Supersonic Jet Noise Reduction Technologies for Gas Turbine Engines

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
David Munday ◽  
Nick Heeb ◽  
Ephraim Gutmark ◽  
Junhui Liu ◽  
K. Kailasanath
Keyword(s):  
Flow Field ◽  
Near Field ◽  
Supersonic Jet ◽  
Acoustic Emissions ◽  
Nozzle Geometry ◽  
Axial Position ◽  
Eddy Simulation ◽  
Image Velocimetry ◽  
Large Eddy ◽  
The Impact

This paper presents observations and simulations of the impact of several technologies on modifying the flow-field and acoustic emissions from supersonic jets from nozzles typical of those used on military aircraft. The flow-field is measured experimentally by shadowgraph and particle image velocimetry. The acoustics are characterized by near- and far-field microphone measurements. The flow- and near-field pressures are simulated by a monotonically integrated large eddy simulation. Use of unstructured grids allows accurate modeling of the nozzle geometry. The emphasis of the work is on “off-design” or nonideally expanded flow conditions. The technologies applied to these nozzles include chevrons, fluidic injection, and fluidically enhanced chevrons. The fluidic injection geometry and the fluidic enhancement geometry follow the approach found successful for subsonic jets by employing jets pitched 60 deg into the flow, impinging on the shear layer just past the tips of the chevrons or in the same axial position when injection is without chevrons.

Supersonic Jet Noise Reduction Using Fluidics, Mechanical Chevrons and Fluidically Enhanced Chevrons

2010 ◽  
Author(s):  
David Munday ◽  
Nick Heeb ◽  
Ephraim Gutmark ◽  
Junhui Liu ◽  
K. Kailasanath
Keyword(s):  
Near Field ◽  
Supersonic Jet ◽  
Acoustic Emissions ◽  
Nozzle Geometry ◽  
Axial Position ◽  
Eddy Simulation ◽  
Image Velocimetry ◽  
Large Eddy ◽  
Nozzle Geometries ◽  
The Impact

This paper presents observations and simulations of the impact of several technologies on modifying the flow field and acoustic emissions from supersonic jets from nozzles typical of those used on military aircraft. The flowfield is measured experimentally by shadowgraph and particle image velocimetry (PIV). The acoustics are characterized by near and far-field microphone measurements. The flow and near-field pressures are simulated by monotonically integrated large-eddy simulation (MILES). Use of unstructured grids allows accurate modeling of the nozzle geometry. The nozzle geometries used in this research are representative of practical engine nozzles. The emphasis of the work is on “off-design” or non-ideally expanded flow conditions. The technologies applied to these nozzles include chevrons, fluidic injection and fluidically enhanced chevrons. The fluidic injection geometry and fluidic enhancement geometry follow the approach found successful for subsonic jets by Alkislar, Krothapalli & Butler [1] employing jets pitched 60° into the flow, impinging on the shear layer just past the tips of the chevrons, or in the same axial position when injection is without chevrons.

Impact of Mechanical Chevrons on Supersonic Jet Flow and Noise

2009 ◽  
Author(s):  
K. Kailasanath ◽  
Junhui Liu ◽  
Ephraim Gutmark ◽  
David Munday ◽  
Steven Martens
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Near Field ◽  
Supersonic Jet ◽  
Initial Step ◽  
Nozzle Geometry ◽  
Jet Flows ◽  
Flow Conditions ◽  
Nozzle Geometries ◽  
The Impact

In this paper, we present observations on the impact of mechanical chevrons on modifying the flow field and noise emanated by supersonic jet flows. These observations are derived from both a monotonically integrated large-eddy simulation (MILES) approach to simulate the near fields of supersonic jet flows and laboratory experiments. The nozzle geometries used in this research are representative of practical engine nozzles. A finite-element flow solver using unstructured grids allows us to model the nozzle geometry accurately and the MILES approach directly computes the large-scale turbulent flow structures. The emphasis of the work is on “off-design” or non-ideally expanded flow conditions. LES for several total pressure ratios under non-ideally expanded flow conditions were simulated and compared to experimental data. The agreement between the predictions and the measurements on the flow field and near-field acoustics is good. After this initial step on validating the computational methodology, the impact of mechanical chevrons on modifying the flow field and hence the near-field acoustics is being investigated. This paper presents the results to date and further details will be presented at the meeting.

scholarly journals Subgrid-scale models and large-eddy simulation of oxygen stream disintegration and mixing with a hydrogen or helium stream at supercritical pressure

2011 ◽  
Vol 679 ◽  
pp. 156-193 ◽  
Author(s):  
EZGI S. TAŞKINOĞLU ◽  
JOSETTE BELLAN
Keyword(s):  
Heat Flux ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Correction Term ◽  
A Priori ◽  
Supercritical Pressure ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

For flows at supercritical pressure, p, the large-eddy simulation (LES) equations consist of the differential conservation equations coupled with a real-gas equation of state, and the equations utilize transport properties depending on the thermodynamic variables. Compared to previous LES models, the differential equations contain not only the subgrid-scale (SGS) fluxes but also new SGS terms, each denoted as a ‘correction’. These additional terms, typically assumed null for atmospheric pressure flows, stem from filtering the differential governing equations and represent differences, other than contributed by the convection terms, between a filtered term and the same term computed as a function of the filtered flow field. In particular, the energy equation contains a heat-flux correction (q-correction) which is the difference between the filtered divergence of the molecular heat flux and the divergence of the molecular heat flux computed as a function of the filtered flow field. We revisit here a previous a priori study where we only had partial success in modelling the q-correction term and show that success can be achieved using a different modelling approach. This a priori analysis, based on a temporal mixing-layer direct numerical simulation database, shows that the focus in modelling the q-correction should be on reconstructing the primitive variable gradients rather than their coefficients, and proposes the approximate deconvolution model (ADM) as an effective means of flow field reconstruction for LES molecular heat-flux calculation. Furthermore, an a posteriori study is conducted for temporal mixing layers initially containing oxygen (O) in the lower stream and hydrogen (H) or helium (He) in the upper stream to examine the benefit of the new model. Results show that for any LES including SGS-flux models (constant-coefficient gradient or scale-similarity models; dynamic-coefficient Smagorinsky/Yoshizawa or mixed Smagorinsky/Yoshizawa/gradient models), the inclusion of the q-correction in LES leads to the theoretical maximum reduction of the SGS molecular heat-flux difference; the remaining error in modelling this new subgrid term is thus irreducible. The impact of the q-correction model first on the molecular heat flux and then on the mean, fluctuations, second-order correlations and spatial distribution of dependent variables is also demonstrated. Discussions on the utilization of the models in general LES are presented.

Study on the Mechanism and Characteristics of Transient Noise of the Steam Discharge Pipes

2018 ◽  
Author(s):  
Lu Dai ◽  
Zhiguo Wei ◽  
Jun Wu ◽  
Yong Liu ◽  
Can Ma ◽  
...  
Keyword(s):  
Flow Field ◽  
Control Valve ◽  
Simulation Method ◽  
Opening Angle ◽  
Key Factors ◽  
Noise Sources ◽  
Steam Power ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

While the steam power plant runs at low load, the drastic vibration and noise of the steam discharge pipes will be induced by the discharging process of high temperature and high pressure steam. Motived by this, the analytical model of inner flow field of the steam discharge pipes is modeled in this paper. The large eddy simulation method is used to analyze the characteristics of the inner flow field of the steam discharge pipes. The mechanism of transient noise in the process of steam discharging, by the comparison of variation law of the inner flow field with different opening angles of control valve or different time, is obtained. On this basis, the K-FWH method is employed to calculate the transient noise of steam discharging. The results show that the key factors of transient noise generation can be owed to the impact effect of steam jet flow on the surface of valve structure, the shear and friction effect induced by the uneven flow, the energy loss of vortex collapse in the process of valve throttling, and the surface noise sources induced by turbulent flow and so on. The throttle noise induced by control valve is presented as significant broadband characteristics in the frequency domain, and the level of transient noise increases with the decreasing of the opening angle of control valve.

Large Eddy Simulations of Static and Rotating Ribbed Channels in Adiabatic and Isothermal Conditions

2017 ◽  
Author(s):  
Thomas Grosnickel ◽  
Florent Duchaine ◽  
Laurent Y. M. Gicquel ◽  
Charlie Koupper
Keyword(s):  
Flow Direction ◽  
Secondary Flows ◽  
Flow Topology ◽  
Time Resolved ◽  
Piv Measurements ◽  
Eddy Simulation ◽  
Image Velocimetry ◽  
Large Eddy ◽  
Rib Turbulators ◽  
The Impact

In an attempt to better understand spatially developing rotating cooling flows, the present study focuses on a computational investigation of a straight, rotating rib roughened cooling channel initially numerically studied by Fransen et al. [1]. The configuration consists of a squared channel equipped with 8 rib turbulators placed with an angle of 90 degrees with respect to the flow direction. The rib pitch-to-height (p/h) ratio is 10 and the height-to-hydraulic diameter (h/Dh) ratio is 0.1. The simulations are based on a case where time resolved two-dimensional Particle Image Velocimetry (PIV) measurements have been performed at the Von Karman Institute (VKI) in a near gas turbine operating condition: the Reynolds number (Re) and the rotation number (Ro) are around 15000 and ± 0.38 respectively. Adiabatic as well as anisothermal conditions have been investigated to evaluate the impact of the wall temperature on the flow, especially in the rotating configurations. Static as well as both positive and negative rotating channels are compared with experimental data. In each case, either an adiabatic or an isothermal wall boundary condition can be computed. In this work, Large Eddy Simulation (LES) results show that the high fidelity CFD model manages very well the turbulence increase (decrease) around the rib in destabilizing (stabilizing) rotation of the ribbed channels. Thanks to the full spatial and temporal description produced by LES, the spatial development of secondary flows are found to be at the origine of observed differences with experimental measurements. Finally, the model is also able to reproduce the differences induced by buoyancy on the flow topology in the near rib region and resulting from an anisothermal flow in rotation.

scholarly journals Exploration of the impact of nearby sources on urban atmospheric inversions using large eddy simulation

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Brian J. Gaudet ◽  
Thomas Lauvaux ◽  
Aijun Deng ◽  
Kenneth J. Davis
Keyword(s):  
Large Eddy Simulation ◽  
Mesoscale Model ◽  
Near Field ◽  
Turbulent Transport ◽  
Analytical Models ◽  
Source Inversion ◽  
Mesoscale Models ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

The Indianapolis Flux Experiment (INFLUX) aims to quantify and improve the effectiveness of inferring greenhouse gas (GHG) source strengths from downstream concentration measurements in urban environments. Mesoscale models such as the Weather Research and Forecasting (WRF) model can provide realistic depictions of planetary boundary layer (PBL) structure and flow fields at horizontal grid lengths (Δx) down to a few km. Nevertheless, a number of potential sources of error exist in the use of mesoscale models for urban inversions, including accurate representation of the dispersion of GHGs by turbulence close to a point source. Here we evaluate the predictive skill of a 1-km chemistry-adapted WRF (WRF-Chem) simulation of daytime CO2 transport from an Indianapolis power plant for a single INFLUX case (28 September 2013). We compare the simulated plume release on domains at different resolutions, as well as on a domain run in large eddy simulation (LES) mode, enabling us to study the impact of both spatial resolution and parameterization of PBL turbulence on the transport of CO2. Sensitivity tests demonstrate that much of the difference between 1-km mesoscale and 111-m LES plumes, including substantially lower maximum concentrations in the mesoscale simulation, is due to the different horizontal resolutions. However, resolution is insufficient to account for the slower rate of ascent of the LES plume with downwind distance, which results in much higher surface concentrations for the LES plume in the near-field but a near absence of tracer aloft. Physics sensitivity experiments and theoretical analytical models demonstrate that this effect is an inherent problem with the parameterization of turbulent transport in the mesoscale PBL scheme. A simple transformation is proposed that may be applied to mesoscale model concentration footprints to correct for their near-field biases. Implications for longer-term source inversion are discussed.

Large-Eddy Simulation of Turbine Rim Seal Flow

2018 ◽  
Author(s):  
Alexej Pogorelov ◽  
Matthias Meinke ◽  
Wolfgang Schröder
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Level Set ◽  
Large Scale ◽  
Stokes Equations ◽  
Axial Flow ◽  
Dominant Mode ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

The flow field in a complete one-stage axial-flow turbine with 30 stator and 62 rotor blades is investigated by large-eddy simulation (LES). To solve the compressible Navier-Stokes equations, a massively parallelized finite-volume flow solver based on an efficient Cartesian cut-cell/level-set approach, which ensures a strict conservation of mass, momentum and energy, is used. This numerical method contains two adaptive Cartesian meshes, one mesh to track the embedded surface boundaries and a second mesh to resolve the fluid domain and to solve the conservation equations. The overall approach allows large scale simulations of turbomachinery applications with multiple relatively moving boundaries in a single frame of reference. The relative motion of the geometries is described by a kinematic motion level-set interface method. The focus of the numerical analysis is on the flow inside the cavity between the stator and the rotor disks. Full 360° computations of the turbine stage with a single lip rim seal geometry are conducted. First, the impact of the mesh resolution on the LES results is analyzed. Second, the LES results are compared to experimental data, followed by a detailed analysis of the flow field inside the rotor-stator wheel space. A dominant mode unrelated to the rotor frequency and its harmonics is identified, which shows a major impact on the ingress of the hot gas into the rotor-stator wheel space.

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