China
Africa
Explore chapters and articles related to this topic
Theoretical and experimental study of acoustic streaming in porous media
Published in J.-L. Auriault, C. Geindreau, P. Royer, J.-F. Bloch, C. Boutin, J. Lewandowska, Poromechanics II, 2020
P. Poesio, G. Ooms, A. Schraven, F. van der Bas
In this paper, we will report about another effect of high-frequency acoustic waves on the flow of a liquid through a porous material; viz the streaming effect due to the damping of the acoustic waves. A travelling acoustic wave in a liquid induces a net steady flow in the direction of its propagation. This effect can only occur when the wave is being attenuated. The phenomenon is called acoustic streaming and is described in detail in the book by Lighthill (Lighthill 1978). From a physical point of view acoustic streaming is due to a transfer of momentum from the travelling acoustic wave to the liquid. A planar, travelling wave with intensity I has momentum: M=Ic2,
Light-Driven Microfluidic Systems
Published in George K. Knopf, Kenji Uchino, Light Driven Micromachines, 2018
In contrast, active micromixers use an external energy source to create disturbances in liquid streams to improve mixing rates (El Moctar et al. 2003; Fujii et al. 2003; Liu et al. 2002b; Suzuki and Ho 2002; Tang et al. 2002; Tsai and Lin 2002). Fujii et al. (2003) reported using an external micropump to generate pressure disturbance to improve mixing. Electrohydrodynamic and electrokinetic disturbance are also reported to improve mixing rates (El Moctar et al. 2003; Tang et al. 2002). Suzuki and Ho (2002) describe a micromixer integrated with electrical conductors that generate magnetic fields, which then move 1–10 μm diameter magnetic beads to create a disturbance in the flow stream. Liu et al. (2002b) reported using the acoustic streaming technique to induce air bubbles in streams where the bubbles disturb the flows to improve mixing. Tsai and Lin (2002) reported utilizing a microheater embedded in microchannels to thermally generate air bubbles that disturb the streams.
Coupling of Sound with Vorticity: Acoustic Streaming
Published in Sergey Leble, Anna Perelomova, Dynamical Projectors Method in Hydro and Electrodynamics, 2018
Acoustic streaming is namely the mean motion of a fluid caused by acoustic waves. Extensive reviews on this subject exist in the Refs [2–4]. The authors of Refs [5,6] have noticed that there is an unresolved issue concerning acoustic streaming, the effect of compressibility, because the starting point in this subject, as usual, is a set of equations describing incompressible liquid. In contrast, sound propagates over compressible fluids so that there is an evident inconsistency that requires the correct interpretation and evaluation of acoustic force in the context of weakly nonlinear flow. The usual method to identify acoustic streaming consists of two successive steps: first, performing a linear combination of these modes, and second, averaging the continuity and momentum equations over one sound period or over an integer number of sound periods [3,7]. This eliminates periodic perturbations, does not account for energy balance, and hence, discards thermal conductivity. It has been well established experimentally that the velocity of streaming depends on the total attenuation, which includes also thermal conductivity. The impact of compressibility, heat conduction and nonperiodicity of sound is not fully clear in the context of acoustic streaming. As usual, streaming in compressible fluids is larger ceteris paribus. It is more evident in a gas than in a liquid. The weakness of the formerly applied methodology is also its inconsistency in distinction of the vorticity and entropy modes, which are both slow and isobaric, as usual. It implies a zero temporal average over the sound period of the partial derivative of total density with respect to time, ∂r/∂t, which includes the contribution of sound and the slowly varying part belonging to the isobaric entropy mode. Hence, the average over the sound period value of ∂r/∂t is no longer zero. The velocity attributable to the entropy mode is also nonzero if the heat conduction of a fluid differs from zero, so it contributes to the total mean velocity. We avoid these inconsistencies by means of the immediate projection of the conservation equations onto dynamic equations governing the vortex flow. Projection results in the correct coupling of the acoustic and nonwave motions. We will consider an example of a fluid with the Maxwell relaxation will be considered, which readily reduces to the Newtonian case at small relaxation times.
Numerical simulation study of acoustic waves propagation and streaming using MRT-lattice Boltzmann method
Published in International Journal for Computational Methods in Engineering Science and Mechanics, 2023
Jaouad Benhamou, Mohammed Jami, Ahmed Mezrhab, Daniel Henry, Valéry Botton
There are many applications of acoustic waves, especially ultrasound waves. For example, in medicine, the signals created can be used for diagnostic or therapeutic purposes [22, 23]. In daily life, the waves can be used for cleaning [24]. In the industrial sector, the acoustic waves generated by a piezoelectric transducer can be used to purify photovoltaic silicon [25]. This purification is obtained through the flow created in the fluid by the propagation of the acoustic waves (acoustic streaming). This streaming is due to the natural attenuation in the fluid of the acoustic wave generated by the transducer vibration. Numerically, it is generally generated by introducing the force induced by the waves (acoustic force) in the numerical code. For CFD methods, the force is added to the Navier-Stokes equations [26], whereas for LBM methods, there are several models for introducing such external force [27]. In any case, the calculation of the acoustic force is a key ingredient for all numerical methods to study acoustic streaming.
Numerical simulation of microfluidic mixing by ultrasonic-induced acoustic streaming
Published in Journal of Dispersion Science and Technology, 2021
Pengfei Geng, Chunxi Li, Xiangyong Ji, Shuai Dong
The acoustic streaming phenomenon exists widely in acoustic microfluidic systems, and it is a stable flow condition induced by the dissipation attenuation of acoustic wave energy propagating in the fluid.[15] A theoretical analysis of acoustic streaming field driven by boundary layer is originally performed by Rayleigh.[16] His theory only describes the acoustic vortices outside the viscous boundary layer, so it is commonly referred to as ‘outer streaming’ as well as ‘Rayleigh streaming’. Subsequently, a more comprehensive boundary layer-driven acoustic streaming theory is proposed by Schlichting[17] and Nyborg,[18] and they found that there is still a violent flow of acoustic vortical flow inside the viscous boundary layer. Therefore, these two styles of streaming flow inside and outside the boundary layer are described as the classic boundary layer-driven fluid flow.
Mechanistic study of ultrasound-assisted solvent leaching of sodium and potassium from an Indian coal using continuous and pulsed modes of operation
Published in Chemical Engineering Communications, 2019
Acoustic streaming occurs mainly due to viscous attenuation and wave interaction with solid boundaries. When it occurs outside the boundary layer, it is called “Eckart streaming,” and when it occurs inside the boundary layer, it is termed “Schlichting streaming” (Gale and Busnaina, 1999). Boundary layer thickness is inversely proportional to the square root of frequency and therefore decreases with increasing frequency. The acoustic streaming velocity increases with increasing frequency and power. This leads to high viscous stress, and, in turn, to accelerated flow. Sahinoglu and Uslu (2013) showed that sonication, in combination with oil agglomeration, has been used for improving coal quality. This study has shown that, apart from breaking down of coal particles, ultrasound also helps in causing cracks on the surface and removing elements such as iron, silica, aluminum, calcium, and potassium. Xin et al. (2013) observed that ultrasound has been used to augment the leaching of zinc residue along with other metal. This was done in the presence of sulfuric acid as a solvent.