Analysis Of Acoustic Streaming Research Articles

Multifidelity Analysis of Acoustic Streaming in Forced Convection Heat Transfer

Abstract This research effort is related to the detailed analysis of the temporal evolution of thermal boundary layer(s) under periodic excitations. In the presence of oscillations, the nonlinear interaction leads to the formation of secondary flows, commonly known as acoustic streaming. However, the small spatial scales and the inherent unsteady nature of streaming have presented challenges for prior numerical investigations. In order to address this void in numerical framework, the development of a three-tier numerical approach is presented. As a first layer of fidelity, a laminar model is developed for fluctuations and streaming flow calculations in laminar flows subjected to traveling wave disturbances. At the next level of fidelity, two-dimensional (2D) U-RANS simulations are conducted across both laminar and turbulent flow regimes. This is geared toward extending the parameter space obtained from laminar model to turbulent flow conditions. As the third level of fidelity, temporally and spatially resolved direct numerical simulation (DNS) simulations are conducted to simulate the application relevant compressible flow environment. The exemplary findings indicate that in certain parameter space, both enhancement and reduction in heat transfer can be obtained through acoustic streaming. Moreover, the extent of heat transfer modulations is greater than alterations in wall shear, thereby surpassing Reynolds analogy.

Finite-element analysis of acoustic streaming generated between a bending transducer and a reflector through second-order approximated forces

Finite-element analysis of acoustic streaming generated between a bending transducer and a reflector through second-order approximated forces

Acoustofluidics 13: Analysis of acoustic streaming by perturbation methods

In this Part 13 of the tutorial series "Acoustofluidics--exploiting ultrasonic standing waves forces and acoustic streaming in microfluidic systems for cell and particle manipulation," the streaming phenomenon is presented from an analytical standpoint, and perturbation methods are developed for analyzing such flows. Acoustic streaming is the phenomenon that takes place when a steady flow field is generated by the absorption of an oscillatory field. This can happen either by attenuation (quartz wind) or by interaction with a boundary. The latter type of streaming can also be generated by an oscillating solid in an otherwise still fluid medium or vibrating enclosure of a fluid body. While we address the first kind of streaming, our focus is largely on the second kind from a practical standpoint for application to microfluidic systems. In this Focus article, we limit the analysis to one- and two-dimensional problems in order to understand the analytical techniques with examples that most-easily illustrate the streaming phenomenon.

Nonzero Mean Oscillatory Flow in Symmetrically-Heated Shallow Enclosures: An Analysis of Acoustic Streaming

The effects of symmetric heating on a nonzero mean oscillatory fluid motion, namely acoustic streaming, in air-filled shallow enclosures and associated thermal convection in transient regime are investigated numerically. The fluid motion is driven by periodic vibration of the enclosure left wall. The vertical walls of the enclosure are adiabatic while the horizontal walls are heated symmetrically. A control-volume method-based explicit time-marching flux-corrected transport algorithm is used to simulate the transport phenomena in the enclosure. A symmetric temperature gradient strongly affects the acoustic streaming structures and velocities. The variation of the steady flow field becomes more noticeable and drastic with increasing wall temperature.

Acoustic streaming caused by the oscillation of an irregular surface.

The analysis of acoustic streaming generated by oscillatory flow over a two‐dimensional flexible boundary will be presented. The time‐averaged slip velocity that results from the gradient of the Reynolds stress is obtained. Of particular interest is the coupling between transverse motion of boundary and longitudinal oscillation of the fluid.

Acoustic streaming in a waveguide with slowly varying height

An analysis of acoustic streaming in a two-dimensional waveguide having slowly varying height is presented. Special attention is paid to waveguides with cross sections that are small compared to the acoustic and/or wall wavelengths. It is shown that the dynamic behavior of the enclosed fluid can be parameterized by the values of three small parameters, ε, 1/S, and 1/R, where ε is the ratio of the typical duct height H0 to the wall wavelength L0, 1/S is the ratio of the typical oscillatory particle displacement U0/ω to the typical duct height H0 and 1/R is the ratio of the oscillatory boundary layer thickness lν to the typical duct height H0. An analytical solution describing the streaming flow in the duct is given in terms of a regular perturbation sequence in ε. It is shown that the oscillatory pressure must satisfy the lossy Webster horn equation to O(ε2) if the no slip boundary condition is to be satisfied. Outside the boundary layer it is shown that the time averaged slip velocity is the sum of two terms. The first term is proportional to the product of the incident and reflected wave amplitudes. The second term is proportional to the difference between the incident and reflected acoustic intensity of the wave. For small values of 1/S, 1/R, and ε the streaming solution given is shown to be valid until εR/S2 becomes of O(1).

Acoustic streaming in a waveguide with slowly varying height

An analysis of acoustic streaming in a two-dimensional waveguide having slowly varying height is presented. Special attention is paid to waveguides with cross sections that are small compared to the acoustic and/or wall wavelength. It is shown that the dynamic behavior of the enclosed fluid can be parametrized by the values of three small parameters ε, 1/S, and 1/R, where ε is the wall slope, S is the oscillatory Strouhal number, and R is the oscillatory Reynolds number. An analytical solution describing the streaming flow is given in terms of a regular perturbation sequence in ε. Outside the boundary layer it is shown that the time averaged slip velocity is the sum of two term. The first terms is proportional to the product of the incident and reflected wave amplitudes. The second is proportional to the difference between incident and reflected acoustic intensities of the wave. It is shown that the streaming solution remains valid until εR/S2 = O(1). The results for a duct with sinusoidally varying height in the incompressible limit and waveguides with a Gaussian variation in height are given.