## Lecture 6: More Complete Code

The total surface force on a 2D line segment is
The curvature times the normal
The pull on one end minus the pull on the other
The surface tension times the normal
The integral of the tangent vector along the segment
All of the above

In the code the surface force on the front is found at
The marker points
Midway between the marker points
At the point closest to the fixed grid
Depends on the location and orientation of the front
At the pressure nodes

To find the surface force on the fixed grid
We find the gradient of the marker function
We find the curvature of the interface
We transfer the curvature from the front to the grid
We transfer the normal vector from the front to the grid
We transfer the total force from the front to the grid

At wall boundaries we adjust the surface tension by assuming
A rigid, no-slip wall
A rigid full-slip wall
Symmetry boundary
A free surface
None of the above

In the present code we
Use the marker to set the viscosity to different values in each fluid
Use the density to set the viscosity to different values in each fluid
Use the pressure to set the viscosity to different values in each fluid
Take the viscosities to be equal
None of the above

When the viscosities in the two fluids are different, we find the viscous terms by
Integrating around the control surface
Using the full velocity deformation tensor
Approximate integrals by the midpoint rule
Interpolate linearly when needed
All of the above

When the viscosities in the two fluids are different, we find the viscous terms for the u-velocity using the
Pressure control volume
Density control volume
u-velocity control volume
v-velocity control volume
None of the above

To make the code third order in time, we need to
Use an implicit time integration
Compute the right hand side two times
Compute the right hand side three times
Compute the right hand side four times
Store several intermediate velocities

A code that is third order in time, when compared to a first order code, is likely to
Run at about the same speed
Run faster
Give less accurate results
Give more accurate results
None of the above

A slightly deformable drop that falls head-on onto a wall
Is likely to breakup in flight
Becomes a permanent flat blob on the wall
Deform and then bounce slightly before settling on the wall
Roll along the wall
None of the above