Owen WilliamsUniversity of Washington Seattle | UW · Department of Aeronautics and Astronautics
Owen Williams
PhD, MEng (Hons)
About
13
Publications
3,478
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
244
Citations
Introduction
I study turbulence and its resulting impact on vehicles, the atmosphere and engineering design. Heat transfer, compressibility and flow separation are all phenomena that greatly impact the design of vehicles or environmental processes but can be very difficult to model accurately. To advance our understanding of these flows, I examine the structure and scaling of turbulence using a combination of novel experiments that push the limits of current measurement technologies, and analysis techniques, such as machine learning and dimensionality reduction methods, that aim to take advantage of the vastly expanding quantity of experimental and computational data currently available.
Additional affiliations
January 2015 - September 2015
September 2012 - June 2013
September 2008 - present
Education
September 2008 - October 2014
September 2004 - June 2008
Independent Researcher
Field of study
- MEng (Hons)
Publications
Publications (13)
Experiments were performed to study two compression corner interactions at Mach 7.2 and at a Reynolds number based on a momentum thickness of 3500. Turning angles were selected such that the flow remained attached for the lower 8° case and a large separation bubble formed for a higher 33° case. The measurements were performed using particle image v...
Particle image velocimetry and filtered Rayleigh scattering experiments were performed over a range of Reynolds numbers to study the scaling and structure of a smooth, flat-plate turbulent boundary layer with a free stream Mach number of 7.5. The measurements indicate few, if any, dynamic differences due to Mach number. Mean and fluctuating streamw...
The effect of varying three-dimensional, cylindrical post-type trip size on the mean and turbulent velocity profiles of a Mach 7.6 turbulent boundary layer is examined using particle image velocimetry. It is shown that the effect of under- and overtripping is to amplify the wake component of the mean velocity profile and outer-layer turbulence inte...
The effects of stable thermal stratification on turbulent boundary layers are experimentally investigated for smooth and rough walls. For weak to moderate stability, the turbulent stresses are seen to scale with the wall shear stress, compensating for changes in fluid density in the same manner as done for compressible flows. This suggests little c...
The response of an initially neutral rough-wall turbulent boundary layer to a change in wall temperature is investigated experimentally. The change causes a localized peak in stable stratification that diffuses and moves away from the wall with downstream distance. The streamwise and wall-normal components of turbulent velocity fluctuations are dam...
A new method for measuring turbulent heat fluxes using a combination of particle image velocimetry and a nanoscale fast-response cold-wire is tested by examining a rough-wall turbulent boundary layer subject to weakly stable stratification. The method has the advantages of simple calibration and setup, as well as providing spatial correlations of v...
We examine the effects of compressibility, slip, and fluid inertia on the frequency response of particle-based velocimetry techniques for supersonic and hypersonic flows by solving the quasi-steady drag equation for solid, spherical particles. We demonstrate that non-continuum and fluid inertial effects significantly affect the particle response un...
This dissertation examines the effects of density gradients on turbulent boundary layer statistics and structure using Particle Image Velocimetry (PIV). Two distinct cases were examined: the thermally stable atmospheric surface layer characteristic of nocturnal or polar conditions, and the hypersonic bounder layer characteristic of high speed aircr...
This dissertation examines the effects of density gradients on turbulent boundary layer statistics and structure using Particle Image Velocimetry (PIV). Two distinct cases were examined: the thermally stable atmospheric surface layer characteristic of nocturnal or polar conditions, and the hypersonic bounder layer characteristic of high speed aircr...
The aim of the current experimental program is to use PIV to measure turbulent statistics within a smooth surface boundary layer at Mach 7.4. It has been shown that the high shear present in a hypersonic boundary layer can lead to an error called peak locking, known to have a significant impact on first order statistics. To limit its effects, parti...
Turbulent fluctuations in hypersonic boundary layers are conventionally collapsed using Morkovin scaling which has been shown to be broadly applicable up to Mach numbers as high as 5. To validate Morkovin’s hypothesis at higher Mach numbers, and help improve our understanding of hypersonic wall-bounded turbulence, we report PIV measurements of two...
The effects of thermal stability on coherent structures in turbulent flat plate boundary layers are examined experimen-tally. Thermocouple and DPIV measurements are reported over a Richardson number range 0 < Ri δ < 0.2. The reduc-tion in wall shear and the damping of the turbulent stresses with increasing stability are qualitatively similar to tha...
