Velocity, Temperature, and Turbulence Measurements in Air for Pipe Flow With Combined Free and Forced Convection

1973 ◽  
Vol 95 (4) ◽  
pp. 445-452 ◽  
Author(s):  
A. D. Carr ◽  
M. A. Connor ◽  
H. O. Buhr
Keyword(s):  
Heat Flux ◽  
Shear Stress ◽  
Reynolds Numbers ◽  
Viscous Sublayer ◽  
Constant Heat Flux ◽  
Experimental Results ◽  
Turbulent Shear ◽  
Low Reynolds Numbers ◽  
Turbulent Shear Stress ◽  
Free And Forced Convection

Experimental results are presented for velocity and temperature profiles and for the turbulence quantities vz′ t′ and vzt, for up-flow of air in a vertical pipe with constant heat flux at Reynolds numbers of 5000 to 14,000. The measurements show that, with increasing heat flux, superimposed free convection effects cause marked distortion of the flow structure at low Reynolds numbers, with the velocity maximum moving from the tube center to a position near the wall. The axial turbulence intensity, vz′, is depressed by increasing heat flux while the temperature intensity, t′, first decreases and then rises, with a shift in the position of the peak intensity away from the wall. On the basis of an analysis developed for heated turbulent flow, the turbulent shear stress and heat flux distributions are calculated from the experimental results. As the flow field becomes appreciably distorted on heating, it is found that the turbulent shear stress becomes very small, while the heat flux distribution suggests an increase in the width of the viscous sublayer.

Investigation of Buoyancy Effects on Heat Transfer Characteristics of Supercritical Carbon Dioxide in Heating Mode

2015 ◽  
Vol 1 (3) ◽  
Author(s):  
Sandeep R. Pidaparti ◽  
Jacob A. McFarland ◽  
Mark M. Mikhaeil ◽  
Mark H. Anderson ◽  
Devesh Ranjan
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Shear Stress ◽  
Wall Temperature ◽  
Reynolds Numbers ◽  
Turbulent Shear ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Turbulent Shear Stress ◽  
Heating Mode

Experiments were performed to investigate the effects of buoyancy on heat transfer characteristics of supercritical carbon dioxide in heating mode. Turbulent flows with Reynolds numbers up to 60,000, at operating pressures of 7.5, 8.1, and 10.2 MPa, were tested in a round tube. Local heat transfer coefficients were obtained from measured wall temperatures over a large set of experimental parameters that varied inlet temperature from 20 to 55°C, mass flux from 150 to 350  kg/m2s, and a maximum heat flux of 65  kW/m2. Horizontal, upward, and downward flows were tested to investigate the unusual heat transfer characteristics due to the effect of buoyancy and flow acceleration caused by large variation in density. In the case of upward flow, severe localized deterioration in heat transfer was observed due to reduction in the turbulent shear stress and is characterized by a sharp increase in wall temperature. In the case of downward flow, turbulent shear stress is enhanced by buoyancy forces, leading to an enhancement in heat transfer. In the case of horizontal flow, flow stratification occurred, leading to a circumferential variation in wall temperature. Thermocouples mounted 180° apart on the tube revealed that the wall temperatures on the top side are significantly higher than the bottom side of the tube. Buoyancy factor calculations for all the test cases indicated that buoyancy effects cannot be ignored even for horizontal flow at Reynolds numbers as high as 20,000. Experimentally determined Nusselt numbers are compared to existing correlations available in the literature. Existing correlations predicted the experimental data within ±30%, with maximum deviation around the pseudocritical point.

Pressure-Induced Torque in Unloaded Hybrid Bearings—A Case Study

1995 ◽  
Vol 209 (3) ◽  
pp. 183-188
Author(s):  
S E Attar ◽  
D Nicolas ◽  
V Lucas ◽  
J Frêne ◽  
V N Constantinescu
Keyword(s):  
Differential Equation ◽  
Experimental Data ◽  
Shear Stress ◽  
Reynolds Numbers ◽  
Turbulent Shear ◽  
Vertical Side ◽  
Turbulent Shear Stress ◽  
Simplified Analysis ◽  
Comparison With Experimental Data

A pressure-induced torque is emphasized in externally pressurized bearings having deep pockets, due to the pressure buildup by shaft rotation on the downstream vertical side of the recess. A standard simplified analysis is presented for both laminar and turbulent operation, with improved values for parameters kx and kx, which intervene in the pressure differential equation, as well as for the Couette turbulent shear stress; the mentioned values are valid for large Reynolds numbers. Comparison with experimental data for a water-lubricated test bearing exhibits the importance of the pressure-induced effect on the torque acting on the stationary member of the bearing.

Turbulent Transfer of Momentum and Heat in a Separated and Reattached Flow over a Blunt Flat Plate

1980 ◽  
Vol 102 (4) ◽  
pp. 749-754 ◽  
Author(s):  
Terukazu Ota ◽  
Nobuhiko Kon
Keyword(s):  
Heat Flux ◽  
Shear Stress ◽  
Flat Plate ◽  
Finite Thickness ◽  
Leading Edge ◽  
Turbulent Heat Flux ◽  
Turbulent Shear ◽  
Turbulent Heat ◽  
Turbulent Shear Stress ◽  
Separated And Reattached Flow

Turbulent shear stress and heat flux were measured with a hot-wire anemometer in the separated, reattached, and redeveloped regions of a two-dimensional incompressible air flow over a flat plate of finite thickness having blunt leading edge. The characteristic features of the turbulent heat flux are found to be nearly equal to those of the turbulent shear stress in the separated and reattached flow regions. However, in the turbulent boundary layer downstream from the reattachment point, the development of turbulent heat flux appears to be much quicker than that of turbulent shear stress. Eddy diffusivities of momentum and heat are evaluated and then the turbulent Prandtl number is estimated in the thermal layer downstream of reattachment. These results are compared with the available previous data.

Impact of fluid turbulent shear stress on failure surface of reservoir bank landslide

2018 ◽  
Vol 11 (22) ◽  
Author(s):  
Xuan Zhang ◽  
Liang Chen ◽  
Faming Zhang ◽  
Chengteng Lv ◽  
Yi feng Zhou
Keyword(s):  
Shear Stress ◽  
Failure Surface ◽  
Turbulent Shear ◽  
Turbulent Shear Stress

Contribution towards a Reynolds-stress closure for low-Reynolds-number turbulence

1976 ◽  
Vol 74 (4) ◽  
pp. 593-610 ◽  
Author(s):  
K. Hanjalić ◽  
B. E. Launder
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Reynolds Stress ◽  
Dissipation Rate ◽  
Numerical Solutions ◽  
Low Reynolds Number ◽  
Transport Processes ◽  
Turbulent Shear ◽  
Turbulent Shear Stress ◽  
Low Reynolds

The problem of closing the Reynolds-stress and dissipation-rate equations at low Reynolds numbers is considered, specific forms being suggested for the direct effects of viscosity on the various transport processes. By noting that the correlation coefficient$\overline{uv^2}/\overline{u^2}\overline{v^2} $is nearly constant over a considerable portion of the low-Reynolds-number region adjacent to a wall the closure is simplified to one requiring the solution of approximated transport equations for only the turbulent shear stress, the turbulent kinetic energy and the energy dissipation rate. Numerical solutions are presented for turbulent channel flow and sink flows at low Reynolds number as well as a case of a severely accelerated boundary layer in which the turbulent shear stress becomes negligible compared with the viscous stresses. Agreement with experiment is generally encouraging.

Conditional Sampling in a Transitional Boundary Layer Under High Freestream Turbulence Conditions

2003 ◽  
Vol 125 (1) ◽  
pp. 28-37 ◽  
Author(s):  
Ralph J. Volino ◽  
Michael P. Schultz ◽  
Christopher M. Pratt
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Streamwise Velocity ◽  
Turbulent Shear ◽  
Conditional Sampling ◽  
Freestream Turbulence ◽  
Mean Velocity ◽  
Transitional Boundary Layer ◽  
Turbulent Shear Stress ◽  
Order Of Magnitude

Conditional sampling has been performed on data from a transitional boundary layer subject to high (initially 9%) freestream turbulence and strong (K=ν/U∞2dU∞/dx as high as 9×10−6) acceleration. Methods for separating the turbulent and nonturbulent zone data based on the instantaneous streamwise velocity and the turbulent shear stress were tested and found to agree. Mean velocity profiles were clearly different in the turbulent and nonturbulent zones, and skin friction coefficients were as much as 70% higher in the turbulent zone. The streamwise fluctuating velocity, in contrast, was only about 10% higher in the turbulent zone. Turbulent shear stress differed by an order of magnitude, and eddy viscosity was three to four times higher in the turbulent zone. Eddy transport in the nonturbulent zone was still significant, however, and the nonturbulent zone did not behave like a laminar boundary layer. Within each of the two zones there was considerable self-similarity from the beginning to the end of transition. This may prove useful for future modeling efforts.

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