A discussion about the velocity distribution commonly used as the boundary condition in surface acoustic wave numerical simulations.

Surface acoustic waves in combination with microfluidics has become an attractive research field regarding its various medical and biological applications. It is sometimes preferred to solve just the fluid domain and apply some boundary conditions to represent other components rather than performing a coupled numerical solution. To account for the piezoelectric actuation, a conventional velocity distribution built by superposing the left-going and right-going surface waves is commonly used as the boundary condition, its correctness is assessed here by comparing it to a coupled solution.