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capilary
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Dynamics of Capillary SurfacesLucero Carmona
Professor John Pelesko and Anson CarterDepartment of MathematicsUniversity of Delaware
Explanation When a rigid container is inserted into a fluid,
the fluid will rise in the container to a height higher than the surrounding liquid
Tube Wedge Sponge
Goals Map mathematically how high the liquid
rises with respect to time Experiment with capillary surfaces to
see if theory is in agreement with data If the preparation of the tube effects
how high the liquid will rise
List of Variables:volume = g = gravityr = radius of capillary tubeZ = extent of rise of the surface of the liquid, measured to the bottom of the meniscus, at time t ≥ 0 = density of the surface of the liquid - = surface tension = the angle that the axis of the tube makes with the horizontal of the stable immobile pool of fluid = contact angle between the surface of the liquid and the wall of the tube
Initial Set-up and Free Body Diagram
Explanation of the Forces Surface Tension Force
Gravitational Force
Poiseulle Viscous Force
Explanation of the Forces End-Effect Drag
Newton's Second Law of Motion
Explanation of Differential EquationFrom our free body diagram and by Newton's Second Law of Motion:
Net Force = Surface Tension Force - End-Effect Drag - Poiseuitte Viscous Force - Gravitational ForceNet Force + End-Effect Drag + Poiseuitte Viscous Force + Gravitational Force - Surface Tension Force = 0 After Subbing back in our terms we get:
By Dividing everything by we get our differential equation:
whereZo = Z(0) = 0
Steady State By setting the time derivatives to zero in the
differential equation and solving for Z, we are able to determine to steady state of the rise
Set - Up Experiments were performed usingsilicon oil and water
Several preparations were used on the set-up to see if altered techniques would produce different results
The preparations included:• Using a non-tampered tube
• Extending the run time and aligning the camera
• Aligning the camera and using an non-tampered tube
•Disinfecting the Tube and aligning the camera
• Pre-wetting the Tube and aligning the camera
Set - Up
The experiments were recorded with the high speed camera.
The movies were recorded with 250 fps for Silicon Oil and 1000 fps for water.
Stills were extracted from the videos and used to process in MatLab.
1 frame out of every 100 were extracted from the Silicon Oil experiments so that 0.4 of a second passed between each frame.
1 frame out of every 25 were extracted from the Water experiments so that 0.025 of a second passed between each frame.
Set - Up
Z
MatLab was then used to measure the rise of the liquid in pixels
Excel and a C-program were used to convert the pixel distances into MM and to print out quick alterations to the data
Capillary Tubes with Silicon Oil
Silicon Oil Data:
Steady State Solution
Initial Velocity
Eigenvalues
Capillary Tube with Water
Water Data:
Steady State Solution
Initial Velocity
Eigenvalues
Previous Experimental Data (Britten 1945)
Water Rising at Angle Data: Steady State Solution
Initial Velocity
Eigenvalues
Results There is still something missing from the
theory that prevents the experimental data to be more accurate
The steady – state is not in agreement with the theory
There is qualitative agreement but not quantitative agreement
Eliminated contamination
Explanation of Wedges When a capillary wedge is inserted into a
fluid, the fluid will rise in the wedge to a height higher than the surrounding liquid
GoalsMap mathematically how high the liquid rises with respect to time
Wedge Set - Up Experiments were performed usingsilicon oil
Two runs were performed with different angles
Experiments were recorded with the high speed camera at 250 fps and 60 fps
Wedge Set - Up
For first experiment, one still out of every 100 were extracted so that 0.4 sec passed between each slide
For second experiment, one still out of every 50 were extracted so that 0.83 sec passed between each slide
MatLab was then used to measure the rise of the liquid in pixels
Excel and a C-program were used to convert the pixel distances into MM and to print out quick alterations to the data
Z
Wedge Data
Explanation of Sponges Capillary action can be seen in porous
sponges
GoalsTo see if porous sponges relate to the capillary tube theory by calculating what the mean radius would be for the pores
Sponge Set - Up Experiments were performed usingwater
Three runs were preformed with varyinglengths
Experiments were recorded with the high speed camera at 250 fps and 60 fps
Sponge Set - Up
For first and second experiments, one still out of every 100 were extracted so that 0.4 sec passed between each slide
For third experiment, one still out of every 50 were extracted so that 0.83 sec passed between each slide
MatLab was then used to measure the rise of the liquid in pixels
Excel and a C-program were used to convert the pixel distances into MM and to print out quick alterations to the data
Z
Sponge DataThe effects of widths and swelling
Future Work Refining experiments to prevent undesirable
influences Constructing a theory for wedges and
sponges Producing agreement between theory and
experimentation for the capillary tubes Allowing for sponges to soak overnight with
observation
References Liquid Rise in a Capillary Tube by W. Britten (1945).
Dynamics of liquid in a circular capillary. The Science of Soap Films and Soap Bubbles by C.
Isenberg, Dover (1992). R. Von Mises and K. O. Fredricks, Fluid Dynamics
(Brown University, Providence, Rhode Island, 1941), pp 137-140.
Further Information http://capillaryteam.pbwiki.com/here
(u, v, w)u - velocity in Z-dirv - velocity in r -dirw - velocity in θ-dir
Explanation of the Forces Poiseulle Viscous Force:
Since we are only considering the liquid movement in the Z-dir:u = u(r)v = w = 0 The shearing stress,τ, will be proportional to the rate of change of velocity across the surface. Due to the variation of u in the r-direction, where μ is the viscosity coefficient:
Since we are dealing with cylindrical coordinates
From the Product Rule we can say that:
Solving for u:
Explanation of the Forces Poiseulle Viscous Force:
If then:
Sub back into the original equation for u:
So then for :
From this we can solve for c: Sub back into the equation for u:
Average Velocity:
Explanation of the Forces Poiseulle Viscous Force:Equation, u, in terms of Average Velocity
Further Anaylsis on shearing stress, τ:
for,
The drag, D, per unit breadth exerted on the wall of the tube for a segment l can be found as: