film_evol_3.m % this function solves the problem with boundary conditions h=h_b, h_xxx+alpha =0 at x=0, and h_x=0, h_xx=delta at x=1
soln_plot.m % plots the film profile at a given snapshot in time
soln_movie.m % creates a movie of the evolution of the film over a given time range
Here is a typical call to these functions:
N=50;
H=.08*ones(1,N);
H(1)=.09; H(50)=.09;
alpha=-50; % magnetic force stronger than gravity
h_b=.1; % fixed boundary condition at the top
delta=2; % the fixed value of the curvature at the bottom
[t,h,X]=film_evol_3(alpha, h_b, delta, N, 15, H);
M=soln_movie(X,h,2,length(t));
A few notes:
The problem being solved is for a tangentially immobile surface, primarily because that is the easiest
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Here is some code I have written to solve the evolution equation
film_evol_3.m % this function solves the problem with boundary conditions h=h_b, h_xxx+alpha =0 at x=0, and h_x=0, h_xx=delta at x=1
soln_plot.m % plots the film profile at a given snapshot in time
soln_movie.m % creates a movie of the evolution of the film over a given time range
A few notes:
- The problem being solved is for a tangentially immobile surface, primarily because that is the easiest
- I have not been
Particular Problems:
Matlab code for numerical solving of evolution equation
Reverse draining of a magnetic soap-film
In this problem, we study the draining of a soap-film with magnetic nanoparticles, under the influence of a magnetic field. We consider the following experiment: form a cylindrical soap-bubble between two parallel plates. On the top plate place a strong bar magnet (field strength >1000 G). If there are no magnetic forces present, the soap-film will drain under the influence of gravity. Due to the effects of marginal regeneration, elements of "black film", which are much thinner than the bulk film and appear invisible to the eye, form in the film and move upwards. Hence the film appears to disappear from the top down. Adding the magnet above the film provides a magnetic pressure in the opposite direction as gravity. If the magnetic force is strong enough, the draining is "reversed", and the film disappears from the bottom up. Th]]>
In the next video, a band of black film has formed in the middle of the cylinder. The film undergoes turbulent motion as some thicker film is pulled to the upper ring and some thicker film falls to the lower ring.
Try to explain this pattern formation...
[DEM] I am going to post a link to thoughts/comments/questions for useful papers
Sources (Please put citations useful to the group here.)
]]>
In the following video, a ring of black film sits in the middle of the cylinder. Rotating the]]>
In the following video, a ring of black film sits in the middle of the cylinder. Rotating the]]>
The draining process is far more complicated and interesting on a molecular level. In the following video, a band of black film has formed in the middle of the cylinder. The film undergoes turbulent motion as some thicker film is pulled to the upper ring and some thicker film falls to the lower ring.
for each paper I read. useful papers
Sources (Please put citations useful to the group here.)
Isenberg, Science of Soap Films and Soap Bubbles
44, 46
"The stars are the heavens"
Magnetic deflections of an elastic membrane
In this problem, we place a magnet near a magnetic soap-film. The magnetic field creates an attraction between the film and the magnet, and induces a competition between magnetic and elastic forces. In similar problems with electrostatics, the "pull-in" phenomenon,]]>
Reverse draining of a magnetic soap-film
field. The experiment is as follows: We consider the following experiment: form a cylindrical soap-bubble between two parallel plates. On the top plate we place a strong bar magnet (field strength >1000 G). IF If there are no magnetic forces present, the soap-film will drain under the influence of gravity. Due to the effects of marginal regeneration, elements of "black film", which are much thinner than the bulk film and appear invisible to the eye, form in the film and move upwards. Hence the film appears to disappear from the top down. Adding the magnet above the film provides a magnetic pressure in the opposite direction as gravity. If the magnetic force is strong enough, the draining is "reversed", and the film disappears from the bottom up. Below is a The video to demonstrate below demonstrates this process:]]>
Reverse draining of a magnetic soap-film
G). Under the influence of gravity, IF there are no magnetic forces present, the soap-film will drain. drain under the influence of gravity. Due to the effects of marginal regeneration, elements of "black film", which are much thinner than the bulk film and appear invisible to the eye, form in the film and move to upwards. Hence the film appears to disappear from the top down. Adding the magnet above the film provides a magnetic pressure in the opposite direction as gravity. If the magnetic force is strong enough, the draining is "reversed", and the film disappears from the bottom up. Below is a video to demonstrate this process:
[DEM] I have been reading a lot of papers the past couple days. I have about a thousand thoughts and questions going through my head, so I am going to post a link to thoughts/comments/questions for each paper.
Sources (Please]]>
Feel free to create links to new pages and organize this information as you see fit.
I think the wiki is a great idea, so I am going to force myself to utilize it... - Derek
Group members
John A. Pelesko
Regan Beckham
Richard J. Braun
Particular Problems:
Reverse draining of a magnetic soap-film
In this problem, we study the draining of a soap-film with magnetic nanoparticles, under the influence of a magnetic field. The experiment is as follows: We form a cylindrical soap-bubble between two parallel plates. On the top plate we place a strong bar magnet (field strength >1000 G). Under the influence of gravity, the soap-film will drain. Due to the effects of marginal regeneration, elements of "black film", which are much thinner than the bulk film and appear invisible to the eye, form in the film and move to
[DEM] I have been reading a lot]]>
A film element falls into the Plateau border
the surfactent surfactant concentration increases.
This occurs all along the border (they only consider the lower border),
In order for the surfactant distribution to equilibriate, the saturated layer becomes unstable, with some elements gaining even higher concentration, others having a normal coverage
]]>
I have really only focused on the introduction portion of this paper so far. The main point is that they present an alternative explanation of the mechanism of marginal regeneration. Here is my interpretation/summary of the process based on their explanation:
- A film element falls into the Plateau border
- The thickness of the element increases, causing the surface area to decrease. As a result, the surfactent concentration increases.
- This occurs all along the border (they only consider the lower border),
- In order for the surfactant distribution to equilibriate, the saturated layer becomes unstable, with some elements gaining even higher concentration, others having a normal coverage
- The elements with high concentration have lower surface tension than their surroundings, and are pulled back into the film where they can expand (vertically)
- The elements (now in th
Elias et al, Magnetic soap films and magnetic soap foams, Coll and Surf A
Source 3Nierstrasz, Frens, Marginal Regeneration and the Marangoni effect, J Coll Int Sci
Source 4
Source Name
]]>
Section 3.2 - Note that their magnetic field strength is varied from 0 to 270 G. We should compare our magnets to these values.
Section 3.1 3.3 - First full paragraph p. 68: This is their heuristic explanation of the effect of the magnetic particles, based on dipole interaction. I do not quite understand this, can anyone explain it to me? It seems pretty important that we (fully) understand this argument.
One particular issue I have with this:
- They only consider flow between meniscus and film at the bottom meniscus. Why? There will also be a meniscus at the top and along the sides. Why is there no comparison between the magnetic dipole interaction energy in these ]]>
Some observations/questions from this paper:
Section 2 - Do we need to worry about magneto-rheological effects? They state: "Magneto-rheological effects are expected when the magnetic field is perpendicular to the vorticity, since the alignment of the magnetic momentums along the field direction prevents the rotation of the particles in the shear."
Section 3.2 - Note that their magnetic field strength is varied from 0 to 270 G. We should compare our magnets to these values.
Section 3.1 - First full paragraph p. 68: This is their heuristic explanation of the effect of the magnetic particles, based on dipole interaction. I do not quite understand this, can anyone explain it to me? It seems pretty important that we (fully) understand this argument.
One particular
]]>