A new approach for evaluating water hammer including the initial state of pressurization of the installation and fluid

[EN] The water hammer phenomenon is well known since the 19th century, while its mathematical formulation, by means of differential equations, is due to works of researchers such us Allievi (1903) and others from the beginning of the 20th century. The equations found in the technical publications produce a strange water hammer when the initial condition is defined assuming an incompressible fluid and a rigid pipe. The correct solution requires solving the water hammer equations for the initial state. When the finite difference method is applied, the initial state is solved by means of a set of non-linear equations. A novel approach is proposed including the initial state of pressurization into the governing equations and hence simplifying the calculus of the initial conditions. Furthermore, a critical reading of the deduction of the equations is done pointing out conceptual inconsistencies and proposing corrections[ES] El fenómeno del golpe de ariete es conocido desde el siglo XIX y su formulación matemática, en término de ecuaciones diferenciales, se debe a los trabajos de Allievi (1902) y otros investigadores del principio del siglo XX. Las ecuaciones presentes en la literatura técnica actual generan un fenómeno anómalo de golpe de ariete cuando el escurrimiento se encuentra en régimen permanente y no se introducen perturbaciones. En el presente trabajo se realiza una lectura crítica de la deducción presente en la literatura señalando las inconsistencias conceptuales. Luego se propone una nueva deducción y un conjunto de ecuaciones diferenciales que articulan consistentemente los conceptos de la mecánica de los fluidos y resuelven la anomalía detectadaKaless, G. (2016). Una nueva aproximación para la evaluación del golpe de ariete incluyendo la condición inicial de presurización de la instalación y del fluido. Ingeniería del Agua. 20(2):59-72. doi:10.4995/ia.2016.3692.SWORD5972202Allievi, L. (1903). Teoria generale del moto perturbato dell'acqua nei tubi in pressione (colpo d'ariete). Associazione Elettotecnica Italiana. Unione Cooperativa Editrice. Italia.Bergant, A., Simpson, A. R. (1994). Estimating unsteady friction in transient cavitating pipe flow. 2nd International Conference on Water Pipeline Systems, 24-26 May, Edinburgh, Scotland, 3-15.Bergant, A., Simpson, A.R., Vitkovsky, J. (2001). Developments in unsteady pipe flow friction modeling. Journal of Hydraulic Research,39(3), 249-257. doi:10.1080/00221680109499828Bergant, A., Tijsseling, A.S., Vítkovský, J.P., Covas, D.I.C., Simpson, A.R., Lambert, M.F. (2008a). Parameters affecting water-hammer wave attenuation, shape and timing. Part 1: Mathematical tools. Journal of Hydraulic Research,46(3), 373-381. doi:10.3826/jhr.2008.2848Bergant, A., Tijsseling, A.S., Vítkovský, J.P., Covas, D.I.C., Simpson, A.R., Lambert, M.F. (2008b). Parameters affecting water-hammer wave attenuation, shape and timing. Part 2: Case studies. Journal of Hydraulic Research,46(3), 382-391. doi:10.3826/jhr.2008.2847Chadwick, A., Morfett, J., Borthwick, M. (2013). Hydraulic in Civil and Environmental Engineering. 5a Edición, CRC Press, London, UK.Chaudry, M. H. (2014). Applied Hydraulic Transients. 3ra Edición. Springer. doi:10.1007/978-1-4614-8538-4Choon, T.W., Aik, L. K., Aik, L. E., Hin, T. T. (2012). Investigation of Water Hammer Effect Through Pipeline System. International Journal on Advanced Science Engineering Informational Technology,2(3), 48-53. doi:10.18517/ijaseit.2.3.196Frizell, J. P. (1898). Pressures resulting from changes of velocity of water in pipes. Transactions of the American Society of Civil Engineers,39, 1-18.Fuertes, V. S., Izquierdo, J., Iglesias, P. L., Cabrera, E., Garcia-Serra, J. (1997). Llenado de tuberías con aire atrapado. Ingeniería del Agua,4(3), 53-63. doi:10.4995/ia.1997.2730Hoffman, J. D. (2001). Numerical methods for engineers and scientist. 2da Edición. Marcel Dekker, New York, USA.Hou, Q., Tijsseling, A. S., Laanearu, J., Annus, I., Koppel, T., Bergant, A., Vuckovic, S., Anderson, A., Westende, J. M. C. (2014). Experimental investigation on rapid filling of a large-scale pipeline. Journal of Hydraulic Engineering, 140(11). doi:10.1061/(ASCE)HY.1943-7900.0000914Karadzic, U., Bulatovic, V., Bergant, A. (2014). Valve-induced water hammer and column separation in a pipeline apparatus. Journal of mechanical Engineering,60(11), 742-754.Korteweg, D. J. (1878). Uber die voortplantingsnelheid van golven in elastische buizen. Tesis doctoral. Universidad de Amsterdam, Paises Bajos.Mambretti, S. (2015). Water hammer simulations. WIT Press. Southampton, UK.Pérez Farrás, L., Guitelman, A. (2005). Estudio de transitorios: golpe de ariete. Universidad de Buenos Aires, Argentina.Tijsseling, A. S., Anderson, A. (2007). Johannes von Kries and the History of Water Hammer. Journal of Hydraulic Engineering,133(1), 1-8. doi:10.1061/(ASCE)0733-9429(2007)133:1(1)Wang, R., Wang, Z., Wang, X., Yang, H., Sun, J. (2014). Water hammer assessment techniques for water distribution systems. Procedia Engineering,70, 1717-1725. doi:10.1016/j.proeng.2014.02.189Zout, F., Hicks, F., Steffler, P. (2002). Transient flow in a rapidly filling horizontal pipe containing trapped air. Journal of Hydraulic Engineering,128(6), 625-634. doi:10.1061/(ASCE)0733-9429(2002)128:6(625

A new approach to define surface/sub-surface transition in gravel beds

The vertical structure of river beds varies temporally and spatially in response to hydraulic regime, sediment mobility, grain size distribution and faunal interaction. Implicit are changes to the active layer depth and bed porosity, both critical in describing processes such as armour layer development, surface-subsurface exchange processes and siltation/ sealing. Whilst measurements of the bed surface are increasingly informed by quantitative and spatial measurement techniques (e.g., laser displacement scanning), material opacity has precluded the full 3D bed structure analysis required to accurately define the surface-subsurface transition. To overcome this problem, this paper provides magnetic resonance imaging (MRI) data of vertical bed porosity profiles. Uniform and bimodal (σ g = 2.1) sand-gravel beds are considered following restructuring under sub-threshold flow durations of 60 and 960 minutes. MRI data are compared to traditional 2.5D laser displacement scans and six robust definitions of the surface-subsurface transition are provided; these form the focus of discussion