Characterization of Turbulent Flow and Pressure Fluctuations Over a Hydrophone by LES

2015 ◽  
Author(s):  
Aidan Bharath ◽  
Dominic Groulx ◽  
Sean Campbell
Keyword(s):  
Turbulent Flow ◽  
Acoustic Noise ◽  
Pressure Fluctuations ◽  
Noise Generation ◽  
Ansys Fluent ◽  
Flow Rates ◽  
Large Eddy ◽  
Pseudo Noise ◽  
The Impact

This paper presents a numerical CFD study of the turbulent flow at up to 4 m/s of water around an underwater hydrophone from the company Ocean Sonics. At such high flow rates in tidal environments, pseudo-noise, coming from turbulence induced pressure fluctuations around the hydrophone, contaminate the acoustic noise reading obtained with the device. Through the use of fine scale large eddy simulations (LES) in ANSYS Fluent, this study shows the impact of increasing flow velocities on the generated turbulence and vorticity, as well as identifying regions in the flow, and geometric aspects of the device, that are playing the larger role in pseudo-noise generation.

scholarly journals Physics-Based Simulations of Flow and Fire Development Downstream of a Canopy

Atmosphere ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 683
Author(s):  
Gilbert Accary ◽  
Duncan Sutherland ◽  
Nicolas Frangieh ◽  
Khalid Moinuddin ◽  
Ibrahim Shamseddine ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Forest Canopy ◽  
Prescribed Burning ◽  
Second Phase ◽  
Flow Conditions ◽  
Developed Turbulence ◽  
Large Eddy ◽  
Long Time ◽  
Two Phases ◽  
The Impact

The behavior of a grassland fire propagating downstream of a forest canopy has been simulated numerically using the fully physics-based wildfire model FIRESTAR3D. This configuration reproduces quite accurately the situation encountered when a wildfire spreads from a forest to an open grassland, as can be the case in a fuel break or a clearing, or during a prescribed burning operation. One of the objectives of this study was to evaluate the impact of the presence of a canopy upstream of a grassfire, especially the modifications of the local wind conditions before and inside a clearing or a fuel break. The knowledge of this kind of information constitutes a major element in improving the safety conditions of forest managers and firefighters in charge of firefighting or prescribed burning operations in such configurations. Another objective was to study the behavior of the fire under realistic turbulent flow conditions, i.e., flow resulting from the interaction between an atmospheric boundary layer (ABL) with a surrounding canopy. Therefore, the study was divided into two phases. The first phase consisted of generating an ABL/canopy turbulent flow above a pine forest (10 m high, 200 m long) using periodic boundary conditions along the streamwise direction. Large Eddy Simulations (LES) were carried out for a sufficiently long time to achieve a quasi-fully developed turbulence. The second phase consisted of simulating the propagation of a surface fire through a grassland, bordered upstream by a forest section (having the same characteristics used for the first step), while imposing the turbulent flow obtained from the first step as a dynamic inlet condition to the domain. The simulations were carried out for a wind speed that ranged between 1 and 12 m/s; these values have allowed the simulations to cover the two regimes of propagation of surfaces fires, namely plume-dominated and wind-driven fires.

The Role of Pressure and Pressure Fluctuations in the Growth of Stress Corrosion Cracks in Line Pipe Steels

1998 ◽  
Author(s):  
Martyn J. Wilmott ◽  
Robert L. Sutherby
Keyword(s):  
Stress Corrosion ◽  
Hoop Stress ◽  
Pipeline Steel ◽  
Pressure Fluctuations ◽  
Operating Pressure ◽  
Pipeline Steels ◽  
Cyclic Stresses ◽  
Neutral Ph ◽  
The Impact

Stress corrosion cracking of pipeline steels involves the interaction of a susceptible material with a corrosive environment under appropriate loading conditions. The stress exerted on pipeline steel is a combination of the internal operating or hoop stress, cyclic stresses due to pressure fluctuations within the pipe, residual stresses developed during pipe manufacture and pipeline construction, as well as other sources of stress such as stress concentrators like corrosion defects and geotechnical stresses. As the internal pressure of an operating pipeline is never static the fluctuations in pressure result in cyclic loading of the pipeline material. Whilst there are many stresses acting on a pipeline the predominant stress is the hoop stress created as a result of the internal operating pressure. In this paper experiments are described which are aimed at determining the effect of pipeline hoop stress on the growth of stress corrosion cracks under neutral pH conditions. The propagation of stress corrosion cracks in pipeline steels at near neutral pH was studied under realistic environmental conditions. The impact of hoop stress on the growth of shallow surface cracks in an X60 pipeline steel was investigated at 40%, 70% and 100% of the specified minimum yield strength of the material. Crack growth rate is shown to be independent of the applied stress in the range studied for these shallow cracks. Cyclic stresses appear to be more important for crack propagation under neutral pH SCC conditions. In light of the results obtained in this test program an attempt was made to characterize the pressure changes occurring on an operating gas pipeline. A computer program was developed to enable characterization of the pressure fluctuations for operating gas pipelines. The results of characterization of pressure histories from a number of operating pipelines are presented.

Noise Prediction of Pressure-Mismatched Jets Using Unstructured Large Eddy Simulation

2011 ◽  
Author(s):  
Yaser Khalighi ◽  
Frank Ham ◽  
Parviz Moin ◽  
Sanjiva K. Lele ◽  
Robert H. Schlinker
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Empirical Models ◽  
Nozzle Geometry ◽  
High Fidelity ◽  
Noise Generation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Generation Mechanisms

It is our premise that significant new advances in the understanding of noise generation mechanisms for jets and realistic methods for reducing this noise can be developed by exploiting high-fidelity computational fluid dynamics: namely large eddy simulation (LES). In LES, the important energy-containing structures in the flow are resolved explicitly, resulting in a time-dependent, three-dimensional realization of the turbulent flow. In the context of LES, the unsteady flow occurring in the jet plume (and its associated sound) can be accurately predicted without resort to adjustable empirical models. In such a framework, the nozzle geometry can be included to directly influence the turbulent flow including its coherent and fine-scale motions. The effects of propulsion system design choices and issues of integration with the airframe can also be logically addressed.

scholarly journals Towards the Large-Eddy Simulation of a full engine: Integration of a 360 azimuthal degrees fan, compressor and combustion chamber. Part II: Comparison against stand-alone simulations

2021 ◽  
pp. 1-16
Author(s):  
Carlos Pérez Arroyo ◽  
Jérôme Dombard ◽  
Florent Duchaine ◽  
Laurent Gicquel ◽  
Benjamin Martin ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Combustion Chamber ◽  
Hot Spot ◽  
Pressure Fluctuations ◽  
Forward Region ◽  
Impeller Blade ◽  
Eddy Simulation ◽  
Blade Passing Frequency ◽  
Large Eddy ◽  
The Impact

Unsteady simulations of various components of a gas-turbine engine are often carried out independently and only share averaged quantities at the component interfaces. In order to study the impact and interactions between components, this work compares results from sectoral stand-alone simulations of a fan, compressor and annular combustion chamber of the DGEN-380 demonstrator engine at take-off conditions against an integrated 360 azimuthal degrees large-eddy simulation with over 2.1 billion cells of all previously listed components. Note that, at take-off conditions the compressor works at transonic conditions and generates an upstream-propagating shock that interacts with the fan modifying the shape of its wake with respect to the stand-alone simulation. Furthermore, the shock is seen as a tone in the pressure spectra at half the impeller blade passing frequency in the forward region of the engine. In the aft region, time-averaged fields are overall similar between stand-alone and integrated simulations but show a deviation in the azimuthal position of the hot-spot at the exit of the combustion chamber due to the addition of the diffuser. Pressure fluctuations generated in the compressor are captured in the combustion chamber as tones in the temperature and pressure spectra at the impeller blade-passing frequency and harmonics as well as an increase in the root-mean-square pressure.

Evaluating the Impact of Free-Stream Turbulence on Convective Cooling of Overhead Conductors Using Large Eddy Simulations (LES)

2018 ◽  
Author(s):  
Mohamed Abdelhady ◽  
David H. Wood
Keyword(s):  
Turbulence Intensity ◽  
Wind Farm ◽  
Free Stream ◽  
Diameter Ratio ◽  
Length Scale ◽  
Ansys Fluent ◽  
Free Stream Turbulence ◽  
Low Wind Speed ◽  
Large Eddy ◽  
The Impact

This study uses Large Eddy Simulation in the ANSYS Fluent software to assess the accuracy of the forced cooling term for the overhead conductor codes, IEEE 738 [1] and CIGRÉ 207 [2], for Real Time Thermal Rating of a wind farm power line. The analysis is done for low wind speed, corresponding to Reynolds Number of 3,000. The primary goal is to calculate Nusselt Number for cylindrical conductors with free-stream turbulence. Calculations showed an increase in convective heat transfer from the low turbulence value by ∼ 30 % at turbulence intensity of 21% and length scale to diameter ratio of 0.4; and an increase of ∼ 19 % at turbulence intensity of 8% and length scale to diameter ratio of 0.4.

Numerical simulation of flow with large eddy simulation at Re = 3900

2019 ◽  
Vol 30 (5) ◽  
pp. 2397-2409 ◽  
Author(s):  
Niaz B. Khan ◽  
Zainah B. Ibrahim ◽  
Mian Ashfaq Ali ◽  
Mohammed Jameel ◽  
Muhammad Ijaz Khan ◽  
...  
Keyword(s):  
Time Interval ◽  
Turbulence Statistics ◽  
Time Step ◽  
Ansys Fluent ◽  
Content Type ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Recirculation Length ◽  
Icem Cfd ◽  
The Impact

Purpose Over the past few decades, the flow around circular cylinders has been one of the highly researched topics in the field of offshore engineering and fluid-structure interaction (FSI). In the current study, numerical simulations for flow around a fixed circular cylinder are performed at Reynolds number (Re) = 3900 with the LES method using the ICEM-CFD and ANSYS Fluent tool for meshing and analysis, respectively. Previously, similar studies have been conducted at the same Reynolds number, but there have been discrepancies in the results, particularly in calculating the recirculation length and angle of separation. In addition, the purpose of this study is to address the impact of time interval averaging to obtain the fully converged solution. Design/methodology/approach This study presents the LES method, using the ICEM-CFD and ANSYS fluent tool for meshing and analysis. Findings In the current study, turbulence statistics are sampled for 25, 50, 75 and 100 vortex-shedding cycles with the CFL value O (1). The recirculation length, angle of separation, hydrodynamic coefficients and the wake behind the cylinder are investigated up to ten diameters. The drag coefficient and Strouhal number are observed to be less sensitive, whereas the recirculation length appeared to be highly dependent on the average time statistics and the non-dimensional time step. Similarly, the mean streamwise and cross-flow velocity are observed to be sensitive to the average time statistics and non-dimensional time step in the wake region near the cylinder. Originality/value In the current investigation, turbulence statistics are sampled for 25, 50, 75 and 100 vortex-shedding cycles with the CFL value O (1), using large eddy simulation method at Re = 3900 around a circular cylinder. The impact of time interval averaging to obtain the fully converged mean flow field is addressed. No such consideration is yet published in the literature.

scholarly journals Numerical and experimental analysis of a tube-and-fin cross-flow heat exchanger with a controlled non-uniform inflow of gas

2021 ◽  
Vol 323 ◽  
pp. 00005
Author(s):  
Tomasz Bury ◽  
Małgorzata Hanuszkiewicz-Drapała
Keyword(s):  
Heat Exchanger ◽  
Water Temperature ◽  
Experimental Test ◽  
Experimental Analysis ◽  
Cross Flow ◽  
Ansys Fluent ◽  
Flow Rates ◽  
Air Inlet ◽  
Flow Heat ◽  
The Impact

The paper presents results of numerical and experimental analyses of a fin-and-tube air-water heat exchanger. The analysed device is a one-row heat exchanger with finned elliptical tubes. The aim of the analyses is to investigate the impact of a controlled non-uniform inflow of air on the heat exchanger performance. The heat exchanger was modelled numerically using the ANSYS Fluent program. The developed model was applied to simulate the heat exchanger operation in the conditions of the uniform inflow of air. Cases of an uncontrolled non-uniform inflow of gas were investigated experimentally, using a purpose-designed test station. On the experimental test station the effect of a controlled non-uniform air inflow was also achieved by placing appropriately shaped inserts in the air inlet duct, directing the air partially to the region of the water inlet header. By controlling the gas inflow, it was possible to significantly enhance the heat exchanger performance. The results of the multivariate numerical analyses conducted for the adopted parameters of the mediums (air and water volumetric flow rates and water temperature) show that the heat exchanger performance can be improved by up to almost 5% compared to a variant with a natural non-uniform air inflow taking place in the exchanger under consideration.

Study on Noise Generation in a High Speed Centrifugal Fan

2012 ◽  
Vol 610-613 ◽  
pp. 2552-2555
Author(s):  
Kishokanna Paramasivam ◽  
Jazair Yahya Wira ◽  
Srithar Rajoo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbulent Flow ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Noise Generation ◽  
Centrifugal Fan ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Computational Fluid Dynamics Cfd

This study presents the investigation of aerodynamics and aeroacoustics of centrifugal fan using commercial computational fluid dynamics (CFD) code. The unsteady turbulent flow of the fan is simulated with Detached Eddy Simulation (DES) and the acoustics sources are computed based on the pressure fluctuations. The Ffowcs Williams and Hawking model is used to predict the tonal noises in aeroacoustics simulation.

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