of different upgrade options. The need to evaluate the hydraulic performance of the existing un-gated spillway was identified. Flow overtopping the chute walls can potentially erode the backfill behind the walls, and, the rockfill on the downstream toe of the embankment. Consequently, this may lead to significant damage of the spillway and may risk the safety of the dam.
Hydraulic analysis of the spillway using a 3-D computational fluid dynamics model was performed for
various flood levels to determine the discharge coefficients and the discharge rating curve. It was also required to identify whether the chute walls need raising to contain the increased discharges. These results were compared with those calculated by other “standard” methods. Such verification provided a level of confidence in the analysis results which were then used in the studies to assess available upgrade options.
In order to have further confidence in the analysis, the computed results were validated against physical test data and some limited information from an actual discharge. Further verification against established theory was conducted by modelling a supercritical flow through a contraction in an open-channel in order to see if the computation could predict the shock wave effect that was observed in physical models as well as full scale channels. A reasonably good correlation was obtained from all validating tests.
This paper presents some background of the proposed dam upgrade, potential upgrade options considered and details of the hydraulic modelling of the spillway. Some interesting flow behaviour caused by the shock wave will be highlighted.
Now showing all 8 search results
-
$15.00
2005 Papers
2005 – Blowering Dam – Spillway Hydraulic Modelling
Learn more
Learn more
David Ho, Karen Riddette, Michael Hogg, Jayanta Sinha and John Roberts
Blowering Dam was constructed in 1968 by the Snowy Mountains Hydro-Electric Authority, on behalf of the Water Conservation and Irrigation Commission. It is a large earth and rockfill embankment dam, approximately 112m high and 808m long, with a concrete chute spillway at the right abutment. The reservoir holds about 1,628GL of water that is mainly for irrigation and supplying an 80MW hydro-electric power station. The dam is owned and operated by State Water Corporation, NSW.
Revisions to the design flood estimate have highlighted the dam requiring an upgrade to cope with increased discharge rates. The NSW Department of Commerce has carried out feasibility studies of different upgrade options. The need to evaluate the hydraulic performance of the existing un-gated spillway was identified. Flow overtopping the chute walls can potentially erode the backfill behind the walls, and, the rockfill on the downstream toe of the embankment. Consequently, this may lead to significant damage of the spillway and may risk the safety of the dam.
Hydraulic analysis of the spillway using a 3-D computational fluid dynamics model was performed for
various flood levels to determine the discharge coefficients and the discharge rating curve. It was also required to identify whether the chute walls need raising to contain the increased discharges. These results were compared with those calculated by other “standard” methods. Such verification provided a level of confidence in the analysis results which were then used in the studies to assess available upgrade options.
In order to have further confidence in the analysis, the computed results were validated against physical test data and some limited information from an actual discharge. Further verification against established theory was conducted by modelling a supercritical flow through a contraction in an open-channel in order to see if the computation could predict the shock wave effect that was observed in physical models as well as full scale channels. A reasonably good correlation was obtained from all validating tests.
This paper presents some background of the proposed dam upgrade, potential upgrade options considered and details of the hydraulic modelling of the spillway. Some interesting flow behaviour caused by the shock wave will be highlighted.
Learn more
-
$15.00
2005 Papers
2005 – BLOWERING DAM – SPILLWAY HYDRAULIC MODELLING
Learn more
Learn more
Blowering Dam was constructed in 1968 by the Snowy Mountains Hydro-Electric Authority, on behalf of the Water Conservation and Irrigation Commission. It is a large earth and rockfill embankment dam, approximately 112m high and 808m long, with a concrete chute spillway at the right abutment. The reservoir holds about 1,628GL of water that is mainly for irrigation and supplying an 80MW hydro-electric power station. The dam is owned and operated by State Water Corporation, NSW.
Revisions to the design flood estimate have highlighted the dam requiring an upgrade to cope with increased discharge rates. The NSW Department of Commerce has carried out feasibility studies of different upgrade options. The need to evaluate the hydraulic performance of the existing un-gated spillway was identified. Flow overtopping the chute walls can potentially erode the backfill behind the walls, and, the rockfill on the downstream toe of the embankment. Consequently, this may lead to significant damage of the spillway and may risk the safety of the dam.
Hydraulic analysis of the spillway using a 3-D computational fluid dynamics model was performed for various flood levels to determine the discharge coefficients and the discharge rating curve. It was also required to identify whether the chute walls need raising to contain the increased discharges. These results were compared with those calculated by other “standard” methods. Such verification provided a level of onfidence in the analysis results which were then used in the studies to assess available upgrade options.
In order to have further confidence in the analysis, the computed results were validated against physical test data and some limited information from an actual discharge. Further verification against established theory was conducted by modelling a supercritical flow through a contraction in an open-channel in order to see if the computation could predict the shock wave effect that was observed in physical models as well as full scale channels. A reasonably good correlation was obtained from all validating tests.
This paper presents some background of the proposed dam upgrade, potential upgrade options considered and details of the hydraulic modelling of the spillway. Some interesting flow behaviour caused by the shock wave will be highlighted.
Learn more
-
$15.00
2006 Papers
2006 – Hydraulic Flow Simulation – Five Years On: Lessons Learned and Future Challenges
Learn more
Learn more
Karen Riddette, David Ho & Julie Edwards
Over the last five years in Australia, the use of computational fluid dynamics for the investigation of water flows through hydraulic structures has been steadily rising. This modelling technique has been successfully applied to a range of dam upgrade projects, helping to assess spillway discharge capacity and structural integrity, and giving insight into flow behaviours including orifice flow, shock wave formation and chute overtopping (Ho et al, 2006). Innovative and cost effective upgrade solutions have been implemented from numerical model studies including baffle plates (Maher and Rodd, 2005) and locking arrangements to protect radial gates from extreme floods.
This paper will begin with a review of recent dam engineering applications, including outlet flow through a fish screen, the performance of a fishway against hydraulic and environmental criteria and pipe flow in a large pumping station. Some of the difficulties and limitations of the modelling technique will be examined together with current research being conducted to address these issues and further validate the numerical results against published data. Some interesting results to date will be reported on elliptical crest discharge, boundary geometry, and model/prototype correlation.
With increasing computing power and software enhancements, the potential applications for numerical simulation in dam engineering continue to grow. This paper will also examine the future outlook and highlight some recent advances such as the thermal simulation of cold water pollution, air entraining flows and combined free-surface and pipe flow in a morning glory spillway.
Learn more
-
$15.00
2006 Papers
2006 – Hydraulic flow simulation – five years on: lessons learned and future challenges
Learn more
Learn more
Karen Riddette, David Ho & Julie Edwards
Over the last five years in Australia, the use of computational fluid dynamics for the investigation of waterflows through hydraulic structures has been steadily rising. This modelling technique has been successfully applied to a range of dam upgrade projects, helping to assess spillway discharge capacity and structural integrity, and giving insight into flow behaviours including orifice flow, shock wave formation and chute overtopping (Ho et al, 2006). Innovative and cost effective upgrade solutions have been implemented from numerical model studies including baffle plates (Maher and Rodd, 2005) and locking arrangements to protect radial gates from extreme floods.
This paper will begin with a review of recent dam engineering applications, including outlet flow through a fish screen, the performance of a fishway against hydraulic and environmental criteria and pipe flow in a large pumping station. Some of the difficulties and limitations of the modelling technique will be examined together with current research being conducted to address these issues and further validate the numerical results against published data. Some interesting results to date will be reported on elliptical crest discharge, boundary geometry, and model/prototype correlation.
With increasing computing power and software enhancements, the potential applications for numerical simulation in dam engineering continue to grow. This paper will also examine the future outlook and highlight some recent advances such as the thermal simulation of cold water pollution, air entraining flows and combined free-surface and pipe flow in a morning glory spillway.
Learn more
-
$15.00
2007 Papers
2007 – Computational fluid dynamics models and physical hydraulic modelling – do we need both? The design of the Hinze Dam Stage 3
Learn more
Learn more
Mike Phillips and Karen Riddette
The use of Computational Fluid Dynamics (CFD) models in the dams industry has increased significantly in recent years and conversely the use of physical hydraulic models has decreased. Typical design approaches for an upgrade of similar magnitude to the Hinze Dam Stage 3 project would have allowed for considerable time to develop a preliminary spillway design before hydraulic modelling was introduced, potentially requiring only one type of model. So is there a need for both types of models?
Because of the complex hydraulics associated with the spillway required for the Hinze Dam Stage 3 raise and accelerated schedule, the utilisation of CFD and 1:50 Froude Scale physical hydraulic models was necessary. Both models were constructed independent of each other. Both models complemented each others strengths and weaknesses, and each provided critical information at the following different stages of design:
• Spillway selection and conceptual design stage – the CFD model results were highly valuable in steering the selection of spillway type and configuration, particularly with visual representations of the ranges of flow for each spillway option.
• Preliminary design – in a one week period, 90 to 95% of the final spillway layout was resolved with interactive modifications of the physical hydraulic model.
• Detailed design – both the physical hydraulic model and the CFD model were utilised to determine water pressures, velocities and water surfaces and evaluate cavitation potential as input to detailed design.
In the case of the Hinze Dam Stage 3 project, it was highly advantageous to utilise a CFD and physical hydraulic model to achieve the design outcomes at each phase of the design. The dual-model study approach also provided advantages for project management of the design and stakeholder involvements.
Keywords: Computational fluid dynamics, CFD, physical hydraulic model, spillway, hydraulics
Learn more
-
$15.00
2012 Papers
2012 – Investigation of stilling basin slab stability for Waipapa Dam Spillway, NZ
Learn more
Learn more
Karen Riddette, Chee Wei Tan, Alan Collins, David Ho
Due to a number of historical stilling basin slab failures around the world, modern basin slab stability assessment approaches now require allowance for hydrodynamic pressure fluctuations. Extreme fluctuations in uplift pressures have been found to occur in hydraulic jumps and plunge pools resulting in high-pressure pulses being transmitted via joints and drainage openings to the underside of the slab. If, peak uplift forces beneath the slab coincide with minimum pressure fluctuations on the top of the slab, the resulting pressure differential can be sufficient to lift a slab. As a result, simple static design based on tailwater depth and mean floor pressures is now considered highly non-conservative.
Through a case study on the Waipapa Dam spillway stilling basin, this paper examines the use of CFD modelling to compute mean hydrodynamic slab pressures taking into account the location of the hydraulic jump and the effect of the impact blocks on the pressure distribution over the slab. By combining the CFD results with empirically-derived pressure fluctuations, uplift scenarios are applied in a FEA model to compute the maximum load in the slab anchors and examine the sensitivity of the stilling basin slabs to uplift failure.
Keywords: Stilling basin, hydrodynamic modelling, CFD, pressure fluctuation, slab stability.
Learn more
-
$15.00
2008 Papers
2008 – Modelling extreme flows over a stepped spillway
Learn more
Learn more
Karen Riddette, David Ho, Mike Phillips
Abstract: Stepped spillways have seen a resurgence in popularity in recent years as new research has better described flow conditions and quantified the energy dissipation capacity of this type of spillway.
While carrying out hydraulic modelling for the Hinze Dam Stage 3 upgrade project using Computational Fluid Dynamics (CFD) analysis, extensive numerical testing and validation of the CFD model for the proposed 0.8H:1V stepped spillway design was undertaken. It was found that for the expected Probable Maximum Flood (PMF) discharge, the high flow depth would result in a non-aerated, non-uniform flow, typically seen in the developing flow region just beyond the spillway crest, occurring over the entire length of the stepped spillway. To date, only limited laboratory studies have been published concerning energy losses in this particular flow regime.
This paper examines the ability of CFD modelling to compute energy dissipation and air entrainment effects in stepped spillways under extreme flow conditions. Where possible, the computed results were validated against limited published data. Some new data obtained by the CFD model is presented for energy loss in the developing flow region that has not been established before.
Keywords: stepped spillway, CFD, energy loss, developing flow.
Learn more
-
$15.00
2008 Papers
2008 – Modelling procedures used for the spillway upgrade for Lake Manchester Dam
Learn more
Learn more
Eric Lesleighter, Bronson McPherson, Karen Riddette, Jon Williams
Abstract: The paper describes in part the hydraulics investigations required for the major upgrade works for Lake Manchester Dam; investigations which utilised two modelling procedures. Following a brief outline of the dam rehabilitation program and works, the inadequacy of the former spillway for the revised hydrology is described. The urgency of the construction program led to the use of CFD modelling following preliminary desk studies of the hydraulics, in order to delineate certain features of the new spillway and the plunge pool area and allow the construction program to be fast-tracked. As part of the overall program to refine the spillway design, and due to the evident complexity of the flows over the spillway, physical hydraulic model studies were also carried out.
The investigations provided a very good opportunity to compare the results from two modelling approaches carried out within the same design activity. Specific results of aspects such as flow patterns, velocities, pressures, and wave action will be compared. A prominent purpose of the paper will be to acknowledge the advantages and limitations of both approaches, and seek to provide the guidelines and advice that designers and dam owners should follow and adopt to ensure the hydraulics requirements of projects are soundly engineered.
Keywords: spillways, physical modelling, numerical modelling, CFD.
Learn more
