Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


Alexis Omilion Thesis OhioLink.pdf (2.5 MB)

ETD Abstract Container

Abstract Header

The Effect of Multiple Scales on Fractal-Grid-Generated Turbulence

Omilion, Alexis Kathleen
http://rave.ohiolink.edu/etdc/view?acc_num=csu1528635554940034

Abstract Details

2018, Master of Science in Mechanical Engineering, Cleveland State University, Washkewicz College of Engineering.
Fractal grids, having patterns that repeat at different length scales, mimic the multi-scale characteristic of objects of complex appearance in nature, such as branching pulmonary network, river network, trees, and cumulus clouds. Understanding the role that multiple length scales have in momentum and energy transport is essential for effective utilization of fractal grids in a wide variety of engineering applications. While previous studies have solidified the dominant effect of the largest scale of fractal grids, effects of the additional scales on the generated turbulent flow remain unclear. This research is to determine how the smaller fractal scales (and the interaction between the multiple scales) influence the turbulence statistics of the induced flow and the pressure drop across a fractal square grid using well-controlled water-tunnel experiments. Instantaneous and ensemble-averaged velocity fields are obtained by a planar Particle Image Velocimetry (PIV) for a set of fractal square grids (N = 1, 2, 3 and 4) at the Reynolds number of 3400. The static pressure drop across the grids are measured by a differential pressure transducer. Flow fields indicate that the multiple jets, wakes and the shear layers produced by the multiple scales are the fundamental flow physics that promote momentum transport in the turbulence. In addition, the multiple scales cause a redistribution of the turbulent kinetic energy and a change in the vortex shedding mechanism behind the grids. The grid of 3 fractal scales (N = 3) produces higher turbulence intensity levels than the grid with 4 fractal scales (N = 4) despite having a lower blockage ratio and pressure drop, owing to the suppression of vortex shedding by the additional scale of the grid of N = 4. To better predict the location of peak turbulence intensity, the wake interaction length scale model is modified to incorporate the effects of the interactions among multiple scales by the effective mesh size and an empirical scaling coefficient Beta. Considering the capability of fractal grids to enhance momentum and energy transport, this work can potentially benefit a wide variety of applications where energy-efficient mixing or convective heat transfer is a key process.
Wei Zhang, PhD (Advisor)
Asuquo Ebiana, PhD (Committee Member)
Thijs Heus, PhD (Committee Member)
Fluid Dynamics
fractal square grid; multi-scale object; passive flow control; turbulence production

Recommended Citations

Citations

  • Omilion, A. K. (2018). The Effect of Multiple Scales on Fractal-Grid-Generated Turbulence [Master's thesis, Cleveland State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=csu1528635554940034

    APA Style (7th edition)

  • Omilion, Alexis. The Effect of Multiple Scales on Fractal-Grid-Generated Turbulence. 2018. Cleveland State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=csu1528635554940034.

    MLA Style (8th edition)

  • Omilion, Alexis. "The Effect of Multiple Scales on Fractal-Grid-Generated Turbulence." Master's thesis, Cleveland State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=csu1528635554940034

    Chicago Manual of Style (17th edition)

csu1528635554940034
364
© 2018, some rights reserved.Creative Commons License The Effect of Multiple Scales on Fractal-Grid-Generated Turbulence by Alexis Kathleen Omilion is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Cleveland State University and OhioLINK.