MARCELO DA SILVA ROCHA

MARCELO DA SILVA ROCHA

(Fonte: Lattes)

Resumo

Possui graduação em Engenharia Civil pela Universidade Federal de Juiz de Fora (1996), mestrado em Engenharia Civil pela Universidade Estadual de Campinas (1998) e doutorado em Engenharia Mecânica pela Universidade de São Paulo (2005). Realizou estágio de pós-doutorado em Engenharia Mecânica na Universidade de São Paulo (2007) e em Engenharia Nuclear no Instituto de Pesquisas Energéticas e Nucleares (2009). Atualmente é Pesquisador Adjunto do Centro de Engenharia Nuclear (CEENG) do Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN). Atua como docente e pesquisador nas áreas de termohidráulica de reatores, energias renováveis, interação fluido-estrutura e aplicações de nanotecnologia. (Texto extraído do Currículo Lattes em 16 nov. 2021)

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Classification of natural circulation two-phase flow image patterns based on self-organizing maps of full frame DCT coefficients
2018 - MESQUITA, ROBERTO N. de; CASTRO, LEONARDO F.; TORRES, WALMIR M.; ROCHA, MARCELO da S.; UMBEHAUN, PEDRO E.; ANDRADE, DELVONEI A.; SABUNDJIAN, GAIANE; MASOTTI, PAULO H.F.
Many of the recent nuclear power plant projects use natural circulation as heat removal mechanism. The accuracy of heat transfer parameters estimation has been improved through models that require precise prediction of two-phase flow pattern transitions. Image patterns of natural circulation instabilities were used to construct an automated classification system based on Self-Organizing Maps (SOMs). The system is used to investigate the more appropriate image features to obtain classification success. An efficient automated classification system based on image features can enable better and faster experimental procedures on two-phase flow phenomena studies. A comparison with a previous fuzzy inference study was foreseen to obtain classification power improvements. In the present work, frequency domain image features were used to characterize three different natural circulation two-phase flow instability stages to serve as input to a SOM clustering algorithm. Full-Frame Discrete Cosine Transform (FFDCT) coefficients were obtained for 32 image samples for each instability stage and were organized as input database for SOM training. A systematic training/test methodology was used to verify the classification method. Image database was obtained from two-phase flow experiments performed on the Natural Circulation Facility (NCF) at Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN), Brazil. A mean right classification rate of 88.75% was obtained for SOMs trained with 50% of database. A mean right classificationrate of 93.98% was obtained for SOMs trained with 75% of data. These mean rates were obtained through 1000 different randomly sampled training data. FFDCT proved to be a very efficient and compact image feature to improve image-based classification systems. Fuzzy inference showed to be more flexible and able to adapt to simpler statistical features from only one image profile. FFDCT features resulted in more precise results when applied to a SOM neural network, though had to be applied to the full original grayscale matrix for all flow images to be classified.
Heat transfer mode in the core of the Angra 2 nuclear power plant during small break loca obtained with RELAP5 code
2013 - SABUNDJIAN, GAIANE; BELCHIOR JUNIOR, ANTONIO; CONTI, THADEU das N.; ROCHA, MARCELO da S.; ANDRADE, DELVONEI A. de; TORRES, WALMIR M.; MACEDO, LUIZ A.; UMBEHAUN, PEDRO E.; MESQUITA, ROBERTO N. de; LIMA, ANA C. de S.
This work aims to identify the heat transfer mode with RELAP5/MOD3.2.gama code in the core of Angra 2 facility. The postulate accident is the Loss of Coolant Accident (LOCA) in the primary circuit for Small Break (SB), which is described in Chapter 15 of the Final Safety Analysis Report of Angra 2 (FSAR). The accident consists basically of the total break of the cold leg of Angra 2 facility. The rupture area considered was 380 cm2, which represents 100% of the primary circuit pipe °ow area. The Emergency Core Cooling System (ECCS) e±ciency is also tested in this accident. In this simulation, failure and repair criteria are adopted for the ECCS components in order to verify the system operation e±ciency - preserving the integrity of the reactor core and guaranteeing its cooling - as expected by the project design. SBLOCA accidents are characterized by a fast blowdown in the primary circuit to values that activate the low pressure injection system followed by the water injection from the accumulators. The thermal-hydraulic processes inherent to the accident phenomenon, such as hot leg vaporization and consequently core vaporization cause inappropriate °ow distribution in the reactor core that can lead to reduction in the core liquid level, up to the point that the ECCS is able to re°ood it. This work shows the mode numbers and the wall convection heat transfer used in the RELAP5 code that were accessed during the execution of the program. The results showed that the numerical simulations with RELAP5 were satisfactory and that the ECCS worked e±ciently, guaranteeing the integrity of the reactor core.
The behaviour of ANGRA 2 nuclear power plant core for a small break LOCA simulated with RELAP5 code
2012 - SABUNDJIAN, GAIANE; ANDRADE, DELVONEI A.; BELCHIOR JUNIOR, ANTONIO; ROCHA, MARCELO da S.; CONTI, THADEU das N.; TORRES, WALMIR M.; UMBEHAUN, PEDRO E.; MESQUITA, ROBERTO N.; MASOTTI, PAULO H.F.
The behavior of ANGRA 2 nuclear power plant core for a small break LOCA simulated with RELAP5 code
2013 - SABUNDJIAN, GAIANE; ANDRADE, DELVONEI A.; BELCHIOR JUNIOR, ANTONIO; ROCHA, MARCELO da S.; CONTI, THADEU N.; TORRES, WALMIR M.; MACEDO, LUIZ A.; UMBEHAUN, PEDRO E.; MESQUITA, ROBERTO N.; MASOTTI, PAULO H.F.; LIMA, ANA C. de S.