scholarly journals Sheet, stream, and shelf flow as progressive ice-bed uncoupling: Byrd Glacier, Antarctica, and Jakobshavn Isbrae, Greenland

2015 ◽  
Vol 9 (4) ◽  
pp. 4271-4354
Author(s):  
T. Hughes ◽  
A. Sargent ◽  
J. Fastook ◽  
K. Purdon ◽  
J. Li ◽  
...  
Keyword(s):  
Stream Flow ◽  
Stokes Equations ◽  
Force Balance ◽  
Navier Stokes ◽  
Ice Shelf ◽  
Sheet Flow ◽  
Lower Yield ◽  
Navier Stokes Equations ◽  
Basal Ice ◽  
Shelf Flow

Abstract. The first-order control of ice thickness and height above sea level is linked to the decreasing strength of ice-bed coupling alone flowlines from an interior ice divide to the calving front of an ice shelf. Uncoupling progresses as a frozen bed progressively thaws for sheet flow, as a thawed bed is progressively drowned for stream flow, and as lateral and/or local grounding vanish for shelf flow. This can reduce ice thicknesses by 90 % and ice elevations by 99 % along flowlines. Original work presented here includes (1) replacing flow and sliding laws for sheet flow with upper and lower yield stresses for creep in cold overlying ice and basal ice sliding over deforming till, respectively, (2) replacing integrating the Navier–Stokes equations for stream flow with geometrical solutions to the force balance, and (3) including resistance to shelf flow caused by lateral confinement in a fjord and local grounding at ice rumples and ice rises. A comparison is made between our approach and two approaches based on continuum mechanics. Applications are made to Byrd Glacier in Antarctica and Jakobshavn Isbrae in Greenland.

scholarly journals Sheet, stream, and shelf flow as progressive ice-bed uncoupling: Byrd Glacier, Antarctica and Jakobshavn Isbrae, Greenland

2016 ◽  
Vol 10 (1) ◽  
pp. 193-225 ◽  
Author(s):  
T. Hughes ◽  
A. Sargent ◽  
J. Fastook ◽  
K. Purdon ◽  
J. Li ◽  
...  
Keyword(s):  
Stream Flow ◽  
Stokes Equations ◽  
Force Balance ◽  
Navier Stokes ◽  
Ice Shelf ◽  
Sheet Flow ◽  
Lower Yield ◽  
Navier Stokes Equations ◽  
Basal Ice ◽  
Shelf Flow

Abstract. The first-order control of ice thickness and height above sea level is linked to the decreasing strength of ice-bed coupling along flowlines from an interior ice divide to the calving front of an ice shelf. Uncoupling progresses as a frozen bed progressively thaws for sheet flow, as a thawed bed is progressively drowned for stream flow, and as lateral and/or local grounding vanish for shelf flow. This can reduce ice thicknesses by 90 % and ice elevations by 99 % along flowlines. Original work presented here includes (1) replacing flow and sliding laws for sheet flow with upper and lower yield stresses for creep in cold overlying ice and basal ice sliding over deforming till, respectively, (2) replacing integrating the Navier–Stokes equations for stream flow with geometrical solutions to the force balance, and (3) including resistance to shelf flow caused by lateral confinement in a fjord and local grounding at ice rumples and ice rises. A comparison is made between our approach and two approaches based on continuum mechanics. Applications are made to Byrd Glacier in Antarctica and Jakobshavn Isbrae in Greenland.

scholarly journals Reply to Basal buoyancy and fast-moving glaciers: in defense of analytic force balance by C. J. van der Veen (2016)

2017 ◽  
Author(s):  
Terence J. Hughes
Keyword(s):  
Stokes Equations ◽  
Traditional Approach ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Geometric Approach ◽  
Force Balance ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Ice Sheet Modeling ◽  
Energy Balances

Abstract. Two approaches to ice-sheet modeling are available. Analytical modeling is the traditional approach. It solves the force (momentum), mass, and energy balances to obtain three-dimensional solutions over time, beginning with the Navier-Stokes equations for the force balance. Geometrical modeling employs simple geometry to solve the force and mass balance in one dimension along ice flow. It is useful primarily to provide the first-order physical basis of ice-sheet modeling for students with little background in mathematics (Hughes, 2012). The geometric approach uses changes in ice-bed coupling along flow to calculate changes in ice elevation and thickness, using floating fraction φ along a flowline or flowband, where φ = 0 for sheet flow, 0 

Dynamics of a polarized vortex ring

1994 ◽  
Vol 260 ◽  
pp. 23-55 ◽  
Author(s):  
D. Virk ◽  
M. V. Melander ◽  
F. Hussain
Keyword(s):  
Turbulent Flows ◽  
Evolutionary Dynamics ◽  
Stokes Equations ◽  
Spatial Separation ◽  
Force Balance ◽  
Degree Of Polarization ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Left Handed ◽  
Local Ratio

This paper builds on our claim that most vortical structures in transitional and turbulent flows are partially polarized. Polarization is inferred by the application of helical wave decomposition. We analyse initially polarized isolated viscous vortex rings through direct numerical simulation of the Navier-Stokes equations using divergence-free axisymmetric eigenfunctions of the curl operator. Integral measures of the degree of polarization, such as the fractions of energy, enstrophy, and helicity associated with right-handed (or left-handed) eigenfunctions, remain nearly constant during evolution, thereby suggesting that polarization is a persistent feature. However, for polarized rings an axial vortex (tail) develops near the axis, where the local ratio of right- to left-handed vorticities develops significant non-uniformities due to spatial separation of peaks of polarized components. Reconnection can occur in rings when polarized and is clearly discerned from the evolution of axisymmetric vortex surfaces; but interestingly, the location of reconnection cannot be inferred from the vorticity magnitude. The ring propagation velocity Up decreases monotonically as the degree of initial polarization increases. Unlike force-balance arguments, two explanations based on vortex dynamics provided here are not restricted to thin rings and predict reduction in Up correctly. These results reveal surprising differences among the evolutionary dynamics of polarized, partially polarized, and unpolarized rings.

An Investigation of Muscle Stresses in Swimming Hydromedusae

2009 ◽  
Author(s):  
Doug Lipinski ◽  
Kamran Mohseni
Keyword(s):  
Stokes Equations ◽  
Original Model ◽  
Force Balance ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Area Of Interest ◽  
Equal Radius ◽  
Muscle Stress ◽  
Pressurized Cylinder ◽  
Walled Cylinder

We investigate several preliminary models for the muscle stress produced during the swimming of a hydromedusa, Sarsia tubulosa, which relate the pressure on the hydromedusa to the stress in the musculature. Our calculations are based on the solution of the Navier-Stokes equations for the flow around a swimming hydromedusa. This numerical model allows us to obtain detailed pressure information in any area of interest on or near the hydromedusa. Initially, we investigate the pressure distribution on the surface of the hydromedusa and find that it is quite uniform in space. We present an original model based on a force balance created using the actual hydromedusa’s geometry and compare the results we obtain to the stress in a pressurized thin walled cylinder or sphere of equal radius. Our model allows us to calculate and estimated muscle stress at any point along the hydromedusa. By doing so, we are able to validate the assumptions made by modeling the subumbrellar cavity as a pressurized cylinder or sphere.

scholarly journals Reply to “Basal buoyancy and fast-moving glaciers: in defense of analytic force balance” by C. J. van der Veen (2016)

2017 ◽  
Vol 11 (4) ◽  
pp. 1685-1689
Author(s):  
Terence J. Hughes
Keyword(s):  
Stokes Equations ◽  
Flow Line ◽  
Traditional Approach ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Geometric Approach ◽  
Force Balance ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Ice Sheet Modeling

Abstract. Two approaches to ice-sheet modeling are available. Analytical modeling is the traditional approach (Van der Veen, 2016). It solves the force (momentum), mass, and energy balances to obtain three-dimensional solutions over time, beginning with the Navier–Stokes equations for the force balance. Geometrical modeling employs simple geometry to solve the force and mass balance in one dimension along ice flow (Hughes, 2012a). It is useful primarily to provide the first-order physical basis of ice-sheet modeling for students with little background in mathematics. The geometric approach uses changes in ice-bed coupling along flow to calculate changes in ice elevation and thickness, using a floating fraction ϕ along a flow line or flow band, where ϕ = 0 for sheet flow, 0 < ϕ < 1 for stream flow, and ϕ = 1 for shelf flow. An attempt is made to reconcile the two approaches.

Collapse Prediction During Hollow Optical Fiber Fabrication

2005 ◽  
Author(s):  
Srinath S. Chakravarthy ◽  
Wilson K. S. Chiu
Keyword(s):  
Temperature Distribution ◽  
Stokes Equations ◽  
Numerical Study ◽  
Surface Force ◽  
Force Balance ◽  
Navier Stokes ◽  
Feed Speed ◽  
Navier Stokes Equations ◽  
Isothermal Analysis ◽  
Crystal Fibers

A numerical study of the drawing of hollow capillary rods over a range of draw speeds and feed speeds, with application to the drawing of photonic crystal fibers is presented. In this study the axisymmetric Navier-Stokes equations are solved numerically using the finite element method. In the numerical study inertia, gravity, surface tension and internal pressurization of the capillary is included and the effect of each of these parameters on the neck down profile is presented. The free surface which defines the neck down profile, is not assumed but is determined using a surface force balance. The results of isothermal and non-isothermal analysis results are compared with experimental, numerical and analytical results from the literature for validation. In the non-isothermal analysis, arbitrary temperature profiles are assumed to represent the temperature distribution in the neck down region and the effect of different temperature distributions on the neck down profile is discussed. The effect of the draw parameters (draw speed and draw down ratio) and the temperature distribution on the collapse of the capillaries is examined. A qualitative discussion on the onset of collapse of the capillary is presented and the effect of the draw parameters on the draw tension is discussed. For isothermal cases, the feed speed dominated the determination of collapse, while the draw speed had a relatively small effect on the collapse. It was found that collapse can be avoided with higher feed speeds and lower temperatures, while the draw tension can be minimized at lower feed speeds and higher temperatures.

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

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