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Portland State University

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Boundary layer

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Full-Text Articles in Engineering

Droplet Jump From A Particle Bed, Karl Cardin, Facundo Cabrera-Booman, Raúl Bayoán Cal Feb 2024

Droplet Jump From A Particle Bed, Karl Cardin, Facundo Cabrera-Booman, Raúl Bayoán Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Drop tower experiments have been performed to study droplet jump from a particle bed across a wide range of fluid viscosities. Here the droplet jumps from the particle bed in response to the apparent step reduction from terrestrial gravity to microgravity when the experiment is dropped and enters free fall. The presence of a particle layer has been found to affect contact line dissipation and the overall jumping behavior of droplets. Additionally, the study has identified the impact of the Ohnesorge number (Oh) on droplet morphology. The investigation has yielded results that not only validate a modified version of the …


Assessing Spacing Impact On Coherent Features In A Wind Turbine Array Boundary Layer, Naseem Ali, Nicholas Hamilton, Dominic Delucia, Raúl Bayoán Cal Feb 2018

Assessing Spacing Impact On Coherent Features In A Wind Turbine Array Boundary Layer, Naseem Ali, Nicholas Hamilton, Dominic Delucia, Raúl Bayoán Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

As wind farms become larger, the spacing between turbines becomes a significant design consideration that can impose serious economic constraints. To investigate the turbulent flow structures in a 4 x 3 Cartesian wind turbine array boundary layer (WTABL), a wind tunnel experiment was carried out parameterizing the streamwise and spanwise wind turbine spacing. Four cases are chosen spacing turbines by 6 or 3D in the streamwise direction, and 3 or 1:5D in the spanwise direction, where D = 12 cm is the rotor diameter. Data are obtained experimentally using stereo particle image velocimetry. Mean streamwise velocity showed maximum …


Conditional Averaging And Classification In The Near Wake Of A Wind Turbine Array Boundary Layer, Sarah E. Smith May 2017

Conditional Averaging And Classification In The Near Wake Of A Wind Turbine Array Boundary Layer, Sarah E. Smith

Undergraduate Research & Mentoring Program

Flow perturbation induced by interaction with a turbine rotor produces considerable turbulence which can alter the productivity of subsequent units within a wind farm. Previous methods have characterized near wake vorticity of a single turbine as well as recovery distance for various turbine array configurations. This study aims to build from previous methods of analysis from the perspective of the rotor well within a turbine array and develop a model to examine points of significant imposition in relation to rotational effects. Hot wire anemometry was employed downstream of a turbine located in the middle of the third row in a …


Structure Functions, Scaling Exponents And Intermittency In The Wake Of A Wind Turbine Array, Naseem Ali, Aleksandr Sergeyevich Aseyev, Raúl Bayoán Cal Feb 2016

Structure Functions, Scaling Exponents And Intermittency In The Wake Of A Wind Turbine Array, Naseem Ali, Aleksandr Sergeyevich Aseyev, Raúl Bayoán Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Hot-wire measurements obtained in a 3 × 3 wind turbine array boundary layer are utilized to analyze high order structure functions, intermittency effects as well as the probability density functions of velocity increments at different scales within the energy cascade. The intermittency exponent is found to be greater in the far-wake region in comparison with the near-wake. At hub height, the intermittency exponent is found to be null. Extended self-similarity scaling exponents of the second, fourth, and fifth order structure functions remain relatively constant as a function of height in the far-wake; whereas in the near-wake, these are highly affected …


Wake Interaction And Power Production Of Variable Height Model Wind Farms, M. H. Vested, N. Hamilton, J. N. Sørensen, Raul Bayoan Cal Jun 2014

Wake Interaction And Power Production Of Variable Height Model Wind Farms, M. H. Vested, N. Hamilton, J. N. Sørensen, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Understanding wake dynamics is an ongoing research topic in wind energy, since wakes have considerable effects on the power production when wind turbines are placed in a wind farm. Wind tunnel experiments have been conducted to study the wake to wake interaction in a model wind farm in tandem with measurements of the extracted power. The aim is to investigate how alternating mast height influences the interaction of the wakes and the power production. Via the use of stereo-particle image velocimetry, the flow field was obtained in the first and last rows of the wind turbine array as a basis …