Fluid circulation and seepage in lake sediment due to propagating and trapped internal waves

Olsthoorn, Jason; Stastna, Marek; Soontiens, Nancy

doi:10.1029/2012wr012552

Cited by 17 publications

(8 citation statements)

References 62 publications

(84 reference statements)

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“…Olsthoorn et al . [] considered a penetration depth, as a function of the aspect ratio of the bed. Their analysis is based on sinusoidal pressure wave patterns, essentially serving as a proxy for the ISW‐induced pressure of depression‐type, forcing the bed.…”

Section: Resultsmentioning

confidence: 99%

“…In the present work, the seepage is not symmetric about the wave trough, because the pressure forcing is translating along the bed. As such, the maximum magnitude of vertical pressure gradient is not under the wave trough, as one would expect for a forcing independent of time [ Olsthoorn et al ., ]. The dimensional vertical pore‐pressure gradient normalized by the buoyant weight of the bed, for the baseline case, is shown in Figure , for saturation values S r = 0.97 and S r = 0.99.…”

Section: Resultsmentioning

confidence: 99%

“…In addition to the driving role of the wavelength, as proposed by Olsthoorn et al . [], the present results highlight the importance of the ISW celerity as controlling factor of penetration depth and, the possibility of bed failure. Lastly, it is noted that since ISWs in deeper waters have a larger amplitude, the vertical accelerations, that influence the nonhydrostatic contribution to the pressure, vary with the total depth as well.…”

Section: Discussionmentioning

confidence: 99%

“…In the present study, this depth is denoted as g 1 0:1 , and is presented in Table 5, for the different bed constituents. Olsthoorn et al [2012] considered a penetration depth, as a function of the aspect ratio of the bed. Their analysis is based on sinusoidal pressure wave patterns, essentially Figure 2.…”

Section: Depth Of Penetration For the Changes Inmentioning

confidence: 99%

“…ISWs of depression have the capacity to induce a strong negative pressure and, consequently, their passage could result in bed failure. Olsthoorn et al [2012] argued that, for trapped ISWs of depression, vertical seepage is greatly enhanced, resulting in fluid being drawn from the bed and, possibly, contributing to the resuspension of particles. If the assumption of very slow motion is disregarded, then time-dependence is introduced.…”

Section: Introductionmentioning

confidence: 99%

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Bed failure induced by internal solitary waves

2017

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The pressure field inside a porous bed induced by the passage of an Internal Solitary Wave (ISW) of depression is examined using high‐accuracy numerical simulations. The velocity and density fields are obtained by solving the Dubreil‐Jacotin‐Long Equation, for a two‐layer, continuously stratified water column. The total wave‐induced pressure across the surface of the bed is computed by vertically integrating for the hydrostatic and nonhydrostatic contributions. The bed is assumed to be a continuum composed of either sand or silt, with a small amount of trapped gas. Results show variations in pore‐water pressure penetrating deeper into more conductive materials and remaining for a prolonged period after the wave has passed. In order to quantify the potential for failure, the vertical pressure gradient is compared against the buoyant weight of the bed. The pressure gradient exceeds this weight for weakly conductive materials. Failure is further enhanced by a decrease in bed saturation, consistent with studies in surface‐wave induced failure. In deeper water, the ISW‐induced pressure is stronger, causing failure only for weakly conductive materials. The pressure associated with the free‐surface displacement that accompanies ISWs is significant, when the water depth is less than 100 m, but has little influence when it is greater than 100 m, where the hydrostatic pressure due to the pycnocline displacement is much larger. Since the pore‐pressure gradient reduces the specific weight of the bed, results show that particles are easier for the flow to suspend, suggesting that pressure contributes to the powerful resuspension events observed in the field.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Depth Of Penetration For the Changes Inmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bed failure induced by internal solitary waves

2017

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Pore pressure in a wind‐swept rippled bed below the suspension threshold

Musa

Takarrouht

Louge

et al. 2014

J. Geophys. Res. Earth Surf.

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Toward elucidating how a wavy porous sand bed perturbs a turbulent flow above its surface, we record pressure within a permeable material resembling the region just below desert ripples, contrasting these delicate measurements with earlier studies on similar impermeable surfaces. We run separate tests in a wind tunnel on two sinusoidal porous ripples with aspect ratio of half crest‐to‐trough amplitude to wavelength of 3% and 6%. For the smaller ratio, pore pressure is a function of streamwise distance with a single delayed harmonic decaying exponentially with depth and proportional to wind speed squared. The resulting pressure on the porous surface is nearly identical to that on a similar impermeable wave. Pore pressure variations at the larger aspect ratio are greater and more complicated. Consistent with the regime map of Kuzan et al. (), the flow separates, creating a depression at crests. Unlike flows on impermeable waves, the porous rippled bed diffuses the depression upstream, reduces surface pressure gradients, and gives rise to a slip velocity, thus affecting the turbulent boundary layer. Pressure gradients within the porous material also generate body forces rising with wind speed squared and ripple aspect ratio, partially counteracting gravity around crests, thereby facilitating the onset of erosion, particularly on ripples of high aspect ratio armored with large surface grains. By establishing how pore pressure gradients scale with ripple aspect ratio and wind speed, our measurements quantify the internal seepage flow that draws dust and humidity beneath the porous surface.

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