scholarly journals Acoustic critical depth and asymptotic absorption of dissipative fluids

2019 ◽  
Vol 145 (5) ◽  
pp. EL367-EL371 ◽  
Author(s):  
Raymond Panneton
Keyword(s):  
Critical Depth ◽  
Dissipative Fluids

Investigation of the influence of the flow structure on the accuracy of flow measurement before a hydrometric structure in an open channel

2020 ◽  
pp. 41-44
Author(s):  
Anatoly Kusher
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Water Flow ◽  
Flow Measurement ◽  
Water Discharge ◽  
Critical Depth ◽  
Flow Measurements ◽  
Study Results ◽  
Flow Velocity Profile ◽  
Upstream Flow

The reliability of water flow measurement in irrigational canals depends on the measurement method and design features of the flow-measuring structure and the upstream flow velocity profile. The flow velocity profile is a function of the channel geometry and wall roughness. The article presents the study results of the influence of the upstream flow velocity profile on the discharge measurement accuracy. For this, the physical and numerical modeling of two structures was carried out: a critical depth flume and a hydrometric overfall in a rectangular channel. According to the data of numerical simulation of the critical depth flume with a uniform and parabolic (1/7) velocity profile in the upstream channel, the values of water discharge differ very little from the experimental values in the laboratory model with a similar geometry (δ < 2 %). In contrast to the critical depth flume, a change in the velocity profile only due to an increase in the height of the bottom roughness by 3 mm causes a decrease of the overfall discharge coefficient by 4…5 %. According to the results of the numerical and physical modeling, it was found that an increase of backwater by hydrometric structure reduces the influence of the upstream flow velocity profile and increases the reliability of water flow measurements.

Study of Ductile-to-Brittle Transition in Single Grit Diamond Scribing of Silicon: Application to Wire Sawing of Silicon Wafers

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Hao Wu ◽  
Shreyes N. Melkote
Keyword(s):  
Hydrostatic Pressure ◽  
Silicon Wafers ◽  
Depth Of Cut ◽  
Critical Depth ◽  
External Hydrostatic Pressure ◽  
Tensile Stresses ◽  
Brittle Transition ◽  
Ductile Mode Cutting ◽  
Critical Depth Of Cut ◽  
Ductile To Brittle Transition

The ductile-to-brittle cutting mode transition in single grit diamond scribing of monocrystalline silicon is investigated in this paper. Specifically, the effects of scriber tip geometry, coefficient of friction, and external hydrostatic pressure on the critical depth of cut associated with ductile-to-brittle transition and crack generation are studied via an eXtended Finite Element Method (XFEM) based model, which is experimentally validated. Scribers with a large tip radius are shown to produce lower tensile stresses and a larger critical depth of cut compared with scribers with a sharp tip. Spherical tipped scribers are shown to generate only surface cracks, while sharp tipped scribers (conical, Berkovich and Vickers) are found to create large subsurface tensile stresses, which can lead to nucleation of subsurface median/lateral cracks. Lowering the friction coefficient tends to increase the critical depth of cut and hence the extent of ductile mode cutting. The results also show that larger critical depth of cut can be obtained under external hydrostatic pressure. This knowledge is expected to be useful in optimizing the design and application of the diamond coated wire employed in fixed abrasive diamond wire sawing of photovoltaic silicon wafers.

Wedge Radius Effects in Mechanical Exfoliation of HOPG: A Molecular Simulation Study

2014 ◽  
Author(s):  
B. Jayasena ◽  
S. Subbiah ◽  
C. D. Reddy
Keyword(s):  
Molecular Dynamics ◽  
Pyrolytic Graphite ◽  
Single Layer ◽  
Layered Material ◽  
Critical Depth ◽  
Graphene Layers ◽  
Highly Ordered Pyrolytic Graphite ◽  
Single Sheet ◽  
Dynamics Simulations ◽  
Atomically Flat

We study the effects of wedge bluntness in mechanically exfoliating graphene layers from highly ordered pyrolytic graphite (HOPG), a layered material. Molecular dynamics simulations show that the layer initiation modes strongly depend on the wedge radius. Force and specific energy signatures are also markedly affected by the radius. Cleaving with a larger wedge radius causes buckling ahead of the wedge; larger the radius more the buckling. A critical depth of insertion of 1.6 A° is seen necessary to cleave a single layer; this is also found to be independent of wedge radius. Hence, with accurate positioning on an atomically flat HOPG surface it is possible to mechanically cleave, using a wedge, a single sheet of graphene even with a blunt wedge.

A Simple Approach to the Study of Wave Patterns

2014 ◽  
Vol 156 (A3) ◽  
Keyword(s):  
Numerical Methods ◽  
Shallow Water ◽  
Froude Number ◽  
Critical Speed ◽  
Graphical Method ◽  
Three Dimensional ◽  
Simple Approach ◽  
Critical Depth ◽  
Simple Manner ◽  
Wave Patterns

The paper revisits some pioneering work of Sir Thomas Havelock on wave patterns with particular attention focused on his graphical method of analysis. Motivated by a desire to explore this method further using numerical methods, it is extended in a simple manner to give three-dimensional illustrations of the wave patterns of a point disturbance in deep and shallow water. All results are confined to the sub- and trans-critical regimes with some obtained very close to the critical Depth Froude Number. Some conclusions are drawn on the wave types produced when operating close to the critical speed and their decay with distance off.

Experiments with critical-depth flumes for measurement of flow in debris-laden streams

1936 ◽  
Vol 17 (2) ◽  
pp. 528 ◽  
Author(s):  
H. G. Wilm ◽  
J. S. Cotton ◽  
H. C. Storey
Keyword(s):  
Critical Depth

scholarly journals Interlocking Spikes for Extreme Mobility

2020 ◽  
Author(s):  
Volker Nannen ◽  
Damian Bover
Keyword(s):  
Fundamental Problem ◽  
Weight Ratio ◽  
Penetration Resistance ◽  
Rake Angle ◽  
Vehicle Stability ◽  
Engineering Science ◽  
Critical Depth ◽  
Low Thrust ◽  
Penetration Force ◽  
Draft Force

The interlock drive system generates traction by penetrating articulated spikes into the ground and by using the natural strength of the ground for traction. A fundamental problem of traction by interlocking spikes is how to penetrate the ground such that the spike will withstand the draft force. The theory of critical depth suggests that a high rake angle reduces soil fragmentation, while vehicle stability and demand for a high pull/weight ratio require a low thrust angle. To satisfy both requirements, we connect an interlocking spike with a high rake angle via a lever arm to a hinge close to the ground for a low thrust angle. The resulting friction of the spike with the soil increases the vertical penetration force during penetration. Experimental data shows that such a spike penetrates soil of a much higher penetration resistance than predicted from an analysis of the forces involved, possibly because the spike follows the path of least resistance. To better understand and improve the potential of interlocking spikes for mobility in extreme terrain, we need a comprehensive experimental analysis. Accepted Paper in Proc. Earth &amp; Space 2020: 17th Biennial ASCE International Conference on Engineering, Science, Construction and Operations in Challenging Environments, ASCE, Seattle WA.

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