Iraj Mortazavi

Passive Control Around the Two-Dimensional Square Back Ahmed Body Using Porous Devices

The control of two-dimensional flows around the square back Ahmed body is achieved by using porous devices added on some parts of the body. The square back Ahmed body is considered either in an open domain or on top of a road. The modeling of the flow in different media is performed by means of the penalization method. A good choice of the location of the porous interfaces yields a significant improvement of the aerodynamic quantities, especially for the square back body.

Quality Modeling of Water Distribution Systems Using Sensitivity Equations

In this paper, unsteady water quality modeling and the associated sensitivity equations are solved for water distribution systems. A new solution algorithm is proposed, designed for slow varying velocity and based on a time splitting method to separate and solve efficiently each phenomenon such as advection and chemical reaction. This numerical approach allows simultaneous solution of both the direct problem and the sensitivity equations. Special attention is given to the treatment of advection, which is handled with a total variation diminishing scheme. The general model presented in this study permits global sensitivity analysis of the system to be performed and its efficiency is illustrated on two pipe networks. The importance of the sensitivity analysis is shown as part of the calibration process on a real network.

Passive flow control around a semi-circular cylinder using porous coatings

In this paper, the passive control of flow past a semi-circular cylinder is investigated. This control is achieved by adding a porous medium between the solid obstacle and the incompressible fluid in order to reduce drag forces and regularize the flow. A vortex-penalization method is chosen to easily model the flow in the different media. Several configurations of the porous layer are investigated and parametric studies are performed in order to determine the most efficient passive flow control devices. This control study can be considered as a first step to propose efficient strategies to regularize the flow around a side-view mirror.

Active procedures to control the flow past the Ahmed body with a 25° rear window

Ahmed body with a 25 degree rear window is used to represent a simpli ed car geometry. Two and three-dimensional simulations are performed to analyse the flow behaviour around such a vehicle. Sucking and blowing jets or slots are added on the body to control the flow. The results presented show that good drag reductions are achieved for a good choice of the active procedure.

Contrôle passif d'écoulements incompressibles autour d'obstacles à l'aide de milieux poreux

Resume Le controle passif de lecoulement derriere un obstacle est obtenu en integrant a lobstacle des zones poreuses. La methode de penalisation est utilisee pour modeliser les differents milieux qui sont tous consideres comme des milieux poreux. Le fluide est identifie a un milieu poreux de permeabilite infinie et le solide a un milieu poreux de permeabilite nulle. Ceci permet de representer simultanenement des milieux fluide, solide et poreux en fonction dun meme parametre. La presence du milieu poreux a linterface entre le solide et le fluide permet de regulariser lecoulement et de reduire de facon significative lenstrophie et la trainee.

A vortex immersed boundary method for bluff-body flows

The aim of this work is to couple vortex methods with the penalization methods in order to take advantage from both of them. This immersed boundary approach maintains the efficiency of vortex methods for high Reynolds numbers focusing the computational task on the rotational zones and avoids their lack on the no-slip boundary conditions replacing the vortex sheet method by the penalization of obstacles. This method that is very appropriate for bluff-body flows is validated for the flow around a circular cylinder on a wide range of Reynolds numbers.

Numerical simulation of a hydraulic Saint-Venant type model with pressure-dependent leakage

Abstract The objective of this paper is to present and validate an improved formulation of the hydraulic network equations that incorporate pressure-dependent leakage in Water Distribution Systems. The formulation is derived from the Navier–Stokes equations and solved using an adequate splitting method. An implicit numerical scheme is used to solve the p -Laplacian equation. The model is validated on a benchmark pipe network.

Comparison of URANS, PANS, LES and DNS of flows around simplified ground vehicles with passive flow manipulation

Flow control of ground vehicles has recently attracted large interest in both industry and academia. The potential in energy savings seems to be considerable and at the moment both passive and active control strategies are explored.

Inverse Transport Method for Determination of Potential Contamination Sources with a Stochastic Framework

Security is an important concern for the water industry nowadays. It is particularly important to have tools that are able to determine the source of contamination once an alarm is raised by the sensor detection system. The objective of this paper is the development of such a model to locate potential sources of contamination. The model solution uses a two-step method. Firstly, a linear sourceresponse transport equation is built based on a backtracking algorithm applied to sensor binary answers. It is followed by a minimum relative entropy method or a least squares method coupled with a Tikhonov regularisation that yields the probability density function of the different potential sources found at the first step. The model have been validated on small networks and applied to a large network under single and multiple contamination scenarios. This research is part of the European project on water network security named SecurEau.

Coupling particle sets of contours and streamline methods for solving convection problems

In this work a particle sets of contours method is coupled with a streamline technique in order to obtain accurate approximations of transport problems. A modified streamline technique is proposed and several bench tests arising in the field of porous media are then simulated to validate the new method.