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The structure of energy-containing turbulence in the outer region of a zero-pressure-gradient boundary layer has been studied using particle image velocimetry (PIV) to measure the instantaneous velocity fields in a streamwise-wall-normal plane. Experiments performed at three Reynolds numbers in the range 930 < Re θ < 6845 show that the boundary layer is(More)
Aortic pathologies such as coarctation, dissection, and aneurysm represent a particularly emergent class of cardiovascular diseases. Computational simulations of aortic flows are growing increasingly important as tools for gaining understanding of these pathologies, as well as for planning their surgical repair. In vitro experiments are required to validate(More)
Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the(More)
The precise dynamics of breakdown in pipe transition is a century-old unresolved problem in fluid mechanics. We demonstrate that the abruptness and mysteriousness attributed to the Osborne Reynolds pipe transition can be partially resolved with a spatially developing direct simulation that carries weakly but finitely perturbed laminar inflow through gradual(More)
It has been known for over six decades that the dissolution of minute amounts of high molecular weight polymers in wall-bounded turbulent flows results in a dramatic reduction in turbulent skin friction by up to 70%. First principles simulations of turbulent flow of model polymer solutions can predict the drag reduction (DR) phenomenon. However, the(More)
Experiments are performed in Taylor-Couette flow where the inner-cylinder angular velocity is modulated in time about zero mean. eory and nonlinear computations have previously found this case to be characterized by two competing modes. Both are axisymmetric and synchronous with the modulation, but have different spatio-temporal symmetries and axial(More)
A simple experiment demonstrates that an average vertical force can be produced by a small vibrator motor attached to a frame constrained to slide vertically on guide wires. The vertical force produced is sufficient to make the sliding element hover, similarly to a biologically inspired robotic insect. We show that this effect depends on the natural(More)