Sound Generation and Propagation in a Centrifugal Pump With the Finite Volume EIF-Approach

2012 ◽  
Author(s):  
Thilo Michels ◽  
Marian Markiewicz ◽  
Otto von Estorff
Keyword(s):  
Finite Volume ◽  
Incompressible Flow ◽  
Acoustic Radiation ◽  
Three Dimensional ◽  
Aerodynamic Noise ◽  
Inviscid Fluid ◽  
Centrifugal Pumps ◽  
Acoustic Analogy ◽  
Alternative Approach ◽  
Unsteady Rans

The development of new methods in the field of numerical aeroacoustics is one of the current research interests. For this kind of approaches, highly efficient methods are necessary. Aerodynamic noise prediction codes in use today are typically based on Lighthill analogies. In this paper an alternative approach is developed and implemented in a three dimensional CFD finite volume code. The method is based on the Expansion about Incompressible Flow (EIF) technique, which was proposed first by Hardin and Pope in 1994. Based on the solution of the incompressible flow, acoustic radiation is obtained in a compressible, inviscid fluid. The advantage of this technique, as compared to unsteady RANS simulations, is that small acoustic perturbations can easily be separated from the fluctuations of the pressure field of the bulk flow, which are some orders of magnitude greater. In comparison to the acoustic analogy approach, the method extends the region of applications towards the moderate Mach numbers (up to Ma = 0.6). Moreover, the flow and acoustic effects are resolved on different length scales. This makes the computations more efficient. The EIF method accounts both for the sound radiation and scattering. In the presented paper a further development towards three dimensional simulations and numerical implementation for centrifugal pumps is presented.

Numerical Assessment of 2D Aeroacoustic Simulations for Landing Gear

2018 ◽  
Author(s):  
Sultan I. Alqash ◽  
Kamran Behdinan
Keyword(s):  
Acoustic Field ◽  
Numerical Study ◽  
Near Field ◽  
Three Dimensional ◽  
Aerodynamic Noise ◽  
Design Stage ◽  
Acoustic Analogy ◽  
Ansys Fluent ◽  
2D Flow ◽  
Field Noise

Landing gears (LG) are primarily designed to support the entire loads of an aircraft during landing, taxiing, and taking off. From aerodynamic design prospective, many of the LG components are exposed to the air flow giving rise to what so-called aerodynamic noise. Numerical study of complex systems such as LG as a three-dimensional (3D) model is not only CPU and memory consuming, but also it is way beyond the demand of industries for quick estimate during the design stage [1–3]. To understand the underlying physics of the flow induced noise, a two-dimensional (2D) flow past a circular cylinder is simulated using ANSYS Fluent. Two different Reynolds numbers, Re = 150 and 90000 are examined. For low Re, two distinct numerical conditions relevant to steady and unsteady flow are simulated and compared to examine the effect of the time dependency on the acoustic field. At high Re, the acoustic field is computed using the built-in Ffowcs William and Hawkings (FW-H) acoustic analogy solver in Fluent. The results show the importance of including the unsteady state term to extract the flow data. The far-field noise prediction is found to be highly dependent on the location of the near-field data.

Prediction of dipole sources and aeroacoustics field for tandem cylinder flow field based on DBEM/hybrid LES

2021 ◽  
Vol 20 (1-2) ◽  
pp. 157-173
Author(s):  
Zhengyu Zheng
Keyword(s):  
Frequency Response ◽  
Three Dimensional ◽  
Circular Cylinders ◽  
Aerodynamic Noise ◽  
Cylinder Surface ◽  
Acoustic Analogy ◽  
Sound Sources ◽  
Noise Interference ◽  
Eddy Simulation ◽  
Dipole Sources

In this paper, the DBEM/Hybrid LES（Directly Boundary Element Method/Hybrid Large Eddy Simulation）technique is applied to predict the aerodynamic noise generated by tandem circular cylinders immersed in a three-dimensional turbulent flow. Utilizing the Lighthill's Acoustic Analogy, the flow pressure fluctuation near the surface of the cylinder is converted into acoustic dipole sources. Taking the dipole sound sources as the actual sound sources, the aeroacoustic field is simulated and analyzed by DBEM. The research shows that: The strong dipole sources are distributed in the collision zone of the downstream cylindrical surface, where the upstream cylinder's shedding vortex colliding to downstream cylinder surface. Both of the amplitude-frequency response and the phase-frequency response of dipole acoustic source are obtained, which is helpful for further research on aerodynamics noise interference and suppression. Good comparisons are obtained between numerical results and BART (Basic Aerodynamic Research Tunnel) experimental data published by NASA.

Multi-field coupling prediction for improving aeroacoustic performance of muffler based on LES and FW-H acoustic analogy methods

2021 ◽  
pp. 1475472X2110054
Author(s):  
H Guo ◽  
YS Wang ◽  
F Zhu ◽  
NN Liu ◽  
C Yang
Keyword(s):  
High Speed ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Aerodynamic Noise ◽  
Acoustic Analogy ◽  
Field Coupling ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Fillet Transition ◽  
Experimental Validations

Based on the large eddy simulation (LES) and Ffowcs Williams and Hawkings (FW-H) equation, a multi-field coupling method is presented for aeroacoustic prediction of a muffler with high-speed and high-temperature exhaust gasflow. A three-dimensional finite-volume model of the muffler is established by using the LES and FW-H acoustic analogy (FW-H-AA) methods. Experimental validations of the simulated results suggest a good accuracy of the combined LES and FW-H-AA approach. Some factors influencing on noise attenuation, such as the gasflow velocity, temperature and the structural parameters of the muffler are analyzed. The results show that the aerodynamic noise and turbulent kinetic energy (TKE) are mainly attributed to the structural mutations in the muffler. The outlet sound pressure level (SPL) increases with the inlet gasflow velocity and decreases with temperature. According to the factor analysis results, the target muffler is modified by adding a fillet transition to the end of inserted tube and redesigning the structures where the TKE concentrated for improving the aerodynamic performance. In terms of the outlet SPL, the inner TKE and the backpressure of the muffler, the modified muffler is significantly improved by the maximum reductions of 3-5dB in SPL, 10–20% in TKE and 0.5–2.5 kPa in backpressure. The presented method might be extended to other kinds of muffler for aeroacoustic calculation and improvement design.

Three-Dimensional Simulation of Highly Unsteady and Isothermal Flow in Centrifugal Pumps for the Local Loss Analysis Including a Wall Function for Entropy Production

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Steffen Melzer ◽  
Andreas Pesch ◽  
Stephan Schepeler ◽  
Tobias Kalkkuhl ◽  
Romuald Skoda
Keyword(s):  
Entropy Production ◽  
Finite Volume ◽  
Three Dimensional ◽  
Isothermal Flow ◽  
Finite Volume Scheme ◽  
Centrifugal Pumps ◽  
Wall Function ◽  
Local Loss ◽  
Loss Analysis ◽  
Wide Range

Abstract A local loss analysis (LLA) based on entropy production is presented for the numerical three-dimensional (3D) simulation of isothermal centrifugal pump flow. A finite volume method and a statistical turbulence model are employed. Wall functions for direct and turbulent entropy production in isothermal flow are derived, implemented in a node-centered finite volume scheme as a postprocessing procedure, and validated on an attached channel flow as well as on separated flow in an asymmetric diffuser. The integrity of the entropy wall function is demonstrated by a loss balance for a wide range of boundary layer resolution in terms of nondimensional wall distance y+≈1 to ≈200. Remaining differences to the total pressure loss are traced back to the particular turbulent wall function for the flow solution within the finite volume solver and vanish toward a wall resolution of the viscous sublayer, i.e., y+≈1. LLA together with the new entropy wall function is applied to highly unsteady isothermal flow in a single-blade pump as well as to part-load operation of a conventional multiblade pump which reveals distinctive flow structures that are associated with entropy production. By these examples, it is demonstrated how efficiency characteristics of centrifugal pumps can be attributed to local loss production in particular flow regions.

Wind Profile Effect on Small Wind Turbine Noise Generation

2014 ◽  
Author(s):  
Aki Grönman ◽  
Jari Backman ◽  
Anna Avramenko
Keyword(s):  
Wind Turbine ◽  
Wind Profile ◽  
Three Dimensional ◽  
Ground Surface ◽  
Aerodynamic Noise ◽  
Speed Ratio ◽  
Small Scale ◽  
Noise Generation ◽  
Acoustic Analogy ◽  
Wind Profiles

Small wind turbines are usually located close to buildings, and therefore, the noise generation can be both annoying and a risk for the health. The number of wind turbine installations is growing, and the request for distributed small scale energy production is one of the future trends in the energy market. The wind behavior is usually non-linear close to the ground surface. Especially, small turbines with low nacelle heights have a relatively declined wind profile at the blades. The chosen modeling approach coupled three-dimensional RANS with the Ffowcs Williams-Hawkings acoustic analogy. A series of numerical simulations was performed to study the reliability of the modeling. Three different grids were used to study the grid independency close to the turbine nominal tip to speed ratio. A reasonable agreement in the noise trends was found between the modeling and the measurements and previous studies. This encouraged us to study three different wind profiles with a down scaled wind turbine model. The results indicate that the aerodynamic noise of small turbines is not markedly affected by the wind profile.

The Source of Aerodynamic Noise

2003 ◽  
Vol 2 (3) ◽  
pp. 241-253 ◽  
Author(s):  
Geoffrey M. Lilley
Keyword(s):  
Wave Equation ◽  
Turbulent Flow ◽  
Stress Tensor ◽  
Stokes Equations ◽  
Acoustic Radiation ◽  
Rate Of Change ◽  
Aerodynamic Noise ◽  
Acoustic Analogy ◽  
Acoustic Interaction ◽  
Uniform Medium

This paper is a tribute to Alan Powell's achievements and his extensive publications in hydro and aeroacoustics.1 The theory of Aerodynamic Noise was established by Sir James Lighthill in 1952. The beauty of Lighthill's treatment was that he based this theory on the exact Navier-Stokes equations and showed, by their rearrangement, how the source of aerodynamic noise could be obtained from exact time-accurate calculations or experiment. Lighthill used the emission or propagation theory whereby an observer in a uniform medium at rest receives acoustic radiation from a distribution of moving sources of sound. Their properties are found using an acoustic analogy. The relevant fluctuations in a turbulent fluid flow can be expressed in terms of Lighthill's stress tensor Tij, which is used to define a distribution of equivalent acoustic sources, which move through an otherwise uniform stationary fluid. An alternative procedure is to concentrate on the acoustic generation and to regard the sources of sound at rest or in motion in a uniform medium moving at a constant speed. (The approach can be extended to consider any arbitrary mean fluid motion.) The advantage of the present approach, involving the convective wave equation is that flow-acoustic interaction becomes part of the solution. In Lighthill's theory, flow-acoustic interaction is either ignored or at best is included as an equivalent source. The purpose of the present paper is to show there is no unique source of aerodynamic noise for it depends on the flow quantity used to describe the radiated sound. The convective wave equation is introduced and shown to involve similar sources to those found by Lighthill for the wave equation in a medium at rest. The source function found for the convective wave equation for a turbulent flow is shown to involve a modified Lighthill's stress tensor, which is non-linear in velocity and temperature fluctuations. It is further shown when the rate of dilatation covariance is examined, which can be derived from Lighthill's solution, that this small quantity, which Lighthill so carefully treated in retaining the exact properties of the compressible flow, is itself directly responsible for the rate of change of volume in the fluid and the creation of the noise which is radiated from the turbulent flow.

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