Numerical study on edge tone with compressible direct numerical simulation: Sound intensity and jet motion

2021 ◽  
pp. 1475472X2110032
Author(s):  
Sho Iwagami ◽  
Ryoya Tabata ◽  
Taizo Kobayashi ◽  
Yuji Hattori ◽  
Kin’ya Takahashi
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Transition Region ◽  
Power Law ◽  
Numerical Study ◽  
Sound Intensity ◽  
Mode Transition ◽  
The Third ◽  
Velocity Variance ◽  
Jet Velocity

A two-dimensional model of the edge tone is studied by a highly accurate and reliable method of direct numerical simulation of the compressible Navier-Stokes equations, and used to verify key features observed in previous experimental and numerical studies, and to discover new features related to the jet motion and the edge tone generation mechanism. The first and second modes of the edge tone that are numerically reproduced agree well with Brown’s equation. In the mode transition region, dynamical mode transition is observed at a fixed jet velocity. For both first and second modes, the pressure distributions are antisymmetric with respect to the edge plate, and the sound intensity is proportional to the fifth power of the jet velocity. These results are consistent with the edge tone being radiated from a dipole-like source. Spatial profiles of the velocity and the velocity variance of the oscillating jet are also investigated for each mode over a range of the jet velocity including the mode transition regime. The amplitude of the velocity oscillation becomes constant with increasing jet velocity, while a measure of the amplitude of the velocity variance profile, which is introduced to characterize the strength of the jet fluctuation and named the ’fluctuation strength’, is proportional to the third power of the jet velocity. Some properties of the fluctuation strength correspond to properties of the sound intensity, including the first mode having larger amplitude than the second mode, and the way of deviating from the power law at smaller values of jet velocity and in the mode transition region. It is proposed that the third-power law exhibited by behavior of the fluctuation strength could be related to the increase of the skewness observed in the velocity profile with increase of jet velocity, and a model calculation is used to support this proposal.

scholarly journals Turbulent Bubble-Laden Channel Flow of Power-Law Fluids: A Direct Numerical Simulation Study

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 40
Author(s):  
Felix Bräuer ◽  
Elias Trautner ◽  
Josef Hasslberger ◽  
Paolo Cifani ◽  
Markus Klein
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Power Law ◽  
Volume Fraction ◽  
Vertical Channel ◽  
Shear Thickening ◽  
Volumetric Flow Rate ◽  
Mean Velocity ◽  
Power Law Fluids ◽  
Gas Volume

The influence of non-Newtonian fluid behavior on the flow statistics of turbulent bubble-laden downflow in a vertical channel is investigated. A Direct Numerical Simulation (DNS) study is conducted for power-law fluids with power-law indexes of 0.7 (shear-thinning), 1 (Newtonian) and 1.3 (shear-thickening) in the liquid phase at a gas volume fraction of 6%. The flow is driven downward by a constant volumetric flow rate corresponding to a friction Reynolds number of Reτ≈127.3. The Eötvös number is varied between Eo=0.3125 and Eo=3.75 in order to investigate the influence of quasi-spherical as well as wobbling bubbles and thus the interplay of the bubble deformability with the power-law behavior of the liquid bulk. The resulting first- and second-order fluid statistics, i.e., the gas fraction, mean velocity and velocity fluctuation profiles across the channel, show clear trends in reply to varying power-law indexes. In addition, it was observed that the bubble oscillations increase with decreasing power-law index. In the channel core, the bubbles significantly increase the dissipation rate, which, in contrast to its behavior at the wall, shows similar orders of magnitude for all power-law indexes.

Numerical Study of Vortex Evolution and Correlation between Twin Swirling Flows

2012 ◽  
Vol 516-517 ◽  
pp. 976-979 ◽  
Author(s):  
Nan Gui
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Numerical Study ◽  
Swirling Flows ◽  
Cyclone Separator ◽  
Velocity Correlation ◽  
Swirl Number ◽  
Swirling Jets ◽  
Swirl Flows ◽  
Energy Engineering

Swirling flows are widely used in energy engineering, such as swirling combustor, cyclone separator in pulverized coal burners. The vortex evolution and correlation between twin swirling flows are investigated via direct numerical simulation. Three typical swirl flows with different swirl number are simulated. The structure of vortex evolution, velocity correlation between the twin flows are illustrated and analyzed in detail. The results show the phase-locked correlation of flow velocity between the twin swirling jets which would be useful and helpful for improving the understanding of aerodynamics of multi-swirling systems.

scholarly journals Direct numerical simulation of primary breakup for power-law biodiesel sprays

2019 ◽  
Vol 158 ◽  
pp. 612-618
Author(s):  
Lianmin Zhao ◽  
Daokuan Jiao ◽  
Xu Xie ◽  
Kui Jiao ◽  
Zhijun Peng ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Power Law ◽  
Primary Breakup

Direct numerical simulation of round turbulent jets in crossflow

2007 ◽  
Vol 574 ◽  
pp. 59-84 ◽  
Author(s):  
SUMAN MUPPIDI ◽  
KRISHNAN MAHESH
Keyword(s):  
Numerical Simulation ◽  
Kinetic Energy ◽  
Direct Numerical Simulation ◽  
Near Field ◽  
Leading Edge ◽  
Turbulent Jets ◽  
Energy Budgets ◽  
Mean Velocity ◽  
Field Peak ◽  
Jet Velocity

Direct numerical simulation is used to study a round turbulent jet in a laminar crossflow. The ratio of bulk jet velocity to free-stream crossflow velocity is 5.7 and the Reynolds number based on the bulk jet velocity and the jet exit diameter is 5000. The mean velocity and turbulent intensities from the simulations are compared to data from the experiments by Su & Mungal (2004) and good agreement is observed. Additional quantities, not available from experiments, are presented. Turbulent kinetic energy budgets are computed for this flow. Examination of the budgets shows that the near field is far from a state of turbulent equilibrium – especially along the jet edges. Also – in the near field – peak kinetic energy production is observed close to the leading edge, while peak dissipation is observed toward the trailing edge of the jet. The results are used to comment upon the difficulty involved in predicting this flow using RANS computations. There exist regions in this flow where the pressure transport term, neglected by some models and poorly modelled by others, is significant. And past the jet exit, the flow is not close to established canonical flows on which most models appear to be based.

A numerical study by using the Chebyshev collocation method for a problem of biological invasion: Fractional Fisher equation

2018 ◽  
Vol 11 (08) ◽  
pp. 1850099 ◽  
Author(s):  
Mohamed M. Khader ◽  
Khaled M. Saad
Keyword(s):  
Numerical Simulation ◽  
Exact Solution ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Collocation Method ◽  
Numerical Study ◽  
Fisher Equation ◽  
Chebyshev Collocation Method ◽  
The Third ◽  
The Finite Difference Method

In this paper, an efficient numerical method is introduced for solving the fractional (Caputo sense) Fisher equation. We use the spectral collocation method which is based upon Chebyshev approximations. The properties of Chebyshev polynomials of the third kind are used to reduce the proposed problem to a system of ODEs, which is solved by the finite difference method (FDM). Some theorems about the convergence analysis are stated and proved. A numerical simulation is given and the results are compared with the exact solution.

scholarly journals Three-dimensional nonadiabatic electron- optical gyrotron systems with inhomogeneous current density

2019 ◽  
Vol 30 ◽  
pp. 09003
Author(s):  
Kseniia Leshcheva ◽  
Vladimir Manuilov ◽  
Arkadiy Goldenberg
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Density Distribution ◽  
Charge Density ◽  
Current Density ◽  
Numerical Study ◽  
Three Dimensional ◽  
Space Charge Density ◽  
Charge Density Distribution ◽  
Optic Systems

The results of a numerical study of the effect of threedimensional perturbations of the space charge density distribution in a nonadiabatic electron-optic systems of gyrotrons are presented. Data of direct numerical simulation using the 3-D program CST Studio Suite are described.

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