Simulations of whistling and the whistling potentiality of an in-duct orifice with linear aeroacoustics

This paper demonstrates a linear aeroacoustic simulation methodology to predict the whistling of an orifice plate in a flow duct. The methodology is based on a linearized Navier–Stokes solver in the frequency domain with the mean flow field taken from a Reynolds-Averaged Navier–Stokes (RANS) solution. The whistling potentiality is investigated via an acoustic energy balance for the in-duct element and good agreement with experimental data is shown. A Nyquist stability criterion based on the simulation data was applied to predict whistling of the orifice when placed in a finite sized duct and experiments were carried out to validate the predictions. The results indicate that although whistling is a nonlinear phenomena caused by an acoustic-flow instability feed-back loop, the linearized Navier–Stokes equations can be used to predict both whistling potentiality and a duct system's ability to whistle or not.     

Process Based Reconstruction of Sandstones and Prediction of Transport Properties

We present a process based method for reconstructing the full three-dimensional microstructure of sandstones. The method utilizes petrographical information obtained from two-dimensional thin sections to stochastically model the results of the main sandstone forming processes – sedimentation, compaction, and diagenesis. We apply the method to generate Fontainebleau sandstone and compare quantitatively the reconstructed microstructure with microtomographic images of the actual sandstone. The comparison shows that the process based reconstruction reproduces adequately important intrinsic properties of the actual sandstone, such as the degree of connectivity, the specific internal surface, and the two-point correlation function. A statistical reconstruction of Fontainebleau sandstone that matches the porosity and two-point correlation function of the microtomography data differs strongly from the actual sandstone in its connectivity properties. Transport properties of the samples are determined by solving numerically the local equations governing the transport. Computed permeabilities and formation factors of process based reconstructions of Fontainebleau sandstone compare well with experimental measurements over a wide range of porosity.