Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Husain, Sarhang M.

Karunarathna, Harshinie U.

Muhammed, Jowhar R.

Reeve, Dominic E.

English

Hydraulic Engineering Repository

Conference Paper, Published VersionHusain, Sarhang M.; Reeve, Dominic E.; Muhammed, Jowhar R.;Karunarathna, Harshinie U.Simulation of Skimming Flow over Moderate SteppedSpillways Using Smoothed Particle HydrodynamicsZur Verfügung gestellt in Kooperation mit/Provided in Cooperation with:Kuratorium für Forschung im Küsteningenieurwesen (KFKI)Verfügbar unter/Available at: https://hdl.handle.net/20.500.11970/109694Vorgeschlagene Zitierweise/Suggested citation:Husain, Sarhang M.; Reeve, Dominic E.; Muhammed, Jowhar R.; Karunarathna, HarshinieU. (2012): Simulation of Skimming Flow over Moderate Stepped Spillways Using SmoothedParticle Hydrodynamics. In: Hagen, S.; Chopra, M.; Madani, K.; Medeiros, S.; Wang, D.(Hg.): ICHE 2012. Proceedings of the 10th International Conference on Hydroscience &Engineering, November 4-8, 2012, Orlando, USA.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.The 10th Int.  Conf. on Hydroscience and Engineering (ICHE-2012), Nov. 4 – Nov. 7, Orlando, USA 394      SIMULATION OF SKIMMING FLOW OVER MODERATE STEPPED SPILLWAYS USING SMOOTHED PARTICLE HYDRODYNAMICS   Sarhang M. Husain1, Dominic E. Reeve2, Jowhar R. Muhammed3, and Harshinie U. Karunarathna4    Stepped spillways are mainly designed to act as energy dissipators and protective measures against cavitation damage. Although air plays a vital role in protecting the surface of this structure against this damage, it may be entirely absent or insufficiently present over the upstream reach of the chute, which is known as the non-aerated flow region, especially with skimming flow conditions (Chanson, 2002). The behaviour of the pressure, as a main parameter to predict the cavitation tendency, in the non-aerated flow region on moderate slopes has been the subject of only a limited number of research studies. Understanding the pressure pattern on the step faces under severe conditions is therefore an important aspect of improving the design of said structures. The current work is a numerical investigation which presents and describes the features of the pressure flow field on the horizontal and vertical faces of steps situated in the non-aerated flow region. The coordinate of the inception point, based on the predicted free water surface level and velocity profile at the outer edge of steps, and are also predicted and compared with the existing experimental results. These are examined under a range of flow rates typical of skimming flow regime on a stepped spillway of 1V:2H bottom inclination.   The present work applies the 2D SPHysics open source code as an implementation of the computational Smoothed Particle Hydrodynamics (SPH) method. This method is characterized by a pure meshfree and Lagrangian approach in which grids, used in grid based methods, are replaced by arbitrarily distributed particles carrying the fluid properties (Monaghan, 1989). This code solves the Navier-Stokes governing equations considering the fluid as weakly compressible which allows the explicit determination of the pressure flow field by solving an equation of state (Gómez-Gesteira et al. 2010). A cubic spline kernel is used as the interpolation function and a Verlet time integration scheme is adopted. The effect of the flow field turbulence is introduced using the SPS technique and the repulsive boundary condition is applied to generate the solid wall particles. Further, the moving least square approach is utilized to stabilize the pressure flow field and the first order kernel correction technique is used to achieve the consistency and normalization conditions of the kernel function. In this study the code is firstly validated against two existing experimental test cases, namely; flow over broad crested weirs carried out by Hager et al. (1994) and a stepped spillway of 1V:2H slope similar to the laboratory model of Meireles et al. (2009). Figure (1) plots the numerical velocity profiles predicted by the SPHysics code and the experimental results gathered by Hager et al. (1994) at x/Ho = 0.5, where x is the distance along the crest originating at its upstream corner, Ho is the approach total head with respect to the crest level, u is the horizontal velocity at distance y measured from the crest. Free surface profiles of                                                  1 PhD Researcher, College of Engineering, University of Swansea, Swansea, SA2 8PP, UK (s.m.h.husain.667316@swansea.ac.uk) or (sarhanghusain@yahoo.co.uk) 2 Professor, College of Engineering, University of Swansea, Swansea, SA2 8PP, UK (d.e.reeve@swansea.ac.uk)  3 Assistant Professor, Department of Water Resources Engineering, University of Duhok, Iraq (jowharus@yahoo.com) 4 Reader, College of Engineering, University of Swansea, Swansea, SA2 8PP, UK ( h.u.karunarantha@swansea.ac.uk) The 10th Int.  Conf. on Hydroscience and Engineering (ICHE-2012), Nov. 4 – Nov. 7, Orlando, USA 395 the experimental and numerical results of skimming flow over the stepped spillway model for three different discharge values represented by the dimensionless parameter hc/h, where hc is the critical flow depth over the crest and h is the step height, are shown in Figure (2). The validated code is then applied to predict the hydrodynamic pressures applied on the step faces under various discharges within the range of skimming flow.    The authors observed that the numerical results, in terms of free surface, velocity and pressure profiles, obtained from the current model are in reasonable agreement with the experimental results. This demonstrates the capability of the SPHysics code, as a particle based scheme, to accurately simulate the flow properties over stepped spillways. Furthermore, from the pressure profiles, on both faces of different steps in the non-aerated flow region, the positions of peak positive and negative pressure values are indicated. Negative pressure values are predicted at some boundary points close to top of the vertical step face with a maximum value at the upper point, whereas the pressure values along the horizontal face are almost positive with a maximum value located far from the step outer edge about 0.35-0.45 the whole length of the horizontal step face.                              (a)                                                                        (b)  Figure 1 (a) Non-dimensional horizontal flow velocity at x/Ho= 0.5  (b) free surface profiles along the chute in the flow direction  REFERENCES  Chanson, H. (2002) The Hydraulics of Stepped Chutes and Spillways, Lisse, A.A. Balkema publishers. Gómez-Gesteira, M., Rogers, B.D., Dalrymple, R.A., Crespo, A.J.C. and Narayanaswamy, M., 2011, User Guide for the SPHysics Code v2.2, http://www.sphysics.org. Hager, H. W., and Schwalt, M. (1994) “Broad-Crested Weir”, Journal of Irrigation and Drainage Engineering, Vol. 120, No.1, pp. 13-26 Meireles, I. and Matos, J. (2009) “Skimming flow in the non-aerated region of stepped spillways over embankment dams”, Journal of Hydraulic Engineering, ASCE, Vol.135, No. 8, pp. 685-689. Monaghan, J., J. (1989) “On the problem of penetration in particle methods”, Journal of Computational Physics, Vol. 82, No. 1, pp.1-15. 

Simulation of Skimming Flow over Moderate Stepped Spillways Using Smoothed Particle Hydrodynamics

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Simulation of Skimming Flow over Moderate Stepped Spillways Using Smoothed Particle Hydrodynamics

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