This work presents the development of a computational algorithm applied to improve the thermal behaviour in the secondary cooling zone of steel billets and blooms produced by continuous casting. A mathematical solidification heat transfer model works integrated with a neural network based algorithm (NNBA) connected to a knowledge base of boundary conditions of operational parameters and metallurgical constraints. The improved strategy selects a set of cooling conditions (in the secondary cooling zone) and metallurgical criteria established to attain high product quality, which are related to a more homogeneous thermal behaviour during solidification. Initially, the results of simulations performed by using the mathematical model are validated against experimental industrial data, and good agreement is observed, in any case examined, permitting the determination of nominal heat transfer conditions by the inverse heat conduction method. By using the numerical model linked to a NNBA results have been produced determining a set of casting conditions, which has permitted better strand surface temperature profile and metallurgical length to be attained during the continuous casting of SAE 1007 billets and SAE 1025 blooms.
The objective of this article is to identify a model able to represent the first harmonic behavior of a rigid cylinder undergoing VIV in the most different cases of a rigid cylinder supported by a spring/damper system. This analysis of the first harmonic behavior is made considering three different non-dimensional variables: the damping coefficient, the reduced velocity and the mass ratio. The challenge is to define a model that represents the changes on the lock-in zone considering the different combination of damping coefficient and mass ratio thus able to represent the different real systems. Two new phenomenological models using the Van der Pol oscillator are studied. They follow the framework of the phenomenological model proposed by Facchinetti et al.
This article presents an active control dedicated to a re-entry problem found in the offshore oil industry. The re-entry operation consists of connecting the bottom end of a very long pipeline to the wellhead, by dynamically modifying the pipeline top-end position, which is linked to a dynamically positioned vessel (DPV). Such long pipelines are usually called risers, because they are used to make the drilling mud or the hydrocarbons rise from the wellhead to the platform. Nowadays, the re-entry operation is often done manually. The use of an active control intends to reduce the operation time and to make it possible even under bad weather conditions. The considered subsea structure can be viewed as a cable submerged in a flow and modelled by the Bernoulli's cable equation, completed with a damping factor, that linearly depends on the structure speed. After some simplifications that are justified in our context, the corresponding model turns out to be differentially flat, a useful property for control design, providing an extension of previous works.
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