Daniel de Wolf

Optimal Dimensioning of Pipe Networks with Application to Gas Transmission Networks

We develop an algorithm to solve the problem of the optimal dimensioning of a fluid gas or water transmission network when the topology of the network is known. The pipe diameters must be chosen to minimize the sum of the investment and operating costs. This two stage problem is solved by application of the bundle method for nonsmooth optimization. The validity of the approach is tested on a problem corresponding to a real situation: the optimal design of a reinforcement of the Belgian gas network.

Design and dimensioning of hydrogen transmission pipeline networks

This work considers the problem of the optimal design of an hydrogen transmission network. This design problem includes the topology determination and the pipelines dimensioning problem. We define a local search method that simultaneously looks for the least cost topology of the network and for the optimal diameter of each pipe. These two problems were generally solved separately these last years. The application to the case of development of future hydrogen pipeline networks in France has been conducted at the local, regional and national levels. We compare the proposed approach with another using Tabu search heuristic.

Optimal dimensioning of pipe networks: the new situation when the distribution and the transportation functions are disconnected

De Wolf and Smeers [9] consider the problem of the optimal dimensioning of a gas transmission network when the topology of the network is known. The pipe diameters must be chosen to minimize the sum of the investment and operating costs. This model does not reflect any more the current situation on the gas industry. Today, the transportation function and gas buying function are separated. This work considers the new situation for the transportation company. We present here first results obtained on the belgian gas network and on a part of the french network.

A Dynamic User Equilibrium Model for Traffic Assignment in Urban Areas

In this paper, we present a model for dynamic traffic assignment in urban transportation networks. The transportation demand is given by the number of users traveling from the same origin to the same destination and having the same desired arrival time. The model determines for each user both the path and the departure time so that he cannot decrease his disutility by unilaterally changing his departure time or/and his path. The disutility measure is given by a generalized travel time function taking into account total path travel time and schedule delays. Departure time choices are restricted to a finite set of instants, but users with same choice of departure time and same first arc on selected path are loaded uniformly on the network during a time interval whose lower bound is the chosen departure time. A finite dimensional variational inequality formulation of the problem is given and the existence of a dynamic user equilibrium is proved. A heuristic method is proposed to compute a dynamic user equilibrium. Numerical results are provided.

Using column generation to solve a coal blending problem

In this paper, we formulate and solve a real life coal blending problem using a Column Generation Approach. The objective of the model is to prescribe optimal mixes of coal to produce coke. The problem is formulated as a mixed integer program. It involves various types of constraints arising from technical considerations of the blending process. The model also incorporates nonlinear constraints. It results in a large-scale problem that cannot be solved by classical operations research methods. Defining three heuristic methods based on column generation techniques, this paper proposes reasonable solutions for the industry.