摘要 :
The use of Linearized Euler Equations for direct prediction of supersonic jet noise issued from a rectangular nozzle is explored and noise directivity is compared with the previous traditional approaches of Large-Eddy Simulations ...
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The use of Linearized Euler Equations for direct prediction of supersonic jet noise issued from a rectangular nozzle is explored and noise directivity is compared with the previous traditional approaches of Large-Eddy Simulations accompanied with Ffowcs-Williams Hawkings method. A new versatile Linearized Euler Equations solver is developed using the OpenFOAM API named "leeFoam". Special treatment of boundary reflections such as implementation of non-reflecting boundary condition along with a sponge zone is introduces. Artificial Acoustic Damping is implemented as a source term to prevent spurious numerical instabilities. It is shown that a finite-volume numerical scheme coupled with proper boundary treatment can produce a stable solution nearly free from reflections. Verification is conducted against analytical results for the propagation of an acoustic pulse in uniform flow. Applicability of this approach to real jets is explored by taking the inflow disturbances to be related to the fundamental frequency of jet and comparing with experimentally measured noise.
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摘要 :
Supersonic jets are essential for various engineering applications, such as propulsion, combustion, and high-speed transportation. However, their high noise levels pose significant challenges, particularly in aviation. Recently, r...
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Supersonic jets are essential for various engineering applications, such as propulsion, combustion, and high-speed transportation. However, their high noise levels pose significant challenges, particularly in aviation. Recently, rectangular jets have gained attention due to their potential advantages, such as higher entrainment rates and more efficient mixing, compared to round jets. This paper presents a comparative high-fidelity study of supersonic-rectangular and round jets, focusing on near-field flow quantities and far-field noise. The simulations are performed using Detached-Eddy Simulations (DES) with the open-source OpenFOAM software, and turbulence statistics are analyzed using spectral proper orthogonal decomposition (SPOD) [1]. The study reveals key differences in the noise of rectangular and round jets, providing insights into the design of more efficient and quieter jet systems for various engineering applications.
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The primary objective of this work is to develop a high-fidelity simulation model for active jet noise control predictions, and to quantify the sound reduction when an external-source frequency mode excitation is imposed on the je...
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The primary objective of this work is to develop a high-fidelity simulation model for active jet noise control predictions, and to quantify the sound reduction when an external-source frequency mode excitation is imposed on the jet flow. Whereas passive approaches using mixing devices, such as chevrons, have been shown to reduce low-frequency noise in jet engines, such approaches often incur an engine performance penalty. The current work investigates an open-loop active noise control (ANC) approach that utilizes an unsteady micro-jet actuator installed in the nozzle lip and injecting air in the streamwise direction to impact the dynamics of the jet coherent structures and thereby directly affect the jet sound sources. In contrast to the passive approaches, the investigated open-loop control design utilizes a localized jet flow excitation that can be adjusted according to the desired control signal specific to the jet mean velocity. The current analysis considers an axisymmetric round jet at Mach 1.8. Numerical studies are verified against previous low-order simulations conducted using Linearized Euler Equations (LEE) solutions coupled with the previously developed reduced-order model (ROM) for jet acoustic source, and compared for the achieved noise reduction against the non-excited jet case study. A high-fidelity analysis involving Detached-Eddy Simulations (DES) is developed using the open-source OpenFOAM software. The obtained results indicate that selected excitation modes reduce the far-field peak jet noise levels by nearly 2 dB, thus supporting possible use of the micro-jet actuation technology as an effective mechanism for jet noise reduction.
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摘要 :
The primary objective of this work is to develop a high-fidelity simulation model for active jet noise control predictions, and to quantify the sound reduction when an external-source frequency mode excitation is imposed on the je...
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The primary objective of this work is to develop a high-fidelity simulation model for active jet noise control predictions, and to quantify the sound reduction when an external-source frequency mode excitation is imposed on the jet flow. Whereas passive approaches using mixing devices, such as chevrons, have been shown to reduce low-frequency noise in jet engines, such approaches often incur an engine performance penalty. The current work investigates an open-loop active noise control (ANC) approach that utilizes an unsteady micro-jet actuator installed in the nozzle lip and injecting air in the streamwise direction to impact the dynamics of the jet coherent structures and thereby directly affect the jet sound sources. In contrast to the passive approaches, the investigated open-loop control design utilizes a localized jet flow excitation that can be adjusted according to the desired control signal specific to the jet mean velocity. The current analysis considers a 3D unheated round jet at Mach 1.8. The high-fidelity approach employs the Detached-Eddy Simulations (DES) developed on the basis of the open-source OpenFOAM software. The results of the current study are compared against the preceding 2D axisymmetric round jet simulations [1], and the previous low-order simulations conducted using Linearized Euler Equations (LEE) solutions coupled with the previously developed reduced-order model (ROM) for jet acoustic source [2]. In contrast to the previous 2D axisymmetric DES study, the obtained results indicate that the selected excitation modes are unable to provide any notable reduction in the far-field response. Further refined studies are needed to clarify if there is an optimal single-frequency excitation that could produce the desired effect.
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Flow field of a slender delta wing (with trailing edge jets to simulate thrust vectoring) is experimentally investigated using volumetric particle image velocimetry. Trailing edge jets were angled at (g)= 20° relative to the root...
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Flow field of a slender delta wing (with trailing edge jets to simulate thrust vectoring) is experimentally investigated using volumetric particle image velocimetry. Trailing edge jets were angled at (g)= 20° relative to the root chord towards the suction side of the delta wing. Flow fields for various jet to free stream velocity ratios were compared with the baseline configuration for a range of angles of attack. The structure of leading-edge vortices for each configuration was analyzed to identify vortex breakdown.
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A hybrid RANS-LES approach is adopted in this work to simulate the vortex dominated flow over a slender delta wing. The turbulent flow around the delta wing is subsonic. The delta wing has a sharp leading edge and a high leading-e...
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A hybrid RANS-LES approach is adopted in this work to simulate the vortex dominated flow over a slender delta wing. The turbulent flow around the delta wing is subsonic. The delta wing has a sharp leading edge and a high leading-edge sweep angle of 80°. A grid sensitivity study is carried out to determine the grid spacing requirement for capturing the vortex roll-up and breakdown. Velocity magnitude values of leading-edge vortices obtained from the simulations are compared with volumetric particle image velocimetry experimental data. Dynamic features of the transient flow, especially the vortex breakdown phenomenon at high angles of attack is discussed.
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摘要 :
Flow field of slender and non-slender delta wings is experimentally investigated using volumetric particle image velocimetry. Structure of the leading-edge vortices for the two configurations are compared. A comparison of the Q-cr...
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Flow field of slender and non-slender delta wings is experimentally investigated using volumetric particle image velocimetry. Structure of the leading-edge vortices for the two configurations are compared. A comparison of the Q-criterion, λ_2-criterion and the λ_(ci)-criterion for vortex identification is also done.
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CubeSat class satellites are being recognized for their potential as utility spacecraft, which can be developed at low cost and in short development time. These factors, coupled with the availability of commercial-off-the-shelf co...
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CubeSat class satellites are being recognized for their potential as utility spacecraft, which can be developed at low cost and in short development time. These factors, coupled with the availability of commercial-off-the-shelf components, have made CubeSats particularly attractive for academia as well as industry, and experimental government missions. However, CubeSats have been questioned for their reliability. This paper presents an approach to increase reliability through rigorous systems engineering practices; an end-to-end design and development life-cycle for CubeSats that implements mission assurance at the various phases of the life-cycle is discussed.
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摘要 :
CubeSat class satellites are being recognized for their potential as utility spacecraft, which can be developed at low cost and in short development time. These factors, coupled with the availability of commercial-off-the-shelf co...
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CubeSat class satellites are being recognized for their potential as utility spacecraft, which can be developed at low cost and in short development time. These factors, coupled with the availability of commercial-off-the-shelf components, have made CubeSats particularly attractive for academia as well as industry, and experimental government missions. However, CubeSats have been questioned for their reliability. This paper presents an approach to increase reliability through rigorous systems engineering practices; an end-to-end design and development life-cycle for CubeSats that implements mission assurance at the various phases of the life-cycle is discussed.
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