Jig Twist Optimization of Mach 0.745 Transonic Truss-Braced Wing Aircraft and High-Fidelity CFD Validation

This paper presents a jig twist optimization study of Mach 0.745 Transonic Truss-Braced Wing (TTBW) aircraft using an in-house developed aero-structural analysis solver VSPAERO coupled to BEAM3D. A vortex-lattice model of the TTBW model is developed, and a transonic and viscous flow correction method is implemented in the VSPAERO model to account for transonic and viscous flow effects. A correction method for the wing-strut interference aerodynamics is developed and applied to the VSPAERO solver. Also, a structural dynamic finite-element model of the TTBW aircraft is developed. This finite-element model includes the geometric nonlinear effect due to the tension in the struts which causes a deflection-dependent nonlinear stiffness. The VSPAERO model is coupled to the corresponding finite-element model to provide a rapid aero-structural analysis. A design flight condition corresponding to Mach 0.745 at 42000 ft is selected for the TTBW aircraft jig twist optimization to reduce the drag coefficient. After the design is implemented, the drag coefficient of the twist optimized TTBW aircraft is reduced about 8 counts. At the end, a high-fidelity CFD solver FUN3D is used to validate the design

Jig Twist Optimization of Mach 0.745 Transonic Truss-Braced Wing Aircraft and High-Fidelity CFD Validation

This paper presents a jig twist optimization study of Mach 0.745 Transonic Truss-Braced Wing (TTBW) aircraft using an in-house developed aero-structural analysis solver VSPAERO coupled to BEAM3D. A vortex-lattice model of the TTBW model is developed, and a transonic and viscous flow correction method is implemented in the VSPAERO model to account for transonic and viscous flow effects. A correction method for the wing-strut interference aerodynamics is developed and applied to the VSPAERO solver. Also, a structural dynamic finite-element model of the TTBW aircraft is developed. This finite-element model includes the geometric nonlinear effect due to the tension in the struts which causes a deflection-dependent nonlinear stiffness. The VSPAERO model is coupled to the corresponding finite-element model to provide a rapid aero-structural analysis. A flight condition corresponding to Mach 0.745 at 42000 ft is selected for the TTBW aircraft jig twist optimization to reduce the drag coefficient. After the design is implemented, the drag coefficient of the twist optimized TTBW aircraft is reduced about 8 counts. At the end, a high-fidelity CFD solver FUN3D is used to validate the design

Acoustic Optimization for Anti-Phase Asymmetric Rotor

This investigation seeks to optimize the implementation of anti-phase alternating trailing edge (TE) patterns for rotor noise suppression. The design objective is to maximize reduction of noise perceived by the community while maintaining the aerodynamic thrust. Computations using a three-dimensional Unsteady-Reynolds-Averaged-Navier-Stokes (URANS) with k-w Shear Stress Transport (SST) turbulence model and Ffowcs-Williams and Hawkings (FW-H) formula are used to obtain aerodynamic thrust and far-field noise level. A parametric acoustic study of 13 configurations of KDE rotor with variable alternating trailing edge period, alternating trailing edge length, and trailing edge deflection angle is conducted. The best design candidate for the KDE rotor has a four-period TE waveform which results in a reduction in far-field noise level of 2.1 dB in the hover condition and a reduction of 1.1 dB in the forward flight condition at 9.7 m/s. A further parametric acoustic study is conducted for a different rotor manufactured by APC. Six APC rotor design candidates are simulated. The best design candidate 4H for the APC rotor results in a reduction in far-field noise level of 4.0 dB in the hover condition and a reduction of 1.3 dB in the forward flight condition at 9.7 m/s. A series of acoustic experiments in the Penn State University (PSU) anechoic chamber have been conducted. In the forward flight condition at 9.7 m/s, the APC anti-phase 4H rotor offers clear evidence of noise suppression capability across a wide range of the azimuthal angle. In the broadband frequency range of 2000-4000 Hz, the APC anti-phase 4H rotor produces as much as 6 dB noise reduction. The experimental results appear to confirm the noise suppression capability of the proposed anti-phase rotor design concepts

Investigation of Transonic Truss-Braced Wing Aircraft Transonic Wing-Strut Interference Effects Using FUN3D

This paper presents a computational study of transonic wing-strut interference effects of Transonic Truss-Braced Wing (TTBW) aircraft using the high-fidelity CFD (Computational Fluid Dynamics) code FUN3D (Fully Unstructured Navier-Stokes Three Dimensional). The study is conducted for the wing-strut and the wing-alone configurations at different Mach numbers and Reynolds numbers. The interference effects are calculated by comparing the wing aerodynamics along the spanwise direction between the wing-strut and the wing-alone configurations. The presence of the strut underneath the wing induces a suction peak on the lower surface of the wing, which causes changes in aerodynamic forces and moments, as well as the aerodynamic center location. The interference effects become more pronounced as the Mach number increases. The Reynolds number has less impact on the interference effects. A transonic wing-strut interference aerodynamic correction method is developed for use in a lower-fidelity tool, VSPAERO [a vortex lattice flow solver], coupled to a finite-element model for rapid flutter analysis

Multi-Objective Gust Load Alleviation Control Designs for an Aeroelastic Wind Tunnel Demonstration Wing

This paper presents several control and gust disturbance estimation techniques applied to a mathematical model of a physical flexible wing wind tunnel model used in ongoing tests at the University of Washington Aeronautical Laboratory's Kirsten Wind Tunnel. Three methods of gust disturbance estimation are presented, followed by three control methods: LQG, Basic Multi-Objective (BMO), and a novel Multi-Objective Prediction Correction (MOPC) controller. The latter of which augments a multi-objective controller, and attempts to correct for errors in the disturbance estimate. A simplified linear simulation of the three controllers is performed and a simple MIMO stability and robustness assessment is performed. Then, the same controllers are simulated in a higher fidelity Simulink environment that captures sampling, saturation and noise effects. This preliminary analysis indicates that the BMO controller provides the best performance and largest stability margins

Combustion Dynamics of Ten-injector Rocket Engine Using Flamelet Progress Variable

The combustion instability is investigated computationally for a ten-injector rocket engine using the compressible flamelet progress variable (FPV) model and detached eddy simulation (DES). An C++ code is developed based on OpenFOAM 4.1 to apply the combustion model. Flamelet tables are generated for methane/oxygen combustion at the background pressure of 200 bar using a 12-species chemical mechanism. The flames at this high pressure level are found having similar structures as those at much lower pressures. A power law is determined to rescale the reaction rate for the progress variable to address the pressure effect. The combustion is also simulated by the one-step-kinetics (OSK) model for comparison with the FPV model. Premixed and diffusion flames are identified locally for both the FPV and OSK models. Study of combustion instability shows that a combined first longitudinal and first tangential mode of 3200 Hz is dominant for the FPV model while the OSK model favors a pure first tangential mode of 2600 Hz. The coupling among pressure oscillation, unsteady transverse flow and helicity fluctuation is discussed. A preliminary study of the resonance in the injectors, which is driven by the acoustic oscillation in the combustion chamber, is also presented.Comment: arXiv admin note: text overlap with arXiv:2108.1204

GT2010-22061 SECONDARY FLOW REDUCTION BY BLADE REDESIGN AND ENDWALL CONTOURING USING AN ADJOINT OPTIMIZATION METHOD

ABSTRACT For low-aspect-ratio turbine blades secondary loss reduction is important for improving performance. This paper presents the application of a viscous adjoint method to reduce secondary loss of a linear cascade. A scalable wall function is implemented in an existing Navier-Stokes flow solver to simulate the secondary flow with reduced requirements on grid density. The simulation result is in good agreement with the experimental data. Entropy production through a blade row is used as the objec GT2010-22061 Copyright © 2010 by ASME and Alstom Technology Ltd. INTRODUCTION At present, further performance improvement of turbomachinery is difficult through traditional design procedures because significant efficiency gains have already been obtained. However, with the fast growth of computational power and advances in numerical methods, Computational Fluid Dynamics (CFD) coupled with advanced optimization algorithms provides a new cost-effective way to improve and optimize turbomachinery design as compared to classical methods based on manual iteration. Many design optimization approaches such as response surface methodology [1, 2], genetic algorithms [3] and finite difference methods A flow solver which can support physically accurate flow solutions is required in the optimization design based on CFD. Not all turbulence models can sufficiently model complex flow. Wilcox gave an overview of turbulence models in his paper In the past several decades, research has been done to improve the efficiency of flow solvers. However, to maintain high accuracy of turbulent flow solution, a fine mesh with a large number of grid points is needed. Kalitzin [6] and Shih In the turbulent flow with low Mach number of a low-aspectratio turbine blade, the flow loss may be categorized as profile loss and secondary loss. In a rather low aspect ratio blade, the secondary flow can influence the entire flow field along the spanwise direction. The theory of secondary flow was described in Horlock's paper Besides the flow solver, an important component in a typ

Ultra-compact optical auto-correlator based on slow-light enhanced third harmonic generation in a silicon photonic crystal waveguide

The ability to use coherent light for material science and applications is directly linked to our ability to measure short optical pulses. While free-space optical methods are well-established, achieving this on a chip would offer the greatest benefit in footprint, performance, flexibility and cost, and allow the integration with complementary signal processing devices. A key goal is to achieve operation at sub-Watt peak power levels and on sub-picosecond timescales. Previous integrated demonstrations require either a temporally synchronized reference pulse, an off-chip spectrometer, or long tunable delay lines. We report the first device capable of achieving single-shot time-domain measurements of near-infrared picosecond pulses based on an ultra-compact integrated CMOS compatible device, with the potential to be fully integrated without any external instrumentation. It relies on optical third-harmonic generation in a slow-light silicon waveguide. Our method can also serve as a powerful in-situ diagnostic tool to directly map, at visible wavelengths, the propagation dynamics of near-infrared pulses in photonic crystals.Comment: 20 pages, 6 figures, 38 reference

Secondary Flow Reduction by Blade Redesign and Endwall Contouring Using an Adjoint Optimization Method

For low-aspect-ratio turbine blades secondary loss reduc-tion is important for improving performance. This paper presents the application of a viscous adjoint method to reduce secondary loss of a linear cascade. A scalable wall function is implemented in an existing Navier-Stokes flow solver to simulate the sec-ondary flow with reduced requirements on grid density. The sim-ulation result is in good agreement with the experimental data. Entropy production through a blade row is used as the objec-tive function in the optimization of blade redesign and endwall contouring. With the adjoint method, the complete gradient in-formation needed for optimization can be obtained by solving the governing flow equations and their corresponding adjoint equa-tions only once, regardless of the number of design parameters. Three design cases are performed with a low-aspect-ratio steam turbine blade tested by Perdichizzi and Dossena. The results demonstrate that it is feasible to reduce flow loss through the redesign of the blade while maintaining the same mass-averaged turning angle. The effects on the profile loss and secondary loss due to the geometry modification of stagger angle, blade shape and endwall profile are presented and analyzed