Carlos R. Ilario da Silva

SUAVE: An Open-Source Environment Enabling Unconventional Vehicle Designs through Higher Fidelity

SUAVE is a conceptual level aircraft design environment that incorporates multiple information sources to analyze unconventional configurations. This work incorporates higherfidelity tools to build upon previous efforts where SUAVE analyzed and optimized several types of aircraft using low-fidelity methods. This is done in an automated way that incorporates three external programs. The first is OpenVSP, which is used for geometry creation, area calculation, and surface meshing. The second is Gmsh, which uses these surface meshes to create volume meshes. The third is SU2, which is used to run Euler CFD simulations. Wetted areas from OpenVSP and lift from SU2 is used to enhance SUAVE’s aerodynamic analyses. We present results for a verification case with the Onera M6 wing, then present mission results with a conventional narrow-body airliner, a supersonic jet, and a blended wing body.

Refraction effects on far-field noise predictions and sources distribution of coplanar coaxial jet flows

In this work, a numerical investigation of the noise from coplanar coaxial jet flows is conducted by using a new aeroacoustics approach called LRT. This method provides the ability to calculate the refraction effects experienced by the sound waves propagating throughout the jet and evaluate their contribution on the far-field noise predictions. A large number of jet operation conditions and nozzles configurations were investigated aiming to understand the sound propagation effects, sources distributions and far-field noise by coplanar coaxial jet flows. This is the second task of a continuous effort of numerical tests to validate the LRT method as fast noise prediction tool. Experimental data were used to corroborate the predictions of the new method which showed considerably good agreements. This fact suggests that the basic theoretical model is valid and that the model theory contains the essential physics of sound generation and propagation by a high subsonic jet.

Comparison of RANS-based methods for the prediction of noise emitted by subsonic turbulent jets

In this paper a comparison between four RANS-based jet noise prediction methods is conducted. We aim to evaluate the differences between methods derived from two mathematical frameworks: the Lighthill equation and the linearized Euler equations. A numerical investigation is shown for different geometries and jet operating conditions: (a) single stream jets with Mach number ranging from 0.5 to 1.0 and temperature ratio of 1.0 and 2.0; (b) single stream jets with the effect of a chevron nozzle at Mach number of 0.9 and temperature ratio of 0.86. The necessary information concerning the statistical properties of the turbulent sources was gathered from a RANS CFD simulation using a k–e turbulence model. Sound pressure level plots are shown for an observer at 90◦ related to the jet axis. Experimental data are used to corroborate the numerical predictions. Predictions based on both mathematical frameworks showed good agreement with experiments, however, methods based on the Lighthill equation present a simpler formulation and rely on less empirical coefficients.

Boundary layer flow interaction with a permeable wall

The interaction of a zero pressure gradient turbulent boundary layer flow with a rough permeable surface has been investigated experimentally. The flow interaction characteristics have been examined using a long flat plate equipped with several surface pressure transducers and pressure taps. Three types of porous materials with different porosities and permeability constants were used in these investigations. To reveal the behavior of turbulent flows over porous surfaces, measurements were performed for the boundary layer growth, energy content of the turbulent structure within the boundary layer, and surface pressure fluctuations, before, over, and after the porous test-section. The interaction of the flow with the porous substrate was found to significantly alter the energy cascade within the boundary layer. Results have also shown that the boundary layer interaction with the rough porous surfaces leads to an increase in the pressure fluctuations exerted on the wall, particularly at low frequencies. The near-field investigations have shown that the penetration of the boundary layer flow into the porous medium can generate an internal hydrodynamic field within the porous medium. This, in turn, reduces the frequency-energy content of the large boundary layer coherent structures and their spanwise correlation length. This study paves the way for further investigation into the interaction of the porous media with different flow fields and development of tailored porous treatments for improving the aerodynamic and aeroacoustic performance of different aero- and hydro-components.The interaction of a zero pressure gradient turbulent boundary layer flow with a rough permeable surface has been investigated experimentally. The flow interaction characteristics have been examined using a long flat plate equipped with several surface pressure transducers and pressure taps. Three types of porous materials with different porosities and permeability constants were used in these investigations. To reveal the behavior of turbulent flows over porous surfaces, measurements were performed for the boundary layer growth, energy content of the turbulent structure within the boundary layer, and surface pressure fluctuations, before, over, and after the porous test-section. The interaction of the flow with the porous substrate was found to significantly alter the energy cascade within the boundary layer. Results have also shown that the boundary layer interaction with the rough porous surfaces leads to an increase in the pressure fluctuations exerted on the wall, particularly at low frequencies. The...

Surrogate Modeling to Enable Higher Fidelity Optimization

This paper investigates the integration of surrogate modeling into the design and optimization process of standard and unconventional aircraft. To this end, an open-source design tool called SUAVE, which was developed to allow multifidelity design and optimization of non-conventional aircraft configurations was used. This work identifies some particular design variable choices that allow for smoother, more robust surrogate modeling (as opposed to variables that make the problem highly multimodal). This methodology was applied to two different aircraft cases, consisting of a regional jet aircraft as well as a diesel-electric general aviation aircraft.

Tandem Cylinder Flow and Noise Control

This paper is concerned with the application of porous coatings as a passive flow control method for reducing the aerodynamic sound from cylinders in tandem. The aim here is to perform a parametric proof-of-concept study to investigate the effectiveness of porous treatment on bare tandem cylinders to control and regularize the vortex shedding and flow within the gap region between the two bluff bodies, and thereby control the aerodynamic sound generation mechanism. The aerodynamic simulations are performed using 2D transient RANS approach with transitional turbulence model and the acoustic computations are carried out using the standard Ffowcs Williams-Hawkings (FW-H) acoustic analogy. Numerical flow and acoustic results are presented for bare tandem cylinders and porous-covered cylinders, with different porosities and thicknesses. Experimental flow and acoustic data are also provided for comparison. Results show that the proper use of porous coatings can lead to robust control of the flow within the gap region, the turbulence level and interaction with the downstream body, and therefore the generation of tonal and broadband noise. It has also been observed that the magnitude and the frequency of the primary tone reduce significantly as a result of the flow regularization. Preliminary experimental results are also provided for a single cylinder, confirming that the use of porous covers can effectively control the lift fluctuation near the primary vortex shedding tone.

Numerical and Empirical Approaches for Jet Noise Reduction: Investigation of Co-Flow Effects

In this paper, the investigation of co-flow effects imposed on a single-stream jet operating at Mach number 0.75 has been performed using Computational Aeroacoustics (CAA) tools and semi-empirical jet noise prediction routines. This is an ongoing research in order to subsidize a jet rig construction under analysis. The main goal is to quantify the noise reduction of a jet by the addition of a secondary coaxial jet. As a secondary objective, the identification of jet’s noise source was sought by looking on the flow dynamics and acoustics evaluated by CFD and CAA methodologies. The combination of two numerical approaches through an analytical propagation Acoustic Solver and semi-empirical databases (ESDU) allowed comparisons of farfield noise levels. Available experimental data were used to corroborate the numerical results.