Study of Surface Roughness Effect on a Bluff Body—The Formation of Asymmetric Separation Bubbles

Alex Mendonça Bimbato, Luiz Antonio Alcântara Pereira and Miguel Hiroo Hirata
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Alex Mendonça Bimbato: School of Engineering, São Paulo State University (UNESP), Guaratinguetá SP 12.516-410, Brazil
Luiz Antonio Alcântara Pereira: Mechanical Engineering Institute, Federal University of Itajubá (UNIFEI), Itajubá MG 37.500-903, Brazil
Miguel Hiroo Hirata: Faculty of Technology, State University of Rio de Janeiro (FAT-UERJ), Resende RJ 27.537-000, Brazil

Energies, 2020, vol. 13, issue 22, 1-20

Abstract: Turbulent flows around bluff bodies are present in a large number of aeronautical, civil, mechanical, naval and oceanic engineering problems and still need comprehension. This paper provides a detailed investigation of turbulent boundary layer flows past a bluff body. The flows are disturbed by superficial roughness effect, one of the most influencing parameters present in engineering applications. A roughness model, recently developed by the authors, is here employed in order to capture the main features of these complex flows. Starting from subcritical Reynolds number simulations (Re = 1.0 × 10 5 ), typical phenomena found on critical and supercritical flow regimes are successfully captured, like non-zero lift force and its direction change, drag crisis followed by a gradual increase on this force, and separation and stagnation points displacement. The main contribution of this paper is to present a wide discussion related with the temporal history of aerodynamic loads of a single rough circular cylinder capturing the occurrence of asymmetric separation bubbles generation. The formation of asymmetric separation bubbles is an intrinsic phenomenon of the physical problem, which is successfully reported by our work. Unfortunately, there is a lack of numerical results available in the literature discussing the problem, which has also motivated the present paper. Previous study of our research group has only discussed the drag crisis, without to investigate its gradual increase and the change on lift force direction. Our results again confirm that the Lagrangian vortex method in association with Large-Eddy Simulation (LES) theory enables the development of two-dimensional roughness models.

Keywords: bluff body aerodynamics; roughness model; boundary layer separation; vortex shedding; Lagrangian vortex method (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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