Mechanisms of generation and noise sources of supersonic jets and the numerical simulation of their gas dynamic and aeroacoustic characteristics

2019 ◽  
pp. 498-515
Author(s):  
К.Н. Волков ◽  
В.Н. Емельянов ◽  
А.И. Цветков ◽  
П.С. Чернышов
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Pressure Ratio ◽  
Numerical Algorithms ◽  
Noise Generation ◽  
Noise Sources ◽  
Simulation Tools ◽  
Underexpanded Jets ◽  
Integral Methods

Интерес к разработке моделей и методов, направленных на изучение механизмов генерации шума в струйных течениях, объясняется постоянно ужесточающимися требованиями по шуму, производимому различными промышленными устройствами. Рассматриваются модели, лежащие в основе вычислительной газовой динамики и аэроакустики, а также интегральные методы расчета шума в дальнем поле и особенности численной реализации соответствующих математических моделей. Возможности разработанных средств численного моделирования демонстрируются на примере расчета шума, генерируемого сверхзвуковыми недорасширенными струями. Обсуждается влияние перепада давления на структуру струи, а также распределения газодинамических и акустических характеристик. Представленные средства численного моделирования задач вычислительной газовой динамики и вычислительной аэроакустики представляют собой инструменты решения исследовательских и инженерных задач, а также служат основой разработки новых методов и вычислительных алгоритмов. The interest in the development of models and methods focused on the study of mechanisms of noise generation in jets is explained by tightening requirements imposed on the noise produced by various industrial devices. The models of computational fluid dynamics and aeroacoustics, the integral methods of farfield noise calculation, and the numerical implementation of the corresponding mathematical models are considered. The capabilities of the developed numerical simulation tools are demonstrated by the solution of practical problems related to the noise generation by supersonic underexpanded jets. The effect of the nozzle pressure ratio on the jet structure and the distribution of gasdynamic and acoustic characteristics is discussed. The developed tools for the numerical solution of problems in the computational fluid dynamics and computational aeroacoustics can be considered as the tools for solving various research and engineering problems and as the basis for the development of new methods and numerical algorithms.

Tonal Noise Reduction in a Radial Fan With Forward-Curved Blades

2014 ◽  
Author(s):  
Manoochehr Darvish ◽  
Bastian Tietjen ◽  
Daniel Beck ◽  
Stefan Frank
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Aerodynamic Performance ◽  
Computational Aeroacoustics ◽  
Experimental Measurements ◽  
Noise Generation ◽  
Tonal Noise ◽  
Outlet Angle ◽  
And Performance ◽  
Impeller Geometry

The main focus of this work is on the geometrical modifications that can be applied to the fan wheel and the volute tongue of a radial fan to reduce the tonal noise. The experimental measurements are performed by using the in-duct method in accordance with ISO 5136. In addition to the experimental measurements, CFD (Computational Fluid Dynamics) and CAA (Computational Aeroacoustics) simulations are carried out to investigate the effects of different modifications on the noise and performance of the fan. It is shown that by modifying the blade outlet angle, the tonal noise of the fan can be reduced without affecting the performance of the fan. Moreover, it is indicated that increasing the number of blades leads to a significant reduction in the tonal noise and also an improvement in the performance. However, this trend is only valid up to a certain number of blades, and a further increment might reduce the aerodynamic performance of the fan. Besides modifying the impeller geometry, new volute tongues are designed and manufactured. It is demonstrated that the shape of the volute tongue plays an important role in the tonal noise generation of the fan. It is possible to reduce the tonal noise by using stepped tongues which produce phase-shift effects that lead to an effective local cancellation of the noise.

Numerical simulation of gravity driven turbidity currents using Computational fluid dynamics

2021 ◽  
Author(s):  
Mayank Rakesh ◽  
Paritosh Kumar Rakesh ◽  
Brajesh Kumar ◽  
Satajit Chowdhury ◽  
Atul Kumar Patidar
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Turbidity Currents ◽  
Gravity Driven

scholarly journals MECHANISMS OF GENERATION AND SOURCES OF NOISE IN SUPERSONIC JETS

Akustika ◽  
2019 ◽  
Vol 32 ◽  
pp. 144-150
Author(s):  
Vladislav Emelyanov ◽  
Aleksey Tsvetkov ◽  
Konstantin Volkov
Keyword(s):  
Pressure Ratio ◽  
Supersonic Jet ◽  
Numerical Data ◽  
Jet Flows ◽  
Noise Generation ◽  
Noise Sources ◽  
Cavity Depth ◽  
Flow Parameters ◽  
Nozzle Pressure ◽  
Physical Pattern

Interest in the development of models and methods focused on the mechanisms of noise generation in jet flows is due to strict noise requirements produced by various industrial devices, as well as the possibilities of using sound in engineering and technological processes. The tools of physical and computational modeling of gas dynamics and aero-acoustics problems are considered, and noise sources and mechanisms of noise generation in supersonic jet flows are discussed. The physical pattern of the flow in free supersonic under-expanded jets is discussed on the basis of experimental and numerical data, as well as the flow structure arising from the interaction of a supersonic under-expanded jet with a cylindrical cavity. The influence of the nozzle pressure ratio and cavity depth on the sound pressure level, amplitude and frequency characteristics of the flow parameters is studied.

scholarly journals An introduction to computational fluid dynamics based on numerical simulation of pulsatile flow in the left coronary artery

2012 ◽  
Vol 3 ◽  
pp. 366-374
Author(s):  
Jarosław Wasilewski ◽  
Kryspin Mirota ◽  
Sylwia Peryt-Stawiarska ◽  
Andrzej Nowakowski ◽  
Lech Poloński ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Coronary Artery ◽  
Pulsatile Flow ◽  
Left Coronary Artery

Effect of Cavities in Suddenly Expanded Flow at Supersonic Mach Number

CFD letters ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 57-71
Author(s):  
Atifatul Ismah Ismail
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mach Number ◽  
Pressure Ratio ◽  
Area Ratio ◽  
Base Pressure ◽  
Sudden Expansion ◽  
Expansion Level ◽  
Computational Fluid Dynamics Cfd ◽  
Base Drag

The contribution from the base drag due to the sub-atmospheric pressure is significant. It can be more than two-thirds of the net drag. There is a need to increase the base pressure and hence decrease the base drag. This research examines the effect of Mach Number on base pressure. To accomplish this objective, it controls the efficacy in an enlarged duct computed by the numerical approach using Computational Fluid Dynamics (CFD) Analysis. This experiment was carried out by considering the expansion level and the aspect cavity ratio. The computational fluid dynamics method is used to model supersonic motion with the sudden expansion, and a convergent-divergent nozzle is used. The Mach number is 1.74 for the present study, and the area ratio is 2.56. The L/D ratio varied from 2, 4, 6, 8, and 10, and the simulated nozzle pressure ratio ranged from 3 to 11. The two-dimensional planar design used commercial software from ANSYS. The airflow from a Mach 1.74 convergent-divergent axi-symmetric nozzle expanded suddenly into circular ducts of diameters 17 and 24.5 mm with and without annular rectangular cavities. The diameter of the duct is taken D=17mm and D=24.5mm. The C-D nozzle was developed and modeled in the present study: K-ε standard wall function turbulence model was used with the commercial computational fluid dynamics (CFD) and validated. The result indicates that the base pressure is impacted by the expansion level, the enlarged duct size, and the passage’s area ratio.

Abstract WP121: An Evaluation of Hemodynamics Across Intracranial Steno-occlusive Lesions by Computational Fluid Dynamics

Stroke ◽  
2016 ◽  
Vol 47 (suppl_1) ◽  
Author(s):  
Florence SY Fan ◽  
Vincent HL Ip ◽  
Alexander YL Lau ◽  
Anne YY Chan ◽  
Lisa WC Au ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Gradient ◽  
Pressure Difference ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Strongly Correlated ◽  
Hemodynamic Parameters ◽  
Moderate Correlation ◽  
Anterior Circulation

Introduction: Intracranial atherosclerotic steno-occlusive disease (ICAS) is a major cause of stroke worldwide and portends a high risk of recurrence. Computational fluid dynamics (CFD) is a novel technique developed to solve and analyze the dynamic effects of fluid flow. We aimed to analyse hemodynamics across ICAS using CFD on processed CTA images and explore the correlation between the degree of arterial stenosis and hemodynamic flow status. Methods: We recruited patients with symptomatic ICAS from Acute Stroke Unit, Prince of Wales Hospital. All patients received CTA and DSA as vascular workup. Using CFD analysis of processed CTA images, we first defined the hemodynamic parameters, including pressure difference, pressure ratio, pressure gradient, shear strain rate ratio (SSR), wall shear stress (WSS) ratio and velocity ratio, across the stenosed vessels, and then we correlated the severity of stenosis as defined by DSA, with these parameters. Results: Among the 53 recruited patients (mean age 62.9 years, 69.8% males), 45 (85%) had lesions in the anterior circulation. The severity of stenosis showed a weak-to-moderate correlation with pressure difference (rs=0.392, p=0.004), pressure ratio (rs=-0.429, p=0.001) and pressure gradient (rs=0.419, p=0.002). There was no significant correlation between the severity of stenosis with SSR ratio, WSS ratio and velocity ratio. Among patients with anterior circulation stroke or TIA, the severity of stenosis showed a weak to moderate correlation with pressure difference (rs=0.381, p=0.01), pressure ratio (rs=-0.426, p=0.004) and pressure gradient (rs=0.407, p=0.005). For patients with posterior circulation stroke or TIA, the severity of stenosis was strongly correlated with pressure difference (rs=0.714, p=0.047) and pressure ratio (rs=-0.714, p=0.047); and very strongly correlated with velocity ratio (rs=0.833, p=0.01). Conclusions: The severity of ICAS showed only weak-to-moderate correlation with hemodynamic parameters across the culprit lesion. Thus, risk stratification and treatment based solely on stenotic severity may be inadequate. Our findings may guide further research in estimating stroke risks and selection of high-risk patients who may benefit from adjunctive treatments.

Numerical Simulation of the Gear Flowmeter Reveal Based on Pumplinx

2014 ◽  
Vol 687-691 ◽  
pp. 679-683 ◽  
Author(s):  
Jun Zhang ◽  
Yong Wu ◽  
Hong Mei Tang ◽  
Chun Ren Tang ◽  
Xian Hua Li
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Numerical Analysis ◽  
Oil Spill ◽  
Practical Work ◽  
Measuring Accuracy ◽  
Internal Gear

The oil spill will directly affect the measuring accuracy of the gear flowmeter, so use the computational fluid dynamics software to calculate the leakage regulation of the internal gear flowmeter is one of the important things. Based on Pumplinx, when the end clearances of the gear flowmeter were 0um, 10um, 20um, 30um, 40um and 50um, the corresponding numerical analysis of spillage was carried out. From the results of numerical analysis, with the increase of the end clearance, the leakage amplification will also increase. In practical work, we should control the end clearance of gear flowmeter strictly while the gear works normally.

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