• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 17
  • 6
  • 5
  • 3
  • 3
  • 1
  • Tagged with
  • 44
  • 44
  • 11
  • 10
  • 9
  • 6
  • 6
  • 6
  • 6
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Numerický model zavzdušňovacího ventilu / Numerical model of air valve

Luňák, Pavel January 2017 (has links)
This diploma thesis deals the formation of water hammer in pipes and the suppress the nega-tive effects especially for the use of protective devices (surge tank, air chamber, air valve and other). The special attention is paid to the use of the air valve, for which it was developed mathematical model. The solution is based on the use of numerical methods Lax-Wendroff with boundary conditions for the air valve.The numerical results are confronted with the ex-periment in conclusion.
42

Měření dynamických charakteristik zpětných armatur / Measurement of dynamic characteristic of check valves

Novák, Jan January 2017 (has links)
Master thesis presents overview of existing types of check valves, their features, uses and issue called "cracking". Experimental part of this thesis focuses on the lift and swing check valves. Results of the measurement are evaluated from non-stationary flow point of view by developing and analyzing static and dynamic characteristics. This thesis takes into account losses and dynamic effects as main viewpoints. Two methods for measuring non-stationary velocities are used. Direct method called Gibson and indirect method laser doppler anemometry. Goal of the master thesis is to increase understanding of the check valves and their applicability.
43

Modelování tlakových pulsací v potrubí / Modelling of pressure pulsations in pipes

Hofírek, Michal January 2017 (has links)
This diploma thesis deals with problem of water hammer in pipes affected by viscoelastic behavior of pipe material. Mathematical model uses pressure dependent speed of sound in water air mixture. For purpose of numerical solution the Method of Characteristics with independent time step is introduced. This method is compared with commonly used methods such as Method of Characteristics (MOC) and Lax Wendroff scheme. Derived model, solved with Method of Characteristics with independent time step, is verified with experimental simulation.
44

Contributions à la commande prédictive des systèmes de lois de conservation / Contribution to predictive control for systems of conservation laws

Pham, Van Thang 06 September 2012 (has links)
La Commande prédictive ou Commande Optimale à Horizon Glissant (COHG) devient de plus en plus populaire dans de nombreuses applications pratiques en raison de ses avantages importants tels que la stabilisation et la prise en compte des contraintes. Elle a été bien étudiée pour des systèmes en dimension finie même dans le cas non linéaire. Cependant, son extension aux systèmes en dimension infinie n'a pas retenu beaucoup d'attention de la part des chercheurs. Ce travail de thèse apporte des contributions à l'application de cette approche aux systèmes de lois de conservation. Nous présentons tout d'abord une preuve de stabilité complète de la COHG pour certaines classes de systèmes en dimension infinie. Ce résultat est ensuite utilisé pour les systèmes hyperboliques 2x2 commandés aux frontières et appliqué à un problème de contrôle de canal d'irrigation. Nous proposons aussi l'extension de cette stratégie au cas de réseaux de systèmes hyperboliques 2x2 en cascade avec une application à un ensemble de canaux d'irrigation connectés. Nous étudions également les avantages de la COHG dans le contexte des systèmes non linéaires et semi-linéaires notamment vis-à-vis des chocs. Toutes les analyses théoriques sont validées par simulation afin d'illustrer l'efficacité de l'approche proposée. / The predictive control or Receding Horizon Optimal Control (RHOC) is becoming increasingly popular in many practical applications due to its significant advantages such as the stabilization and constraints handling. It has been well studied for finite dimensional systems even in the nonlinear case. However, its extension to infinite dimensional systems has not received much attention from researchers. This thesis proposes contributions on the application of this approach to systems of conservation laws. We present a complete proof of stability of RHOC for some classes of infinite dimensional systems. This result is then used for 2x2 hyperbolic systems with boundary control, and applied to an irrigation canal. We also propose the extension of this strategy to networks of cascaded 2x2 hyperbolic systems with an application to a set of connected irrigation canals. Furthermore, we study the benefits of RHOC in the context of nonlinear and semi-linear systems in particular with respect to the problem of shocks. All theoretical analyzes are validated by simulation in order to illustrate the effectiveness of the proposed approach.

Page generated in 0.0739 seconds