Haljasmaa, Igor V.
(2006)
On the drag of fluid and solid particles freely moving in a continuous medium.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Despite the abundance of experimental results on the free motion of solid, liquid, and gaseous particles under various conditions, there is no successful systematization of a drag curve across all three phases. Empirical models offered in the past can be quite useful within the limits of a particular class. However, they lack the capability to explain differences in hydrodynamic behavior across all types from one generalized prospective. The ultimate goal of this study is to provide such a systematic description based on a complete set of non-dimensional parameters, using contemporary knowledge along with our experiments on free particle motion in a quiescent medium. As a result of experimental studies directed at this objective, instability in particle steady rectilinear motion was identified which was shown to correspond to a bifurcation in the drag curve. Significantly, the onset of this bifurcation did not in general coincide with the onset of vortex shedding around the particle. The particle/ medium density ratio appears to play an important role in the onset point and the characteristics of the non-rectilinear motion, though this parameter was not taken into account in most previous parametric studies. Within the fluid mechanics community, the fluid particle viscosity ratio is generally believed to play a negligible role in particle motion in contaminated media. However, as a damping factor, particle viscosity can be important for the onset of shape instability and shape oscillations. Based on our experimental results, along with previous experimental, analytical and numerical works of various authors, a systematic description of the particle drag is suggested.The fundamental results described above were applied to the specific problem of maintaining CO2 particles in a fixed viewing region in a countercurrent flow column for long term studies. Countercurrent flow with chosen velocity profiles and tapered column geometry were used to stabilize the buoyant particles in the laboratory frame while minimizing the deviation of the CO2 particle from the natural free rising (or sinking) motion in the ocean. Design optimization for the experimental unit, limitations of the stabilization process, and parameters affecting particle behavior are discussed.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
27 September 2006 |
| Date Type: |
Completion |
| Defense Date: |
19 June 2006 |
| Approval Date: |
27 September 2006 |
| Submission Date: |
24 July 2006 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Mechanical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
bifurcation; bubble; drag curve; drop; Morton number; solid sphere |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-07242006-003502/, etd-07242006-003502 |
| Date Deposited: |
10 Nov 2011 19:53 |
| Last Modified: |
15 Nov 2016 13:46 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/8557 |
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