Experimental investigation of the turbulent near wake flow field of multiscale/fractal grids

---

Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Havacılık ve Uzay Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2018

Öğrenci: HOOMAN AMIRI HAZAVEH

Danışman: OĞUZ UZOL

Özet:

Turbulent near-field flow of three different fractal grids, as well as conventional square grid, is investigated using two-dimensional particle image velocimetry. All grids are designed to maintain similar solidity, effective mesh size, and the smallest thickness for comparison. Experiments are conducted at a Reynolds number of 12000 based on effective mesh size. The instantaneous velocity field is realized on four sets of 35 equally spaced horizontal planes downstream of turbulence-generating-grids. Threedimensional mean flow is reconstructed by stitching aforementioned horizontal planes, extending to 22 effective mesh size downstream of each grid. Additional mean flow variables are then obtained by rotating horizontal planes to the corresponding vertical ones in grids comprising geometrical symmetry. Turbulent mixing characteristics in the near-wake region are assessed and turbulent kinetic energy production, decay, and dissipation rate as well as estimation of length scales downstream of turbulence-generating-grids are carried out. It has been shown that grids with different fractal patterns can be used as a passive devices to custom tailor turbulence even in the non-homogeneous anisotropic near grid region. Dissipation rate coefficient is also shown to be not constant in the near-wake region.