scholarly journals A numerical procedure for an inviscid stability analysis of an axisymmetric jet

1983 ◽  
Author(s):  
Elizabeth F Moore
Keyword(s):  
Stability Analysis ◽  
Numerical Procedure ◽  
Axisymmetric Jet

Thermoacoustic Stability Analysis of a Full-Annular Lean Combustor for Heavy-Duty Applications

2021 ◽  
Author(s):  
Daniele Pampaloni ◽  
Antonio Andreini ◽  
Alessandro Marini ◽  
Giovanni Riccio ◽  
Gianni Ceccherini
Keyword(s):  
Stability Analysis ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Numerical Procedure ◽  
Pollutant Emissions ◽  
Computational Time ◽  
Heavy Duty ◽  
Operational Parameters ◽  
3D Fem ◽  
Wide Range

Abstract Thermoacoustic characterization of gas turbine combustion systems is of primary importance for successful development of gas turbine technology, to meet the stringent targets on pollutant emissions. In this context, it becomes more and more necessary to develop reliable tools to be used in the industrial design process. The dynamics of a lean-premixed full-annular combustor for heavy-duty applications has been numerically studied in this work. The well-established CFD-SI method has been used to investigate the flame response varying operational parameters such as the flame temperature (global equivalence ratio) and the fuel split between premixed and pilot fuel injections: such a wide range experimental characterization represents an opportunity to validate the employed numerical methods and to give a deeper insight into the flame dynamics. URANS simulations have been performed, due to their affordable computational costs from the industrial perspective, after validating their accuracy through the comparison against LES results. Furthermore, an approach where the pilot and the premixed flame responses are analyzed separately is proposed, exploiting the independence of their evolution. The calculated FTFs have been implemented in a 3D FEM model of the chamber, in order to perform linear stability analysis and to validate the numerical approach. A boundary condition for rotational periodicity based on Bloch-Wave theory has been implemented into the Helmholtz solver and validated against full-annular chamber simulations, allowing a significant reduction in computational time. The reliability of the numerical procedure has been assessed through the comparison against full-annular experimental results.

Extensions to the generalized method of slices for stability analysis

1983 ◽  
Vol 20 (1) ◽  
pp. 104-119 ◽  
Author(s):  
Zu-Yu Chen ◽  
N. R. Morgenstern
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Computer Program ◽  
Factor Of Safety ◽  
Numerical Procedure ◽  
Slope Stability Analysis ◽  
Methods Of Analysis

Extensions are suggested to the generalized method of slices that is commonly used in slope stability analysis. It is shown that restrictions exist on the assumptions used to make the problem statically determinate. In addition, a numerical procedure has been developed to find the bounds to the factor of safety, subject to additional requirements of physical admissibility. As a result of these developments it has been possible to produce a revised computer program that appears to overcome the problems of convergence experienced by other programs in current use. Results obtained with this new analysis confirm the reliability of several methods of analysis used in practice.

Stability Analysis of a Rough Journal Bearing Considering Cavitation Effects

2005 ◽  
Vol 127 (1) ◽  
pp. 112-119 ◽  
Author(s):  
T. V. V. L. N. Rao ◽  
Jerzy T. Sawicki
Keyword(s):  
Stability Analysis ◽  
Governing Equation ◽  
Journal Bearing ◽  
Numerical Procedure ◽  
Instability Threshold ◽  
Bearing Surface ◽  
Surface Configuration

A modified governing equation is derived incorporating the effects of roughness and cavitation in a journal bearing. The available theories of Reynolds roughness and cavitation algorithm proposed by Elrod are utilized in this work to develop a numerical procedure for stability analysis of a liquid lubricated rough journal bearing. The Elrod generalized theory of Reynolds roughness provides a governing equation based on the surface configuration. The Elrod cavitation algorithm conserves mass throughout the bearing and automatically predicts the full film and cavitation regions using a switch function. The roughness is considered on either or both the bearing and journal surfaces. The instability threshold speed increases significantly for the roughness patterns on the grooved bearing surface only at higher eccentricity ratios. The threshold speed increases significantly with increase in the inclination of herringbone type striated roughness patterns on the journal surface from 110° to 150°.

scholarly journals A Gallery of Root Locus of Fractional Systems

2013 ◽  
Author(s):  
J. A. Tenreiro Machado
Keyword(s):  
Stability Analysis ◽  
Transfer Functions ◽  
Numerical Procedure ◽  
Root Locus ◽  
Closed Loop System ◽  
Fractional Systems ◽  
Finite Precision ◽  
Know How ◽  
The Stability ◽  
Fractional Orders

The root locus (RL) is a classical tool for the stability analysis of integer order linear systems, but its application in the fractional counterpart poses some difficulties. Therefore, researchers have mainly preferred to adopt frequency based methods. Nevertheless, recently the RL was considered for the stability analysis of fractional systems. One first method is by tacking advantage of commensurable expressions that occur when truncating fractional orders up to a finite precision. The second method consists of searching the complex plane for solutions of the characteristic equation using a numerical procedure. The resulting charts are insightful about the characteristics of the closed-loop system that outperform the frequency response methods. Given the limited know how in this particular topic and the shortage of literature, this study explores several types of fractional-order transfer functions and presents the corresponding RL.

A method for locating critical slip surfaces in slope stability analysis

2001 ◽  
Vol 38 (2) ◽  
pp. 328-337 ◽  
Author(s):  
Da-Yong Zhu
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Factor Of Safety ◽  
High Efficiency ◽  
Slip Surface ◽  
Numerical Procedure ◽  
Slope Stability Analysis ◽  
Case Examples ◽  
Slip Surfaces ◽  
Global And Local

This paper presents a new method for locating critical slip surfaces of general shapes in slope stability analysis. On the basis of the principle of optimality, along with the method of slices, a critical slip field (CSF) in a slope is postulated which consists of a family of slip surfaces having maximum values of unbalanced thrust forces at exit points on the slope face. A numerical procedure is developed for constructing the CSF. The critical slip surface having minimum factor of safety is included in the CSF. All the critical slip surfaces corresponding to all of the exit points are thus determined consecutively, resulting in a global critical slip field (GCSF) which exhibits both global and local slope stability. Comparisons with other methods are made which indicate the high efficiency and accuracy of the proposed approach. Applications of the proposed method to two case examples are given, the results of which demonstrate its applicability to practical engineering.Key words: slope, stability, analysis, factor of safety, critical slip field.

scholarly journals Dynamic and Static Combination Analysis Method of Slope Stability Analysis during Earthquake

2014 ◽  
Vol 2014 ◽  
pp. 1-13
Author(s):  
Liang Lu ◽  
Zongjian Wang ◽  
Xiaoyuan Huang ◽  
Bin Zheng ◽  
Katsuhiko Arai
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Slope Failure ◽  
Numerical Procedure ◽  
Critical Value ◽  
Model Tests ◽  
Laboratory Model ◽  
Response Analysis ◽  
Seismic Slope Stability ◽  
Plastic Displacement

The results of laboratory model tests for simulating the slope failure due to vibration, including unreinforced slope and the slope reinforced by using geotextile, show that the slope failure occurs when a cumulative plastic displacement exceeds a certain critical value. To overcome the defects of conventional stability analysis, which evaluates the slope characteristics only by its strength parameters, a numerical procedure considering the stiffness and deformation of materials and geosynthetics is proposed to evaluate the seismic slope stability. In the proposed procedure, the failure of slope is defined when the cumulative plastic displacement calculated by a dynamic response analysis using actual seismic wave exceeds the critical value of displacement estimated by a static stability analysis considering seismic coefficient. The proposed procedure is applied to the laboratory model tests and an actual failure of slope in earthquake. The case study shows the possibility that the proposed procedure gives the realistic evaluation of seismic slope stability.

scholarly journals Computer Simulations for Stability Analysis of a Numerical Procedure for Crossbar Packet Switch

2017 ◽  
Vol 15 (3) ◽  
pp. 7-11
Author(s):  
T. Tashev ◽  
V. Monov ◽  
R. Tasheva
Keyword(s):  
Stability Analysis ◽  
Computer Simulations ◽  
Input Data ◽  
Traffic Simulation ◽  
Numerical Procedure ◽  
Uniform Load ◽  
Link Type ◽  
Computational Structure ◽  
Packet Switch ◽  
The Stability

Abstract The paper is concerned with the problem of calculating the bound of the throughput (THR) of a crossbar packet switch. For this purpose a suitable numerical procedure is used. The input data for the procedure are the results of computer simulations executed on a grid-computational structure (www.hpc.acad.bg). The modeling of the THR uses MiMa-algorithm for a crossbar packet switch, specified by the apparatus of Generalized Nets. For studying the stability of the numerical procedure we use a modified family of patterns for i.i.d. Bernoulli uniform load traffic simulation. The obtained results show that the numerical procedure is stable which means that small input perturbations result in small changes in the output.

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