Simulations of the Flow Generated by Fluidic Inserts for Supersonic Jet Noise Reduction Based on Steady RANS Simulations PDF Download
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Author: Matthew Kapusta
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The investigation of military jet noise prediction and reduction is an ongoing activity. Supersonic military jets radiate higher noise levels than commercial aircraft and are not subject to noise requirements. The noise generating mechanisms for high-speed jets are not entirely understood, making it difficult to set strict noise standards similar to those imposed for commercial aircraft. However, many noise reduction techniques have been applied to attempt to alleviate environmental and health concerns. Little success has been achieved to date for noise reduction of exhaust jets on supersonic tactical aircraft.A newly developed method involves a system that generates fluidic inserts in a supersonic nozzle flow to produce noise reduction. Numerical simulations have been performed for a military-style basline nozzle and with the noise reduction method of fluidic inserts used at a design Mach number of 1.65 and at various off design conditions. The purpose of the current numerical study is to provide insight for the flow field generated by the fluidic inserts used to reduce supersonic jet noise. The supersonic jet simulations are based on the use of high fidelity meshes combined with advanced CFD technology. Steady Reynolds-averaged Navier-Stokes (RANS) simulations are used to predict the flow field. Noise measurements have been performed experimentally and the results from the numerical simulations provide a correlation between aerodynamic properties and the corresponding noise reduction. The complex nozzle geometry is modeled using both an unstructured mesh and a multiblock structured mesh. The grids are generated by ANSYS ICEM and Gridgen respectively. The numerical simulations are performed using ANSYS CFX and Wind-US. The simulations with Wind-US use the Spalart-Allmaras turbulence model, while the simulations with ANSYS CFX use the Menter SST turbulence model. The results from the two flow solvers are compared and provide good agreement. The objective is to simulate a military-style nozzle, which resembles engines of the GE F404 family, with fluidic inserts. The purpose of the fluidic inserts is to alter the flow field similar to that of a hard wall corrugation in order to reduce components of noise radiation. The addition of the fluidic inserts increases the complexity of the flow field for the supersonic jet. The numerical simulations performed help to better distinguish the effects on the flow field due to the fluidic inserts. Preliminary work has been performed on a simpler geometry to provide further insight to the effect of the fluidic inserts on the supersonic jet flow field. These simulations are performed by fluid injection into a supersonic freestream over a flat plate. All numerical simulations used a freestream Mach number of 1.5. The numerical simulations used a wide range of pressure ratios for injecting the fluid into the supersonic freestream. By changing the pressure ratio of the fluid injection, the deflection of the freestream flow was better understood. Simulations on a full three dimensional nozzle with fluidic inserts were performed with conditions based on the preliminary studies. Parameters such as total pressure and total temperature provide a representation of the fluidic insert shape. Other integrated flow properties at the nozzle exit such as streamwise vorticity and pressure differential were used to correlate with the noise reduction seen in the experiments.
Author: Matthew Kapusta
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The investigation of military jet noise prediction and reduction is an ongoing activity. Supersonic military jets radiate higher noise levels than commercial aircraft and are not subject to noise requirements. The noise generating mechanisms for high-speed jets are not entirely understood, making it difficult to set strict noise standards similar to those imposed for commercial aircraft. However, many noise reduction techniques have been applied to attempt to alleviate environmental and health concerns. Little success has been achieved to date for noise reduction of exhaust jets on supersonic tactical aircraft.A newly developed method involves a system that generates fluidic inserts in a supersonic nozzle flow to produce noise reduction. Numerical simulations have been performed for a military-style basline nozzle and with the noise reduction method of fluidic inserts used at a design Mach number of 1.65 and at various off design conditions. The purpose of the current numerical study is to provide insight for the flow field generated by the fluidic inserts used to reduce supersonic jet noise. The supersonic jet simulations are based on the use of high fidelity meshes combined with advanced CFD technology. Steady Reynolds-averaged Navier-Stokes (RANS) simulations are used to predict the flow field. Noise measurements have been performed experimentally and the results from the numerical simulations provide a correlation between aerodynamic properties and the corresponding noise reduction. The complex nozzle geometry is modeled using both an unstructured mesh and a multiblock structured mesh. The grids are generated by ANSYS ICEM and Gridgen respectively. The numerical simulations are performed using ANSYS CFX and Wind-US. The simulations with Wind-US use the Spalart-Allmaras turbulence model, while the simulations with ANSYS CFX use the Menter SST turbulence model. The results from the two flow solvers are compared and provide good agreement. The objective is to simulate a military-style nozzle, which resembles engines of the GE F404 family, with fluidic inserts. The purpose of the fluidic inserts is to alter the flow field similar to that of a hard wall corrugation in order to reduce components of noise radiation. The addition of the fluidic inserts increases the complexity of the flow field for the supersonic jet. The numerical simulations performed help to better distinguish the effects on the flow field due to the fluidic inserts. Preliminary work has been performed on a simpler geometry to provide further insight to the effect of the fluidic inserts on the supersonic jet flow field. These simulations are performed by fluid injection into a supersonic freestream over a flat plate. All numerical simulations used a freestream Mach number of 1.5. The numerical simulations used a wide range of pressure ratios for injecting the fluid into the supersonic freestream. By changing the pressure ratio of the fluid injection, the deflection of the freestream flow was better understood. Simulations on a full three dimensional nozzle with fluidic inserts were performed with conditions based on the preliminary studies. Parameters such as total pressure and total temperature provide a representation of the fluidic insert shape. Other integrated flow properties at the nozzle exit such as streamwise vorticity and pressure differential were used to correlate with the noise reduction seen in the experiments.
Author: Jacob Lampenfield
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
This investigation of military jet noise prediction and reduction is a continuation from previous projects and is still ongoing. Numerical simulations have been performed on baseline nozzles and nozzles with the addition of fluidic inserts. The design Mach number of the nozzle is 1.65, but only the over-expanded Mach number of 1.36 has been analyzed. The fluidic inserts have been generated using different numbers of injectors and injector hole sizes. The supersonic military style jet simulation makes use of advanced meshes combined with CFD technology. Steady Reynolds-averaged Navier-Stokes (RANS) simulations are produced by the CFD technology and used to predict and understand the flow field. Through collaboration with experimental noise measurements, a correlation between flow field properties and noise reduction is examined. The ANSYS suite is used to create grids and run simulations by using ANSYS-ICEM and ANSYS-CFX respectively. The geometry of the nozzle is modeled using an unstructured hexahedral mesh. The Menter SST turbulence model with a wall function is used inside of the CFX-Solver. The objective is to further simulate a military-style nozzle, similar to the GE F404 family, with added fluidic inserts. Previous simulations have been conducted and new simulations were planned and performed based on information gathered from the previous simulations and experiments. The fluidic inserts are used to alter the flow field to achieve the same effect of hard wall corrugations, which have been shown to reduce noise levels. The numerical simulations are used to help understand the effects on the flow field created by the fluidic inserts and to attempt to find flow parameters that can be correlated to noise reduction. Simulations were first run on a simpler geometry to give an understanding of the fluidic inserts. They were conducted by having three injectors exhausting into a supersonic boundary layer. The freestream Mach number was 1.5 to simulate the inside of the nozzle. A study was then conducted to see the effect of a change in downstream injector angle on the fluidic insert. There was also a study of an increase Reynolds number as three different sized nozzles were modeled. The first size is a small nozzle with an exit diameter of 0.885 inches. The nozzle size was then increased by a factor of 1.2 to an exit diameter of 1.06 inches. A third nozzle was then modeled to recreate the nozzle used in the GE experiments. This nozzle had a diameter of 5.07 inches. The results from all the simulations were then compared to experimental acoustic data. Flow parameters were then integrated from each simulation to attempt to find a correlation to noise reduction. Parameters such as streamwise vorticity, turbulent kinetic energy, and Q criterion were all analyzed.
Author: James Falcone
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Extremely high levels of noise, capable of damaging the human ear, are emitted from theexhaust leaving military grade aircraft engines. Military personnel, specifically those on the decksof aircraft carriers, are regularly exposed to this dangerous noise and as a result often sustainpermanent hearing damage. A novel approach to reducing the noise levels experienced by thesepersonnel is through the use of fluid inserts in the diverging section of an aircraft engines nozzle.These fluid inserts blow additional air into the exhaust flow which has been shown to effectivelyreduce noise. This study sought to further the understanding of the flow physics by which thefluid inserts can reduce noise. Pressure surveys of a scaled GE 404 class engine nozzle werecompleted with and without the use of fluid inserts. The alterations created by the fluid inserts inthe downstream flow are visualized and discussed. The experimental results are also compared toRANS CFD simulations of jets from the same nozzle and operating conditions to further evaluatethe computations and improve future simulations.Throughout the duration of the experiments, jet asymmetries were also carefully explored forthe baseline jet as well as the fluid insert jet. Asymmetries within a jet can have an impact onnoise reduction by unknowingly redistributing the flow in undesirable ways. The reasons for theseasymmetries are proposed.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 116
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A new compressible Navier-Stokes code in cylindrical coordinates was developed for investigating axisymmetric wakes of bluff-based bodies in supersonic flows. In this code, high-order compact finite differences derived for non-equidistant grids are employed and a new stare-of-the-art axis treatment is incorporated. Additionally, the fully three-dimensional transport equations for turbulent kinetic energy and turbulent dissipation are implemented to enable (steady or unsteady) Reynolds Averaged Navier Stokes (RANS) simulations. Furthermore, a new "Flow Simulation Methodology" (FSM) was developed for computing complex compressible flows. The centerpiece of FSM) is a strategy to provide the proper amount of modeling of the subgrid scales. This is accomplished by a "contribution function" which locally and instantaneously compares the smallest relevant scales to the local grid size. The contribution function is designed such that it provides no modeling if the computation is locally well resolved so that the computation approaches a Direct Numerical Simulation (DNS) in the fine grid limit, or provides modeling of all scales in the coarse grid limit and thus approaches an unsteady PANS (URANS) calculation. In between these resolution limits, the contribution function adjusts the necessary modeling for the unresolved scales while the larger (resolved) scales are computed as in traditional Large Eddy Simulations (LES) . Preliminary results have shown that the new high- order code has great advantages for supersonic base flow simulations and that calculations, in particular together with FSM), will allow simulations of supersonic base flows at much higher Reynolds numbers than possible with conventional LES.
Author: Michael Rybalko
Publisher:
ISBN:
Category :
Languages : en
Pages : 98
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721276707
Category :
Languages : en
Pages : 26
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Book Description
An acoustic prediction capability for supersonic axisymmetric jets was developed on the basis of OVERFLOW Navier-Stokes CFD (Computational Fluid Dynamics) code of NASA Langley Research Center. Reynolds-averaged turbulent stresses in the flow field are modeled with the aid of Spalart-Allmaras one-equation turbulence model. Appropriate acoustic and outflow boundary conditions were implemented to compute time-dependent acoustic pressure in the nonlinear source-field. Based on the specification of acoustic pressure, its temporal and normal derivatives on the Kirchhoff surface, the near-field and the far-field sound pressure levels are computed via Kirchhoff surface integral, with the Kirchhoff surface chosen to enclose the nonlinear sound source region described by the CFD code. The methods are validated by a comparison of the predictions of sound pressure levels with the available data for an axisymmetric turbulent supersonic (Mach 2) perfectly expanded jet. Kandula, Max and Caimi, Raoul and Steinrock, T. (Technical Monitor) Kennedy Space Center NASA/TM-2001-210263, NAS 1.15:210263
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 48
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Author: Alexander J. Smits
Publisher: Springer Science & Business Media
ISBN: 0387263055
Category : Science
Languages : en
Pages : 418
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Book Description
A good understanding of turbulent compressible flows is essential to the design and operation of high-speed vehicles. Such flows occur, for example, in the external flow over the surfaces of supersonic aircraft, and in the internal flow through the engines. Our ability to predict the aerodynamic lift, drag, propulsion and maneuverability of high-speed vehicles is crucially dependent on our knowledge of turbulent shear layers, and our understanding of their behavior in the presence of shock waves and regions of changing pressure. Turbulent Shear Layers in Supersonic Flow provides a comprehensive introduction to the field, and helps provide a basis for future work in this area. Wherever possible we use the available experimental work, and the results from numerical simulations to illustrate and develop a physical understanding of turbulent compressible flows.
Author: Holger Babinsky
Publisher: Cambridge University Press
ISBN: 1139498649
Category : Technology & Engineering
Languages : en
Pages : 481
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Book Description
Shock wave-boundary-layer interaction (SBLI) is a fundamental phenomenon in gas dynamics that is observed in many practical situations, ranging from transonic aircraft wings to hypersonic vehicles and engines. SBLIs have the potential to pose serious problems in a flowfield; hence they often prove to be a critical - or even design limiting - issue for many aerospace applications. This is the first book devoted solely to a comprehensive, state-of-the-art explanation of this phenomenon. It includes a description of the basic fluid mechanics of SBLIs plus contributions from leading international experts who share their insight into their physics and the impact they have in practical flow situations. This book is for practitioners and graduate students in aerodynamics who wish to familiarize themselves with all aspects of SBLI flows. It is a valuable resource for specialists because it compiles experimental, computational and theoretical knowledge in one place.
Author: Milton A. Beheim
Publisher:
ISBN:
Category : Gases at high temperatures
Languages : en
Pages : 52
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