scholarly journals Numerical Simulation Panel Vibrations of Aircraft When the Effect of Acoustic Pressure Oscillations

2015 ◽  
Vol 15 (4) ◽  
pp. 31-40
Author(s):  
M. A. Samoylov ◽  
Keyword(s):  
Numerical Simulation ◽  
Acoustic Pressure ◽  
Pressure Oscillations

Numerical Simulation of Acoustic Field for the Miniature Cylindrical Transducer with a Rectangular Hole

2011 ◽  
Vol 421 ◽  
pp. 739-742
Author(s):  
Li Li Yu ◽  
Jin Hua Zhao ◽  
Quan Zhou Zhao ◽  
Chun Hui
Keyword(s):  
Numerical Simulation ◽  
Acoustic Field ◽  
Focal Plane ◽  
Optimization Design ◽  
Acoustic Pressure ◽  
Pressure Amplitude ◽  
Hole Size ◽  
Rectangular Hole ◽  
Cylindrical Transducer ◽  
Focusing Properties

In this paper the characteristics of acoustic field for miniature cylindrical focused transducer with a hole was studied in order to instruct the optimization design of the transducer for both realizing visualization and improving the treatment effect. Then the acoustic field was simulated numerically with different parameters of hole. It is found that position of focus is almost unchanged but acoustic pressure amplitude declines. In addition the performance of transverse focusing for the focal plane and levels length of acoustic pressure are lowered. Moreover, if size of transducer and rigidity of material permit, the area and ratio of width to height for the hole should be reduced appropriately to improve the focusing properties. And it is deduced that area and ratio of width to height for the cylinder can be increased to achieve the same therapeutic effect with a fixed hole size.

The Numerical Simulation for Vibroacoustic Phenomena of a Slender Elastic Shell

2012 ◽  
Vol 479-481 ◽  
pp. 1365-1370
Author(s):  
Zhi Xi Yang ◽  
Sheng Hua Qiu
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Thin Shell ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Elastic Shell ◽  
Numerical Examples ◽  
Longitudinal Acoustic ◽  
3 Dimensional ◽  
Variational Formulas

The vibroacoustic phenomena for the slender elastic thin shell filled with water by finite element method is introduced in this paper. The unsymmetric (u, p) variational formulas and finite element procedures are implemented for 3 dimensional structures of vibroacoustic environment based on the displacement field u and the fluid acoustic pressure field p. As illustrated by numerical examples, the longitudinal acoustic pressure eigenmodes will be occurred besides the transverse bendable eigenmodes of the slender shell, nonetheless the eigenvalues and the order of eigenmodes for the fluid acoustic pressure field can only be determined by the flexibility and geometry stiffness of the slender shell.

scholarly journals Investigation on Acoustic Properties of Thruster Chamber with Coaxial Injectors and Plenum Chamber

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Dekun Gao ◽  
Jianxiu Qin ◽  
Huiqiang Zhang
Keyword(s):  
Acoustic Pressure ◽  
Rocket Engine ◽  
Pressure Oscillation ◽  
Acoustic Mode ◽  
Acoustic Properties ◽  
Pressure Oscillations ◽  
Plenum Chamber ◽  
Model Chamber ◽  
Pressure Peak ◽  
Tuning Frequency

Based on the URANS equation, a numerical simulation is carried out for acoustic properties of the thruster chamber with coaxial injectors and plenum chamber in a liquid rocket engine. Pressure oscillations with multiacoustic modes are successfully excited in the chamber by using the constant volume bomb method. FFT analysis is applied to obtain the acoustic properties of eigenfrequencies, power amplitudes, and damping rates for each excited acoustic mode. Compared with the acoustic properties in the model chamber with and without an injector as well as with and without the plenum chamber, it can be found that the injector with one open end and one half-open end still can work as a quarter-wave resonator. The power amplitudes of the acoustic mode can be suppressed significantly when its eigenfrequency is close to the tuning frequency of the injector, which is achieved by Cutting down the pressure Peak and Raising up the pressure Trough (CPRT). Compared with the acoustic properties in the model chamber with and without the plenum chamber, it can be found that 1L acoustic pressure oscillation is inhibited completely by the plenum chamber and other acoustic pressure oscillations are also suppressed in a different extent. The injector and plenum chamber have a little effect on the eigenfrequencies and damping rate of each acoustic mode. For multimode pressure oscillation, it is better for tuning frequency of the injector closing to the lower eigenfrequency acoustic mode, which will be effective for suppression of these multiacoustic modes simultaneously.

Acoustic pressure oscillations in the decay envelope of the initial shock radiated by an underwater explosion

2021 ◽  
Vol 150 (4) ◽  
pp. A114-A114
Author(s):  
Andrew R. McNeese ◽  
Preston S. Wilson ◽  
David P. Knobles ◽  
Peter H. Dahl ◽  
David Dall'Osto ◽  
...  
Keyword(s):  
Acoustic Pressure ◽  
Underwater Explosion ◽  
Pressure Oscillations ◽  
Initial Shock

scholarly journals Role of Shear Layer Instability in Driving Pressure Oscillations in a Backward Facing Step Combustor

2016 ◽  
Author(s):  
Srinivas K. Kirthy ◽  
Santosh Hemchandra ◽  
Seunghyuck Hong ◽  
Santosh Shanbhogue ◽  
Ahmed F. Ghoniem
Keyword(s):  
Stability Analysis ◽  
Shear Layer ◽  
Acoustic Pressure ◽  
Combustion Instability ◽  
High Amplitude ◽  
Open Loop ◽  
Hydrodynamic Modes ◽  
Pressure Oscillations ◽  
Layer Mode ◽  
Low Amplitude

This paper presents a global hydrodynamic stability analysis of flow fields in a backward facing step combustor, assuming weakly non-parallel flow. The baseline experiments in a ‘long’ combustor of length of 5.0 m shows the presence of two combustion instability states characterized by coherent low and high amplitude acoustic pressure oscillations. The analysis is performed for Propane-air mixtures at three values of ϕ = 0.63, 0.72 and 0.85 which correspond to quiet, low amplitude and high amplitude instability states in the long combustor experiments. Base flow velocity and density fields for the hydrodynamic stability analysis are determined from time averaged PIV measurements made after the length of the duct downstream of the step has been shortened to eliminate acoustic pressure oscillations. The analysis shows that the shear layer mode is self-excited for the ϕ = 0.72 case with an oscillation frequency close to that of the long combustor’s fundamental acoustic mode. We show from an analysis of the weakly forced, variable density Navier-Stokes equations that self-excited hydrodynamic modes can be weakly receptive to forcing — suggesting that the low amplitude instability in the long combustor is due to semi-open loop forcing of heat release oscillations by the shear layer mode. At ϕ = 0.85 the flow is hydrodynamically globally stable but locally convectively unstable. Spatial amplification of velocity disturbances by the convectively unstable flow causes high amplitude combustion instability in the long combustor case. These results show that combustion instability can be sustained by acoustic and hydrodynamic modes being either strongly coupled, resulting in fully closed loop forcing, or weakly coupled, resulting in semi-open loop forcing of the flame by a self-excited hydrodynamic mode.

scholarly journals Measuring the phase between fluctuating pressure and flame radiation intensity in a cylindrical combustion chamber

2019 ◽  
Author(s):  
S. Gröning ◽  
J.S. Hardi ◽  
D. Suslov ◽  
M. Oschwald
Keyword(s):  
Energy Transfer ◽  
Phase Shift ◽  
Heat Release ◽  
Acoustic Pressure ◽  
Dynamic Pressure ◽  
Rocket Engine ◽  
Pressure Sensors ◽  
Pressure Oscillations ◽  
Flame Radiation ◽  
Rate Oscillations

The energy transfer from the heat release of the combustion to the acoustic pressure oscillations is the driving element of combustion instabilities. This energy transfer is described by the Rayleigh criterion and depends on the phase shift between the pressure and heat release rate oscillations. A research rocket engine combustor, operated with the propellant combination hydrogen/oxygen, was equipped with dynamic pressure sensors and fibre optical probes to measure the flame radiation. This setup has been used for a phase shift analysis study which showed that unstable operation is characterized by a phase shift leading to an energy transfer from the heat release to the acoustic pressure oscillations.

scholarly journals Methane hydrogen laminar burning velocity blending laws in horizontal open-ended flame tube rig

2022 ◽  
Vol 1217 (1) ◽  
pp. 012013
Author(s):  
N A Amaludin ◽  
M Morrow ◽  
R Woolley ◽  
A E Amaludin
Keyword(s):  
Flame Propagation ◽  
Acoustic Pressure ◽  
Burning Velocity ◽  
Horizontal Tube ◽  
Hydrogen Gas ◽  
Hydrogen Fuel ◽  
Laminar Burning Velocity ◽  
Pressure Oscillations ◽  
Fuel Blends ◽  
Kinetics Of

Abstract Different fuel properties and chemical kinetics of two different fuels would make it challenging to predict the combustion parameters of a binary fuel. Understanding the effect of blending methane and hydrogen gas is the main focus of this paper. Utilizing a horizontal tube combustion rig, methane-hydrogen fuel blends were created using blending laws from past literature, over a range of equivalence ratios from 0.6 – 1.2 were studied, while keeping one combustion parameter constant, the theoretical laminar burning velocity. The selected theoretical laminar burning velocity for all the mixtures tested were kept constant at 0.6 ms−1. Different factors affected the flame propagation across the tube, including acoustic pressure oscillations, heat loss from the rig, and obvious difference in hydrogen percentage in the fuel blends. The average experimental laminar burning velocity of all the flames was 0.368 ms−1, compared to the expected value of 0.6 ms−1. In an attempt to keep the theoretical laminar burning velocity constant for different mixtures, it was discovered that this did not promise the same flame propagation behaviour for the tested mixtures. Further experimentation and analysis are required in order to better understand the underlying interaction of the fuel blends.

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