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The application of the Immersed Boundary ͑IB͒ method to simulate incompressible, turbulent flows around complex configurations is illustrated; the IB is based on the use of non-body conformal grids, and the effect of the presence of a body in the flow is accounted for by modifying the governing equations. Turbulence is modeled using standard… (More)

- M D de Tullio, L Afferrante, G Demelio, G Pascazio, R Verzicco
- Journal of biomechanics
- 2011

Two different aortic prostheses can be used for performing the Bentall procedure: a standard straight graft and the Valsalva graft that better reproduces the aortic root anatomy. The aim of the present work is to study the effect of the graft geometry on the blood flow when a bileaflet mechanical heart valve is used, as well as to evaluate the stress… (More)

- Jin-Qiang Zhong, Richard J A M Stevens, Herman J H Clercx, Roberto Verzicco, Detlef Lohse, Guenter Ahlers
- Physical review letters
- 2009

Experimental and numerical data for the heat transfer as a function of the Rayleigh, Prandtl, and Rossby numbers in turbulent rotating Rayleigh-Bénard convection are presented. For relatively small Ra approximately 10(8) and large Pr modest rotation can enhance the heat transfer by up to 30%. At larger Ra there is less heat-transfer enhancement, and at… (More)

- R P J Kunnen, H J H Clercx, B J Geurts, L J A van Bokhoven, R A D Akkermans, R Verzicco
- Physical review. E, Statistical, nonlinear, and…
- 2008

Direct numerical simulation and stereoscopic particle image velocimetry of turbulent convection are used to gather spatial data for the calculation of structure functions. We wish to add to the ongoing discussion in the literature whether temperature acts as an active or passive scalar in turbulent convection, with consequences for structure-function… (More)

- Guenter Ahlers, Eberhard Bodenschatz, +5 authors Roberto Verzicco
- Physical review letters
- 2012

We report results for the temperature profiles of turbulent Rayleigh-Bénard convection (RBC) in the interior of a cylindrical sample of aspect ratio Γ≡D/L=0.50 (D and L are the diameter and height, respectively). Both in the classical and in the ultimate state of RBC we find that the temperature varies as A×ln(z/L)+B, where z is the distance from the bottom… (More)

- M D de Tullio, G Pascazio, L Weltert, R De Paulis, R Verzicco
- Philosophical transactions. Series A…
- 2011

The in vivo evaluation of prosthetic device performance is often difficult, if not impossible. In particular, in order to deal with potential problems such as thrombosis, haemolysis, etc., which could arise when a patient undergoes heart valve replacement, a thorough understanding of the blood flow dynamics inside the devices interacting with natural or… (More)

- Erwin P van der Poel, Rodolfo Ostilla-Mónico, Roberto Verzicco, Detlef Lohse
- Physical review. E, Statistical, nonlinear, and…
- 2014

The effect of various velocity boundary condition is studied in two-dimensional Rayleigh-Bénard convection. Combinations of no-slip, stress-free, and periodic boundary conditions are used on both the sidewalls and the horizontal plates. For the studied Rayleigh numbers Ra between 10(8) and 10(11) the heat transport is lower for Γ=0.33 than for Γ=1 in case… (More)

(Received ?? and in revised form ??) Results from direct numerical simulations for three dimensional Rayleigh-Bénard con-vection in a cylindrical cell of aspect ratio 1/2 and P r = 0.7 are presented. They span five decades of Ra from 2 × 10 6 to 2 × 10 11. Good numerical resolution with grid spacing ∼ Kolmogorov scale turns out to be crucial to accurately… (More)

- Luca Weltert, Marco D de Tullio, +5 authors Ruggero De Paulis
- Interactive cardiovascular and thoracic surgery
- 2013

OBJECTIVES
In the belief that stress is the main determinant of leaflet quality deterioration, we sought to evaluate the effect of annular and/or sino-tubular junction dilatation on leaflet stress. A finite element computer-assisted stress analysis was used to model four different anatomic conditions and analyse the consequent stress pattern on the aortic… (More)

- Rajaram Lakkaraju, Richard J A M Stevens, +4 authors Detlef Lohse
- Physical review. E, Statistical, nonlinear, and…
- 2012

We numerically investigate the radial dependence of the velocity and temperature fluctuations and of the time-averaged heat flux j ¯(r) in a cylindrical Rayleigh-Bénard cell with aspect ratio Γ=1 for Rayleigh numbers Ra between 2×10^{6} and 2×10^{9} at a fixed Prandtl number Pr=5.2. The numerical results reveal that the heat flux close to the sidewall is… (More)