Turbulence Control in Wall Jets

Turbulence Control in Wall Jets
Author: Jonathan Latim
Publisher:
Total Pages: 118
Release: 2016
Genre: Boundary layer
ISBN:

The turbulent boundary layer has been the focus of many studies over the last century or so due to its engineering significance. Recent studies have shown that the turbulent boundary layer encapsulates extremely energetic large-scale structures which play a much more significant role in its dynamics than has been previously thought. Further, these large scales amplitude and frequency modulate the finer scales of turbulence. This offers a path to control wall turbulence by controlling the large-scales of the flow. The focus of this thesis is to establish ways to manipulate the energy of the large-scale structures in a model turbulent boundary layer and characterize its effect. The plane wall jet was chosen as the model flow field because it is possible to perturb/excite the large-scales at the onset of turbulence independent of the finer scales of turbulence. Hot-wire anemometry was used to carryout velocity measurements in at plane wall jet at streamwise locations up to three hundred times the jet exit slot height. Three different passive perturbation configurations were used to manipulate the energy of the large-scale structures of the plane wall jet. The different perturbation configurations used were a rod, sandpaper and sandpaper and a still wire. All the perturbations were carried out in the vicinity of the jet exit. The unforced wall jet was used as the baseline to compare the effect of these perturbations. All the perturbation cases were able to alter the energy of the large-scale structures in the flow. However, the large-scale structures were shown to be most energetic and reached closest to the wall in the flow that was perturbed using the rod than in all other flow cases at all streamwise positions considered. Last but not least, tic and reached closest to the wall in the flow that was perturbed using the sandpaper and the sandpaper and string configurations showed less energetic large-scale structures at all streamwise locations than in an unforced wall jet. However, the large-scale structures in the sandpaper and string configuration were more energetic than the large scale structures in the sandpaper configuration at all streamwise locations.

The Isolated Synthetic Jet in Crossflow

The Isolated Synthetic Jet in Crossflow
Author: Norman W. Schaeffler
Publisher: BiblioGov
Total Pages: 40
Release: 2013-08
Genre:
ISBN: 9781289280154

An overview of the data acquisition, reduction, and uncertainty of experimental measurements made of the flowfield created by the interaction of an isolated synthetic jet and a turbulent boundary layer is presented. The experimental measurements were undertaken to serve as the second of three computational fluid dynamics validation databases for Active Flow Control. The validation databases were presented at the NASA Langley Research Center Workshop on CFD Validation of Synthetic Jets and Turbulent Separation Control in March, 2004. Detailed measurements were made to document the boundary conditions for the flow and also for the phase-averaged flowfield itself. Three component Laser-Doppler Velocimetry, 2-D Particle Image Velocimetry, and Stereo Particle Image Velocimetry were utilized to document the phase-averaged velocity field and the turbulent stresses.

Wind Tunnels and Experimental Fluid Dynamics Research

Wind Tunnels and Experimental Fluid Dynamics Research
Author: Jorge Colman Lerner
Publisher: BoD – Books on Demand
Total Pages: 728
Release: 2011-07-27
Genre: Science
ISBN: 9533076232

The book "Wind Tunnels and Experimental Fluid Dynamics Research" is comprised of 33 chapters divided in five sections. The first 12 chapters discuss wind tunnel facilities and experiments in incompressible flow, while the next seven chapters deal with building dynamics, flow control and fluid mechanics. Third section of the book is dedicated to chapters discussing aerodynamic field measurements and real full scale analysis (chapters 20-22). Chapters in the last two sections deal with turbulent structure analysis (chapters 23-25) and wind tunnels in compressible flow (chapters 26-33). Contributions from a large number of international experts make this publication a highly valuable resource in wind tunnels and fluid dynamics field of research.

Flow Control

Flow Control
Author: Thomas C. Corke
Publisher: Cambridge University Press
Total Pages: 482
Release: 2024-04-11
Genre: Technology & Engineering
ISBN: 110896253X

This book provides a comprehensive treatment of passive and active flow control in fluid dynamics, with an emphasis on utilizing fluid instabilities for enhancing control performance. Examples are given from a wide range of technologically important flow fields occurring in aerospace applications, from low-subsonic to hypersonic Mach numbers. This essential book can be used for both research and teaching on the topics of fluid instabilities, fluid measurement and flow actuator techniques, and problem sets are provided at the end of each chapter to reinforce key concepts and further extend readers' understanding of the field. The solutions manual is available as a online resource for instructors. The text is well suited for both graduate students in fluid dynamics and for practising engineers in the aerodynamics design field.