Guido Buzzi-Ferraris

BzzMath: Library Overview and Recent Advances in Numerical Methods

Abstract This paper gives an overview of the numerical methods included in BzzMath library. The library is written in C++, exploits the features of object-oriented programming, and is free for non-commercial applications at www.chem.polimi.it/homes/gbuzzi .

A Combination of Parallel Computing and Object-Oriented Programming to Improve Optimizer Robustness and Efficiency

Abstract This research activity is mainly aimed at showing potentialities in coupling object-oriented programming with parallel computing. Wide margins of benefits could be obtained in algorithm efficiency and robustness with a relative small programming effort. The case of unconstrained multi-dimensional optimization is proposed as quantitative example.

Outlier detection in large data sets

Abstract In this paper we propose a method for correctly detecting outliers based on a new technique developed to simultaneously evaluate mean, variance and outliers. This method is capable of self-regulating its robustness to suit the experimental data set under analysis, so as to overcome shortcomings of: (i) nonrobust methods such as the least sum of squares; (ii) the need of the user in defining a trimmed sub-set of experimental points such as in least trimmed sum of squares; and (iii) the possibility to read the data set only once to evaluate the mean, variance, and outliers of a population by preserving robustness.

Criteria for Outliers Detection in Nonlinear Regression Problems

Abstract This research activity deals with robust methods for parameters estimation of nonlinear models and the outliers detection. It specifically discusses some advances in criteria to discriminate among gross errors, bad experimental design, and inadequate model selection. All the methods and the criteria proposed in this work are implemented in BzzMath library, a free scientific tool to solve numerical problems.

Process Dynamic Optimization Using ROMeo

Abstract The present research activity is aimed at demonstrating the feasibility of dynamic realtime optimization (D-RTO) on the industrial scale. Some well-established and field-proven tools, such as ROMeo™ for real-time optimization (RTO) and DynSim™ for dynamic simulation, are combined with very performing solvers for differential systems (BzzMath library) and specific methods (multiple shooting) to obtain a full-integrated solution for D-RTO. A steam-cracking furnace is selected as validation case: the SPYRO® -based dynamic simulation is developed using FORTRAN, C++, and DynSim™ and it is integrated in ROMeo™ to perform the D-RTO. A quantitative comparison between the traditional RTO and the D-RTO is also provided.

Total plant integrated optimization of sulfur recovery and steam generation for Claus processes using detailed kinetic schemes

Abstract Multiscale process modeling is very appealing methodology for process optimization since it highlights certain issues that remain unexplored with conventional methodologies and debottlenecks certain potentialities that remain unexploited in chemical plants. In this work, a kinetic model with 2400 reactions and 140 species is implemented in a proper reactor network to characterize the thermal furnace and the waste heat boiler of sulfur recovery units; the network with detailed kinetics is the kernel of a Claus process simulation that include all the unit operations and the catalytic train. By doing so, reliable estimation of acid gas conversion, elemental sulfur recovery, and steam generation is achieved with the possibility to carry out an integrated process-energy optimization at the total plant scale.

Better Reformulation of Kinetic Models

Abstract This short note proposes two model reformulations to improve the Hougen–Watson mathematical form of kinetic models and validate them on a typical heterogeneous kinetic problem.

The solution of very large non-linear algebraic systems

Abstract The manuscript discusses the feasibility and the methods for solving systems of non-linear algebraic equations, the main numerical subjects being convergence tests, stop criteria, and expedients for large and sparse systems. After a detailed discussion on the features of large non-linear systems, the paper focuses on the numerical simulation of complex combustion devices and on the formation of macro- and micro-pollutants. This quantification is not possible by simply introducing a detailed kinetic scheme into a fluid dynamics (CFD) code, especially when considering turbulent flows. Actually, the resulting problem would reach a so huge dimension that is still in orders of magnitude larger than the feasible one (by means of modern computing devices). To overcome this obstacle it is possible to implement a separate and dedicated kinetic post-processor (KPP) that, starting from the CFD output data, allows simulating numerically the turbulent reactive systems by means of a detailed kinetic scheme. The resulting numerical problem consists of a very large, non-linear algebraic system comprising a few millions of unknowns and equations. The manuscript describes the KPP organization and structure as well as the numerical challenges and difficulties that one has to overcome to get the final numerical solution.

New trends in building numerical programs

This manuscript focuses the attention on the possibility that some basic programs for solving numerical problems have to be revised. The fundamental case of linear system solution and related concepts is proposed as example of the different ways to approach a problem using object-oriented programming and procedural approaches. vailable online 13 July 2010 eywords: bject-oriented programming arallel computing inear systems The different points of view shows that the traditional approach adopted to deem the conditioning of a system as well as all existing programs to solve linear systems need to be revised. A brief discussion deals with the possibility of parallelizing programs for personal computers and with interaction of parallel computing and object-oriented programming.

Modelling in the documentation level using mosaic and numerical libraries

In the today’s constellation of globally operating enterprises, the workforce is locally decentralized. Engineering tasks are increasingly divided up under several work groups that are situated at different premises. Information technology is used to coordinate the collaboration and to merge the results. Due to its versatility and adaptability, the cooperation on the Internet becomes increasingly important. One key issue in this development is the placement of applications in the Internet (cloud computing). Another important issue is the centralized access of cooperative results. Such centralized information may be stored in internet-based knowledge databases. With regard to the above developments, it seems to make sense to have a modelling environment working as a web application connected to a model database. Such a modelling environment should be linked to a strong numeric library. Such a library should contain reliable and very performing algorithms for solving ordinary differential equation (ODE) systems and differential and algebraic equation (DAE) systems. It should also be able to automatically recognize the sparsity and the structure of the Jacobians and to automatically select the best set of algorithms to integrate the differential system. By the help of these measures the computational time should be reduced significantly. In this contribution the MOSAIC modelling environment and the BzzMath library are presented and some main characteristics are described.