www.acsprf.org

In this project, we mainly focus on the dynamics of suspended particles inside a cylinder partially blocked by depositions, and calculate pressure-loss in such conduits. For this purpose, we analyze many-body hydrodynamic interactions inside a conduit so that the effect of the bounding wall and other particles on the motion of suspended bodies can be quantified. Such detailed description of particle dynamics is essential for understanding clustering process in an obstructed channel and transport phenomena involving suspension. The funding from ACS helped substantially to study these processes.

The key mathematical issue in this problem is to find an efficient way to account for a large number of disconnected dissimilar boundaries representing many colloidal particles and the conduit. This is why we have developed a new algorithm “Basis Transformation Method”. Such new computational tool enables us to describe general many-body viscous dynamics inside a vessel. As a result, it can be possible to explain clustering processes in an obstructed channel and motion of suspended bodies inside microscopic conduits. 

Key results:

The important results of this research have been either published or in the process of getting published. The key findings are documented in the list below.

1) The general creeping motion of a finite-sized sphere inside a narrow cylinder is described by using basis transformation method.

2) The increase in channel-resistivity due to the presence of deposited particles is computed.

3) The effect of particle-wall and interparticle hydrodynamic interactions on the rheological properties of a confined suspension is studied.

4) The motion of small particles around a fixed large body inside a narrow vessel is determined.

5) The increase in flow-induced stress on a deposited particle due to the presence of suspended solute is estimated.

6) Dynamics of sedimenting spheres inside a narrow conduit is analyzed.

7) Equation of motion for time-dependent penetration length of a fluid column inside a narrow pore is derived.

Scientific and technological impact:

The primary contribution of this project is the development of a new method that can precisely compute effects of confining cylinders on multiparticle systems. These effects are especially significant in microchannels where hydrodynamic interactions among particles are enhanced tremendously due to the confinement. This method can be widely applicable because of its efficiency and generality.

This research quantitatively describes several important phenomena like viscous losses in partially blocked microchannels, suspension dynamics inside confinements, and flow induced stresses on suspended and deposited particles. Understanding of these processes is extremely important for improvement of filters and reactors. These detailed studies will predict which microstructure is best suited for particle removal or least prone to blockage. Moreover, our pressure-drop calculations give estimates of hydrodynamic losses in these channels. Similarly, computation of hydrodynamic forces on particles can be used for flow-assisted cleansing of the microconduits. Hence, our findings can be directly applied in many technological applications related to petrochemical industry.

Student education and their career development:

This grant has supported four graduate students during different stages of their graduate studies. Three of these students are PhD students whereas the remaining one has pursued an MS degree.

One of the PhD students has graduated after completing his share of work in this project at the end of 2010. He has been supported by this grant for nearly a couple of years. The research during his stay enables him to secure a post doctoral position in which he is current being trained to be a future faculty.

The MS student has also graduated in 2010. He was partially supported by the PRF grant for a year. He is currently pursuing MBA degree after a period of industrial job.

The other two PhD students have been partially supported by the PRF grant. One of them is graduating in Fall 2011, whereas other is planning to stay another year. Both of them are now supported by NSF funding which was secured by the PI on the basis of the research supported by ACS.

Impact on the career of the PI:

The funding helped the PI to obtain very important results describing colloidal dynamics inside a conduit. Such findings gave credibility to his research for which he has been able to attract recent funding from NSF for research on related topic.

 It is to be noted that a general methodology like “Basis Transformation Method” is applicable not only in the analysis of colloidal dynamics but also in solving elasticity or electrodynamics problems. Hence, in the future, the PI will be able to analyze different physical systems where the home-grown “Basis Transformation Method” will be used extensively.