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Now showing items 21-40 of 51

    • From travelling waves to mild chaos: a supercritical bifurcation cascade in pipe flow 

      Mellibovsky Elstein, Fernando; Eckhardt, Bruno (2012-10-25)
      Article
      Restricted access - publisher's policy
      We study numerically a succession of transitions in pipe Poiseuille flow that leads from simple travelling waves to waves with chaotic time-dependence. The waves at the origin of the bifurcation cascade possess a shift-reflect ...

    • Fully nonlinear mode competition in magnetised Taylor-Couette flow 

      Ayats López, Roger; Deguchi, Kengo; Mellibovsky Elstein, Fernando; Meseguer Serrano, Álvaro (2020-08-25)
      Article
      Open Access
      We study the nonlinear mode competition of various spiral instabilities in magnetised Taylor-Couette flow. The resulting finite-amplitude mixed-mode solution branches are tracked using the annular-parallelogram periodic ...

    • Histeretical behaviour of two-dimensional vortex shedding past the NACA0012 airfoil at ultra-low Reynolds number 

      Mellibovsky Elstein, Fernando (2022)
      Conference report
      Open Access
      We unfold the complex transition route from steady to chaotic dynamics of the two-dimensional flow past the NACA0012 airfoil upon increasing the angle of attack a at the ultra-low Reynolds number Re = 5300. Hopf, forward ...

    • Instability mechanisms and transition scenarios of spiral turbulence in Taylor-Couette flow 

      Meseguer Serrano, Álvaro; Mellibovsky Elstein, Fernando; Àvila Cañellas, Marc; Marqués Truyol, Francisco (2009-10)
      Article
      Open Access
      Alternating laminar and turbulent helical bands appearing in shear flows between counterrotating cylinders are accurately computed and the near-wall instability phenomena responsible for their generation identified for the ...

    • Large eddy simulation of optimal synthetic jet actuation on a SD7003 airfoil in post-stall conditions 

      Monshi Tousi, Navid; Bergadà Granyó, Josep Maria; Mellibovsky Elstein, Fernando (2022-08)
      Article
      Open Access
      Aerodynamic performances may be optimised by the appropriate tuning of Active Flow Control (AFC) parameters. For the first time, we couple Genetic Algorithms (GA) with an unsteady Reynolds-Averaged Navier-Stokes (RANS) ...

    • Mean structure of the supercritical turbulent spiral in Taylor–Couette flow 

      Wang, Baoying; Mellibovsky Elstein, Fernando; Ayats López, Roger; Deguchi, Kengo; Meseguer Serrano, Álvaro (Royal Society, 2023-03-13)
      Article
      Open Access
      The large-scale laminar/turbulent spiral patterns that appear in the linearly unstable regime of counter-rotating Taylor–Couette flow are investigated from a statistical perspective by means of direct numerical simulation. ...

    • NACA 2412 performance modification via using AFC 

      Summ, Thorsten; Prakash, Bhanu; Bergadà Granyó, Josep Maria; Wierschem, Andreas; Mellibovsky Elstein, Fernando (2017)
      Conference report
      Restricted access - publisher's policy
      The NACA 2412 profile was numerically studied via employing 2D-DNS and implementing Active Flow Control (AFC), the Reynolds number considered was 6757, being the angle of attack of 8º. Initially, the basic flow without ...

    • New applications of numerical simulation based on lattice Boltzmann method at high Reynolds numbers 

      An, Bo; Bergadà Granyó, Josep Maria; Mellibovsky Elstein, Fernando; Sang, WM (2020-03-15)
      Article
      Restricted access - publisher's policy
      In order to study the flow behavior at high Reynolds numbers, two modified models, known as the multiple-relaxation-time lattice Boltzmann method (MRT-LBM) and large-eddy-simulation lattice Boltzmann method (LES-LBM), have ...

    • Numerical investigation on the flow around a square cylinder with an upstream splitter plate at low Reynolds numbers 

      An, Bo; Bergadà Granyó, Josep Maria; Mellibovsky Elstein, Fernando; Sang, W.M.; Xi, C. (2020-03-13)
      Article
      Open Access
      The present study focuses on the flow over a 2D square cylinder with a plate placed in front of it. An in-house code using the lattice Boltzmann method was employed for all the simulations presented. Few cases were simulated ...

    • Onset of temporal dynamics within a low reynolds-number laminar fluidic oscillator 

      Sarwar, Wasim; Bergadà Granyó, Josep Maria; Mellibovsky Elstein, Fernando (2021-02-18)
      Article
      Open Access
      We investigate the onset of temporal dynamics of a fluidic oscillator (FO) in the laminar regime at very low Reynolds number ( where and are the velocity and channel height at inlet, and is the kinematic viscosity of the ...

    • Optimization of synthetic jet actuation on a SD7003 airfoil in stall conditions 

      Monshi Tousi, Navid; El Mansy, Reda; Mellibovsky Elstein, Fernando; Bergadà Granyó, Josep Maria (2022)
      Conference report
      Open Access
      We optimise a set of Synthetic Jet (SJ) Active Flow Control (AFC) parameters on a SD7003 airfoil in order to maximise lift and aerodynamic efficiency. 2D-RANS with the Spallart Almaras (SA) turbulence model is employed in ...

    • Otterboard hydrodynamic performance testing in flume tank and wind tunnel facilities 

      Mellibovsky Elstein, Fernando; Prat Farran, Joana d'Arc; Notti, Emilio; Sala, Antonello (2018-02-01)
      Article
      Open Access
      © 2017 Elsevier LtdTwo pelagic otterboards, previously tested in a wind tunnel, have been tested in a flume tank prior to their analysis in real working conditions in sea trials. This intermediate step aims at providing ...

    • Parametric analysis of active flow control using steady suction and steady blowing 

      Prakash, Bhanu; Mellibovsky Elstein, Fernando; Bergadà Granyó, Josep Maria (2017)
      Conference report
      Restricted access - publisher's policy
      Active Flow Control is implemented over NACA 2412 airfoil using Steady Suctionand Steady Blowing techniques. The pre-stall angle of attack (AOA) 12 0 is studied at a high Reynolds number (Re chord ) of 3.1*10 6 for ...

    • Parametric analysis of the flow past a square cylinder in the interface of two different-velocity streams 

      Elmansy, Reda Mohamed Yousyf Abdallah; Bergadà Granyó, Josep Maria; Sarwar, Wasim; Mellibovsky Elstein, Fernando (2024-05-13)
      Article
      Open Access
      We address the linear stability of the two-dimensional incompressible flow past a square cylinder immersed in the wake of an upstream splitter plate, which separates two streams of different velocities, UT (top) and UB ...

    • PROPULSIÓ AERONÀUTICA (Examen parcial, 2n quadrimestre) 

      Mellibovsky Elstein, Fernando (Universitat Politècnica de Catalunya, 2024-04-02)
      Exam
      Restricted access to the UPC academic community

    • PROPULSIÓ AERONÀUTICA (Examen parcial, 2n quadrimestre) 

      Mellibovsky Elstein, Fernando (Universitat Politècnica de Catalunya, 2023-04-12)
      Exam
      Restricted access to the UPC academic community

    • Self-sustainment of coherent structures in counter-rotating Taylor-Couette flow 

      Wang, Baoying; Ayats, Roger; Deguchi, Kengo; Mellibovsky Elstein, Fernando; Meseguer Serrano, Álvaro (Cambridge University Press, 2022-11-25)
      Article
      Open Access
      We investigate the local self-sustained process underlying spiral turbulence in counter-rotating Taylor–Couette flow using a periodic annular domain, shaped as a parallelogram, two of whose sides are aligned with the ...

    • Shear instabilities in Taylor-Couette flow 

      Meseguer Serrano, Álvaro; Mellibovsky Elstein, Fernando; Marqués Truyol, Francisco; Àvila Cañellas, Marc (Springer, 2009-09-09)
      Conference lecture
      Restricted access - publisher's policy
      Subcritical instabilities in small gap Taylor-Couette (TCF) problem are studied numerically when both cylinders rotate in opposite directions. The computations are carried out for a radius ratio A first exploration is ...

    • Square cavity flow driven by two mutually facing sliding walls 

      An, Bo; Bergadà Granyó, Josep Maria; Sang, Weimin; Li, Dong; Mellibovsky Elstein, Fernando (2023-07)
      Article
      Open Access
      We investigate the flow inside a 2D square cavity driven by the motion of two mutually facing walls independently sliding at different speeds. The exploration, which employs the lattice Boltzmann method (LBM), extends on ...

    • Square cylinder downstream of two different-velocity streams 

      El Mansy, Reda; Monshi Tousi, Navid; Bergadà Granyó, Josep Maria; Mellibovsky Elstein, Fernando (2022)
      Conference lecture
      Open Access
      We study the flow past a square cylinder immersed in the wake of an upstream splitter plate separating two different-velocity streams. The bottom stream Reynolds number, ReB = 56 is kept constant for all cases, while the ...