Abstract
The microflow and stirring around paramagnetic particle microchains, referred to as microrotors, are modeled as a circular cylinder rotating about its radial axis at very low Reynolds number. Time scales for momentum transfer under these conditions are determined to be much smaller than those for boundary movement, hence a quasi-steady approximation can be used. The flow is derived at every instant from the case of a steady motion of a horizontally translating cylinder, with the rotation approximated to a series of differential incremental translations. A numerical simulation is used to determine the pathlines and material lines of virtual point fluid elements, which were analyzed to understand the behavior of the flow around the microrotor. The results indicate the flow to be unsteady, with chaotic advection observed in the system. The fluid motion is primarily two-dimensional, parallel to the rotational plane, with mixing limited to the immediate area around the rotating cylinder. Fluid layers, up to many cylinder diameters, in the axial direction experience the disturbance. Elliptic and star shaped pathlines, including periodic orbits, are observed depending on the fluid element's initial location. The trajectories and phase angles compare well with the experimental results, as well as with data from particle dynamics simulations. Material lines and streaklines display stretching and folding, which are indicative of the chaotic behavior and stirring characteristics of the system. The material lines have similar lengths for the same amount of rotation at different speeds, and the effect of rotational speeds appears to be primarily to change the time of mixing. The results are expected to help in the design of a particle microrotor based sensing technique.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 201-208 |
| Number of pages | 8 |
| Journal | Lab on a Chip - Miniaturisation for Chemistry and Biology |
| Volume | 4 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jun 2004 |
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ASJC Scopus subject areas
- Clinical Biochemistry
Cite this
Modeling microflow and stirring around a microrotor in creeping flow using a quasi-steady-state analysis. / Vuppu, Anil K.; Garcia, Antonio; Saha, Sanjoy K.; Phelan, Patrick; Hayes, Mark; Calhoun, Ronald.
In: Lab on a Chip - Miniaturisation for Chemistry and Biology, Vol. 4, No. 3, 06.2004, p. 201-208.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Modeling microflow and stirring around a microrotor in creeping flow using a quasi-steady-state analysis
AU - Vuppu, Anil K.
AU - Garcia, Antonio
AU - Saha, Sanjoy K.
AU - Phelan, Patrick
AU - Hayes, Mark
AU - Calhoun, Ronald
PY - 2004/6
Y1 - 2004/6
N2 - The microflow and stirring around paramagnetic particle microchains, referred to as microrotors, are modeled as a circular cylinder rotating about its radial axis at very low Reynolds number. Time scales for momentum transfer under these conditions are determined to be much smaller than those for boundary movement, hence a quasi-steady approximation can be used. The flow is derived at every instant from the case of a steady motion of a horizontally translating cylinder, with the rotation approximated to a series of differential incremental translations. A numerical simulation is used to determine the pathlines and material lines of virtual point fluid elements, which were analyzed to understand the behavior of the flow around the microrotor. The results indicate the flow to be unsteady, with chaotic advection observed in the system. The fluid motion is primarily two-dimensional, parallel to the rotational plane, with mixing limited to the immediate area around the rotating cylinder. Fluid layers, up to many cylinder diameters, in the axial direction experience the disturbance. Elliptic and star shaped pathlines, including periodic orbits, are observed depending on the fluid element's initial location. The trajectories and phase angles compare well with the experimental results, as well as with data from particle dynamics simulations. Material lines and streaklines display stretching and folding, which are indicative of the chaotic behavior and stirring characteristics of the system. The material lines have similar lengths for the same amount of rotation at different speeds, and the effect of rotational speeds appears to be primarily to change the time of mixing. The results are expected to help in the design of a particle microrotor based sensing technique.
AB - The microflow and stirring around paramagnetic particle microchains, referred to as microrotors, are modeled as a circular cylinder rotating about its radial axis at very low Reynolds number. Time scales for momentum transfer under these conditions are determined to be much smaller than those for boundary movement, hence a quasi-steady approximation can be used. The flow is derived at every instant from the case of a steady motion of a horizontally translating cylinder, with the rotation approximated to a series of differential incremental translations. A numerical simulation is used to determine the pathlines and material lines of virtual point fluid elements, which were analyzed to understand the behavior of the flow around the microrotor. The results indicate the flow to be unsteady, with chaotic advection observed in the system. The fluid motion is primarily two-dimensional, parallel to the rotational plane, with mixing limited to the immediate area around the rotating cylinder. Fluid layers, up to many cylinder diameters, in the axial direction experience the disturbance. Elliptic and star shaped pathlines, including periodic orbits, are observed depending on the fluid element's initial location. The trajectories and phase angles compare well with the experimental results, as well as with data from particle dynamics simulations. Material lines and streaklines display stretching and folding, which are indicative of the chaotic behavior and stirring characteristics of the system. The material lines have similar lengths for the same amount of rotation at different speeds, and the effect of rotational speeds appears to be primarily to change the time of mixing. The results are expected to help in the design of a particle microrotor based sensing technique.
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UR - http://www.scopus.com/inward/citedby.url?scp=3142691797&partnerID=8YFLogxK
U2 - 10.1039/b314007e
DO - 10.1039/b314007e
M3 - Article
C2 - 15159779
AN - SCOPUS:3142691797
VL - 4
SP - 201
EP - 208
JO - Lab on a Chip - Miniaturisation for Chemistry and Biology
JF - Lab on a Chip - Miniaturisation for Chemistry and Biology
SN - 1473-0197
IS - 3
ER -