Heat and momentum transfer in the wall region of a cylindrical vessel mixed by a turbine impeller

1979 ◽  
Vol 44 (3) ◽  
pp. 684-699 ◽  
Author(s):  
Ivan Fořt ◽  
Jiří Placek ◽  
Frederyk Strek ◽  
Zdislaw Jaworski ◽  
Joana Karcz
Keyword(s):  
Momentum Transfer ◽  
Cylindrical Vessel ◽  
Temperature Fields ◽  
Wall Region ◽  
Turbulent Heat ◽  
Turbulent Regime ◽  
Region Flow ◽  
Velocity And Temperature Fields ◽  
Heat And Momentum Transfer ◽  
Turbine Impeller

Velocity and temperature fields have been described in the wall region of a cylindrical vessel equipped with radial baffles mixed by a standard six-blade disc turbine impeller under the turbulent regime of the flow in a homogeneous Newtonian charge. The results of experiments offer conclusions regarding the mechanism of the turbulent flow in individual subregions of the wall region together with the method of description of the flow in these regions as a sequence of impinging wall turbulent streams. Based on the theory of analogy the results on the turbulent heat and momentum transfer have been compared and confirm validity of the Chilton-Colburn analogy in which the characteristic quantities for the calculation of the local friction factor are parameters of the wall region flow - the characteristic velocity and the characteristic thickness of the wall region.

Structure of Turbulent Velocity and Temperature Fluctuations in Fully Developed Pipe Flow

1979 ◽  
Vol 101 (1) ◽  
pp. 15-22 ◽  
Author(s):  
M. Hishida ◽  
Y. Nagano
Keyword(s):  
Pipe Flow ◽  
Dominant Role ◽  
Temperature Fluctuations ◽  
Temperature Fields ◽  
Inertial Subrange ◽  
Wall Region ◽  
Turbulent Heat ◽  
Temperature Spectrum ◽  
Axial Heat ◽  
Heat Transport Process

An experimental investigation of the turbulent structure of velocity and temperature fields has been made in fully developed pipe flow of air. In the near-wall region, the coherent quasi-ordered structure plays a dominant role in the turbulent heat transport process. The turbulent axial heat flux as well as the intensities of velocity and temperature fluctuations reach their maximums in this region, but these maximum points are different. The nondimensional intensities of velocity and temperature fluctuations are well described with the “logarithmic law” in the turbulent part of the wall region where the velocity-temperature cross-correlation coefficient is nearly constant. In the turbulent core, the velocity and temperature fluctuations are less correlated. The spectra of velocity and temperature fluctuations present −1 slope at low wavenumbers in the wall region and −5/3 slope in the inertial subrange. The temperature spectrum for the inertial-diffusive subrange indicates the −8/3 power-law.

scholarly journals Bolgiano scale in confined Rayleigh–Taylor turbulence

2011 ◽  
Vol 690 ◽  
pp. 426-440 ◽  
Author(s):  
G. Boffetta ◽  
F. De Lillo ◽  
A. Mazzino ◽  
S. Musacchio
Keyword(s):  
Turbulent Mixing ◽  
Mixing Layer ◽  
Three Dimensional ◽  
Convective Cell ◽  
Temperature Fields ◽  
Turbulent Regime ◽  
Geometrical Constraint ◽  
Scaling Properties ◽  
Turbulent Mixing Layer ◽  
Velocity And Temperature Fields

AbstractWe investigate the statistical properties of Rayleigh–Taylor turbulence in a three-dimensional convective cell of high aspect ratio, in which one transverse side is much smaller that the others. By means of high-resolution numerical simulation we study the development of the turbulent mixing layer and the scaling properties of the velocity and temperature fields. We show that the system undergoes a transition from a three- to two-dimensional turbulent regime when the width of the turbulent mixing layer becomes larger than the scale of confinement. In the late stage of the evolution the convective flow is characterized by the coexistence of Kolmogorov–Obukhov and Bolgiano–Obukhov scaling at small and large scales, respectively. These regimes are separated by the Bolgiano scale, which is determined by the scale of confinement of the flow. Our results show that the emergence of the Bolgiano–Obukhov scaling in Rayleigh–Taylor turbulence is connected to the onset of an upscale energy transfer induced by the geometrical constraint of the flow.

Spectral measurements of turbulent momentum transfer in fully developed pipe flow

1973 ◽  
Vol 61 (1) ◽  
pp. 173-186 ◽  
Author(s):  
K. Bremhorst ◽  
T. B. Walker
Keyword(s):  
Momentum Transfer ◽  
Pipe Flow ◽  
Negative Transfer ◽  
Turbulent Heat Transfer ◽  
Wall Region ◽  
Turbulent Heat ◽  
Spectral Measurements ◽  
Transfer Processes ◽  
Spectral Components ◽  
Turbulent Momentum

Measurements of the spectral components of turbulent momentum transfer for fully developed pipe flow are presented. The results indicate that near the wall (y+ < 15) two types of momentum transfer processes occur. A net positive transfer takes place in the higher frequency range of the energy-containing part of the turbulence spectrum whereas a net negative transfer returns low momentum to the wall region at the lower end of the spectrum. Examination of the turbulence at various y+ shows that the significant features of the turbulence spectra scale on frequency at any given Reynolds number, thus leading to an interpretation of the flow structure which is consistent with the hydrogen-bubble visualization data of Runstadler, Kline & Reynolds (1963). The results are consistent with a flow model in which disturbances extend from the sublayer to the core of the flow. Recent turbulent heat transfer measurements are also interpreted successfully by this model.

scholarly journals Power Input of High-Speed Rotary Impellers

10.14311/280 ◽  
2001 ◽  
Vol 41 (6) ◽  
Author(s):  
K. R. Beshay ◽  
J. Kratěna ◽  
I. Fořt ◽  
O. Brůha
Keyword(s):  
Pitch Angle ◽  
High Speed ◽  
Power Input ◽  
Cylindrical Vessel ◽  
Turbulent Regime ◽  
Power Dependence ◽  
Rushton Turbine ◽  
Weak Influence ◽  
Turbine Impeller ◽  
Blade Pitch Angle

This paper presents the results of an experimental investigation of the power input of pitched blade impellers and standard Rushton turbine impellers in a cylindrical vessel provided with four radial baffles at its wall under a turbulent regime of flow of an agitated liquid. The influence of the geometry of the pitched blade impellers (pitch angle, number of blades) and the off-bottom impeller clearance of both high-speed impellers tested on the impeller power input is determined in two sizes of the cylindrical vessel (0.3 m and 0.8 m diameter of vessel). A strain gauge torquemeter is used in the small vessel and a phase shift mechanical torquemeter is used in the large vessel. All results of the experiments correspond to the condition that the Reynolds number modified for the impeller exceeds ten thousand. The results of this study show that the significant influence of the separating disk thickness of the turbine impeller corresponds fairly well to the empirical equations presented in the literature. Both the influence of the number of impeller blades and the blade pitch angle of the pitched blade impeller were expressed quantitatively by means of the power dependence of the recently published correlations: the higher the pitch angle and the number of blades, the higher the values of the impeller power input. Finally, it follows from results of this study that the impeller off-bottom clearance has a weak influence on the power input of the Rushton turbine impeller, but with decreasing impeller off-bottom clearance the power input of the pitched blade impeller increases significantly.

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