Computational Study of of Flow Structures Within Microfluidic Channels with Trapezoidal Cross-Section
Open Access
- Author:
- Pradipta, Gregorius Rangga
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Ali Borhan, Thesis Supervisor
Andrew Zydney, Thesis Honors Advisor - Keywords:
- Computational
Fluid Dynamics
Computational Fluid Dynamics
Microfluidics
trapezoidal channel
navier-stokes
numerical simulation
asymptotic
shear stress
equilibrium position
particle focusing
particle trajectory - Abstract:
- Inertial focusing in non-circular channels has become one of the most prominent microfluidic methods in achieving size-based particle separation for a particle-laden flow, relying on the hydrodynamic forces produced by the flow such as the shear-gradient force, wall-lift force, and rotational lift (Magnus) force. To achieve greater degrees of separation, the flow field within the channel can be modified by varying the cross-section geometry, changing the flow Reynolds number, or introducing curvature to the channel. To understand how each modification affects the base flow, numerical simulations were done using three-dimensional models of microchannels with trapezoidal cross-section geometry. Trapezoidal channels can be viewed as a perturbation of rectangular channels with the addition of a small angle elevating the top wall. The channel asymmetry induced an asymmetrical flow field, affecting distribution of velocities across the cross-section, which ultimately increased the velocity gradient near the longer vertical wall. Additionally, this distribution magnified vorticity within the channel in comparison to a rectangular channel, inducing a higher degree of rotation within the flow. As the angle was increased, distributions of velocity and vorticity became more non-uniform, creating small pockets of minimum and maximum values across the cross section. Increasing the channel Reynolds number produced a thinner boundary layer near the walls, making velocity distribution slightly more uniform, however also induced more rotation across the crosssection. All three modifications either affect the velocity gradient, which would change the stress distribution and affect shear-gradient force, or affect vorticity distribution, which would change Magnus force. Understanding how these changes would affect force field affecting the particle is crucial in performing a particle trajectory calculation to determine equilibrium positions for particles. The simulation results were also compared to the leading order analytical solution developed through asymptotic expansion, yielding similar results.