ShapeFactor.md

User Function USF_ShapeFactor

General Information

• USF Fortran File: USF_ShapeFactor.f90

• USF Name: LateralFriction_x and LateralFriction_y

• Required Input Variable(s): None

General Description

This user function return the modified gravity force -g +(1-f)(g.t).t where t is the tangent vector to the upper surface and f the shape factor. The shape factor f can be given or calculated as a function of h(x,t) for rectangular or parabola valley shapes.

This solver works only in 2D (no sense in 3D). It works for non-structured mesh.

SIF contents

Here are the three options to use the USF_ShapeFactor user function. In the first option, the shape factor f is simply given as a parameter Shape Factor:

Body Force 1
  Flow BodyForce 1 = Variable Coordinate 1
     Real Procedure "ElmerIceUSF" "ShapeFactorGravity_x"
  Flow BodyForce 2 = Variable Coordinate 1
     Real Procedure "ElmerIceUSF" "ShapeFactorGravity_y"
  Shape Gravity 1 = Real  0.0                                 
  Shape Gravity 2 = Real -9.7696e15       

  Shape Factor = real $shapefactor
End

In the second option, the shape factor f is computed for a rectangular valley of given width:

Body Force 1
  Flow BodyForce 1 = Variable Coordinate 1
     Real Procedure "ElmerIceUSF" "ShapeFactorGravity_x"
  Flow BodyForce 2 = Variable Coordinate 1
     Real Procedure "ElmerIceUSF" "ShapeFactorGravity_y"
  Shape Gravity 1 = Real  0.0                                 
  Shape Gravity 2 = Real -9.7696e15       

  Rectangle Shape = Logical True
  Rectangle Width = Real 2.0e3
End

In the third option, the shape factor f is computed for the parabola type transverse valley y = b + az^2*, where a is given by the Parabola afactor keyword and b is the bedrock elevation of the central line:

Body Force 1
  Flow BodyForce 1 = Variable Coordinate 1
     Real Procedure "ElmerIceUSF" "ShapeFactorGravity_x"
  Flow BodyForce 2 = Variable Coordinate 1
     Real Procedure "ElmerIceUSF" "ShapeFactorGravity_y"
  Shape Gravity 1 = Real  0.0                                 
  Shape Gravity 2 = Real -9.7696e15       
  
  Parabola Shape = Logical True
  Parabola afactor = Real 0.0005
End

In all cases, the two keywords Shape Bedrock and Shape Surface are used to locate nodes belonging on the bedrock and surface boundaries, respectively.

! Bedrock
Boundary Condition 1
  Target Boundaries = 1
  ...
  Shape Bedrock = Logical True
End

! Upper Surface
Boundary Condition 3
  Target Boundaries = 3
  ...
  Shape Surface = Logical True
End

Examples

An example using the user function USF_ShapeFactor can be found in [ELMER_TRUNK]/elmerice/Tests/ShapeFactor.

Reference

When used this solver can be cited using the following references: Jay-Allemand M., F. Gillet-Chaulet, O. Gagliardini and M. Nodet, 2011. Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge. The Cryosphere, 5, p. 659-672, doi:10.5194/tc-5-659-2011.