Sökning: "vortex formation"

Visar resultat 11 - 15 av 41 avhandlingar innehållade orden vortex formation.

  1. 11. Mitigation of Pressure Pulsations in Axial turbine draft tube with jet injection or solid rod protrusion: A Numerical investigation

    Författare :Henrik Holmström; Cécile Münch-Alligné; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Vortex rope mitigation; vortex rope; Strömningslära; Fluid Mechanics;

    Sammanfattning : The introduction of intermittent renewable energy sources, such as wind and solar power, to the power grid, demands some hydraulic turbines to operate at unfavorable operating conditions not initially designed for. Strong swirl develops at loads below the best efficiency point, (BEP) due to angle mismatch between the guide vanes and the fixed runner blades typical for Francis and Propeller turbines. LÄS MER

  3. 12. Physiological aspects on intracardiac blood flow

    Författare :Per Arvidsson; Lund Klinisk fysiologi; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; magnetic resonance imaging; 4D flow; physiology; cardiac development; kinetic energy; hemodynamic force; vortex ring formation;

    Sammanfattning : Magnetic resonance imaging enables detailed in vivo study of complex flow through 3D, time-resolved phase contrast imaging (4D flow). 4D flow may reveal previously unknown aspects of the physiology of intracardiac blood flow, and possibly elucidate pathophysiological processes that have yet to manifest themselves outside the heart. LÄS MER

  4. 13. Computational Modelling for Cavitation and Tip Vortex Flows

    Författare :Abolfazl Asnaghi; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Cavitation; SST k − ω; OpenFOAM; Propeller; LES; Numerical simulation; Cur- vature correction; Elliptical foil; Inception; Twisted Delft foil;

    Sammanfattning : Cavitation often brings negative effects, such as performance degradation, noise, vibration, and material damage, to marine propulsion systems, but for optimum performance, cavitation is almost inevitable. Therefore, it is necessary to better understand cavitation in order to maximize the performance without encounter- ing severe problems. LÄS MER

  5. 14. FLOW FIELD IN A HIGH HEAD FRANCIS TURBINE DRAFT TUBE DURING TRANSIENT OPERATIONS

    Författare :Rahul Goyal; Michel J. Cervantes; Bhupendra K. Gandhi; Gabriel Ciocan; Lisa Prahl; Ramis Orlu; Gunilla Andree; Andrea Toffolo; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Francis turbine; Steady state; Transient; Particle Image Velocimetry; Vortex Rope; Strömningslära; Fluid Mechanics;

    Sammanfattning : Hydroelectricity plays an important role to balance the stability of grid network.  In order to improve the stability of presently high loaded grids, hydropower plants are being operated over a wide range of operations and experiencing frequent start-stop, load rejection, and load acceptance. LÄS MER

  7. 15. Dynamics of Exhaust Valve Flows and Confined Bluff Body Vortex Shedding

    Författare :Marcus Winroth; P. Henrik Alfredsson; Knud Erik Meyer; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : This thesis can be divided into two interconnected topics; engine exhaust-valve flows and confined bluff-body vortex shedding. When optimising engine flow systems it is common to use low order simulation tools that require empirical inputs, for instance with respect to flow losses across the exhaust valves. LÄS MER