Abstract

The development of more and more potent computers and the recent research in the field of hidroinformatics makes possible the free surface flow modelling in two dimensions caused by earthen dam failures. In this paper, the results obtained by uni-dimensional model (HEC-RAS) and two-dimensional model (CARPA) are compared. The use of the HEC-RAS software assumes the hypothesis of unidimensionality to be true, no infiltration and existence of a minimal initial flow. The comparison is made by analyzing the effect of these hypothesis in the downstream flow hydrographs. The used models reproduce the water discharge generated by a possible failure of dam number 1 of the 5th District of the Segarra-Garrigues Irrigation Project in the Ebro river basin in Spain.

Abstract

This study presents the results from detailed experiments of the two-phase pressurized flow behavior during the rapid filling of a large-scale pipeline. The physical scale of this experiment is close to the practical situation in many industrial plants. Pressure transducers, water-level meters, thermometers, void fraction meters, and flow meters were used to measure the two-phase unsteady flow dynamics. The main focus is on the water–air interface evolution during filling and the overall behavior of the lengthening water column. It is observed that the leading liquid front does not entirely fill the pipe cross section; flow stratification and mixing occurs. Although flow regime transition is a rather complex phenomenon, certain features of the observed transition pattern are explained qualitatively and quantitatively. The water flow during the entire filling behaves as a rigid column as the open empty pipe in front of the water column provides sufficient room for the water column to occupy without invoking air compressibility effects. As a preliminary evaluation of how these large-scale experiments can feed into improving mathematical modeling of rapid pipe filling, a comparison with a typical one-dimensional rigid-column model is made. Keywords: Experimentation, Large-scale pipeline, Unsteady flow, Two-phase flow, Air–water interface, Flow-regime transition

Abstract

In this study, the boundary layer flow of an incompressible viscous fluid over an unsteady curved stretching surface is investigated in the presence of a variable applied magnetic field. Since the geometry is curved, the basic flow equations of the present problem are modeled using curvilinear coordinates. The obtained system is then reduced into nonlinear ordinary differential equations in two dependent quantities namely the fluid pressure and velocity by introducing suitable transformations. A numerical solution for fluid pressure and velocity is obtained by using a shooting method using Runge–Kutta integration scheme. The effects of various physical parameters on the fluid velocity and pressure distribution are shown through graphs and are discussed in detail. The comparison between the present and the existing results in the literature in special case for flat unsteady stretching, i.e. (K→∞K→∞ ), is found in good agreement.