Aerodynamic Interference of Cascade Blades in Synchronized Oscillation

1955 ◽  
Vol 22 (4) ◽  
pp. 503-508
Author(s):  
Chieh-Chien Chang ◽  
Wen-Hwa Chu
Keyword(s):  
Hypergeometric Functions ◽  
Aerodynamic Load ◽  
Characteristic Parameters ◽  
Harmonic Oscillations ◽  
Wake Interference ◽  
Reduced Frequency ◽  
Inaccurate Estimation ◽  
Aerodynamic Interference ◽  
Two Parameters ◽  
Single Oscillation

Abstract The failure of a compressor is sometimes due to flutter of the blades. Essentially, this problem is equivalent to a cascade in oscillation. The present analysis is to find the aerodynamic load on cascade in synchronized harmonic oscillations, pitching, and flapping. Conformal mapping is used. Two characteristic parameters are involved in the force and moment. One is μ which is related to the gap-chord ratio. The other is k which is known as reduced frequency. The main results are expressed in terms of these two parameters. Most can be reduced to closed form. The rest are given in graphs. The wake interference involves one new function C(μ,k) which is related to a ratio of two hypergeometric functions and which reduces to Theodorsen’s function C(k) in the limit of infinite gap. In a certain range of frequency and gap-chord ratio, the analysis shows quantitatively that single-oscillation airfoil theory may lead to inaccurate estimation of interference effect between blades.

scholarly journals Cable Suspension and Balance System with Low Support Interference and Vibration for Effective Wind Tunnel Tests

2021 ◽  
Author(s):  
Keum-Yong Park ◽  
Yeol-Hun Sung ◽  
Jae-Hung Han
Keyword(s):  
Wind Tunnel ◽  
Vibration Suppression ◽  
Aerodynamic Load ◽  
Test Model ◽  
Wind Tunnel Tests ◽  
Balance System ◽  
Motion Responses ◽  
Vibration Responses ◽  
Aerodynamic Interference ◽  
Support Interference

AbstractA cable-driven model support concept is suggested and implemented in this paper. In this case, it is a cable suspension and balance system (CSBS), which has the advantages of low support interference and reduced vibration responses for effective wind tunnel tests. This system is designed for both model motion control and aerodynamic load measurements. In the CSBS, the required position or the attitude of the test model is realized by eight motors, which adjust the length, velocity, and acceleration of the corresponding cables. Aerodynamic load measurements are accomplished by a cable balance consisting of eight load cells connected to the assigned cables. The motion responses and load measurement outputs were in good agreement with the reference data. The effectiveness of the CSBS against aerodynamic interference and vibration is experimentally demonstrated through comparative tests with a rear sting and a crescent sting support (CSS). The advantages of the CSBS are examined through several wind tunnel tests of a NACA0015 airfoil model. The cable support of the CSBS clearly showed less aerodynamic interference than the rear sting with a CSS, judging from the drag coefficient profile. Additionally, the CSBS showed excellent vibration suppression characteristics at all angles of attack.

On the Stresses in a Rotating Disk of Variable Thickness

1952 ◽  
Vol 19 (3) ◽  
pp. 263-266
Author(s):  
Ti-Chiang Lee
Keyword(s):  
Variable Thickness ◽  
Stress Function ◽  
Hypergeometric Functions ◽  
Analytic Solution ◽  
Radial Distance ◽  
Rotating Disk ◽  
Numerical Examples ◽  
Confluent Hypergeometric Functions ◽  
Method Of Solution ◽  
Two Parameters

Abstract This paper presents an analytic solution of the stresses in a rotating disk of variable thickness. By introducing two parameters, the profile of the disk is assumed to vary exponentially with any power of the radial distance from the center of the disk. In some respects this solution may be considered as a generalization of Malkin’s solution, but it differs essentially from the latter in the method of solution. Here, the stresses are solved through a stress function instead of being solved directly. The required stress function is expressed in terms of confluent hypergeometric functions. Numerical examples are also shown for illustration.

scholarly journals Shape and dimension estimations of landslide rupture zones via correlations of characteristic parameters

2019 ◽  
Author(s):  
Gisela Domej ◽  
Céline Bourdeau ◽  
Luca Lenti ◽  
Salvatore Martino
Keyword(s):  
Entire Range ◽  
The Other ◽  
Rupture Zone ◽  
Characteristic Parameters ◽  
Second Stage ◽  
Lack Of Information ◽  
Initial Rupture ◽  
Proper Estimation ◽  
Two Parameters ◽  
Linear Regressions

Abstract. For many geotechnical purposes, the proper estimation of shapes and dimensions of landslide rupture zones is of significant importance. Very often this exact delineation is difficult due to the lack of information on rupture zone extents in 3D. Based on a global landslide inventory, this study presents a refined statistical analysis correlating dimension-related and shape-related parameters characterizing a rupture zone in 3D to its volume. Dimension-parameters are approximated by linear regressions increasing with greater volumes, whereas shape-related parameters appear stable throughout the entire range of volumes. Revealing themselves as very stable, these correlations can be used, hence, to extrapolate from a distinct parameter to the volume of a landslide rupture zone. In a second stage, ratios of dimension-related parameters are correlated with rupture zone volumes. Also, this type of correlation delivers very stable results showing that ratios are constant throughout the entire range of volumes. Making use of this ratio consistency, it is possible to deduce one of the two parameters when the other one is given. This latter aspect seems to be promising for remote sensing surveys when initial rupture areas or rupture volumes should be delineated.

scholarly journals Shape and Dimension Estimations of Landslide Rupture Zones via Correlations of Characteristic Parameters

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 198
Author(s):  
Gisela Domej ◽  
Céline Bourdeau ◽  
Luca Lenti ◽  
Salvatore Martino ◽  
Kacper Pluta
Keyword(s):  
Entire Range ◽  
The Other ◽  
Rupture Zone ◽  
Characteristic Parameters ◽  
Second Stage ◽  
Lack Of Information ◽  
Initial Rupture ◽  
Proper Estimation ◽  
Two Parameters ◽  
Linear Regressions

For many geotechnical purposes, the proper estimation of shapes and dimensions of landslide rupture zones is of significant importance. Very often, this exact delineation is difficult due to the lack of information on rupture zone extents in 3D. Based on a global landslide inventory, this work presents statistical analyses correlating dimension-related and shape-related parameters characterizing a rupture zone in 3D to its volume. Dimension-related parameters are approximated by linear regressions increasing with greater volumes, whereas shape-related parameters appear stable throughout the entire range of volumes. Revealing themselves as very stable, these correlations can be used, hence, to extrapolate from a distinct parameter to the volume of a landslide rupture zone. In a second stage, ratios of dimension-related parameters are correlated with rupture zone volumes. Furthermore, this type of correlation delivers very stable results showing that ratios are constant throughout the entire range of volumes. Making use of this ratio consistency, it is possible to deduce one of the two parameters when the other one is given. This latter aspect seems to be promising for remote sensing surveys when initial rupture areas or rupture volumes should be delineated or for numerical modeling of landslides in 3D.

Fatigue Crack Growth Simulation in Railway Axles

2011 ◽  
Vol 488-489 ◽  
pp. 407-410
Author(s):  
Antonio De Iorio ◽  
Marzio Grasso ◽  
F. Penta ◽  
G. P. Pucillo
Keyword(s):  
Crack Growth ◽  
Damage Tolerance ◽  
Growth Models ◽  
Characteristic Parameters ◽  
Linear Elastic ◽  
Crack Growth Simulation ◽  
Propagation Law ◽  
Stationary Loading ◽  
Elastic Fracture ◽  
Two Parameters

In order to carry out the railway axle design according to the “Damage Tolerance” philosophy, reliable crack-growth models for these kind of components are necessary. Indeed, damage tolerance principles have received more and more attention from railway technical community, thanks to its ambitious task concerning the inspection intervals prevision of railway components subjected to non-stationary loading conditions. In this paper, a simple routine is exposed that is able to calculate the characteristic parameters of the Linear Elastic Fracture Mechanics (LEFM) for a generic cracked mechanical component. Such parameters are then used in a two parameters propagation law to estimate the necessary time for a crack to become critical.

Numerical Study of Aerodynamic Forces of Two Airfoils in Tandem Configuration at Low Reynolds Number

2021 ◽  
Author(s):  
N. Hosseini ◽  
M. Tadjfar ◽  
A. Abba
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Low Reynolds Number ◽  
Aerodynamic Forces ◽  
Tandem Configuration ◽  
Pitching Airfoil ◽  
Reduced Frequency ◽  
Low Reynolds ◽  
Lift And Drag ◽  
Two Parameters

Abstract For a tandem airfoil configuration, an airfoil is placed in the wake of an upstream airfoil. This interaction affects the aerodynamic forces of the airfoils, especially the downstream one. In the present study a tandem configuration consists of an upstream pitching airfoil and a downstream stationary airfoil is investigated. This study aims to investigate the role of reduced frequency and pitch amplitude of the upstream airfoil’s motion on lift and drag coefficients of two airfoils. These two parameters play an important role in the formation of vortices. The investigation is done for Selig-Donovan 7003 (SD7003) airfoils at low Reynolds number of 30,000 using a computational fluid dynamics. Incompressible URANS equations were employed for solving the flow field. It was found that for a fixed reduced frequency of 0.5 thrust is produced on the hindfoil for a part of cycle for different pitch amplitudes from light to deep stall while for a fixed pitch amplitude at different reduced frequencies high level of thrust or drag can be produced. The reason is related to the type and intensity of vortex-blade interaction.

Unsteady Gaseous Diffusion Associated With a Fully Cavitating Oscillating Flat-Plate Hydrofoil

1991 ◽  
Vol 113 (2) ◽  
pp. 290-294
Author(s):  
K. Ravindra ◽  
B. R. Parkin
Keyword(s):  
Turbulent Flow ◽  
Flat Plate ◽  
Diffusion Rate ◽  
Diffusion Theory ◽  
Mass Diffusion ◽  
Gas Pressure ◽  
Harmonic Oscillations ◽  
Gaseous Diffusion ◽  
Gas Entrainment ◽  
Reduced Frequency

This paper gives an analysis of convective gaseous diffusion into a full cavity behind an oscillating flat-plate hydrofoil in a turbulent flow. The unsteady diffusion theory accounts for fluctuations of cavity gas pressure and length which are assumed to be harmonic oscillations but are not necessarily in phase with the hydrofoil motion. A diffusive lag function is found which, for a given reduced frequency, determines the instantaneous diffusion rate as a product of the lag function and the quasisteady mass diffusion. The present results can be used to study the rate of gas entrainment from the cavity into the wake behind the oscillating cavity.

A mathematical model for quinone-herbicide competition in the reaction centres of Rhodobacter sphaeroides

2002 ◽  
Vol 29 (4) ◽  
pp. 443 ◽  
Author(s):  
Andrea Halmschlager ◽  
Júlia Tandori ◽  
Massimo Trotta ◽  
László Rinyu ◽  
Ilona Pfeiffer ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Equilibrium Constants ◽  
Simple Algebra ◽  
Quantitative Model ◽  
Characteristic Parameters ◽  
Oscillation Pattern ◽  
Reaction Centres ◽  
Two Parameters ◽  
The Mathematical Model ◽  
Best Fit

A quantitative model describing the amplitude of semiquinone absorption in photosynthetic reaction centres after successive flashes in the presence of increasing inhibitor concentration is presented. By using relatively simple algebra, the semiquinone signals can be calculated and fitted to the oscillation pattern by optimizing only two parameters; the electron and quinone equilibrium constants, Ke and Kq, respectively. In this work we expand our earlier model [Tandori et al. (1991) Photosynthetica 25, 159–166] by introducing the inhibitor equilibrium constant, Ki, describing the best fit of the model to the measured oscillation pattern. We found that there are characteristic parameters of the measured and normalized signal, and of those calculated from the mathematical model, which fit well with competitive Michaelis-Menten kinetics.

scholarly journals Contiguous Function Relations for k-Hypergeometric Functions

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Shahid Mubeen ◽  
Gauhar Rahman ◽  
Abdur Rehman ◽  
Mammona Naz
Keyword(s):  
Hypergeometric Functions ◽  
Research Work ◽  
Research Paper ◽  
Two Parameters

In this research work, our aim is to determine the contiguous function relations for k-hypergeometric functions with one parameter corresponding to Gauss fifteen contiguous function relations for hypergeometric functions and also obtain contiguous function relations for two parameters. Throughout in this research paper, we find out the contiguous function relations for both the cases in terms of a new parameter k>0. Obviously if k→1, then the contiguous function relations for k-hypergeometric functions are Gauss contiguous function relations.

Oscillating Slender Wings with Leading-Edge Separation

1966 ◽  
Vol 17 (4) ◽  
pp. 311-331 ◽  
Author(s):  
D. G. Randall
Keyword(s):  
Cross Sections ◽  
Reasonable Agreement ◽  
Theoretical Study ◽  
Leading Edge ◽  
Two Dimensional ◽  
Harmonic Oscillations ◽  
Delta Wings ◽  
Reduced Frequency ◽  
Straight Lines ◽  
Edge Separation

SummaryA theoretical study is made of the aerodynamics of wings executing simple harmonic oscillations. The wings considered are slender and infinite-simally thin; they may have curved leading edges and be cambered, but their cross sections must be straight lines. The value of the reduced frequency is assumed to be such that the flow is governed by the two-dimensional Laplace equation.Leading-edge separation is simulated by a line vortex joined to the leading edge by a cut. The strength and position of the vortex and the values of the generalised forces can be determined by the theory. Results have been calculated for flat delta wings and a flat gothic wing; they are in reasonable agreement with experiment.

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