Search for dissertations about: "damping"

Showing result 21 - 25 of 367 swedish dissertations containing the word damping.

2. 21. Bridge Monitoring to Allow for Reliable Dynamic FE Modelling : A Case Study of the New Årsta Railway Bridge

   Author : Johan Wiberg; Håkan Sundquist; Raid Karoumi; Björn Paulsson; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; bridge monitoring; FE modelling; signal analysis; torsion; warping; modulus of elasticity; natural frequency; damping; finite differences; Civil engineering and architecture; Samhällsbyggnadsteknik och arkitektur;

   Abstract : Today’s bridge design work in many cases demands a trustworthy dynamic analysis instead of using the traditional dynamic amplification factors. In this thesis a reliable 3D Bernoulli-Euler beam finite element model of the New Årsta Railway Bridge was prepared for thorough dynamic analysis using in situ bridge monitoring for correlation. READ MORE

4. 22. Studies of sound generation and propagation in flow ducts

   Author : Fabrice Ducret; Mats Åbom; Andy Moorhouse; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; two-port; plane wave; HVAC system; tailpipe; exhaust system; flexible duct; pipe; reflection coefficient; impedance; flow noise; vorticity; damping; scaling laws; impedance; transmission loss; perforated plate; slit; non linearity; Acoustics; Akustik;

   Abstract : This thesis contains three papers investigating problems of interest for noise control in ducts. The first part of this thesis treats the sound propagation in rectangular ducts with flexible walls. Various experimental techniques are performed to measure the internal sound propagation and radiation to the surrounding. READ MORE

5. 23. Potential Flow Panel Methods for the Calculation of Free-surface Flows with Lift

   Author : Carl-Erik Janson; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; desingularized; shape optimization; Rankine source; waves; OCTOPUS; dipole; MMA; Dawson operator; boundary layer; vortex; Method of Moving Asymptotes; nonlinear; sailing yacht; four point operator; surface piercing wing; Navier-Stokes; numerical method; lift force; raised panel method; discrete Fourier transform; collocation point shift; potential flow; CFD; free surface; induced drag; SHIPFLOW; dispersion; damping; analytical method; hydrofoil;

   Abstract : Two non-linear Rankine-source panel methods are developed and implemented in the same computer code. The first method uses a four-point upwind operator on the free-surface to compute the velocity derivatives and to enforce the radiation condition while the second method uses an analytical expression for the velocity derivatives and a collocation point shift one panel upstream to prevent upstream waves. READ MORE

6. 24. Modeling and Verification of Ultra-Fast Electro-Mechanical Actuators for HVDC Breakers

   Author : Ara Bissal; Göran Engdahl; Elena Lomonova; KTH; []
   Keywords : Actuators; Armature; Capacitors; Circuit breakers; Coils; Damping; Eddy currents; Elasticity; Electro-mechanical devices; Electromagnetic forces; Finite element methods; HVDC transmission; Image motion analysis; Magnetic domains; Magnetic flux; Magnetic forces; Magnetic materials; Magnets; Thermal analysis; Electrical Engineering; Elektro- och systemteknik;

   Abstract : The continuously increasing demand for clean renewable energy has rekindled interest in multi-terminal high voltage direct current (HVDC) grids. Although such grids have several advantages and a great potential, their materialization has been thwarted due to the absence of HVDC breakers. READ MORE

7. 25. Analysis of VSC-based HVDC systems

   Author : Georgios Stamatiou; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; HVDC; MMC; MTDC; Poor damping; Symbolic eigenvalue expressions; Droop control; Passivity Analysis; Net damping; Frequency Domain Analysis; VSC;

   Abstract : The main objective of this thesis is to perform stability and control studies in the area of VSC-HVDC systems. A major part of the investigation focuses on the development of procedures, whose aim is to understand, explain and avoid poorly-damped conditions or instability that may appear due to dc-side resonances, which stem from the interaction of converters and passive elements in such systems. READ MORE