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The plume produced by a cluster of two high area-ratio thrust optimized parabolic contour nozzles is visualized by way of retroreflective shadowgraphy. Both steady and transient operations of the nozzles (start-up and shut-down) were conducted in the anechoic chamber and high speed flow facility at The University of Texas at Austin. Both nozzles...conference paper 2015
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We present some preliminary results of direct numerical simulations of three-dimensional, temporal, plane mixing layers with variable density. The simulations are run with a parallel in-house code that solves the Navier-Stokes equations in the Low-Mach number approximation, using a novel algorithm based on an extended version of the velocity...conference paper 2015
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Direct numerical simulations (DNS) of inertial wave attractors have been carried out in a librating Taylor-Couette system with broken mirror symmetry in the radial-axial cross-section. The inertial wave excitation mechanism and its localisation at the edges was clarified by applying boundary layer theory. Additional resonance peaks in the...conference paper 2015
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We report on measurements of the ultimate-state transition in turbulent Rayleigh-B\'enard convection obtained in a large facility known as the ``Uboot of G\"ottingen" and using pressurized sulfur hexafluoride as the convecting fluid. We found that the transition occurs over a range of $Ra$ which becomes more narrow as $\Gamma$ increases, ranging...conference paper 2015
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The evolution of coherent structures in a flat plate boundary layer transition induced by the cylinder wake is investigated using the particle image velocimetry (PIV) technique. The finite-time Lyapunov exponent (FTLE), which characterizes the amount of stretching about the flow trajectory, is used to extract the Lagrangian coherent structures....conference paper 2015
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We present direct numerical simulations of Taylor-Couette flow with grooved walls up to inner cylinder Reynolds number of $Re_i=3.76\times10^4$, corresponding to Taylor number of $Ta=2.15\times10^9$. The simulations are performed at a fixed radius ratio $\eta=r_i/r_o=0.714$. The grooves are axisymmetric V-shaped obstacles attached to the wall...conference paper 2015
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The turbulent Couette flow with a forward-facing step (sudden contraction) is investigated experimentally and numerically. The particle image velocimetry (PIV) measurement and direct numerical simulation (DNS) prove peculiar turbulence behavior, the counter-gradient diffusion of the Reynolds stress, near the front part of the corner separation...conference paper 2015
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Buoyant, turbulent convective heat transfer around cylindrical rods arranged in bundles is a technically relevant heat transfer configuration which finds application in steam generators, cooling of reactor core fuel assemblies and heat exchangers in general. Most of the research performed so far considered forced convection conditions on...conference paper 2015
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Abstract Influence of small-scale turbulence on cloud droplets spatial distribution was analyzed by examination of motion of inertial droplets in a simple model of a vortex tube aligned at arbitrary angle to gravity force. Both analytical calculations and numerical simulations demonstrated characteristic features of the motion such as...conference paper 2015
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We present a unifying solution framework for the linearized gas-dynamical equations for a two-dimensional (2-D) linearly-sheared unbounded homentropic compressible flow using Lie symmetry classification. The full set of symmetries that are admitted by the underlying system of equations are employed to systematically derive three distinct...conference paper 2015
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Recent experimental results on large scale coherent steady states observed in experimental turbulent von Kármán flows are revisited from a statistical mechanics perspective. We argue that the coherent steady states may be described as the equilibrium states of ad hoc lattice models, that can be used to define global properties of von Kármán...conference paper 2015
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The so-called alpha-effect for large scale fields occurring in turbulent MHD flows is a typically invoked mechanism for mean field generation in all astrophysical objects such as stars, planets, accretions disks, galaxies etc. Although the resistivity of the fluid tends to damp the magnetic fields growth it is helpful in generation of the large...conference paper 2015
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Direct numerical simulations (DNS) have been performed in order to investigate the interaction of freestream turbulence and crossflow generated instability on a swept wing. The experiments by [3] and [1] are selected as the reference cases. In those experiments the authors explore the interaction between different freestream turbulence...conference paper 2015
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Two-phase Taylor-Couette flow is simulated using the Euler-Lagrange approach, where the dispersed phase is treated as point particles with effective forces such as drag, lift, added mass and buoyancy acting on them. Two-way coupling is implemented between the carrier and the dispersed phase allowing us to study the interaction between the point...conference paper 2015
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In the presence of solid-body rotation and density stratification, turbulent flows may exhibit an inverse as well as a direct cascade. We investigate the role of turbulence and waves in these energy cascades, focusing on the inverse cascade. This is done through a normal mode decomposition of the dynamical fields in a set of direct numerical...conference paper 2015
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Colliding droplets or particles in turbulent flows are important in applications ranging from rain formation in clouds to aerosol production in process engineering. To reduce the computational costs when simulating such flows, kinematic simulation (KS) is frequently applied as a cheap surrogate for direct numerical simulation (DNS) of the...conference paper 2015
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We report a new thermal boundary layer equation for turbulent Rayleigh-Benard convection for Prandtl number P>1that takes into account the effect of turbulent fluctuations. These fluctuations are neglected in existing equations, which are based on steady-state and laminar assumptions. Using this new equation, we derive analytically the mean...conference paper 2015
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We analyze one-way coupling DNS of heavy particles in homogeneous turbulent flow over a large range of Stokes numbers at Rλ= 180. We focus on preferential concentration and clustering aspects, and more particularly on their dynamical properties.conference paper 2015
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Direct numerical simulations of the fully developed turbulent flow through a porous channel and duct are performed based on the spectral element code Nek5000. The volume-averaged Navier-Stokes (VANS) equations are implemented in order to describe the flow in the composite medium. The numerical simulations of the VANS equations are carried out at...conference paper 2015
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We report on measurements of the mean-flow Reynolds number ReU and the rms fluctuation Reynolds number ReV in turbulent Rayleigh-Bénard convection as a function of the Rayleigh number Ra for 4 x 1011 < Ra < 2 1014 and Pr ' 0:8. Both can be described by the same power law with an effective exponent = 0:44, in agreement with predictions for ReU...conference paper 2015