Time-dependent effects in high viscosity fluid dynamics

The cooling air in a rotating machine is subject to windage as it passes over the rotor surface, particularly for cases where nonaxisymmetric features such as boltheads are encountered. The ability to accurately predict windage can help reduce the quantity of cooling air required, resulting in increased efficiency. Previous work has shown that the steady computational fluid dynamics solutions can give reasonable predictions for the effects of bolts on disc moment for a rotor–stator cavity with throughflow but flow velocities and disc temperature are not well predicted. Large fluctuations in velocities have been observed experimentally in some cases. Time-dependent computational fluid dynamics simulations reported here bring to light the unsteady nature of the flow. Unsteady Reynolds-averaged Navier–Stokes calculations for 120° and 360° models of the rotor–stator cavity with 9 and 18 bolts were performed in order to better understand the flow physics. Although the rotor–stator cavity with bolts is geometrically steady in the rotating frame of reference, it was found that the bolts generate unsteadiness which creates time-dependent rotating flow features within the cavity. At low throughflow conditions, the unsteady flow significantly increases the average disc temperature.

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Determination and Fire Analysis of Gob Characteristics Using CFD

Energies ◽

10.3390/en13205274 ◽

2020 ◽

Vol 13 (20) ◽

pp. 5274

Author(s):

Florencio Fernández-Alaiz ◽

Ana Maria Castañón ◽

Fernando Gómez-Fernández ◽

Antonio Bernardo-Sánchez ◽

Marc Bascompta

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Experimental Tests ◽

The Self ◽

Time Dependent ◽

Scale Analysis ◽

Dynamics Modelling ◽

Gob Area ◽

Time Dependent Analysis ◽

Waste Coal

A laboratory-scale analysis using coal from an underground mine was carried out, emulating a mixture from the gob area in an actual mine, consisting of waste, coal, and free space for the flow of air. Experimental tests and computational fluid dynamics modelling were done to define and verify the behavior of the collapsed region in a time-dependent analysis. In addition, the characteristics of coal were defined, regarding the self-combustion, combustion rate, and pollutants generated in each stage of the fire. The results achieved are useful for determining the behavior of the collapsed area in full-scale conditions and to provide valuable information to study different scenarios of a potential fire in a real sublevel coal mine regarding how the heat is spread in the gob and how pollutants are generated.

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Optical diagnostics of the structure and evolution of buoyant jets in a high-viscosity fluid

Optoelectronics Instrumentation and Data Processing ◽

10.3103/s8756699014050045 ◽

2014 ◽

Vol 50 (5) ◽

pp. 466-473 ◽

Cited By ~ 3

Author(s):

V. A. Arbuzov ◽

E. V. Arbuzov ◽

V. S. Berdnikov ◽

N. S. Bufetov ◽

Yu. N. Dubnishchev ◽

...

Keyword(s):

Optical Diagnostics ◽

High Viscosity ◽

Buoyant Jets ◽

Viscosity Fluid

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Numerical Calculation of Pressure Fluctuations in the Volute of a Centrifugal Fan

Journal of Fluids Engineering ◽

10.1115/1.2170121 ◽

2005 ◽

Vol 128 (2) ◽

pp. 359-369 ◽

Cited By ~ 35

Author(s):

Rafael Ballesteros-Tajadura ◽

Sandra Velarde-Suárez ◽

Juan Pablo Hurtado-Cruz ◽

Carlos Santolaria-Morros

Keyword(s):

Fluid Dynamics ◽

Pressure Fluctuations ◽

Three Dimensional ◽

Power Spectra ◽

Operating Conditions ◽

Experimental Results ◽

Time Dependent ◽

Centrifugal Fan ◽

Wall Pressure Fluctuations ◽

Good Agreement

In this work, a numerical model has been applied in order to obtain the wall pressure fluctuations at the volute of an industrial centrifugal fan. The numerical results have been compared to experimental results obtained in the same machine. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT®. This code has been employed to calculate the time-dependent pressure both in the impeller and in the volute. In this way, the pressure fluctuations in some locations over the volute wall have been obtained. The power spectra of these fluctuations have been obtained, showing an important peak at the blade passing frequency. The amplitude of this peak presents the highest values near the volute tongue, but the spatial pattern over the volute extension is different depending on the operating conditions. A good agreement has been found between the numerical and the experimental results.

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