Thermodynamic Stability Condition of Swirling Flows in Convergent Vortex Tubes

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F49777513%3A23640%2F19%3A43958159" target="_blank" >RIV/49777513:23640/19:43958159 - isvavai.cz</a>

Výsledek na webu

—

DOI - Digital Object Identifier

—

Jazyk výsledku

angličtina

Název v původním jazyce

Thermodynamic Stability Condition of Swirling Flows in Convergent Vortex Tubes

Popis výsledku v původním jazyce

Swirling flows are important for technical applications that require high heat transfer and enhanced fluid mixing such as cyclone cooling applications. However, the flow in such systems is unstable and thus vortex breakdown may occur. In order to improve the physical understanding of this phenomenon a numerical analysis of convergent vortex tubes is presented here. A swirl chamber featuring a constant diameter was compared to three different geometries comprising linearly decreasing diameters in flow direction. The latter ones reached a convergence angle of 0.41°, 0.61° and 0.72°. The numerical calculations were conducted as Delayed Detached Eddy Simulations at a Reynolds number of 10,000 and a Swirl number of 5.3. The data was analyzed in terms of axial and circumferential velocity distributions, local swirl strength as well as a thermodynamic stability condition that is based on the second law of thermodynamics. The results show that convergent vortex tubes cause a flow acceleration in circumferential and axial direction. Thus, a favorable pressure gradient in axial direction arises, which counteracts the axial backflow and hence prevents the vortex breakdown phenomenon. However, the analysis of the thermodynamic stability condition seems to indicate that convergent geometries are in general not capable of increasing the overall flow stability.

Název v anglickém jazyce

Thermodynamic Stability Condition of Swirling Flows in Convergent Vortex Tubes

Popis výsledku anglicky

Swirling flows are important for technical applications that require high heat transfer and enhanced fluid mixing such as cyclone cooling applications. However, the flow in such systems is unstable and thus vortex breakdown may occur. In order to improve the physical understanding of this phenomenon a numerical analysis of convergent vortex tubes is presented here. A swirl chamber featuring a constant diameter was compared to three different geometries comprising linearly decreasing diameters in flow direction. The latter ones reached a convergence angle of 0.41°, 0.61° and 0.72°. The numerical calculations were conducted as Delayed Detached Eddy Simulations at a Reynolds number of 10,000 and a Swirl number of 5.3. The data was analyzed in terms of axial and circumferential velocity distributions, local swirl strength as well as a thermodynamic stability condition that is based on the second law of thermodynamics. The results show that convergent vortex tubes cause a flow acceleration in circumferential and axial direction. Thus, a favorable pressure gradient in axial direction arises, which counteracts the axial backflow and hence prevents the vortex breakdown phenomenon. However, the analysis of the thermodynamic stability condition seems to indicate that convergent geometries are in general not capable of increasing the overall flow stability.

Druh

O - Ostatní výsledky

CEP obor

—

OECD FORD obor

20303 - Thermodynamics

Projekt

<a href="/cs/project/LO1402" target="_blank" >LO1402: CENTEM+</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů