Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 36 for “"critical-shear"”.
-
Changes in Streambank Erodibility and Critical Shear Stress Due to Surface Subaerial Processes
… studies have shown that soil erodibility and critical shear stress are highly influenced by weathering processes such as freeze-thaw cycling and wet-dry cycling. Despite over forty years of research attributing changes in soil properties over time to climate-dependent variables, little …
-
Evaluation of an In Situ Measurement Technique for Streambank Critical Shear Stress and Soil Erodibility
… a simple in situ method of measuring streambank critical shear stress (Ï c) and soil erodibility (kd). Previous research showed streambank kd and Ï c can vary by up to four orders of magnitude at a single site; therefore, it is essential to determine if the large range is due to natural …
-
Evaluation of the Jet Test Method for determining the erosional properties of Cohesive Soils; A Numerical Approach
… device is an in situ method of determining the critical shear stress and soil erodibility of cohesive soils. A constant velocity jet, applied perpendicular to the soil surface, creates a scour hole which is measured at discrete time intervals. While the results of these tests are able to provide …
-
Fundamental study of nucleation and heteroepitaxial thin film growth using ionized source beam
… neutral nozzle beam case. Also, the resulting critical shear stress acting on the interface between the cluster and the substrate showed that the critical shear stress of ionized clusters was one order of magnitude higher than that of neutral clusters. These results indicate that the two …
-
Baroclinic instability of a meridionally varying basic state
… It is shown in chapter three that, near minimum critical shear, meridional variation of the potential vorticity gradient of the basic flow can introduce dramatic changes in the structure of the normal modes. Some aspects of resonant triad dynamics in a meridionally uniform, vertically sheared, …
-
The Role of Instantaneous Forces in Particle Movement
… rates, most of which use some comparison between shear stress and critical shear stress. The critical shear stress is determined by the point of incipient motion. Researchers have attempted to predict bed load transport both deterministically with mean parameters and stochastically attempting to …
-
Mechanics of Aggregated Alumina Suspensions: Behavior Under Shear and Compression
A series of experiments performed in a novel shear cell clearly demonstrate that the presence of a combined load alters the mechanical response for an aggregated suspension. Imposing a shear field on the particle network reduces the compressive strength of the network. The magnitude of this …
-
Headcut retreat resulting from plunge pool erosion in a 3D landscape evolution model
… the relevant soil parameters (erodibility and critical shear stress). The model was analyzed to study its behavior as its input parameters changed, and its output was compared to experimental observations. Next, the plunge pool mechanism was implemented in an existing 3D landscape evolution …
-
Instabilities in layered liquids induced by external fields
… like liquids is destabilized by an applied shear. After destabilization, two typical scenarios are observed in a steady state situation: i) The layers are oriented perpendicular to the vorticity direction of the flow, i.e., they lie in the plane spanned by the velocity and the gradient …
-
Bedload transport: the effects of particle shape and an investigation of a wide range of transport rates
… particles indicates that the reference transport critical shear stress for the median surface grain size is approximately 2 to 3 times higher than those for more spherical particles. This conclusion indicates a lower susceptibility of disc-like particles to initial entrainment and lower transport …
-
The Transient Flow Rheology and Instabilities of Polyethylene Melts
… the linear and non-linear behaviour (for lower shear rates) of these polyethylenes were determined from dynamic (oscillatory) experiments and stepstrain experiments performed using the Rheametrics (RDS), parallel-plate rheameter. Similar measurements using a capillary geometry with the MPR were …
-
The Transient Flow Rheology and Instabilities of Polyethylene Melts
… the linear and non-linear behaviour (for lower shear rates) of these polyethylenes were determined from dynamic (oscillatory) experiments and stepstrain experiments performed using the Rheametrics (RDS), parallel-plate rheameter. Similar measurements using a capillary geometry with the MPR were …
-
The Role of Geomorphic Features and Hydrologic Processes on Sediment Clusters in Gravel-Bed Rivers, Washington: A Field-Based Approach
… clusters were also tracked, and the velocity and critical shear stress required to entrain particles were calculated to determine the possible effects of clusters on the entrainment of sediment. An improved understanding of how clusters develop, evolve and affect the entrainment of sediment under …
-
Characterizing soil erosion potential using electrical resistivity imaging
… grain size, percent clay, compaction, and shear strength. Many of these characteristics also influence soil in situ bulk electrical resistivity (ER) measurements. The objective of this study was to characterize soil erosion potential by correlating the in situ ER of soil with erodibility …
-
Incipient Motion Under Shallow Flow Conditions
… and high Froude number on the dimensionless critical shear stress (Shields parameter). Spherical particles of four different densities and an 8mm diameter were used as movable test material. The relative depth ranged from 2 to 12 and the Froude number ranged from 0.36 to 1.29. The results …
-
The Effects of Vegetation on Stream Bank Erosion
… was addressed by measuring the erodibility and critical shear stress of rooted bank soils in situ using a submerged jet test device. Additionally, several soil, vegetation, and stream chemistry factors that could potentially impact the fluvial entrainment of soils were measured. A total of 25 …
-
Predicting Sediment Detachment and Channel Scour in the Process-Based Planning Model ANSWERS-2000
… disturbed watersheds was updated to include a critical-shear rill detachment subroutine, an improved interrill detachment subroutine, and a channel scour subroutine. The existing version of ANSWERS-2000 did not simulate channel scour. The original detachment equations used in the model were …
-
An analytical and experimental study of crack extension in center- notched composites
… plate with a center line crack to obtain critical stress and crack growth direction predictions. An elasticity solution for an infinite plate with a center elliptical flaw is also used to obtain qualitative predictions of the location of crack initiation around the border of an actual …
-
Flow-Induced Self Assembly in Micellar Fluids with Applications to Nanomanufacturing
… transitions in surfactant solutions under simple shear as well as porous medium flows, and how they are influenced by the presence of added salt First, we study the effect of salt concentration on the shear rheology of ionic surfactant solutions in simple shear flow. It is shown that for a given …
-
Micromechanics of deformation and stress evolution in thin films and patterned lines on substrates
… underneath the indenter tip approached the critical shear strength of the material. Theories of dislocation activity were confirmed with planar TEM photos of nanoindented Cu films. In order to examine the atomistics of such phenomena, an experimental 2-D atomic simulation was developed, via …
Page 1 of 2