BAGUS NUGROHO
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  • Home
  • Biography
  • Qualifications
  • Publications
  • Research
    • Research Topics >
      • Converging - Diverging Riblets
      • Surface Roughness
      • Ship Biofoulings
      • Mars Supersonic Parachute
      • Unmanned Combat Aerial Vehicle
      • Submarine Hydrodynamics
      • Destroyer Ship Aerodynamics
      • Vortex Generator For Flow Control
    • Research Fundings
    • Research Collaborations
  • University Teaching
  • Thermography
  • Outreach Activities
    • High-school engineering competition
    • Election Supervisory Committee
    • Indonesian Student Association in Australia
    • Election Committee
  • Galleries
    • Fluid Mechanics Arts >
      • Art gallery 1
      • Art gallery 2
      • Art gallery 3
    • Airshow Photos
  • In media
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​​​​Converging - Diverging Riblets

Inspired by the microscopic skin topology of fast swimming sharks, a unique class of directional surfaces arranged in a converging-diverging (herringbone) pattern are studied experimentally in a zero pressure gradient turbulent boundary layers. Measurements  show that these small surfaces are able to generate large-scale counter rotating roll-modes/vortices within the turbulent boundary layer, resulting in dramatic spanwise variation in the boundary layer thickness (50% variation for the strongest case).  The strong perturbation effect from these surfaces to the overall flow dynamics seems unusual, considering that their peak-to-trough height is approximately only 1% of the boundary layer thickness.
AIM
To investigate the effect of converging-diverging riblet-type surface roughness on zero pressure gradient turbulent boundary layers.
METHODS
The experiments are performed in an open-return blower wind-tunnel located in the Walter Basset Aerodynamics Laboratory at The University of Melbourne. The measurements are performed using single-normal Hot-Wires and Cross-wires mounted to an automated two-dimensional traverse capable of moving in both the spanwise and wall-normal directions. A series of riblet tiles are manufactured to cover the entire test section of the wind-tunnel.​
RESULTS
Kevin, J.P. Monty, H. Ba, G. Pathokinda, B. Nugroho, J. Barros, K. Christensen, N. Hutchins (2017) Cross-stream stereoscopic PIV of a modified turbulent boundary layer over directional surface pattern. Journal of Fluid Mechanics. 813:412-435.

B. Nugroho, N. Hutchins, J.P. Monty (2013) Large-scale spanwise periodicity in a turbulent boundary layer induced by highly ordered and directional surface roughness.  International Journal of Heat and Fluid Flow.  41:90-102.

A Mohammadikarachi, M. Z. Yousif, B Nugroho, H. C Lim. (2024) An exhaustive review of studies on bio-inspired convergent–divergent riblets. Ocean Engineering. 295, 116965

Experiment figures

Headline figure courtesy of Jung Hoon Lee, click the link below for full video
http://dx.doi.org/10.1103/APS.DFD.2014.GFM.V0054
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