Therefore, by using a viscoelastic fluid, a nonlinear microfluidic circuit can be obtained.īased on the viscoelastic fluid, many microfluidic logical components are developed for microfluidics applications 18, 19, 20. However, other studies 11, 12, 13, 14 show that viscoelastic fluid can induce nonlinear characteristic from its elastic property even at extremely low Re conditions 15, 16, 17. On the other hand, realizing nonlinear behavior of Newtonian fluid for microfluidic components remains large challenging as extremely high pressure is required to achieve high Re number condition 10. For real application, these methods usually require complex control systems. While in microfluidic component, the logical function usually relies on the formation of droplets 7, bubbles 8 or circuits with valve switches 9. Traditionally, fluidic logical functions are implemented in macro-scale devices at high Reynolds ( Re) number flows by taking the advantage of the nonlinear property of Newtonian fluid 6. Its resistance to extreme conditions of shock, vibration or radiation is also desired for many applications. Much attention has been paid to the fluid logic component due to its advantages of no extra mechanical structure, low cost and high reliability. Such devices has been developed into functional dynamic elements like amplifiers and triodes, and exhibit logical operations similar as electronic components 1, 2, 3, 4, 5. An innovative way is also developed to characterize the relaxation time of the viscoelastic fluid by modulating the frequency of the square wave force.įluid has been widely used as the medium for energy and force transmission in control systems named as fluidic devices. The velocity response of the applied square waves with different periods shows more flexible modulation signal types than constant force and step force. Through both time domain and frequency domain analysis on the fluid velocity response, it is revealed that the oscillation damping originates from the fluid viscosity while the oscillation frequency is dependent on the fluid elasticity. The external body forces like constant force, step force and square wave force are applied at the inlet of the channel. Responses in various forms like damped harmonic oscillation and periodic oscillation are induced and modulated depending on the fluid intrinsic properties like the viscosity and the elasticity. The velocity response is derived using the Oldroyd-B constitutive model in OpenFOAM. Here, we investigate the transient response of a viscoelastic Poiseuille flow in a two-dimensional channel driven by external body forces in different forms. As a non-Newtonian fluid, the viscoelastic fluid exhibits significant elastic response which does not raise in Newtonian fluid. Transient flow responses of viscoelastic fluids to different external body forces are studied.
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