On the sound speed in two-fluid mixtures and the implications for CFD model validation

TL;DR

This paper investigates the complex behavior of sound speed in two-fluid mixtures, compares theoretical models with experiments, and discusses the impact of wave speed accuracy on CFD model validation.

Contribution

It analyzes how different two-fluid models affect sound speed predictions and highlights the importance of accurate wave speed modeling for reliable CFD simulations.

Findings

Analytical sound speed expressions vary significantly across models.

Experimental values of sound speed are compared with model predictions.

Inaccurate wave speeds in CFD models lead to erroneous numerical solutions.

Abstract

Study of the propagation of sound in a single non-ideal fluid originates with Stokes in 1845 and Kirchhoff in 1868. The situation is much more complex in the case of two-fluid flow, both from the physical point of view, as the configuration of the flow matters greatly, and from the analytical point of view. The principle two-fluid models currently in use for CFD are the focus of this article. It is shown that analytical expressions for the speed of sound depend heavily on the chosen model. These sound speed expressions are compared with experimental values. The consequences for CFD models are discussed in the final section of this paper. It is found that numerical models with inaccurate wave speeds lead to incorrect numerical solutions, despite the accuracy of the numerical scheme.