Leonardo S. Nanía

Experimental Study of Subcritical Dividing Flow in an Equal-Width, Four-Branch Junction

An experimental study of the subcritical dividing flow in an equal-width, four-branch junction with two inflows and two outflows is presented. A brief description of the flow characteristics is given. From the analysis of test data, a linear relationship among five nondimensional parameters, including inflow ratio, outflow ratio, Froude number of inflow in one direction, outflow depth ratio, and outflow aspect ratio, is proposed and proven to successfully predict the flow distribution in the junction. It can be used to solve the dividing flow problem in a street junction, and it can be included as a part of a numerical model of a street network involving subcritical flows.

Surface stormwater hazard assessment in steep urban areas. Case of the city of Mendoza, Argentina

The current paper focusses on the hazard assessment associated with urban runoff on streets. A review of the existing criteria to evaluate such a hazard is made. Two new criteria based on theoretical analysis of the waters force acting on a static pedestrian are presented: no slipping criterion and stability to tilt criterion. According to these criteria, either a maximum depth, or a maximum velocity or some relation between depths and velocities should be fulfilled in order to guarantee the pedestrians and drivers safety in the case of medium to large storms. A one-dimensional numerical model is used to solve the urban storm runoff within a street network. This model is applied to an urban watershed of the city of Mendoza (Argentina), obtaining the runoff values belonging to return periods of 5, 10 and 25 years. The results are evaluated bearing in mind four hazard criteria. In conclusion, the numerical model is shown to be a useful tool in relation to the application of the hazards criteria. It is also conclude that an effort should be made to determine specific hazard criteria based on experimental data.

Inlet Spacing Considering the Risk Associated to Runoff. Application to Streets and Critical Points of the City of Barcelona

In this work an analysis of the street flow and the risk criteria adopted in the city of Barcelona, associated to the street discharge is presented. After selecting some risk criteria concerning maximum water depths, velocities or combination of both, a hydrologic and hydraulic analysis is made considering for some longitudinal street slope values, the discharge pattern produced by a 10 year return period rainfall, with different inlet types and inlet spacing. The discharge pattern stabilizes at a maximum discharge, whose associated depth and velocity are used to verify risk factors previously established. Thus we can see for every inlet type and street slope, which one is the optimal inlet spacing in order to match with the proposed risk criteria. These values are used in the reform of old streets and in the design of new collecting stormwater systems.

Influence of Channel Width on Flow Distribution in Four-Branch Junctions with Supercritical Flow: Experimental Approach

AbstractAn experimental study of the supercritical dividing flow in a right-angle, four-branch junction with different channel widths is presented. Lateral-to-mainstream width ratios of 1∶1, 2∶3, and 1∶2 were used to establish the influence of the channel width on the flow distribution. A brief description of the flow characteristics is given. Types I and II flow patterns are confirmed by the experiments in the range of the studied variables. Existing flow distribution models were adapted for width ratios other than 1∶1 and tested for Type II, subregime 3 flow pattern, finding poor results. Other existing flow distribution models for Type II, subregimes 1 and 2 flow pattern and a width ratio of 1∶1 give a very good fit with the experimental data. A new flow distribution model for Type II, subregimes 1 and 2 flow pattern and width ratios of 2∶3 and 1∶2 was proposed, which is a function of the Froude number and the width ratio. A former model for predicting the flow distribution in equal-width (1∶1 width ra...

A robust and fast model for simulating street flooding

This work is part of a long term project which aims to simulate (1) the hydrology, (2) street flows, (3) flow interception at inlets and (4) storm-sewer flows in urban areas. The present work describes the application of the model using only the first two modules. The hydrologic model (first module) transforms rainfall to runoff using the kinematic wave approximation and simulating the infiltration process with the Green-Ampt method. The street model (second module) is based on a finite volume-shock capturing scheme that solves the full conservative Saint-Venant equations and can be used to simulate subcritical and supercritical flows. The formulation of boundary conditions at the street crossings in the street model is general and can be used for any number of streets, any combination of inflowing and outflowing streets, and any flow type (e.g., supercritical flows). The model using the first two modules is fast and robust and it has several potential applications. Perhaps the most important one is that it can be used in new urban developments to identify critical zones of urban flooding (e.g., zones with high water depths and flow velocities) in order to take appropriate measures of drainage control (e.g., to increase capacity of inlets). This model can also be used in developed urban areas to locate the critical areas in case of inlet clogging. In order to illustrate the capabilities of the model (first two modules) it was applied to an urban catchment in the village of Dolton, a southern suburb of Chicago. The watershed of this village drains to the dropshaft CDS-51 in the Calumet TARP (Tunel and Reservoir Plan) system which is operated by the Metropolitan Water Reclamation District of Greater Chicago. The fact that this model is fast makes suitable its application to large urban areas.

Experimental and numerical modelling of symmetrical four-branch supercritical cross junction flow

The discussers congratulate the authors for their work and would like to raise some questions and comments about their results and statements. The paper compares (i) the computed with the measured flow depths for five flow configurations and (ii) the computed with the measured discharges for more than 200 configurations. The authors found discrepancies concerning the prediction of the location and the thickness of the oblique jumps mainly because these are set on one cell in the numerical model. The discussers argue that the prediction of the discharge distribution at the junction through a “quality indicator” as suggested by the authors, namely EQT in Section 4.2, p. 728, is somewhat misleading. The authors compared the difference between the computed and measured outflows in the x direction with the total inflow discharge, whereas they should have used the measured outflow in the x direction as EQT