Congrès International d'Architecture Moderne

About: Congrès International d'Architecture Moderne is a based out in . It is known for research contribution in the topics: Boundary value problem & Jet (fluid). The organization has 393 authors who have published 403 publications receiving 4104 citations.

Numerical and Experimental Estimation of the Turbine Blade Damper Efficiency

Abstract: Prevention of high cycle fatigue failures of blades caused by increased level of vibrational stresses is important problem in engine design and development. Different types of dampers are usually installed under the blade platforms in the region between the shanks of adjacent blades are usually used to reduce the vibrational stresses in the turbine blades. The action of these dampers is based on the vibrational energy dissipation by the dry friction forces arising due to the relative displacement of the contacting surfaces of the damper and the blade. Adoption of a reliable choice of damper design mass and stiffness at the design stage of the aircraft engines requires an experimentally validated estimation of its damping efficiency and its influence on the blade frequency characteristics. The dampers need to be tested under conditions that are maximally close to the operational conditions. This paper presents an analysis of the stress gauging results of a turbine wheel with box-type dampers of various mass. The tests were carried out on a dynamic bench where resonance oscillations of a stage for a given mode were excited by one of the harmonics to a given rotational speed under the corresponding forces pressing the dampers onto the blade platform. An estimation of the damper efficiency in a wider range of pressing forces was also obtained by conducting the laboratory tests using on a specially designed vibration unit that simulates the dampers effect on a set of three blades. Numerical analysis of the damper mass and stiffness influence on the frequency and damping characteristics of a real turbine wheel was performed. Obtained experimental data and the GAP model of contact interaction of the insert with blades were used in the MSC. Nastran software package. Analysis showed a satisfactory correlation between the calculated and experimental estimates of the decrease in resonant stresses and resonance frequency changes when the dampers are inserted. The results presented here confirm the possibility of increasing the reliability of the choice of mass and stiffness of turbine blade dampers at the design stage.

Protective Measures of Healthcare Professionals to Face COVID-19: Case of China and Morocco

Abstract: A novel virus has emerged to the world causing a new pandemic of respiratory infection. On February 2020, the World Health Organization named it Corona disease 2019. The emergence of this epidemic was first reported in Wuhan, China in late December 2019, before it spread to other countries. In response to this pandemic, the World Health Organization has stressed the need for strengthening health professionals worldwide. Indeed, adequate protective measures can help protect patients and staff from the transmission of a highly infectious disease. Managing COVID-19 patients exposes healthcare professionals to the risk of contracting the disease and transmitting it to those around them. This risk is very high because of the mode of transmission of SARS-CoV-2, which is transmitted by inhalation, contact with droplets and infected surfaces which makes it a very contagious disease. Thus, adequate precautions in healthcare establishments can help mitigate this risk, such as adopting several protective measures including personal protective equipment. By the same vein, healthcare professionals run a high risk of anxiety, stress, depression and burnout when managing COVID-19 patients. Therefore, the protection of the mental health of these health workers also includes psychological support measures. In this regard, this article purports to describe the health and safety measures related to the prevention of the risk of COVID-19 infection to health professionals in China and Morocco. On the other hand, it seeks to present the psychological support measures for these agents in the two aforementioned countries.

Reflection of a Rarefaction Wave from the Center of Symmetry: Theoretical Analysis of the Flow Features and Calculation by the Method of Characteristics

Abstract: For an unsteady spherical rarefaction wave in an ideal (inviscid and non-heat-conducting) gas, the features of the flow near the reflection of the first characteristic from the center of symmetry are investigated. Computations performed by the method of characteristics on nearly uniform grids usually used in such problems reveal sawtooth irregularities in the parameter distributions near the reflection point, whereas similar irregularities in the cylindrical and plane cases are absent. The amplitudes of the irregularities and the sizes of the domains where they are observed remain nearly unchanged when the number of points of the characteristic grid is increased by many times. Away from the reflection point in both time and space, the numerical solution completely “forgets” about the irregularities. This finding explains why these irregularities were ignored or overlooked earlier, but the nature of this phenomenon remains an open question. The present study has established that the spherical rarefaction flow near the reflection point differs fundamentally in structure from its plane and cylindrical counterparts. In the spherical case, the rarefaction flow near the reflection point was found to be nearly conical (entirely conical in the linear approximation). Allowance for this feature in the method of characteristics led to continuous regular distributions of the parameters. The performed analysis and computations revealed that a spherical rarefaction wave is strengthened (cumulates) theoretically unlimitedly in a small neighborhood of the reflection point (center of symmetry) of the first characteristic. Moreover, the claim that a gradient catastrophe occurs in this neighborhood was found to be untenable.

Solving integral equations with generalized Neumann kernel using global simpler GMRES for numerical conformal mapping

Abstract: We study a numerical approach for solving integral equation with adjoint generalized Neumann kernel related to conformal mapping. Previously, computation of conformal mapping of M + 1 connected regions require solving at least M + 1 integral equations with adjoint generalized Neumann kernel separately. We apply global simpler GMRES which solve nonsymmetric system with multiple right-hand sides to solve M + 1 integral equations simultaneously. We also apply fast multipole method for several matrix vector products in every iteration of global simpler GMRES. Numerical example is given to illustrate the effectiveness of the proposed method.