Showing papers by "Manoochehr Koochesfahani published in 2017"
TL;DR: The experimental mean velocity profiles and their wall-normal derivatives up to second order are shown to convincingly agree with existing DNS data, including the apparent variations with Reynolds number.
Abstract: Physical interpretations and especially analytical considerations benefit from the ability to accurately estimate derivatives of experimentally measured statistical profiles. Toward this aim, experiments were conducted to investigate the efficacy of single-component molecular tagging velocimetry (1c-MTV) to measure mean velocity profiles that can be differentiated multiple times. Critical effects here pertain to finite measurement uncertainty in the presence of high spatial resolution. Measurements acquired in fully developed turbulent channel flow over a friction Reynolds number range from 390 to 1800 are used to investigate these issues. Each measured profile contains about 880 equally spaced data points that span from near the edge of the viscous sublayer to the channel centreline. As a result of the high spatial resolution, even very small levels of uncertainty in the data adversely affect the capacity to produce smooth velocity derivative profiles. It is demonstrated that the present 1c-MTV measurements can be differentiated twice, with the resulting profile remaining smooth and accurate. The experimental mean velocity profiles and their wall-normal derivatives up to second order are shown to convincingly agree with existing DNS data, including the apparent variations with Reynolds number.
15 citations
Patent•
10 Feb 2017TL;DR: In this article, the rotational Doppler shift from microparticles intersecting the beam focus was measured using a spatially shaped beam with a superposition of Laguerre-Gaussian modes.
Abstract: The superposition of Laguerre-Gaussian guided into and scattered by a particle in a rotated fluid allows the detection of the rotational of the fluid. The presented system allows for virtually real-time determination of vorticity characterization in a fluid. The system allows the direct measurements of fluid flow vorticity using a spatially shaped beam with a superposition of Laguerre-Gaussian modes that reports on the rotational Doppler shift from microparticles intersecting the beam focus.
2 citations