Baburaj A. Puthenveettil

Bio: Baburaj A. Puthenveettil is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Rayleigh number & Natural convection. The author has an hindex of 10, co-authored 31 publications receiving 327 citations. Previous affiliations of Baburaj A. Puthenveettil include Indian Institute of Science.

Scaling in concentration-driven convection boundary layers with transpiration

Abstract: We study concentration-driven natural convection boundary layers on horizontal surfaces, subjected to a weak, surface normal, uniform blowing velocity within the boundary layer. We then show that the above profile matches the experimentally observed mean concentration profile within the boundary layers that form on the top surface of a membrane, when a weak flow is forced gravitationally from below the horizontal membrane that has brine above it and water below it. A similar match between the theoretical scaling of the species boundary layer thickness and its experimentally observed variation is also shown to occur.

Horizontal velocity field near the hot plate in turbulent natural convection

Abstract: We study the velocity field in a horizontal (x-y) plane 1.5 mm above the hot plate in turbulent natural convection using PIV at a Rayleigh number Raw=106 and Prandtl number Pr=5.2. The plane of measurement is inside the velocity boundary layer estimated from the natural convection boundary layer equations[7] as well as inside the velocity boundary layer due to the large scale flow[2, 5].The boundary layer comprises of line plumes with sinking fluid between them. The instantaneous velocity variation from the center of the sinking fluid to the line plumes is found to deviate with the classical Prandtl-Blasius laminar boundary layer profile, which is assumed to be the nature of boundary layer by the GL theory [2, 5]. Our results agree well with the natural convection boundary layer profile. The time averaged mean velocity variation deviates from both natural convection and Blasius type profiles as expected as it depends on the orientation of the line plumes. Our measurement result is a proof to the theory of the presence of a natural convection boundary layer on both sides of a line plume [10].

Effect of Large-Scale Flow on the Boundary Layer Velocity Field in Turbulent Convection

Abstract: We study the effect of shear by the inherent large-scale flow in the bulk on the boundary layers on the hot plate in Rayleigh–Benard convection for a range of Prandtl numbers 4.69 ≤ Pr ≤ 5.88 and Rayleigh numbers 105 ≤ Ra ≤ 109. We observe that, at each Ra, at an instant, the distribution of horizontal velocities within the boundary layer in a horizontal plane is either of a unimodal nature or of a bimodal nature. Unimodal distributions occur either at low Ra or at high Ra while the bimodal distributions occur more at intermediate Ra. The peak of the unimodal distribution at low Ra occurs at values at around Vbl, the natural convection boundary layer velocity while the peak of the unimodal PDFs at high Ra occur at values greater than or equal to Vsh, the large-scale flow velocity. In the case of bimodal distributions, the first peak occurs in between Vbl and Vsh while the second peak occurs after Vsh. We show that the second peak of the bimodal distribution and the unimodal peak which occur at ≥Vsh scales as Vsh scales with Ra. The first peak of bimodal distribution and the single peak occurring at around Vbl scales with Ra as the natural convection boundary layer velocity forced by shear.

Shape and motion of drops in the inertial regime

Abstract: In this paper, we report experimental results on the shape and motion of a mercury droplet, placed in a horizontally rotating cylinder in the rpm range 8-93, so that the Reynolds number of the drop 2500

Boundary Layer Theory

Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Heat transfer and large scale dynamics in turbulent Rayleigh-Bénard convection

Abstract: The progress in our understanding of several aspects of turbulent Rayleigh-Benard convection is reviewed. The focus is on the question of how the Nusselt number and the Reynolds number depend on the Rayleigh number Ra and the Prandtl number Pr, and on how the thicknesses of the thermal and the kinetic boundary layers scale with Ra and Pr. Non-Oberbeck-Boussinesq effects and the dynamics of the large scale convection roll are addressed as well. The review ends with a list of challenges for future research on the turbulent Rayleigh-Benard system.

Small-Scale Properties of Turbulent Rayleigh-Bénard Convection

Abstract: The properties of the structure functions and other small-scale quantities in turbulent Rayleigh-Benard convection are reviewed, from an experimental, theoretical, and numerical point of view. In particular, we address the question of whether, and if so where in the flow, the so-called Bolgiano-Obukhov scaling exists, i.e., Sθ(r) ∼ r2/5 for the second-order temperature structure function and Su(r) ∼ r6/5 for the second-order velocity structure function. Apart from the anisotropy and inhomogeneity of the flow, insufficiently high Rayleigh numbers, and intermittency corrections (which all hinder the identification of such a potential regime), there are also reasons, as a matter of principle, why such a scaling regime may be limited to at most a decade, namely the lack of clear scale separation between the Bolgiano length scale LB and the height of the cell.

New perspectives in turbulent Rayleigh-Bénard convection.

Abstract: Recent experimental, numerical and theoretical advances in turbulent Rayleigh-Benard convection are presented. Particular emphasis is given to the physics and structure of the thermal and velocity boundary layers which play a key role for the better understanding of the turbulent transport of heat and momentum in convection at high and very high Rayleigh numbers. We also discuss important extensions of Rayleigh-Benard convection such as non-Oberbeck-Boussinesq effects and convection with phase changes.