Fluid Dynamics in Microgravity .:. Go Up

I. Scientific Objectives

A common area of study in microgravity deals with unhindered capillarity. In the presence of gravity, fluid in a tube will rise to a specific height based on the contact angle, surface tension, and diameter of apparatus (Giancoli 1998, p. 296.). In microgravity, capillary tubes can be used to pump liquids the entire length of the tube (Stange, et al. 2003, Siegel 1961, NASA CAPL-2, 2004, ZARM 2004). In April of 2005 (Tualatin High School Physics, 2005), a group of students used capillarity with water to eject droplets into the air with limited results due to the wetting characteristics of water and glass. Therefore, we intend to use silicone fluids and small geometries to obtain more consistent results. We propose to use this capillarity to investigate three different fluid experiments dealing with liquid dynamics in microgravity, related to creating droplets in microgravity. The three experiments will deal with capillary rise in a tapered tube, capillary flow through a tube with a constriction, and splitting droplets that have already left a tube.

With a tapered tube, our first experiment, we expect the velocity of the flow to increase due to the restricted area, like a garden hose with a thumb over the end. Inertia may hinder this example of capillary action depending on the tube’s immersion depth as a greater force would be required to overcome the force of attraction between the tube and the fluid. It is our hypothesis for this experiment that the angle at which the tube tapers will cause the liquid to rise at a greater rate.

Regarding a restricted tube, like the hourglass shape, we are expecting the velocity of the liquid to increase as it approaches the point of restriction. At the point of greatest restriction, we hypothesize that the velocity will be great enough to propel a droplet into the air within the tube above the constriction.

For the standard capillary tube attempting to send a drop into a collision with a razor blade we hypothesize that the droplet that is rising out of the tube will have enough force due to its velocity to cut itself in half by the razor blade that is fixed some distance above the tube.

Our intent is to use the non-volatile fluid 3M Fluorinert Dielekrica (FC-77). The results of the ZARM experiment (Stange et al., 2003 ) show that this fluid will rise to heights of 80mm to 100mm for tube diameters of 11mm within the 2.2-second window that we have in the DIME drop tower.

We will be constructing our experiment out of clear polycarbonate plastic. It will be divide into three separate compartments with three different experiments, one in each compartment. In the bottom of each compartment they will each have their own reservoir for silicon solution. We will use the provided video camera and a backlight inside the experiment apparatus to view the results of our experiment. Experiments will be mounted on clear plastic so that they can be easily placed in their compartments, and the tubes will be easily accessible for the cleaning and the preparation of the experiment.

The purpose of this experiment is to examine the dynamics of fluids in microgravity. A benefit from this experiment would be to increase our understanding of the dynamics of fluids. Perhaps airborne droplets can be used as a form of fluid transport for packaging small amounts of liquid, or for combustion.

II Technical Plan

Our apparatus will be composed of a Plexiglas container with a removable lid that will be holding another Plexiglas chamber (Figure 1). This inner container will be divided into three separate chambers, each approximately 3.68 cm wide and deep, and containing about 50 cc of silicone fluid (Figure 2). We will immerse the various tube designs in the fluid to a certain point. The tubes will be mounted to a back plate inside the chambers so that they will not be moved around during free fall (Figure 3). We will have three tube designs per drop (one in each chamber) in order to test a variety of theories for a fluid dynamics in microgravity, including a tapered tube, a restricted tube in an “hour glass” shape, and a tube with a razor blade in the drop’s path of collision to attempt to slice the droplet in half.

We will set up the capillary tube designs inside the plastic container filled with the designated amount of fluid (using the fixed levels and submersions). We will then double-check everything before the drop. The apparatus will then be dropped and the provided camera will capture the movement of the liquids in (and, hopefully out) of the capillary tubes. As the container is dropped in the microgravity environment, we expect a series of events to occur during the experiment. Our first prediction is that the silicon fluid in the tapered tube will climb the walls of the tube and be ejected out of the end. With the tube designed to send a droplet into a path of collision with the razor blade we believe that the drop will be sliced in two, rather than to cling to the blade and continue climbing upwards. Finally, with the “hourglass” tube, we believe that the silicon fluid will eject at the restricted point, instead of going through the restriction point and continue climbing the walls of the tube.

The rugged design of the apparatus will allow it to survive the drop and be used multiple times. The tubes will be held in place to assure their safety, however, replacements will be ready if necessary. In addition, the air bags will ensure the safety of the apparatus as a whole when it is finished with its drop in microgravity. We will derive our data from analysis of the drop video.

Using information we have gathered (from previous DIME water droplet experiments, etc.) we should be able to successfully launch multiple drops of water and witness the drops performing the various events described in the experiment setup within a 2.2 sec time frame. Our hope is that this will be enough time for the fluid in each design to climb up and out of the walls of the capillary tube.

In order to test the durability of the drop apparatus we will take extra care in its design to ensure its stability. Before the actual drop, we will check each component of the apparatus to make sure it will do what is needed and survive the drop in order to be used multiple times, as well as to ensure the stability of each tube and the precision of each experiment.

III Team Organization

Our team is a fully capable, large group of motivated students that is prepared to dive into a project of great magnitude such as this. Our goal in working on this project is to divide the work evenly among the team members to insure that we carry an equal load and use our unique abilities to accomplish the task we have at hand. On completion of these tasks, we will share our work with our fellow teammates to verify that all components have been completed and that there are no miscalculations or overlooked factors.

We have all worked together in physics classes and understand each member’s work habits and abilities. Working together on labs and studying for tests is not foreign to us, so we already know how to divide the workload according to each individual’s abilities and skill level, which balancing the tasks between team members. Additionally, as a rather large group of seven, we have the blessing of being able to combine many different minds and ideas as opposed to only a few. We have the ability to get together and bounce ideas off each other to find the best solution or get the best idea we could possibly have. Some of us have great skills with the conceptual and theoretical understanding of physics, while others have a superb ability to research and analyze with great efficiency. With so many different mindsets and abilities our team, along with the help of our team advisor, has come together to function as a well-rounded physics research team.

Since our team is so large, only four out of the seven people on our team will be selected to visit the Glenn Research Center. The dilemma in this is the negative feelings that may arise from the individuals who will not be selected to go. However, each team member has an initiative and love for physics that goes beyond the material aspect of this project that is getting to travel to Cleveland. So, we will work together in a way that will represent our school and state well, free from the influences of materialism and selfishness. In the end, we will know that we did our best to work together as a team of equals and to explore the limits of our physical world.

IV Resource Credits

Bibliography

Stange, M., Dreyer, M. E., & Rath H. J. (2003). Capillary driven flow in circular cylindrical tubes. Physics of Fluids. 15(9) 2587-2601

Siegel, R. (1961). Transient Capillary Rise in Reduced and Zero Gravity Fields. Journal of Appl. Mech. 83 165-170

Tualatin High School Physics Research (2005). Creating Isolated Droplets in Microgravity, Retrieved November 8, 2005 from

http://tuhsphysics.ttsd.k12.or.us/Research/DIME05/Final/index.htm

ZARM Center of Applied Space Technology and Microgravity. (2004). Capillary Rise in Tubes. Retrieved October 5, 2004, from

http://www.zarm.uni-bremen.de/2forschung/grenzph/isoterm/cap_rise/index.htm

NASA National Space and Aeronautics Administration. (1995). Capillary Pumped Loop-2 (CAPL-2). Retrieved October 7, 2004, from

http://ssppgse.gsfc.nasa.gov/hh/capl/capl.html

Physics – Principles with Applications. Giancoli, D. (1998). Physics – Principles with Applications. (5th ed.). New Jersey: Prentice Hall.