Incompressible Turbulent Flow in a Permeable-Walled Duct

1972 ◽  
Vol 94 (2) ◽  
pp. 314-319 ◽  
Author(s):  
E. M. Sparrow ◽  
V. K. Jonsson ◽  
G. S. Beavers ◽  
R. G. Owen
Keyword(s):  
Turbulent Flow ◽  
Turbulent Transport ◽  
Maximum Velocity ◽  
Porous Wall ◽  
Velocity Slip ◽  
Transport Processes ◽  
Porous Surface ◽  
Damping Factor ◽  
Wide Range ◽  
Fully Developed Turbulent Flow

An analysis is made of fully developed turbulent flow in a parallel-plate channel having one porous bounding wall. A velocity slip model is employed to characterize the boundary condition at the porous surface. The turbulent transport processes in the channel are represented via the Prandtl mixing length concept in conjunction with a modified form of the Van Driest damping factor. Numerical results are obtained for Reynolds numbers ranging from 5000 to 200,000 and for a wide range of values of a dimensionless slip grouping. The results show that velocity slip at the porous surface brings about a reduction in the friction factor, the extent of the reduction being accentuated with increasing Reynolds number. The velocity slip also causes a skewing of the velocity profiles, such that the location of the maximum velocity is shifted toward the porous wall.

An Analysis of Heat Transfer for Fully Developed Turbulent Flow in Concentric Annuli

1968 ◽  
Vol 90 (1) ◽  
pp. 43-50 ◽  
Author(s):  
N. W. Wilson ◽  
J. O. Medwell
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Maximum Velocity ◽  
Dimensionless Form ◽  
Temperature Distributions ◽  
Wide Range ◽  
Fully Developed Turbulent Flow ◽  
Heat And Momentum Transfer

The heat and momentum transfer analogy is employed to analyze the heat transfer phenomena for turbulent flow in concentric annuli. A modification of the velocity distribution due to Van Driest is assumed and equations in dimensionless form are developed to predict: (a) the position of maximum velocity in the annulus; (b) the friction factor-Reynolds number relationship, and (c) temperature distributions and heat transfer relations over a wide range of Reynolds number and Prandtl modulus.

Numerical Prediction of Turbulent Flow in Rotating Cavities

1988 ◽  
Vol 110 (2) ◽  
pp. 202-211 ◽  
Author(s):  
A. P. Morse
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Predictive Accuracy ◽  
Turbulent Transport ◽  
Reynolds Numbers ◽  
Spreading Rate ◽  
Flow Conditions ◽  
Wide Range ◽  
Ekman Layers ◽  
Radial Outflow

Predictions of the isothermal, incompressible flow in the cavity formed between two corotating plane disks and a peripheral shroud have been obtained using an elliptic calculation procedure and a low turbulence Reynolds number k–ε model for the estimation of turbulent transport. Both radial inflow and outflow are investigated for a wide range of flow conditions involving rotational Reynolds numbers up to ∼106. Although predictive accuracy is generally good, the computed flow in the Ekman layers for radial outflow often displays a retarded spreading rate and a tendency to laminarize under conditions that are known from experiment to produce turbulent flow.

Theoretical Distributions of Heat Transfer Downstream of a Backstep in Supersonic Turbulent Flow

1972 ◽  
Vol 94 (1) ◽  
pp. 87-94 ◽  
Author(s):  
J. P. Lamb ◽  
C. G. Hood
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Turbulent Flow ◽  
Wall Temperature ◽  
Control Volume ◽  
Convective Transport ◽  
Transport Processes ◽  
Independent Variables ◽  
Test Conditions ◽  
Wide Range

A physically perceptive model is presented for the flow field and convective transport processes in the vicinity of reattachment of a planar, supersonic, turbulent flow. Control volume methods are utilized extensively in the analysis and the restating integral equations are solved by various numerical search techniques. The analysis enables one to determine significant parameters in the flow field as well as the heat transfer distribution and associated wall temperature of the reattachment surface. Also presented is a general correlation of predicted results for the convection process in terms of pertinent independent variables. The correlated results are shown to agree with measurements for a wide range of test conditions.

Turbulent flow in smooth concentric annuli with small radius ratios

1974 ◽  
Vol 64 (2) ◽  
pp. 263-288 ◽  
Author(s):  
K. Rehme
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Turbulent Flow ◽  
Strong Influence ◽  
Maximum Velocity ◽  
Small Radius ◽  
Stress Distributions ◽  
Number Range ◽  
Fully Developed Turbulent Flow ◽  
Flow Through

Fully developed turbulent flow through three concentric annuli was investigated experimentally for a Reynolds-number rangeRe= 2 × 104−2 × 105. Measurements were made of the pressure drop, the positions of zero shear stress and maximum velocity, and the velocity distribution in annuli of radius ratios α = 0.02, 0.04 and 0.1, respectively. The results for the key problem in the flow through annuli, the position of zero shear stress, showed that this position is not coincident with the position of maximum velocity. Furthermore, the investigation showed the strong influence of spacers on the velocity and shear-stress distributions. The numerous theoretical and experimental results in the literature which are based on the coincidence of the positions of zero shear stress and maximum velocity are not in agreement with reality.

scholarly journals Development of mathematical model for co-firing pulverized coal and biomass in experimental furnace

2018 ◽  
Vol 22 (1 Part B) ◽  
pp. 709-719 ◽  
Author(s):  
Aleksandar Milicevic ◽  
Srdjan Belosevic ◽  
Ivan Tomanovic ◽  
Nenad Crnomarkovic ◽  
Dragan Tucakovic
Keyword(s):  
Mathematical Model ◽  
Turbulent Transport ◽  
Combustion Process ◽  
Computer Code ◽  
Transport Processes ◽  
Pulverized Coal ◽  
Combustion Model ◽  
Two Phase ◽  
Processes And Reactions ◽  
Wide Range

A comprehensive mathematical model for prediction of turbulent transport processes and reactions during co-combustion of pulverized fuels in furnace fired by 150 kW swirl stabilized-burner has been developed. Numerical simulations have been carried out by using an in-house developed computer code, with Euler-Lagrangian approach to the two-phase flow modelling and sub-models for individual phases during complex combustion process: evaporation, devolatilization, combustion of volatiles, and char combustion. For sub-model of coal devolatilization the approach of Merrick is adopted, while for biomass devolatilization the combination models of Merrick, and of Xu and Tomita are selected. Products of devolatilization of both the pulverized coal and biomass are considered to contain the primary gaseous volatiles and tar, which further decomposes to secondary gaseous volatiles and residual soot. The residual soot in tar and carbon in coal and biomass char are oxidized directly, with ash remaining. For volatiles combustion the finite rate/eddy break-up model is chosen, while for char oxidation the combined kinetic-diffusion model is used. The comprehensive combustion model is validated against available experimental data from the case-study cylindrical furnace. The agreement of the simulations with the data for the main species in the furnace is quite good, while some discrepancies from experimental values are found in the core zone. The presented model is a good basis for further research of co-combustion processes and is able to provide analysis of wide range of pulverized fuels, i. e. coal and biomass. At the same time, the model is relatively simple numerical tool for effective and practical use.

Effect of Wetting on Friction Factors for Turbulent Flow of Mercury in Annuli

1976 ◽  
Vol 98 (1) ◽  
pp. 113-116 ◽  
Author(s):  
O. E. Dwyer ◽  
P. J. Hlavac ◽  
B. G. Nimmo
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Maximum Velocity ◽  
Outer Wall ◽  
Limited Range ◽  
Friction Factors ◽  
Fully Developed Turbulent Flow

Friction factors were determined for fully developed turbulent flow of mercury in smooth concentric annuli under conditions where either both walls were unwetted, or both were wetted, or the inner wall was wetted and the outer one unwetted. Three radius ratios (r2/r1) were used, i.e., 2.09, 2.78, and 4.00. Unwetted walls gave the lowest friction factors, which were practically independent of the r2/r1 ratio over the limited range tested. The factors were 10 ± 1 percent higher than the commonly accepted values for smooth pipes (at the same Reynolds number). The highest friction factors were obtained with the inner wall wetted and the outer wall unwetted, and the greater the r2/r1 ratio the greater was the effect. For example, at r2/r1 = 4.00, the friction factors were 9.9% greater than for the situation when both walls were unwetted. The wetting conditions affected the location of the radius of maximum velocity (rm); and it was found that the nearer rm approached r2, the higher was the friction factor.

Prediction of Recirculating, Swirling, Turbulent Flow in Rotating Disc Systems

1976 ◽  
Vol 18 (3) ◽  
pp. 142-148 ◽  
Author(s):  
A. D. Gosman ◽  
F. C. Lockwood ◽  
J. N. Loughhead
Keyword(s):  
Experimental Data ◽  
Finite Difference ◽  
Turbulent Flow ◽  
Turbulent Transport ◽  
Transport Processes ◽  
Two Dimensional ◽  
Rotating Disc ◽  
Rigorous Testing ◽  
Source Flow ◽  
Good Agreement

Predictions were made of the swirling, recirculating, turbulent flow between a rotating and a stationary shrouded disc with an axial source flow. A two-dimensional finite-difference procedure was used. Turbulent transport processes were calculated with the aid of a turbulence model involving the solution of two differential equations. Comparison of predicted disc torque with experimental data showed good agreement. Details of the predicted flow between the discs are presented and shown to be plausible; they also highlight the need for detailed hydrodynamic measurements in these types of flows to aid more rigorous testing of the method.

Radial Distributions of Temporal-Mean Peripheral Velocity and Pressure for Fully Developed Turbulent Flow in Curved Channels

1960 ◽  
Vol 82 (3) ◽  
pp. 528-536 ◽  
Author(s):  
A. W. Marris
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Rectangular Cross Section ◽  
Width Ratio ◽  
Curved Channels ◽  
Peripheral Velocity ◽  
Wide Range ◽  
Fully Developed Turbulent Flow ◽  
The Mean ◽  
Moving Fluid

Experimental results are presented for the radial distributions of pressure and peripheral velocity for the turbulent flow of water in two closed curved channels of rectangular cross section and large depth-to-width ratio. The traverses were taken at the equatorial section of the channel and sufficiently far around the curve for the effect of curvature on the mean motion to be fully established. The two channels employed had widely differing mean-radius-to-width ratios n. The data obtained for a wide range of flow rates in the channel with a larger n indicated that Reynolds similarity existed between the flows in this channel. These data are compared with the pressure and velocity profiles predicted by potential flow theory and with a semiempirical logarithmic velocity distribution. Results obtained for the channel with smaller n showed that at above a certain Reynolds number an anomaly occurred in the flow, manifesting itself as an unstable “belt” of faster moving fluid, which moved outward from the inner wall as the Reynolds number was increased. This effect, considered to be the consequence of upstream stall, was accompanied by an adverse longitudinal-pressure gradient at the inner wall of the channel. It appeared to be eliminated by the insertion of an upstream splitter vane.

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