The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Jovica V. Milanovic - One of the best experts on this subject based on the ideXlab platform.
-
towards development of equivalent model of hybrid renewable energy source plant for Small Disturbance stability studies
IEEE PowerTech Conference, 2021Co-Authors: Ana Radovanovic, Yue Wang, Jovica V. MilanovicAbstract:Over the past years, the focus of the research on hybrid renewable energy source (HRES) plants has been on the economic advantages of their integration into power systems. This paper investigates the contribution of the HRES plant to system Small Disturbance stability and proposes dynamic equivalent model (DEM) of HRES plant for Small Disturbance stability studies. The analysis takes into consideration typical annual HRES plant compositions identified by applying a clustering method to historical plant production data. Damping and frequency of the least damped electromechanical mode are used for assessing the similarity in the impact of HRES plant compositions on system stability. A transfer function-based DEM of the whole HRES plant is then proposed for each group of plant compositions resulting in similar system stability performance. The results have shown that a Small number of low-order DEMs can represent the whole plant in Small Disturbance stability studies during the year.
-
efficient identification of critical uncertainties affecting Small Disturbance stability of power systems considering parameter correlation
Power and Energy Society General Meeting, 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:Identification of the most critical uncertainties will facilitate better system operation and control with reduced monitoring by system operators and stakeholders. A significant level of correlation, however, exists between some uncertain parameters which could impact power system stability. There is a need to jointly address these two issues. This paper presents a novel approach to model correlated uncertainties within a sensitivity analysis framework to identify critical parameters affecting power system stability. The Morris screening method of sensitivity analysis, which has been previously shown to be highly accurate and efficient has been modified to account for the correlation between uncertainties. Application of this improved method is demonstrated by ranking the critical uncertainties that affect the Small-Disturbance rotor angle stability of a power system.
-
application of game theoretic approaches for identification of critical parameters affecting power system Small Disturbance stability
International Journal of Electrical Power & Energy Systems, 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:Abstract This paper evaluates a number of game theoretic (GT) approaches with the aim of assessing their suitability to identify the most influential parameters affecting the Small-Disturbance stability of a power system. Identification of the most influential parameters affecting system stability will facilitate cost-effective operation and control of a power system in general as it would require limited network monitoring, control and modelling effort by system operators and stakeholders. After identifying the most influential parameters the financial and human resources could be adequately prioritised and deployed to solve or prevent power system stability problems. A priority ranking procedure based on a GT approach has the advantage, compared to other techniques, of considering simultaneously the effect of individual and all possible combinatorial effects of the uncertain parameters (or players in a game context). In this study, the most influential players have been identified through a multi-level approach considering the power flow in the network (by optimal power flow), Small Disturbance stability aspects (by modal analysis), rational behavior of individual players (by a sensitivity technique) and formation of groups between players (by cooperative game theory). Various GT approaches have been considered namely Shapley Value, Aumann Shapley, Nucleolus, and τ -value approach in order to compare and assess their suitability for power system applications. The results are illustrated using two test networks and considering several approaches of sensitivity analysis and different degrees of variability in the considered uncertainties.
-
The Influence of Load on Risk-Based Small-Disturbance Security Profile of a Power System
IEEE Transactions on Power Systems, 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:This paper establishes a generic severity function that can be used to produce power system security risk profiles. It is illustrated by analyzing the impacts of system load attributes on the Small-Disturbance rotor angle stability of a power system. The load attributes contributing to the oscillatory modes can be considered as inherent uncertain variables within power systems and include load power variations, load composition, and load model parameters. Uncertainty in the renewable power generation is also incorporated in the probabilistic modelling and risk assessment to demonstrate the flexibility of the approach. A novel approach is proposed to select the severity functions to logically represent Small-Disturbance security margin. The risk profile of a power system has been presented considering the probability density functions of power system critical modal damping and a selected set of severity functions. The analysis techniques developed are illustrated with a modified version of the 68-bus NETS-NYPS power system with a high amount of renewable power penetration. The relative importance of the load attributes and the impact of these attributes on stability boundaries have been identified at varying risk levels with respect to their contribution to Small-Disturbance stability.
-
The Influence of Load on Risk-Based Small-Disturbance Security Profile of a Power System
2018 IEEE Power & Energy Society General Meeting (PESGM), 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:This paper establishes a generic severity function that can be used to produce power system security risk profiles. It is illustrated by analyzing the impacts of system load attributes on the Small-Disturbance rotor angle stability of a power system. The load attributes contributing to the oscillatory modes can be considered as inherent uncertain variables within power systems and include load power variations, load composition, and load model parameters. Uncertainty in the renewable power generation is also incorporated in the probabilistic modelling and risk assessment to demonstrate the flexibility of the approach. A novel approach is proposed to select the severity functions to logically represent Small-Disturbance security margin. The risk profile of a power system has been presented considering the probability density functions (pdfs) of power system critical modal damping and a selected set of severity functions. The analysis techniques developed are illustrated with a modified version of the 68-bus NETS-NYPS power system with a high amount of renewable power penetration. The relative importance of the load attributes and the impact of these attributes on stability boundaries has been identified at varying risk levels with respect to their contribution to Small-Disturbance stability.
Robin Preece - One of the best experts on this subject based on the ideXlab platform.
-
efficient identification of critical uncertainties affecting Small Disturbance stability of power systems considering parameter correlation
Power and Energy Society General Meeting, 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:Identification of the most critical uncertainties will facilitate better system operation and control with reduced monitoring by system operators and stakeholders. A significant level of correlation, however, exists between some uncertain parameters which could impact power system stability. There is a need to jointly address these two issues. This paper presents a novel approach to model correlated uncertainties within a sensitivity analysis framework to identify critical parameters affecting power system stability. The Morris screening method of sensitivity analysis, which has been previously shown to be highly accurate and efficient has been modified to account for the correlation between uncertainties. Application of this improved method is demonstrated by ranking the critical uncertainties that affect the Small-Disturbance rotor angle stability of a power system.
-
influence of stochastic dependence on Small Disturbance stability and ranking uncertainties
IEEE Transactions on Power Systems, 2018Co-Authors: Kazi N. Hasan, Robin PreeceAbstract:A high level of stochastic dependence (or correlation) exists between different uncertainties (i.e., loads and renewable generation), which is nonlinear and non-Gaussian and it affects power system stability. Accurate modeling of stochastic dependence becomes more important and influential as the penetration of correlated uncertainties (such as renewable generation) increases in the network. The stochastic dependence between uncertainties can be modeled using 1) copula theory and 2) joint probability distributions. These methods have been implemented in this paper and their performances have been compared in assessing the Small-Disturbance stability of a power system. The value of modeling stochastic dependence with increased renewables has been assessed. Subsequently, the critical uncertainties that most affect the damping of the most critical oscillatory mode have been identified and ranked in terms of their influence using advanced global sensitivity analysis techniques. This has enabled the quantification and identification of the impact of modeling stochastic dependence on the raking of critical uncertainties. The results suggest that multivariate Gaussian copula is the most suitable approach for modeling correlation as it shows consistently low error even at higher levels of renewable energy penetration into the power system.
-
application of game theoretic approaches for identification of critical parameters affecting power system Small Disturbance stability
International Journal of Electrical Power & Energy Systems, 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:Abstract This paper evaluates a number of game theoretic (GT) approaches with the aim of assessing their suitability to identify the most influential parameters affecting the Small-Disturbance stability of a power system. Identification of the most influential parameters affecting system stability will facilitate cost-effective operation and control of a power system in general as it would require limited network monitoring, control and modelling effort by system operators and stakeholders. After identifying the most influential parameters the financial and human resources could be adequately prioritised and deployed to solve or prevent power system stability problems. A priority ranking procedure based on a GT approach has the advantage, compared to other techniques, of considering simultaneously the effect of individual and all possible combinatorial effects of the uncertain parameters (or players in a game context). In this study, the most influential players have been identified through a multi-level approach considering the power flow in the network (by optimal power flow), Small Disturbance stability aspects (by modal analysis), rational behavior of individual players (by a sensitivity technique) and formation of groups between players (by cooperative game theory). Various GT approaches have been considered namely Shapley Value, Aumann Shapley, Nucleolus, and τ -value approach in order to compare and assess their suitability for power system applications. The results are illustrated using two test networks and considering several approaches of sensitivity analysis and different degrees of variability in the considered uncertainties.
-
The Influence of Load on Risk-Based Small-Disturbance Security Profile of a Power System
IEEE Transactions on Power Systems, 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:This paper establishes a generic severity function that can be used to produce power system security risk profiles. It is illustrated by analyzing the impacts of system load attributes on the Small-Disturbance rotor angle stability of a power system. The load attributes contributing to the oscillatory modes can be considered as inherent uncertain variables within power systems and include load power variations, load composition, and load model parameters. Uncertainty in the renewable power generation is also incorporated in the probabilistic modelling and risk assessment to demonstrate the flexibility of the approach. A novel approach is proposed to select the severity functions to logically represent Small-Disturbance security margin. The risk profile of a power system has been presented considering the probability density functions of power system critical modal damping and a selected set of severity functions. The analysis techniques developed are illustrated with a modified version of the 68-bus NETS-NYPS power system with a high amount of renewable power penetration. The relative importance of the load attributes and the impact of these attributes on stability boundaries have been identified at varying risk levels with respect to their contribution to Small-Disturbance stability.
-
The Influence of Load on Risk-Based Small-Disturbance Security Profile of a Power System
2018 IEEE Power & Energy Society General Meeting (PESGM), 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:This paper establishes a generic severity function that can be used to produce power system security risk profiles. It is illustrated by analyzing the impacts of system load attributes on the Small-Disturbance rotor angle stability of a power system. The load attributes contributing to the oscillatory modes can be considered as inherent uncertain variables within power systems and include load power variations, load composition, and load model parameters. Uncertainty in the renewable power generation is also incorporated in the probabilistic modelling and risk assessment to demonstrate the flexibility of the approach. A novel approach is proposed to select the severity functions to logically represent Small-Disturbance security margin. The risk profile of a power system has been presented considering the probability density functions (pdfs) of power system critical modal damping and a selected set of severity functions. The analysis techniques developed are illustrated with a modified version of the 68-bus NETS-NYPS power system with a high amount of renewable power penetration. The relative importance of the load attributes and the impact of these attributes on stability boundaries has been identified at varying risk levels with respect to their contribution to Small-Disturbance stability.
David J. Hill - One of the best experts on this subject based on the ideXlab platform.
-
decentralized event triggered frequency regulation for multi area power systems
Automatica, 2021Co-Authors: Luwei Yang, Tao Liu, David J. HillAbstract:Abstract To achieve a better frequency control performance for multi-area power systems, this paper proposes a novel decentralized event-triggered control (ETC) algorithm for automatic generation control (AGC) to replace the traditional periodic sampling/communication mechanism. For each control area, decentralized event-triggering conditions that only depend on locally available information are designed for the control center to determine time instants when to sample the frequency and for each communication channel to decide instants when to broadcast corresponding information. Further, a strictly positive dwell time is introduced to prevent Zeno behaviors. Small Disturbance frequency stability of the interconnected power network under the developed ETC law is analyzed, and a sufficient stability criterion on the selection of event-triggered parameters is established. Case studies on a three-area test system illustrate the effectiveness and efficiency of our method.
-
Small Disturbance voltage stability of power systems dependence on network structure
IEEE Transactions on Power Systems, 2020Co-Authors: Wanjun Huang, David J. Hill, Xinran ZhangAbstract:This paper investigates the impact of network structures on Small-Disturbance voltage stability of power systems in the long-term. A differential-algebraic model is established in terms of network topology characteristics and the aggregate nonlinear recovery load model. We define the weighted load connectivity (WLC) as an index to indicate the stability of network structures. Then robust stability assessment is used to eliminate the impact of uncertain recovery time of loads. The Monte Carlo method is used to study the relationship between WLC and Small-Disturbance voltage stability (SDVS) for a broad range of network topologies and parameters. We discover from the simulation results that the network with a larger value of WLC has a stronger ability to maintain SDVS. To further study the impact of renewable energy sources (RESs), we improve the system model by including an inverter-based distributed generator in parallel with each aggregated nonlinear dynamic load. The simulation results of the Hong Kong power grid show that the WLC can still indicate the stability of network structures effectively, and the systems with more stable network structures are less impacted by the penetration of RESs. The proposed WLC appears useful in providing guidance for power network planning and operation.
-
Network-Based Analysis of Small-Disturbance Angle Stability of Power Systems
IEEE Transactions on Control of Network Systems, 2018Co-Authors: Yue Song, David J. HillAbstract:This paper investigates Small-Disturbance angle stability of power systems with emphasis on the role of power network topology, which sheds new light on the instability mechanism. We introduce the concepts of active power flow graph and critical lines. It is shown that the inertia of the Laplacian matrix of this graph provides information on the stability and type of an equilibrium point. Then, the instability mechanism is elaborated from the impact of critical lines on the inertia of the Laplacian matrix. A stability criterion in terms of a critical line-based matrix is established. This criterion is a necessary and sufficient condition to judge the stability and type of an equilibrium point. It includes the existing results in the literature and applies to the unsolved cases where the critical lines exist but do not form cutsets. Moreover, we introduce the concept of equivalent weight between a pair of buses. Another stability criterion in terms of the equivalent weight is developed, from which the Small-Disturbance instability can be interpreted as the “electrical antagonism” between some buses in the power network resulting from the critical lines. The equivalent weight can also be used as a stability index and provides guidance for system operation. The obtained results are illustrated by numerical simulations.
-
Small Disturbance angle stability analysis of microgrids a graph theory viewpoint
International Conference on Control Applications, 2015Co-Authors: Yue Song, David J. Hill, Tao LiuAbstract:This paper is concerned with Small-Disturbance angle stability of microgrids from a graph theory perspective. Firstly, we build up the structure preserving model for mi-crogrids, and introduce the concept of the active power flow graph, the Laplacian matrix and the critical lines. We show that Small-Disturbance stability is equivalent to the positive semi-definiteness of the Laplacian matrix, and it is the critical lines that cause instability. Then, we elaborate the impact of the critical lines on Small-Disturbance stability. A stability criterion is proposed, which is a matrix inequality in terms of the critical lines. This criterion also indicates the type of unstable equilibrium point (UEP) and can be considered as a supplement to eigenvalue-based Small-Disturbance analysis. The obtained results are validated by using a modified IEEE 9-bus test system.
-
power system voltage Small Disturbance stability studies based on the power flow equation
Iet Generation Transmission & Distribution, 2010Co-Authors: G Y Cao, David J. HillAbstract:This study first studies power system Small-Disturbance stability at the operating point where the power flow (PF) equation encounters a saddle-node bifurcation. The authors demonstrate that the linearised model of the differential-algebraic equation (DAE) that describes the power system dynamics will have a zero eigenvalue at the equilibrium precisely when the PF Jacobian is singular. Note that the PF equation and DAE models are general ones. This clarifies a point in previous contributions on this relationship. Numerical results for two power system examples are used to demonstrate the theory, and finally the extension of the theory is discussed for the limit-induced bifurcation associated with the PF equation when some generators reach their reactive power limits.
Kazi N. Hasan - One of the best experts on this subject based on the ideXlab platform.
-
efficient identification of critical uncertainties affecting Small Disturbance stability of power systems considering parameter correlation
Power and Energy Society General Meeting, 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:Identification of the most critical uncertainties will facilitate better system operation and control with reduced monitoring by system operators and stakeholders. A significant level of correlation, however, exists between some uncertain parameters which could impact power system stability. There is a need to jointly address these two issues. This paper presents a novel approach to model correlated uncertainties within a sensitivity analysis framework to identify critical parameters affecting power system stability. The Morris screening method of sensitivity analysis, which has been previously shown to be highly accurate and efficient has been modified to account for the correlation between uncertainties. Application of this improved method is demonstrated by ranking the critical uncertainties that affect the Small-Disturbance rotor angle stability of a power system.
-
influence of stochastic dependence on Small Disturbance stability and ranking uncertainties
IEEE Transactions on Power Systems, 2018Co-Authors: Kazi N. Hasan, Robin PreeceAbstract:A high level of stochastic dependence (or correlation) exists between different uncertainties (i.e., loads and renewable generation), which is nonlinear and non-Gaussian and it affects power system stability. Accurate modeling of stochastic dependence becomes more important and influential as the penetration of correlated uncertainties (such as renewable generation) increases in the network. The stochastic dependence between uncertainties can be modeled using 1) copula theory and 2) joint probability distributions. These methods have been implemented in this paper and their performances have been compared in assessing the Small-Disturbance stability of a power system. The value of modeling stochastic dependence with increased renewables has been assessed. Subsequently, the critical uncertainties that most affect the damping of the most critical oscillatory mode have been identified and ranked in terms of their influence using advanced global sensitivity analysis techniques. This has enabled the quantification and identification of the impact of modeling stochastic dependence on the raking of critical uncertainties. The results suggest that multivariate Gaussian copula is the most suitable approach for modeling correlation as it shows consistently low error even at higher levels of renewable energy penetration into the power system.
-
application of game theoretic approaches for identification of critical parameters affecting power system Small Disturbance stability
International Journal of Electrical Power & Energy Systems, 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:Abstract This paper evaluates a number of game theoretic (GT) approaches with the aim of assessing their suitability to identify the most influential parameters affecting the Small-Disturbance stability of a power system. Identification of the most influential parameters affecting system stability will facilitate cost-effective operation and control of a power system in general as it would require limited network monitoring, control and modelling effort by system operators and stakeholders. After identifying the most influential parameters the financial and human resources could be adequately prioritised and deployed to solve or prevent power system stability problems. A priority ranking procedure based on a GT approach has the advantage, compared to other techniques, of considering simultaneously the effect of individual and all possible combinatorial effects of the uncertain parameters (or players in a game context). In this study, the most influential players have been identified through a multi-level approach considering the power flow in the network (by optimal power flow), Small Disturbance stability aspects (by modal analysis), rational behavior of individual players (by a sensitivity technique) and formation of groups between players (by cooperative game theory). Various GT approaches have been considered namely Shapley Value, Aumann Shapley, Nucleolus, and τ -value approach in order to compare and assess their suitability for power system applications. The results are illustrated using two test networks and considering several approaches of sensitivity analysis and different degrees of variability in the considered uncertainties.
-
The Influence of Load on Risk-Based Small-Disturbance Security Profile of a Power System
IEEE Transactions on Power Systems, 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:This paper establishes a generic severity function that can be used to produce power system security risk profiles. It is illustrated by analyzing the impacts of system load attributes on the Small-Disturbance rotor angle stability of a power system. The load attributes contributing to the oscillatory modes can be considered as inherent uncertain variables within power systems and include load power variations, load composition, and load model parameters. Uncertainty in the renewable power generation is also incorporated in the probabilistic modelling and risk assessment to demonstrate the flexibility of the approach. A novel approach is proposed to select the severity functions to logically represent Small-Disturbance security margin. The risk profile of a power system has been presented considering the probability density functions of power system critical modal damping and a selected set of severity functions. The analysis techniques developed are illustrated with a modified version of the 68-bus NETS-NYPS power system with a high amount of renewable power penetration. The relative importance of the load attributes and the impact of these attributes on stability boundaries have been identified at varying risk levels with respect to their contribution to Small-Disturbance stability.
-
The Influence of Load on Risk-Based Small-Disturbance Security Profile of a Power System
2018 IEEE Power & Energy Society General Meeting (PESGM), 2018Co-Authors: Kazi N. Hasan, Robin Preece, Jovica V. MilanovicAbstract:This paper establishes a generic severity function that can be used to produce power system security risk profiles. It is illustrated by analyzing the impacts of system load attributes on the Small-Disturbance rotor angle stability of a power system. The load attributes contributing to the oscillatory modes can be considered as inherent uncertain variables within power systems and include load power variations, load composition, and load model parameters. Uncertainty in the renewable power generation is also incorporated in the probabilistic modelling and risk assessment to demonstrate the flexibility of the approach. A novel approach is proposed to select the severity functions to logically represent Small-Disturbance security margin. The risk profile of a power system has been presented considering the probability density functions (pdfs) of power system critical modal damping and a selected set of severity functions. The analysis techniques developed are illustrated with a modified version of the 68-bus NETS-NYPS power system with a high amount of renewable power penetration. The relative importance of the load attributes and the impact of these attributes on stability boundaries has been identified at varying risk levels with respect to their contribution to Small-Disturbance stability.
Suncica Canic - One of the best experts on this subject based on the ideXlab platform.
-
a proof of existence of perturbed steady transonic shocks via a free boundary problem
Communications on Pure and Applied Mathematics, 2000Co-Authors: Suncica Canic, Barbara Lee Keyfitz, Gary M LiebermanAbstract:We prove the existence of a solution of a free boundary problem for the transonic Small-Disturbance equation. The free boundary is the position of a transonic shock dividing two regions of smooth flow. Assuming inviscid, irrotational flow, as modeled by the transonic Small-Disturbance equation, the equation is hyperbolic upstream where the flow is supersonic, and elliptic in the downstream subsonic region. To study the stability of a uniform planar transonic shock, we consider perturbation by a steady C1+ϵ upstream Disturbance. If the upstream Disturbance is Small in a C1 sense, then there is a steady solution in which the downstream flow and the transonic shock are Holder-continuous perturbations of the uniform configuration. This result provides a new use of inviscid perturbation techniques to demonstrate, in two dimensions, the stability of transonic shock waves of the type that appear, for example, over the wing of an airplane, along an airfoil, or as bow shocks in a flow with a supersonic free-stream velocity. © 2000 John Wiley & Sons, Inc.
-
free boundary problems for the unsteady transonic Small Disturbance equation transonic regular reflection
Methods and applications of analysis, 2000Co-Authors: Suncica Canic, Eun Heui Kim, Barbara Lee KeyfitzAbstract:We formulate and solve a transonic regular reflection problem for the unsteady transonic Small Disturbance equation, using a free boundary problem approach. Our method applies to self-similar shock reflection when the incident shock angle is large enough to permit a regular reflection configuration with a subsonic state behind the reflected shock. For the Small-Disturbance approximation in weak shock reflection, this corresponds to relatively large wedge angles. One contribution of this paper is the development of an asymptotic formula for the reflected shock, far from the reflection point, and for the subsonic state far downstream. These asymptotic series are valid for the Small-Disturbance approximation, for any incident shock angles. The main result in the paper is an existence theorem for the nonuniform subsonic flow behind the reflected shock. The flow velocity satisfies a quasilinear elliptic equation which is coupled to the Rankine-Hugoniot equations for the reflected shock, forming a free boundary problem on part of the boundary. Because the equation is not uniformly elliptic in the entire domain, we introduce a cut off to give a bounded domain, and also cut offs to the coefficients. Our result is incomplete in the following sense: we have been unable to remove the cut offs entirely. However, we prove that the flow we have constructed solves the original problem in a domain of finite size around the reflection point.
-
riemann problems for the two dimensional unsteady transonic Small Disturbance equation
Siam Journal on Applied Mathematics, 1998Co-Authors: Suncica Canic, Barbara Lee KeyfitzAbstract:We study a two-parameter family of Riemann problems for the unsteady transonic Small Disturbance (UTSD) equation, also called the two-dimensional Burgers equation, which is used to model the transition from regular to Mach reflection for weak shock waves. The related initial-value problem consists of oblique shock data in the upper half-plane, with two parameters a and b corresponding to the slopes of the initial shock waves. The study of quasi-steady solutions leads to a problem that changes type when written in self-similar coordinates. The problem is hyperbolic in the region where the flow is supersonic, and elliptic where the flow is subsonic.In this paper we give a complete description of the flow in the hyperbolic region by resolving the hyperbolic wave interactions in the form of quasi-one-dimensional Riemann problems. In the region of physical space where the flow is subsonic, we pose the related free-boundary problems and discuss the behavior of the subsonic solution using results from our previo...
-
an elliptic problem arising from the unsteady transonic Small Disturbance equation
Other Information: PBD: 14 Sep 1995, 1995Co-Authors: Suncica Canic, Barbara Lee KeyfitzAbstract:Abstract We prove a theorem on existence of a weak solution of the Dirichlet problem for a quasilinear elliptic equation with a degeneracy on one part of the boundary. The degeneracy is of a type (“Keldysh type”) associated with singular behavior—blow-up of a derivative—at the boundary. We define an associated operator which is continuous, pseudo-monotone and coercive and show that a weak solution displaying singular behavior at the boundary exists.
