Verification and Application of Time-domain Impedance Boundary Conditions in Combined CFD and CAA Simulations Purdue University

Format:

Book

Conference/Event

Author/Creator:

Li, Ang, author.

Contributor:

Chen, Jun

Liu, Yangfan

Conference Name:

Noise and Vibration Conference & Exhibition (2021-09-07 : Grand Rapids & Online, Michigan, United States)

Language:

English

Physical Description:

1 online resource cm

Place of Publication:

Warrendale, PA SAE International 2021

Summary:

In computational fluid dynamic (CFD) and computational aeroacoustics (CAA) simulations, the wall surface is normally treated as a purely reflective wall. However, some surface treatments are usually applied in experiments. Thus, the results obtained by the simulation and experiment are sometimes not comparable. In the aeroacoustics community, impedance is a quantity to characterize the properties of an acoustically treated surface. id est reflectivity and absorption. One of the major numerical challenges in CAA simulations is to define acoustically well-posed boundary conditions. Basically, the impedance boundary condition is a frequency-domain boundary condition. However, CFD and CAA simulations are time-domain computations, which means the frequency-domain impedance boundary condition cannot be applied in simulations. Therefore, several methods, including the three-parameter model, the z-transform method, and the reflection coefficient model, were developed. In the present study, the modeling of the reflection coefficient is implemented and is verified by the case with and without the mean flow effect. A coupling method that combines the time-domain impedance boundary condition and Large Eddy Simulations (LES) is proposed. A channel flow with wall-impedance is simulated at different flow velocities. The results of the flow field are validated by the case with purely reflective wall-impedance. For the flow with wall-impedance, the flow field and near-wall turbulence structure are analyzed and compared to the structure obtained by the impermeable wall. In addition, the wall impedance contributes to noise reduction in the near-wall region. In a summary, the time-domain impedance boundary condition used in the present study is valid for simple cases, id est channel flow, and is expected to be applied in other complicated cases in the future

Notes:

Vendor supplied data

Publisher Number:

2021-01-1048

Access Restriction:

Restricted for use by site license