Experimental and Numerical Study of the Vibration of Stationary and Rotating Annular Disks

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Salem Bashmal ◽  
Rama Bhat ◽  
Subhash Rakheja
Keyword(s):  
Boundary Conditions ◽  
Numerical Study ◽  
Numerical Results ◽  
Experimental Investigations ◽  
Modal Characteristics ◽  
Out Of Plane ◽  
Modes Of Vibration ◽  
Vibration Responses ◽  
Support Conditions ◽  
Annular Disks

Numerical and experimental investigations are carried out to study the combined effect of rotation and support nonuniformity on the modal characteristics of circular thick disks. The laboratory experiments on stationary and rotating circular disks are conducted to investigate the effects of partial support conditions on the in-plane and out-of-plane vibration responses of annular disks with different radius ratios. Numerical results suggested that the nonuniformity of the support along the circumferential directions of the boundaries affects the modal characteristics of the disk along the in-plane and out-of-plane directions, while introducing additional coupling between the modes. Specifically, some of the frequency peaks in the frequency spectrum obtained under uniform boundary conditions split into two distinct peaks in the presence of a point support. The results show that the in-plane modes of vibration are comparable with those associated with out-of-plane modes and are contributing to the total noise radiation. The coupling between in-plane and out-of-plane modes is found to be quite significant due to the nonuniformity of the boundary conditions. The experimental study confirms the split in natural frequencies of the disk that is observed in the numerical results due to both rotation and support nonuniformity. The applicability and accuracy of the formulations is further examined through analysis of modal characteristics of a railway wheel in contact with the rail.

On the Reliability of RANS and URANS Numerical Results for High-Pressure Turbine Simulations: A Benchmark Experimental and Numerical Study on Performance and Interstage Flow Behavior of High-Pressure Turbines at Design and Off-Design Conditions Using Two Different Turbine Designs

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
M. T. Schobeiri ◽  
S. Abdelfattah
Keyword(s):  
High Pressure ◽  
Numerical Study ◽  
Flow Behavior ◽  
Sensitivity Study ◽  
Numerical Results ◽  
Experimental Investigations ◽  
Predictive Capability ◽  
Two Stage ◽  
Flow Through ◽  
And Performance

Improved computational fluid dynamics tools based on Reynolds-averaged Navier–Stokes (RANS) equations have shown that the behavior of simple flow cases can be predicted with a reasonable degree of accuracy. Their predictive capability, however, substantially diminishes whenever major secondary vortices, adverse pressure gradients, and wake-boundary layer interactions are present. Flow through high-pressure (HP) turbine components uniquely incorporates almost all of the above features, interacting with each other and determining the efficiency and performance of the turbine. Thus, the degree of accuracy of predicting the flow through a HP turbine can be viewed as an appropriate benchmark test for evaluating the predictive capability of any RANS-based method. Detailed numerical and experimental investigations of different HP turbines presented in this paper have revealed substantial differences between the experimental and the numerical results pertaining to the individual flow quantities. This paper aims at identifying the quantities whose simulation inaccuracies are pre-eminently responsible for the aforementioned differences. This task requires (a) a meticulous experimental investigation of all individual thermofluid quantities and their interactions resulting in an integral behavior of the turbomachine in terms of efficiency and performance, (b) a detailed numerical investigation using appropriate grid densities based on simulation sensitivity, and (c) steady and transient simulations to ensure their impact on the final numerical results. To perform the above experimental and numerical tasks, two different HP turbines were investigated: (1) a two-stage turbine with moderately compound-leaned stator blades and (2) a three-stage turbine rotor with compound-leaned stator and rotor blades. Both turbines have been thoroughly measured and numerically simulated using RANS and URANS. Detailed interstage radial and circumferential traversing presents a complete flow picture of the second stage. Performance measurements were carried out for design and off-design rotational speeds. For comparison with numerical simulations, the turbines were numerically modeled using a commercially available code. An extensive mesh sensitivity study was performed to achieve a grid-independent accuracy for both steady and transient analysis. Comparison of RANS/URANS results with the experimental ones revealed differences in total pressure for the two-stage turbine of up to 5%. A significantly lower difference of less than 0.2% is observed for the three-stage turbine with specially designed blades to suppress the secondary flow losses. Analyzing the physical background of a RANS-based solver, it was argued that the differences of individual quantities exhibited in the paper were attributed to the deficiencies in dissipation and transition models.

A 3D BOUNDARY ELEMENT METHOD FOR DETERMINATION OF ACOUSTIC EIGENFREQUENCIES CONSIDERING ADMITTANCE BOUNDARY CONDITIONS

1993 ◽  
Vol 01 (04) ◽  
pp. 455-468 ◽  
Author(s):  
Z. S. CHEN ◽  
G. HOFSTETTER ◽  
H. A. MANG
Keyword(s):  
Boundary Element Method ◽  
Boundary Conditions ◽  
Boundary Element ◽  
Large Scale ◽  
Numerical Study ◽  
Numerical Algorithms ◽  
Numerical Results ◽  
Simple Problem ◽  
Element Method

A 3D boundary element method for the determination of the acoustic eigenfrequencies of car compartments, characterized by a unified treatment of Robin, Dirichlet, and Neumann boundary conditions, is presented. The drawback of frequency-dependent matrices of the eigenvalue problem is overcome by means of the Particular Integral Method. Thus, the standard numerical algorithms for the extraction of eigenvalues can be applied. The numerical study contains both a comparison of numerical results with analytical solutions of a simple problem with different types of boundary conditions and a comparison of numerical results of a large-scale problem with respective numerical results, computed on the basis of the finite element method. In addition, for the latter example, different numerical algorithms for the eigenvalue extraction are examined.

Numerical Prediction of the Aerodynamic Tonal Noise in a Centrifugal Fan

2002 ◽  
Author(s):  
Sandra Velarde-Sua´rez ◽  
Rafael Ballesteros-Tajadura ◽  
Carlos Santolaria-Morros ◽  
Joaqui´n Ferna´ndez-Francos
Keyword(s):  
Numerical Simulation ◽  
Unsteady Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Experimental Investigations ◽  
Noise Generation ◽  
Centrifugal Fan ◽  
Tonal Noise ◽  
Interaction Phenomena

In this work, a numerical study about the aerodynamic tonal noise generation in an industrial centrifugal fan with backward curved blades has been carried out. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been performed. Special attention has been focused on the impeller-volute interaction phenomena, analysing the influence of the distance between the impeller and the volute tongue. The numerical results have been contrasted using previous experimental investigations carried out in the same machine.

scholarly journals The Influence of Symmetrical Boundary Conditions on the Structural Behaviour of Sandwich Panels Subjected to Torsion

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2093 ◽  
Author(s):  
Zbigniew Pozorski ◽  
Szymon Wojciechowski
Keyword(s):  
Boundary Conditions ◽  
Numerical Models ◽  
Sandwich Panels ◽  
Structural Response ◽  
Numerical Results ◽  
Beam Model ◽  
Structural Behaviour ◽  
High Agreement ◽  
Various Boundary Conditions ◽  
Support Conditions

The paper discusses the influence of load and support conditions on the behaviour of sandwich panels subjected to torsion. 3-D numerical models are presented, in which various boundary conditions have been defined. The case of the load causing the concentrated torque in the span is analyzed, and the load definition affects the structural response. The numerical results were compared with the results obtained for the analytical beam model, which included both free torsion and secondary warping torsion. The conditions under which the models achieve a high agreement between the results were determined, but the significant sensitivity of the solution was also indicated. In each case of the considered load and boundary conditions, the structural response shows appropriate symmetry.

scholarly journals Numerical models development for unidirectional air flow diffusers with lobed and circular orifices

2019 ◽  
Vol 111 ◽  
pp. 01049
Author(s):  
Laurentiu Tacutu ◽  
Ilinca Nastase ◽  
Florin Bode ◽  
Cristiana Croitoru ◽  
Catalin Lungu
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Numerical Study ◽  
Numerical Models ◽  
Ventilation System ◽  
Numerical Results ◽  
Airflow Distribution ◽  
Numerical Grid ◽  
Computational Resources ◽  
Real Scale

In order to achieve more realistic boundary conditions on the inlet of a ventilation system it is necessary to study the influences of the air diffuser orifices geometry on the airflow distribution in the enclosure. Integrating these orifices directly in a real scale air diffuser for a numerical study will result in a huge computational grid which will translate in huge computational resources and a much larger calculation time. The solution, in this case, was the numerical simulation of the airflow through small parts of the studied air diffuser. Later, the numerical results will be implemented as boundary conditions in the unidirectional diffuser of a numerical simulation that represents a real scale operating room (OR). In the current study two diffusers with different orifices were studied, one having circular („O”) and the other one lobbed („+”) orifices. The initial numerical model had 25 orifices on the diffuser, but because of the very large numerical grid resulted for the initial meshes (>35 million tetrahedral cells), a solution with only 4 orifices was chosen for this study. A mesh independency study was made for these two types of air diffusers. The numerical studies were made using RANS method, with SST k-ω turbulence model in steady state conditions. The numerical results obtained with the first step models showed very good agreement with the PIV stereoscopic experimental measurements.

Experimental Investigation on the Modal Characteristics of Rolling Thick Disk

2012 ◽  
Author(s):  
S. Bashmal ◽  
R. Bhat ◽  
S. Rakheja
Keyword(s):  
Boundary Conditions ◽  
Travelling Waves ◽  
Three Dimensional ◽  
Thick Disk ◽  
Combined Effect ◽  
Experimental Investigations ◽  
Three Dimensional Model ◽  
Annular Disk ◽  
Modal Characteristics ◽  
Non Linear

Analytical and experimental investigations are carried out to study the combined effect of rotation and support non-uniformity on the modal characteristics of circular thick disks. A three-dimensional model is implemented to study the coupled in-plane and out-of-plane modes of a thick disk and present the variations of the travelling waves with respect to rotating and fixed coordinates. The initial stiffening due to rotation is introduced by developing a non-linear model that permits the coupling between static and dynamic problems. The present formulation is generalized to account for the stiffening effects for disks subject to non-uniform boundary conditions, where the initial displacement cannot be considered as axisymmetric. The general non-linear problem of a rotating annular disk subject to non-uniform boundary conditions is, then, investigated. The laboratory experiments on stationary and rotating circular disks under selected boundary conditions are carried out to demonstrate the validity of the analytical methods in terms of vibration and acoustic emission behaviour. The experimental results examine the combined effect of rotation and point support on the disk. The experimental study confirms the split in natural frequencies of the disk that was observed in the analytical results due to both rotation and support non-uniformity.

Using Ansys for Design and Numerical Study of a Specific Fixed Wing UAV

2018 ◽  
Vol 55 (4) ◽  
pp. 652-657 ◽  
Author(s):  
Gabriel Murariu ◽  
Razvan Adrian Mahu ◽  
Adrian Gabriel Murariu ◽  
Mihai Daniel Dragu ◽  
Lucian P. Georgescu ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Unmanned Aerial Vehicle ◽  
Numerical Study ◽  
Flight Time ◽  
Cluster System ◽  
Numerical Results ◽  
Operational Performance ◽  
Gliding Flight ◽  
Aerial Vehicle ◽  
Constant Altitude

This article presents the design of a specific unmanned aerial vehicle UAV prototype own building. Our UAV is a flying wing type and is able to take off with a little boost. This system happily combines some major advantages taken from planes namely the ability to fly horizontal, at a constant altitude and of course, the great advantage of a long flight-time. The aerodynamic models presented in this paper are optimized to improve the operational performance of this aerial vehicle, especially in terms of stability and the possibility of a long gliding flight-time. Both aspects are very important for the increasing of the goals� efficiency and for the getting work jobs. The presented simulations were obtained using ANSYS 13 installed on our university� cluster system. In a next step the numerical results will be compared with those during experimental flights. This paper presents the main results obtained from numerical simulations and the obtained magnitudes of the main flight coefficients.

scholarly journals A numerical study of the impact perforation of sandwich panels with graded hollow sphere cores

2021 ◽  
Vol 13 (4) ◽  
pp. 168781402110094
Author(s):  
Ibrahim Elnasri ◽  
Han Zhao
Keyword(s):  
Boundary Conditions ◽  
Hollow Sphere ◽  
Sandwich Panel ◽  
Numerical Study ◽  
Sandwich Panels ◽  
Hopkinson Bar ◽  
Core Density ◽  
The Core ◽  
The Impact ◽  
Force Displacement

In this study, we numerically investigate the impact perforation of sandwich panels made of 0.8 mm 2024-T3 aluminum alloy skin sheets and graded polymeric hollow sphere cores with four different gradient profiles. A suitable numerical model was conducted using the LS-DYNA code, calibrated with an inverse perforation test, instrumented with a Hopkinson bar, and validated using experimental data from the literature. Moreover, the effects of quasi-static loading, landing rates, and boundary conditions on the perforation resistance of the studied graded core sandwich panels were discussed. The simulation results showed that the piercing force–displacement response of the graded core sandwich panels is affected by the core density gradient profiles. Besides, the energy absorption capability can be effectively enhanced by modifying the arrangement of the core layers with unclumping boundary conditions in the graded core sandwich panel, which is rather too hard to achieve with clumping boundary conditions.

scholarly journals Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1079
Author(s):  
Lena Mahl ◽  
Patrick Heneka ◽  
Martin Henning ◽  
Roman B. Weichert
Keyword(s):  
Boundary Conditions ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Three Dimensional ◽  
Free Water ◽  
Lateral Wall ◽  
Lateral Spreading ◽  
Propagation Length ◽  
Vertical Slot ◽  
Surface Jets

The efficiency of a fishway is determined by the ability of immigrating fish to follow its attraction flow (i.e., its jet) to locate and enter the fishway entrance. The hydraulic characteristics of fishway entrance jets can be simplified using findings from widely investigated surface jets produced by shaped nozzles. However, the effect of the different boundary conditions of fishway entrance jets (characterized by vertical entrance slots) compared to nozzle jets must be considered. We investigate the downstream propagation of attraction jets from the vertical slot of a fishway entrance into a quiescent tailrace, considering the following boundary conditions not considered for nozzle jets: (1) slot geometry, (2) turbulence characteristics of the approach flow to the slot, and (3) presence of a lateral wall downstream of the slot. We quantify the effect of these boundary conditions using three-dimensional hydrodynamic-numeric flow simulations with DES and RANS turbulence models and a volume-of-fluid method (VoF) to simulate the free water surface. In addition, we compare jet propagation with existing analytical methods for describing jet propagations from nozzles. We show that a turbulent and inhomogeneous approach flow towards a vertical slot reduces the propagation length of the slot jet in the tailrace due to increased lateral spreading compared to that of a jet produced by a shaped nozzle. An additional lateral wall in the tailrace reduces lateral spreading and significantly increases the propagation length. For highly turbulent flows at fishway entrances, the RANS model tends to overestimate the jet propagation compared to the transient DES model.

The study of the nonlinear vibration of S-S and C-C laminated composite conical shells on elastic foundations through an approximate method

2021 ◽  
pp. 095440622110214
Author(s):  
Shahin Mohammadrezazadeh ◽  
Ali Asghar Jafari
Keyword(s):  
Boundary Conditions ◽  
Nonlinear Vibration ◽  
Approximate Method ◽  
Laminated Composite ◽  
Vertex Angle ◽  
Nonlinear Frequency ◽  
Conical Shells ◽  
Elastic Foundations ◽  
Vibration Responses ◽  
Comparison Of The Results

This paper investigates the nonlinear vibration responses of laminated composite conical shells surrounded by elastic foundations under S-S and C-C boundary conditions via an approximate approach. The laminated composite conical shells are modeled based on classical shell theory of Love employing von Karman nonlinear theory. Nonlinear vibration equation of the conical shells is extracted by handling Lagrange method. The linear and nonlinear vibration responses are obtained via an approximate method which combines Lindstedt-Poincare method with modal analysis. The validation of this study is carried out through the comparison of the results of this study with results of published literature. The effects of several parameters including the constants of elastic foundations, boundary conditions, total thickness, length, large edge radius and semi-vertex angle on the values of fundamental linear frequency and curves of amplitude parameter versus nonlinear frequency ratio for laminated composite conical shells with both S-S and C-C boundary conditions are investigated.

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