Acoustic radiation loading on cylindrical vibrators in an inviscid fluid with axial flow

1990 ◽  
Vol 87 (S1) ◽  
pp. S74-S74
Author(s):  
D. D. Ebenezer ◽  
Peter R. Stepanishen
Keyword(s):  
Acoustic Radiation ◽  
Axial Flow ◽  
Inviscid Fluid

Blocking in the Rotating Axial Flow in a Corotating Flexible Shell

2008 ◽  
Vol 76 (1) ◽  
Author(s):  
F. Gosselin ◽  
M. P. Païdoussis
Keyword(s):  
Traveling Waves ◽  
Physical Phenomenon ◽  
Axial Flow ◽  
Critical Value ◽  
Inviscid Fluid ◽  
Shell Wall ◽  
Stagnation Region ◽  
Linear Dynamics ◽  
Shell Equations ◽  
Rotating Cylindrical Shell

By coupling the Donnell–Mushtari shell equations to an analytical inviscid fluid solution, the linear dynamics of a rotating cylindrical shell with a corotating axial fluid flow is studied. Previously discovered mathematical singularities in the flow solution are explained here by the physical phenomenon of blocking. From a reference frame moving with the traveling waves in the shell wall, the flow is identical to the flow in a rigid varicose tube. When the ratio of rotation rate to flow velocity approaches a critical value, the phenomenon of blocking creates a stagnation region between the humps of the wall. Since the linear model cannot account for this phenomenon, the solution blows up.

Interaction acoustic radiation force and torque on a cluster of spheres suspended in an inviscid fluid

2014 ◽  
Vol 135 (4) ◽  
pp. 2345-2345
Author(s):  
Jose Henrique A. Andrade ◽  
Mahdi Azarpeyvand ◽  
Glauber T. Silva
Keyword(s):  
Acoustic Radiation ◽  
Radiation Force ◽  
Acoustic Radiation Force ◽  
Inviscid Fluid

scholarly journals Inviscid Modes within the Boundary-Layer Flow of a Rotating Disk with Wall Suction and in an External Free-Stream

Mathematics ◽  
2021 ◽  
Vol 9 (22) ◽  
pp. 2967
Author(s):  
Bashar Al Saeedi ◽  
Zahir Hussain
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Axial Flow ◽  
Rotating Disk ◽  
Disk Surface ◽  
Inviscid Fluid ◽  
Turbulent Transition ◽  
Boundary Layer Instability ◽  
Layer Flow ◽  
High Reynolds

The purpose of this paper is to investigate the linear stability analysis for the laminar-turbulent transition region of the high-Reynolds-number instabilities for the boundary layer flow on a rotating disk. This investigation considers axial flow along the surface-normal direction, by studying analytical expressions for the steady solution, laminar, incompressible and inviscid fluid of the boundary layer flow due to a rotating disk in the presence of a uniform injection and suction. Essentially, the physical problem represents flow entrainment into the boundary layer from the axial flow, which is transferred by the spinning disk surface into flow in the azimuthal and radial directions. In addition, through the formation of spiral vortices, the boundary layer instability is visualised which develops along the surface in spiral nature. To this end, this study illustrates that combining axial flow and suction together may act to stabilize the boundary layer flow for inviscid modes.

scholarly journals A Fluidelastic Model for the Nonlinear Dynamics of Two-Dimensional Inverted Flags

2019 ◽  
Author(s):  
Mohammad Tavallaeinejad ◽  
Michael P. Païdoussis ◽  
Mathias Legrand ◽  
Mojtaba Kheiri
Keyword(s):  
Large Amplitude ◽  
Fluid Dynamic ◽  
Time Integration ◽  
Dynamic Modelling ◽  
Axial Flow ◽  
Beam Theory ◽  
Leading Edge ◽  
Elastic Model ◽  
Inviscid Fluid ◽  
Mass Ratio

Abstract A nonlinear fluid-elastic model is proposed for the study of the dynamics of inverted flags. The quasi-steady version of Theodorsen’s unsteady aerodynamic theory is used for inviscid fluid-dynamic modelling of the deforming flag in axial flow. Polhamus’s leading edge suction analogy is employed to model flow separation effects from the free end at moderate angles of attack via a nonlinear vortex-lift force. The flag is modelled structurally via a geometrically-exact Euler-Bernoulli beam theory. Using the extended Hamilton’s principle, the nonlinear partial-integro-differential equation governing the dynamics of the inverted flag in terms of the angle of rotation of the flag is obtained. The equation of motion is discretised spatially via the Galerkin method and is integrated in time via Gear’s backward differentiation formula. The bifurcation diagrams are obtained using a time-integration method and pseudo-arclength continuation. It is shown that inverted flags undergo multiple bifurcations with respect to flow velocity, and they generally exhibit four dynamical states: (i) stretched-straight, (ii) buckled, (iii) deflected-flapping, and (iv) large-amplitude flapping. Also, flapping of inverted flags probably develops through fluid-elastic instabilities. Our findings suggest that the system dynamics is sensitive to the mass ratio. It is shown that the mass ratio parameter does not affect the stability of the stretched-straight state and the onset of divergence; however, it controls the possibility of a direct transition from static undeflected equilibrium to large-amplitude flapping motion and it affects the amplitude of large-amplitude flapping.

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.

Penetration of a blade into a vortex core: vorticity response and unsteady blade forces

1996 ◽  
Vol 306 ◽  
pp. 83-109 ◽  
Author(s):  
J. S. Marshall ◽  
J. R. Grant
Keyword(s):  
Vortex Core ◽  
Three Dimensional ◽  
Axial Flow ◽  
The Body ◽  
Computational Method ◽  
Inviscid Fluid ◽  
Control Points ◽  
Unsteady Force ◽  
Vorticity Transport ◽  
Vortex Axis

Numerical calculations are performed for the problem of penetration into a vortex core of a blade travelling normal to the vortex axis, where the plane formed by the blade span and the direction of blade motion coincides with the normal plane of the vortex axis at the point of penetration. The calculations are based on a computational method, applicable for unsteady three-dimensional flow past immersed bodies, in which a collocation solution of the vorticity transport equation is obtained on a set of Lagrangian control points. Differences between this method and other Lagrangian vorticity-based methods in the literature are discussed. Lagrangian methods of this type are particularly attractive for problems of unsteady vortex-body interaction, since control points need only be placed on the surface of the body and in regions of the flow with non-negligible vorticity magnitude. The computations for normal blade-vortex interaction (BVI) are performed for an inviscid fluid and focus on the relationship between the vortex core deformation due to penetration of the blade into the vortex ambient position and the resulting unsteady pressure field and unsteady force acting on the blade. Computations for cases with different vortex circulations are performed, and the accuracy of an approximate formulation using rapid distortion theory is assessed by comparison with the full computational results for unsteady blade force. The force generated from blade penetration into the vortex ambient position is found to be of a comparable magnitude to various other types of unsteady BVI forces, such as that due to cutting of the vortex axial flow.

scholarly journals Numerical Determination of the Secondary Acoustic Radiation Force on a Small Sphere in a Plane Standing Wave Field

Micromachines ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 431 ◽  
Author(s):  
Simon ◽  
Andrade ◽  
Desmulliez ◽  
Riehle ◽  
Bernassau
Keyword(s):  
Finite Element ◽  
Numerical Methods ◽  
Acoustic Waves ◽  
Acoustic Radiation ◽  
Direct Calculation ◽  
Radiation Force ◽  
Acoustic Radiation Force ◽  
Spherical Particles ◽  
Inviscid Fluid ◽  
Finite Element Software

Two numerical methods based on the Finite Element Method are presented for calculating the secondary acoustic radiation force between interacting spherical particles. The first model only considers the acoustic waves scattering off a single particle, while the second model includes re-scattering effects between the two interacting spheres. The 2D axisymmetric simplified model combines the Gor’kov potential approach with acoustic simulations to find the interacting forces between two small compressible spheres in an inviscid fluid. The second model is based on 3D simulations of the acoustic field and uses the tensor integral method for direct calculation of the force. The results obtained by both models are compared with analytical equations, showing good agreement between them. The 2D and 3D models take, respectively, seconds and tens of seconds to achieve a convergence error of less than 1%. In comparison with previous models, the numerical methods presented herein can be easily implemented in commercial Finite Element software packages, where surface integrals are available, making it a suitable tool for investigating interparticle forces in acoustic manipulation devices.

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