Benchmarking a simplified model for acoustic streaming in SAW acoustofluidics

Area of Science:

• Acoustofluidics
• Computational Fluid Dynamics
• Surface Acoustic Waves

Background:

• Acoustic streaming simulation in surface acoustic wave (SAW) devices is vital for acoustofluidic applications.
• Traditional modeling methods (RSM, ALE) are computationally expensive.
• The validity of simplified models for acoustic streaming under Stokes-slip boundary conditions is not well-established.

Purpose of the Study:

• To systematically evaluate a simplified model for acoustic streaming in SAW devices using a viscous acoustic body force and slip velocity.
• To determine the applicability of the simplified model for standing SAW (SSAW) and traveling SAW (TSAW) devices across various channel heights.
• To provide guidelines for accurate and efficient simulation of acoustic streaming.

Main Methods:

• Introduction of a model difference factor (D) to quantify model accuracy.
• Simulation of acoustic streaming in SSAW and TSAW devices under Stokes-slip boundary conditions.
• Analysis of the transition between Rayleigh and Eckart streaming regimes based on normalized channel height (h).

Main Results:

• The simplified model is valid (D≤0.2) for h≥0.8 (SSAW) and h≥1.5 (TSAW), offering significant computational savings.
• A critical height (h_c≈0.43-0.58) was identified for the transition from boundary-driven to bulk streaming.
• Slip velocity becomes negligible at higher channel heights (h≥1.1 for SSAW, h≥2.0 for TSAW), where analytical approximations are applicable.
• An improved layered approach failed under Stokes-slip conditions, unlike under no-slip conditions.

Conclusions:

• The simplified model provides a computationally efficient and accurate method for simulating acoustic streaming in SAW devices.
• Clear guidelines are established for selecting the appropriate simulation approach based on device geometry and streaming regime.
• This research facilitates optimized design of acoustofluidic devices for various operational scenarios.