Turbulent free convection above a heated plate inclined at a small angle to the horizontal

1963 ◽  
Vol 16 (2) ◽  
pp. 282-312 ◽  
Author(s):  
D. J. Tritton
Keyword(s):  
Temperature Field ◽  
Velocity Field ◽  
Small Angle ◽  
Large Scale ◽  
Temperature Fluctuations ◽  
Platinum Resistance ◽  
Heated Plate ◽  
Lower Edge ◽  
Mean Temperature ◽  
The Mean

An investigation has been made of the structure of the motion above a heated plate inclined at a small angle (about 10°) to the horizontal. The turbulence is considered in terms of the similarities to and differences from the motion above an exactly horizontal surface. One effect of inclination is, of course, that there is also a mean motion.Accurate data on the mean temperature field and the intensity of the temperature fluctuations have been obtained with platinum resistance thermometers, the signals being processed electronically. More approximate information on the velocity field has been obtained with quartz fibre anemometers. These results have been supplemented qualitatively by simultaneous observations of the temperature and velocity fluctuations and also by smoke experiments.The principal features of the flow inferred from these observations are as follows. The heat transfer and the mean temperature field are not much altered by the inclination, though small, not very systematic, variations may result from the complexities of the velocity field. This supports the view that the mean temperature field is largely governed by the large-scale motions. The temperature fluctuations show a systematic variation with distance from the lower edge and resemble those above a horizontal plate when this distance is large. The largescale motions of the turbulence start close to the lower edge, but the smaller eddies do not attain full intensity until the air has moved some distance up the plate. The mean velocity receives a sizable contribution from a ‘through-flow’ between the side-walls. Superimposed on this are developments that show that the momentum transfer processes are complex and certainly not capable of representation by any simple theory such as an eddy viscosity. On the lower part of the plate there is surprisingly large acceleration, but further up the mixing action of the small eddies has a decelerating effect.

scholarly journals Stochastic analysis of field-scale heat advection in heterogeneous aquifers

2012 ◽  
Vol 16 (3) ◽  
pp. 641-648 ◽  
Author(s):  
C.-M. Chang ◽  
H.-D. Yeh
Keyword(s):  
Temperature Field ◽  
Heat Transport ◽  
Stochastic Analysis ◽  
Transport Model ◽  
Field Scale ◽  
Heat Advection ◽  
Rate Of Growth ◽  
Second Moments ◽  
Mean Temperature ◽  
The Mean

Abstract. Owing to the analogy between the solute and heat transport processes, it can be expected that the rate of growth of the spatial second moments of the heat flux in a heterogeneous aquifer over relatively large space scales is greater than that predicted by applying the classical heat transport model. The motivation of stochastic analysis of heat transport at the field scale is therefore to quantify the enhanced growth of the field-scale second moments caused by the spatially varying specific discharge field. Within the framework of stochastic theory, an effective advection-dispersion equation containing effective parameters (namely, the macrodispersion coefficients) is developed to model the mean temperature field. The rate of growth of the field-scale spatial second moments of the mean temperature field in the principal coordinate directions is described by the macrodispersion coefficient. The variance of the temperature field is also developed to characterize the reliability to be anticipated in applying the mean heat transport model. It is found that the heterogeneity of the medium and the correlation length of the log hydraulic conductivity are important in enhancing the field-scale heat advection, while the effective thermal conductivity plays the role in reducing the field-scale heat advection.

Heat transfer in a periodic boundary layer near a two-dimensional stagnation point

1972 ◽  
Vol 56 (4) ◽  
pp. 619-627 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Temperature Field ◽  
Velocity Field ◽  
Stagnation Point ◽  
High Frequency ◽  
High Frequency Oscillation ◽  
Main Stream ◽  
Two Dimensional ◽  
Mean Temperature

Following the previous velocity-field study (Ishigaki 1970), this paper studies how the temperature field in the laminar boundary layer near a two-dimensional stagnation point responds to the main-stream oscillation. The time-mean temperature field is of particular interest and is studied in detail. The velocity field is treated as known and is taken from the previous paper. In § 3 the solutions over the whole frequency range are obtained under the assumption of small amplitude oscillation and the results are compared with the existing approximate solutions for low and high frequency in terms of heat transfer. Time-mean heat transfer decreases at low frequency, but slightly increases at high frequency. Two factors that cause time-mean modification of the temperature field are examined quantitatively. In § 4 the finite amplitude case is treated under the assumption of high-frequency oscillation and a few examples of the time-mean temperature profile are shown.

scholarly journals Rossby Waves and the Interannual and Interdecadal Variability of Temperature and Salinity off California

2009 ◽  
Vol 39 (10) ◽  
pp. 2543-2561 ◽  
Author(s):  
Marcelo Dottori ◽  
Allan J. Clarke
Keyword(s):  
Sea Level ◽  
Rossby Wave ◽  
Large Scale ◽  
Southern California ◽  
Rossby Waves ◽  
Salinity Gradient ◽  
Time Derivative ◽  
Temperature Fluctuations ◽  
Dynamic Height ◽  
The Mean

Abstract Previous work has shown that large-scale interannual Rossby waves, largely remotely generated by equatorial winds, propagate westward from the coast off southern California. These waves have a large-scale anomalous alongshore velocity field that is proportional to the time derivative of the interannual sea level anomaly. Using these results, a theory is developed for interannual perturbations to a mean density field that varies both vertically and alongshore, like that for the California Current region off southern California. Because both the anomalous vertical and alongshore currents are proportional to the time derivative of the interannual sea level, the theory suggests that the anomalous currents associated with the Rossby waves, acting on the mean temperature field, should induce temperature fluctuations proportional to the anomalous dynamic height. The alongshore and vertical advections contribute to the temperature fluctuations in the same sense, a higher-than-normal sea level, for example, resulting in downward and poleward displacement of warmer water and a local higher-than-normal temperature. Near the surface, alongshore advection dominates vertical advection but both contribute comparably near the thermocline and below. The correlation of observed temperature and dynamic height anomalies from the California Cooperative Oceanic Fisheries Investigation (CalCOFI) data is positive, which is consistent with the theory. The correlation is highest (r ≈ 0.8) near 100-m depth in the thermocline. Although the correlation falls toward the surface, it is still between 0.5 and 0.6, suggesting that the advection mechanism is a major contributor to the temperature anomalies there. The anomalous Rossby wave currents, acting on the mean background salinity gradient, also induce salinity anomalies. At halocline depths of 100–200 m, consistent with the theory, the correlation of observed CalCOFI salinity and dynamic height anomalies is negative and large in magnitude (r ≈ −0.8). However, the surface salinity anomaly is not due to Rossby wave dynamics; instead, much of it is driven by the alongshore wind stress, which it lags by 4 months.

Passive Scalar Turbulent Channel Flow at Pr=25: DNS-LES Approach

2007 ◽  
Author(s):  
Iztok Tiselj ◽  
Luka Sˇtrubelj
Keyword(s):  
Heat Transfer ◽  
Velocity Field ◽  
Buffer Layer ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Passive Scalar ◽  
Temperature Profiles ◽  
Temperature Scales ◽  
Mean Temperature ◽  
The Mean

DNS-LES numerical simulations of a passive scalar field in the turbulent channel flow were performed at friction Reynolds number Re_Tau = 180 and Prandtl number Pr = 25. Direct numerical simulation is used for description of the velocity field. Temperature field is described with LES-like approach with the smallest resolved temperature scales equal to the smallest scales of the velocity field. The consistency of the applied physical modelling and pseudo-spectral scheme is tested with the grid refinement study (grid refine ∼3 times in each direction) and with comparison of the results with the existing DNS simulations of Schwertfirm and Manhart (2006) at the same conditions. The comparison shows that the proposed approach produces very accurate mean temperature profiles, heat transfer coefficients and other low-order moments of the turbulent thermal field. It is shown that the mean temperature profiles near the wall can be accurately predicted even when the temperature scales between the Batchelor and Kolmogorov scale are not resolved. The key to the success of the proposed approach lies in the fact that the large-scale structures govern the turbulent heat transfer at high Prandtl numbers, while the role of the sub-Kolmogorov temperature scales in the diffusive sublayer and the thermal buffer layer (y+<5) is practically negligible. The contribution of the sub-Kolmogorov thermal scales becomes relevant above the thermal buffer layer (y+>5), where the unresolved temperature scales affect spectra and RMS temperature fluctuations, but not the log-law shape of the mean temperature profile and the mean heat transfer coefficient.

scholarly journals Prediction and Measurement of Mass, Heat, and Momentum Transport in a Nonreacting Turbulent Flow of a Jet in an Opposing Stream

1981 ◽  
Vol 103 (1) ◽  
pp. 127-132 ◽  
Author(s):  
S. E. Elghobashi ◽  
G. S. Samuelsen ◽  
J. E. Wuerer ◽  
J. C. LaRue
Keyword(s):  
Velocity Field ◽  
Kinetic Energy ◽  
Turbulent Diffusion ◽  
Dissipation Rate ◽  
Temperature Fluctuations ◽  
Scalar Fields ◽  
Momentum Transport ◽  
Mean Square ◽  
Mean Flow ◽  
The Mean

The paper addresses the measurement and prediction of heat, mass, and momentum transport in a confined axisymmetric turbulent nonreacting flow of a jet in an opposing stream. The predictions are obtained by solving numerically the conservation equations of the mean flow and the transport equations of the kinetic energy of turbulence and its dissipation rate and the mean square temperature fluctuations. The predicted velocity field is in agreement with the experiment, but the predicted scalar fields point to the need of examining the employed model of a scalar turbulent diffusion.

scholarly journals Stochastic analysis of field-scale heat advection in heterogeneous aquifers

2011 ◽  
Vol 8 (6) ◽  
pp. 10311-10331
Author(s):  
C.-M. Chang ◽  
H.-D. Yeh
Keyword(s):  
Temperature Field ◽  
Heat Transport ◽  
Stochastic Analysis ◽  
Transport Model ◽  
Field Scale ◽  
Heat Advection ◽  
Rate Of Growth ◽  
Second Moments ◽  
Mean Temperature ◽  
The Mean

Abstract. Owing to the analogy between the solute and heat transport processes, it can be expected that the rate of growth of the spatial second moments of the heat flux in a heterogeneous aquifer over relatively large space scales is greater than that predicted by applying the classical heat transport model. The motivation of stochastic analysis of heat transport at the field scale is therefore to quantify the enhanced growth of the field-scale second moments caused by the spatially varying specific discharge field. Within the framework of stochastic theory, an effective advection-dispersion equation containing effective parameters (namely, the macrodispersion coefficients) is developed to model the mean temperature field. The rate of growth of the field-scale spatial second moments of the mean temperature field in the principal coordinate directions is described by the macrodispersion coefficient. The variance of the temperature field is also developed to characterize the reliability to be anticipated in applying the mean heat transport model. It is found that the heterogeneity of the medium and the correlation length of the log hydraulic conductivity are important in enhancing the field-scale heat advection, while the effective thermal conductivity plays the role in reducing the field-scale heat advection.

scholarly journals Temperature spectrum of the solar wind turbulence

2020 ◽  
pp. 227-231
Author(s):  
G. Gogoberidze ◽  
G. Machabeli ◽  
Yu. Voitenko
Keyword(s):  
Solar Wind ◽  
Temperature Fluctuations ◽  
High Amplitude ◽  
Magnetic Fluctuations ◽  
Thermal Velocity ◽  
Temperature Spectrum ◽  
Apparent Contradiction ◽  
Mean Temperature ◽  
Temperature Spectra ◽  
The Mean

We show that there exists apparent contradiction between the temperature spectra derived from the Spektr-R data and the temperature spectra predicted theoretically. We show that the temperature fluctuations can be correctly estimated from the Spektr-R data only if the mean temperature is isotropic. Since the mean temperature in the solar wind is usually anisotropic, the derived fluctuations appear to be pseudo-temperature rather than temperature. These pseudo-temperature fluctuations are driven by the high-amplitude magnetic fluctuations in Alfvén waves rather than the fluctuations of temperature or thermal velocity.

Experimental Study on Convective Heat Transfer for Turbulent Flow in a Square Duct With a Ribbed Rough Wall (Characteristics of Mean Temperature Field)

1994 ◽  
Vol 116 (2) ◽  
pp. 332-340 ◽  
Author(s):  
M. Hirota ◽  
H. Fujita ◽  
H. Yokosawa
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Turbulent Flow ◽  
Cross Section ◽  
Rough Wall ◽  
Turbulent Shear ◽  
Turbulent Heat ◽  
Square Duct ◽  
Mean Temperature ◽  
The Mean

This paper presents experimental results concerning a time-mean temperature field obtained in forced convection heat transfer for a turbulent flow through a square duct with a ribbed rough bottom wall. The secondary flow pattern in the duct is reflected in the distribution of the local Nusselt number, the values of which on the smooth walls of the rough duct are 1.71~1.97 times those of the smooth duct. In the upper half cross section near the upper smooth wall opposite the bottom ribbed rough wall, the profile of the mean temperature distribution is similar to that of the primary flow velocity distribution, and the validity of the temperature inner law was confirmed. However, in the lower half cross section near the bottom ribbed rough wall, the dissimilarity between the mean velocity and the mean temperature fields becomes pronounced, and the inner law is not valid for mean temperature distributions. The mechanism of the heat transfer near the ribbed rough wall was examined based on the transport equations of turbulent shear stress and turbulent heat flux.

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