15 research outputs found
High-Order Shock-Capturing Methods for Study of Shock-Induced Turbulent Mixing with Adaptive Mesh Refinement Simulations
No abstract availabl
An assessment of multicomponent flow models and interface capturing schemes for spherical bubble dynamics
Numerical simulation of bubble dynamics and cavitation is challenging; even
the seemingly simple problem of a collapsing spherical bubble is difficult to
compute accurately with a general, three-dimensional, compressible,
multicomponent flow solver. Difficulties arise due to both the physical model
and the numerical method chosen for its solution. We consider the 5-equation
model of Allaire et al. [1], the 5-equation model of Kapila et al. [2], and the
6-equation model of Saurel et al. [3] as candidate approaches for spherical
bubble dynamics, and both MUSCL and WENO interface-capturing methods are
implemented and compared. We demonstrate the inadequacy of the traditional
5-equation model of Allaire et al. [1] for spherical bubble collapse problems
and explain the corresponding advantages of the augmented model of Kapila et
al. [2] for representing this phenomenon. Quantitative comparisons between the
augmented 5-equation and 6-equation models for three-dimensional bubble
collapse problems demonstrate the versatility of pressure-disequilibrium
models. Lastly, the performance of pressure disequilibrium model for
representing a three-dimensional spherical bubble collapse for different bubble
interior/exterior pressure ratios is evaluated for different numerical methods.
Pathologies associated with each factor and their origins are identified and
discussed
Noise Characteristics of a Four-Jet Impingement Device Inside a Broadband Engine Noise Simulator
The noise generation mechanisms for four directly impinging supersonic jets are investigated employing implicit large eddy simulations with a higher-order accurate weighted essentially non-oscillatory shock-capturing scheme. Impinging jet devices are often used as an experimental apparatus to emulate a broadband noise source. Although such devices have been used in many experiments, a detailed investigation of the noise generation mechanisms has not been conducted before. Thus, the underlying physical mechanisms that are responsible for the generation of sound waves are not well understood. The flow field is highly complex and contains a wide range of temporal and spatial scales relevant for noise generation. Proper orthogonal decomposition of the flow field is utilized to characterize the unsteady nature of the flow field involving unsteady shock oscillations, large coherent turbulent flow structures, and the sporadic appearance of vortex tubes in the center of the impingement region. The causality method based on Lighthill's acoustic analogy is applied to link fluctuations of flow quantities inside the source region to the acoustic pressure in the far field. It will be demonstrated that the entropy fluctuation term in the Lighthill's stress tensor plays a vital role in the noise generation process. Consequently, the understanding of the noise generation mechanisms is employed to develop a reduced-order linear acoustic model of the four-jet impingement device. Finally, three linear acoustic FJID models are used as broadband noise sources inside an engine nacelle and the acoustic scattering results are validated against far-field acoustic experimental data