PTV measurement of the spanwise component of aeolian transport in steady state

O’Brien, Patrick; Neuman, Cheryl McKenna

doi:10.1016/j.aeolia.2015.11.005

Cited by 22 publications

(25 citation statements)

References 37 publications

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“…(a) Particle size distribution for experimental sand and (b) sample of a particle being identified and tracked using the Expected Particle Area Search algorithms for particle tracking velocimetry, described in detail in O'Brien and McKenna Neuman ().…”

Section: Methodsmentioning

confidence: 99%

“…As described in detail in O'Brien () and O'Brien and McKenna Neuman (, ), the particle tracking velocimetry (PTV) system operated at the Trent Environmental Wind Tunnel facility consists of a 1 W, 532 nm, Nd‐Yag laser, a pco.dimax HD™ high‐speed camera, and software developed in‐house that automatically identifies and tracks particles using a method known as Expected Particle Area Searching (EPAS). This PTV system exclusively samples particles traveling parallel with the mean airflow at ~10 kHz, from 0.05 mm above the bed surface up to 50 mm, allowing for substantial overlap with the wind speed measurements obtained with a vertically traversing pitot tube (Figure b).…”

Section: Methodsmentioning

confidence: 99%

“…As described in detail in O'Brien (2018) and O'Brien and McKenna Neuman (2016, 2017, the particle tracking velocimetry (PTV) system operated at the Trent Environmental Wind Tunnel facility consists of a 1 W, 532 nm, Nd-Yag laser, a pco.dimax HD™ high-speed camera, and software developed in-house that automatically identifies and tracks particles using a method known as Expected Particle Area Searching (EPAS). Note.…”

Section: Particle Tracking Velocimetry Sampling Design and Efficiencymentioning

confidence: 99%

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Experimental Validation of the Near‐Bed Particle‐Borne Stress Profile in Aeolian Transport Systems

O’Brien

Neuman

2019

JGR Earth Surface

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Self‐regulation of sediment transport by wind is widely assumed to derive from the partitioning of momentum from the fluid flow to the particle cloud. Consequently, the fluid stress on the bed surface is suggested by some to drop below that required to entrain particles, while the cloud is sustained by particle ricochet and splash that derive from the impacts of particles moving ballistically along the bed surface. While these theoretical constructs underpin present‐day numerical models of aeolian saltation, the particle‐borne stress has never been measured directly in either a laboratory or field setting. Such measurements are required for model validation and calibration of numerical simulations and were undertaken in vertical profile in the Trent Environmental Wind Tunnel using particle tracking velocimetry. Test sand was normally distributed with a median diameter of 590 μm. Particle momentum was calculated from the diameter and velocity of each image pair captured using high‐speed photography and then summed within each elevation band. The median diameter of the air‐borne particles was found to increase with friction velocity (u*), suggestive of sorting of the bed surface, and to decrease with elevation. Within a two‐dimensional framework, the vertical and windward components of the particle velocity were found to increase with elevation, with u* having little to no influence. Confirming the results of previous numerical simulations, these experiments show that the normalized particle‐borne stress increases exponentially toward the bed surface; however, within the lowest few millimeters where particle splash dominates, no consistent change is observed with elevation.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Particle Tracking Velocimetry Sampling Design and Efficiencymentioning

confidence: 99%

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Experimental Validation of the Near‐Bed Particle‐Borne Stress Profile in Aeolian Transport Systems

O’Brien

Neuman

2019

JGR Earth Surface

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“…The quantification of threshold wind speeds was laid on a foundation of terrestrial (ambient condition) wind tunnel research (Bagnold, 1941), which continues to advance our understanding through increasingly sophisticated instrumentation and experiments (Holstein-Rathlou et al, 2013;Bennett et al, 2015 and references therein;O'Brien and McKenna Neuman, 2016;Yu et al, 2017). Planetary wind tunnels, which simulate atmospheric density on planetary body surfaces ( Merrison et al, 2009;Burr et al, 2015b;Swann and Ewing, 2016;Williams and Smith, 2017, and references therein), have enabled the exploration of the effects on aeolian transport of extraterrestrial boundary conditions.…”

Section: Introductionmentioning

confidence: 99%

A wind tunnel study of the effect of intermediate density ratio on saltation threshold

Burr¹,

Sutton²,

Emery³

et al. 2020

Aeolian Research

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An expression for aeolian saltation threshold-the minimum wind speed required to initially entrain sediment particles into saltation-is used in modeling aeolian processes and the formation of aeolian landforms on Earth and other planetary bodies. Previous experiments under high-fluid-density conditions in the Venus Wind Tunnel (VWT) concluded that this threshold is a function of the ratio of the density of the particle to the density of the entraining fluid (ρp/ρ). A curve for the dimensionless threshold parameter, A, as a function of (ρp/ρ), was derived [Iversen et al. 1987]. In this work, we revisit this curve of A(ρp/ρ) using data from the Titan Wind Tunnel (TWT) [Burr et al., 2015b]. We use both previous and newly collected TWT data of freestream threshold wind speed spanning a range of density ratio conditions to derive friction wind speeds and then values for A. The TWT-derived data generally overly the VWT data used to derive the density ratio curve, although showing greater variability and an apparent offset to slightly higher values. We derive a new density ratio curve from the aggregated threshold data using the same format as the previous expression but with new values for the two exponential parameters. These TWT data provide additional constraints on the transitional portion of the density ratio curve between the low density ratio conditions of flume data and the high density ratio conditions of Mars Surface Wind Tunnel data.

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“…Intermittent saltation has been measured, described, and modeled in a number of published studies (see Lee ; Rasmussen and Sørensen ; Spies and others ; Andreotti and others ; Ellis and others ; Pfeifer and Schönfeldt ; Dupont and others ; Martin and others ; Bauer and Davidson‐Arnott ; Carniero and others ; Li and McKenna Neuman ; Wang and Zheng ; or O'Brien and McKenna Neuman ). There are several motivations for investigations such as these.…”

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confidence: 99%

Intermittent Aeolian Saltation: A Protocol For Quantification

Sherman

Ellis

et al. 2018

Geographical Review

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The quantification of saltation intermittency-the proportion of time when sand transport occurs-provides valuable information about the nature of aeolian systems, including insights concerning threshold conditions for sand transport. Intermittency has been measured in numerous studies, but a lack of measurement standardization often makes the comparison of results difficult. Four methodological factors influence estimates of intermittency: sample frequency, sample duration, sample area, and sensor elevation. For a given transport rate, the value of intermittency may decrease with sensor elevation, increased sample frequency, or decreased sensor area; it may increase or decrease as a consequence of sample duration. We therefore simulate the influences of these factors and suggest a common protocol for measuring and reporting intermittency based on measurements at 1 Hz with 100 mm 2 sensor area at 50 mm elevation above the surface, or equivalent values.

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PTV measurement of the spanwise component of aeolian transport in steady state

Cited by 22 publications

References 37 publications

Experimental Validation of the Near‐Bed Particle‐Borne Stress Profile in Aeolian Transport Systems

Experimental Validation of the Near‐Bed Particle‐Borne Stress Profile in Aeolian Transport Systems

A wind tunnel study of the effect of intermediate density ratio on saltation threshold

Intermittent Aeolian Saltation: A Protocol For Quantification

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