Biomedical subjects

A Kwang-Hua Chu

Publications and source records attributed to A Kwang-Hua Chu.

6 recordsLinked to original sources

PubMed2005

Linear stability of acoustic streaming flows in microchannels.

We study the stability of acoustic streaming flows of fluids induced by a small-amplitude surface acoustic wave propagating along the walls of a confined parallel-plane microchannel or microslab in the incompressible flow regime. The secondary (Navier) slip flows are of negligible effect on the stability characteristic compared with the primary (Navier) slip flow. The governing equation, which was derived by considering the weakly nonlinear coupling between the wavy interface and the viscous fluid, is obtained by taking into account the (Navier) slip conditions and then the eigenvalue problem is solved by a verified numerical code together with the associated dynamic and kinematic conditions. The value of the critical Reynolds number was found to be near 1441 which is smaller than the value 5772 for conventional pressure-driven flows.

Journal Article↗

PubMed2004

Transport control within a microtube.

Investigation of the entrainment of gases induced by a surface wave propagating along the wall of a microtube is conducted by using a relaxed model with slip velocity boundary conditions. Flow patterns tuned by critical reflux values a0, Knudsen numbers, Reynolds numbers, and the wave number are demonstrated. Results show that once the cross section of the microtube is narrowed down (slip velocity increasing) there are earlier backward flows and the flow pattern is much more complicated. Our results should be useful for the design of micro total analytical systems.

Computer Simulation↗

PubMed2003

Stability of acoustic streaming flows in plane channels.

We study the stability of acoustic streaming flows of normal fluids induced by a small-amplitude surface acoustic wave propagating along the walls of a confined parallel-plane channel or slab in the incompressible flow regime. The secondary flows derived are of negligible effect to the stability characteristic after comparing with the primary flow. The governing equation which was derived by considering the weakly nonlinear coupling between the wavy wall and viscous fluid is obtained and then the eigenvalue problem is solved by a numerical code together with the associated dynamic and kinematic conditions. The value of the critical Reynolds number was found to be near 4873 which is smaller than the case 5772 for conventional pressure-driven flows.

Journal Article↗

PubMed2003

Electrokinetic flows in a microdomain.

The discrete kinetic approach and diffuse-reflection type boundary conditions are adopted to solve the transport problem for many charged particles flowing along a microslab (or channel of a wide constriction within a confined slender microdomain). The preliminary results show that there are selected orientations related to the nontrivial velocity-slip fields for a range of Knudsen numbers if there is a nonboundary-driven forcing along the streamwise direction. As the Knudsen number increases, the value of this selected orientation decreases and the cross-stream velocity profile becomes relatively flat. Our results qualitatively resemble those reported by Burgreen and Nakache or Paul et al.

Journal Article↗

PubMed2003

Theoretical study of stability problems for transport in a deformable microfabricated channel.

We investigate the stability problem related to the basic flows induced by peristaltic transport within the bounded deformable walls which are common in micro- andor nanobiotechnological applications. The neutral stability boundary is obtained by solving the relevant Orr-Sommerfeld equation via a verified preconditioned complex-matrix solver. The critical Reynolds number (when the wall is deformable) is 2886.5 which is much less than the conventional rigid-wall case ( approximately 5772, obtained by Orszag based on the spectral method).

Journal Article↗

PubMed2002

Spectral problem for dilute atomic gases using discrete Uhling-Uhlenbeck operators.

Effects of free orientations (theta which is related to the relative direction of scattering of particles with respect to the normal of the propagating plane-wave front) using four-velocity model for the dispersion relationship of ultrasound propagation in dilute atomic (hard-sphere particles of Bose and Fermi statistics) gases are presented. We address the dispersion relations thus obtained by the relevant parameter rho (a blocking factor) or B which describes the Bose and Fermi particles for the quantum analog of the discrete Boltzmann system when B is positive (and rho=1) and negative (and rho=-1), respectively. The preliminary results show that there is no attenuation when the parameter theta equals pi/4 for all Bs.

Journal Article↗