Some experiments on the secondary flow in pipe bends

1956 ◽  
Vol 234 (1198) ◽  
pp. 335-346 ◽  
Keyword(s):  
Differential Equation ◽  
Secondary Flow ◽  
Air Flow ◽  
Experimental Results ◽  
Radius Of Curvature ◽  
General Behaviour ◽  
Sine Curve ◽  
Uniform Velocity ◽  
Non Linear ◽  
Flow Through

Secondary vorticity in the direction of flow is developed after fluid with a non-uniform velocity passes through a bend. The secondary flow may be increased or decreased by reversal of the radius of curvature of the bend, depending on the location of the reversal. The general behaviour of the secondary flow in a bend in which the radius of curvature is repeatedly reversed is analyzed by assuming the centre line of the bend is a sine curve. The resulting differential equation describing the flow is non-linear, and a variety of solutions are obtained for different entry conditions. These solutions are compared with experimental results obtained from observations of the air flow through various configurations of pipe.

scholarly journals CFD study on the effects of boundary conditions on air flow through an air-cooled condenser

2018 ◽  
Vol 180 ◽  
pp. 02103
Author(s):  
Zdeněk Sumara ◽  
Michal Šochman
Keyword(s):  
Velocity Field ◽  
Boundary Conditions ◽  
Air Flow ◽  
Virtual Model ◽  
Numerical Schemes ◽  
Rans Equations ◽  
Uniform Velocity ◽  
Flow Through ◽  
Air Flows ◽  
Turbulent Models

This study focuses on the effects of boundary conditions on effectiveness of an air-cooled condenser (ACC). Heat duty of ACC is very often calculated for ideal uniform velocity field which does not correspond to reality. Therefore, this study studies the effect of wind and different landscapes on air flow through ACC. For this study software OpenFOAM was used and the flow was simulated with the use of RANS equations. For verification of numerical setup a model of one ACC cell with dimensions of platform 1.5×1.5 [m] was used. In this experiment static pressures behind fan and air flows through a model of surface of condenser for different rpm of fan were measured. In OpenFOAM software a virtual clone of this experiment was built and different meshes, turbulent models and numerical schemes were tested. After tuning up numerical setup virtual model of real ACC system was built. Influence of wind, landscape and height of ACC on air flow through ACC has been investigated.

3D CFD Investigation of Air Flow Behind a Porous Fence Using Different Turbulence Models

2014 ◽  
Author(s):  
Yizhong Xu ◽  
Mohamad Y. Mustafa ◽  
Geanette Polanco
Keyword(s):  
Velocity Profile ◽  
Turbulence Model ◽  
Air Flow ◽  
Turbulence Models ◽  
Experimental Results ◽  
Turbulence Structure ◽  
Cfd Modelling ◽  
Lack Of Information ◽  
Vertical Velocity Profile ◽  
Flow Through

Even after many years of the application of numerical CFD techniques to flow through porous fences, still there is disagreement between researchers regarding the best turbulence model to be implemented in this field. Moreover, different sources claim to have achieved good agreement between numerical results and experimental data; however, it is not always possible to compare numerical and experimental results due to the lack of information or variations in test conditions. In this paper, five different turbulence models namely; K-ε models (standard, RNG and Realizable) and K-ω models (Standard and SST), have been applied through a 3D CFD model to investigate air flow behind a porous panel, under the same conditions (boundary conditions and numerical schemes). Results are compared with wind tunnel experiments. Comparison is based on the vertical velocity profile at a location 925 mm downstream of the fence along its center line. All models were capable of reproducing the velocity profile, however, some turbulence models over-predicted the reduction of velocity while it was under-predicted by other models, however, discrepancy between CFD modelling and experimental results was kept around 20%. Comprehensive description of the turbulence structure and the streamlines highlight the fact that the criterion for selecting the best turbulence model cannot rely only on the velocity comparison at one location, it must also include other variables.

A Calculation Procedure for Three-Dimensional, Time-Dependent, Inviscid, Compressible Flow through Turbomachine Blades of any Geometry

1979 ◽  
Vol 21 (1) ◽  
pp. 39-49 ◽  
Author(s):  
C. Bosman ◽  
J. Highton
Keyword(s):  
Secondary Flow ◽  
Compressible Flow ◽  
Subsonic Flow ◽  
Three Dimensional ◽  
Experimental Results ◽  
Time Dependent ◽  
Two Dimensional ◽  
Through Flow ◽  
Flow Through ◽  
Inviscid Compressible Flow

A method for calculating three-dimensional, time-dependent, inviscid, subsonic flow is presented. Application is made to flow through the rotor of a small radial inflow turbine and comparison with conventional through-flow calculations and experimental results is made. The nature of the strong secondary flow in this rotor indicates the probable inadequacy of the two-dimensional calculations which is confirmed by the comparison.

Numerical and experimental results on the dispersion of a solute in a fluid in lamin/ar flow through a tube

1962 ◽  
Vol 269 (1338) ◽  
pp. 352-367 ◽  
Keyword(s):  
Differential Equation ◽  
Partial Differential Equation ◽  
Approximate Solution ◽  
Numerical Solution ◽  
Circular Tube ◽  
Experimental Results ◽  
Dilute Solution ◽  
Pure Solvent ◽  
Flow Through ◽  
Good Agreement

The longitudinal dispersion of a solute is studied for the process in which pure solvent slowly displaces solution in a circular tube. Good agreement is obtained between a numerical solution of the partial differential equation describing the process and experimental results for water displacing a dilute solution of potassium permanganate. The range of applicability of Sir Geoffrey Taylor’s approximate solution is discussed. An improved approximate solution is presented with a much wider range of validity. This improved approximation is based on the numerical solution of the equation describing the process.

Interaction of a Whirling Rotor with a Vibrating Stator across a Clearance Annulus

1968 ◽  
Vol 10 (1) ◽  
pp. 1-12 ◽  
Author(s):  
H. F. Black
Keyword(s):  
Dry Friction ◽  
Ball Bearing ◽  
Radial Symmetry ◽  
Experimental Results ◽  
Equilibrium Conditions ◽  
General Behaviour ◽  
Mass Unbalance ◽  
Jump Phenomena ◽  
Rotor Stator Interaction ◽  
Rotor Mass

Where a rotor runs within a clearance space, the clearance being comparable with rotor mass unbalance, the synchronous whirling behaviour of the rotor may be considerably affected by intermittent interaction with the stator at the clearance position. Discontinuity and jump phenomena may occur: in general, behaviour will be different with increasing speed from that with decreasing speed, and in either case zones may exist in which rotor-stator interaction is possible but not certain. In the analysis here presented, rotor and stator are regarded as linear multi-degree-of-freedom systems including damping; dry friction at the clearance space is taken into account. Discussion is limited to cases with radial symmetry, and interaction is assumed limited to the position of the clearance space. Polar receptances are used to establish equilibrium conditions with interaction, and speed zones are defined within which interaction may occur. Some hypothetical cases are fully explored, demonstrating that rotor-stator interactions may occur in a variety of forms and circumstances. Interactions with dry friction counterwhirling are also considered. Some experimental results on counterwhirl within a ball bearing are given and qualitatively compared with theory.

scholarly journals Steady Motion of Ice Sheets

1980 ◽  
Vol 25 (92) ◽  
pp. 229-246 ◽  
Author(s):  
L. W. Morland ◽  
I. R. Johnson
Keyword(s):  
Differential Equation ◽  
Linear Differential Equation ◽  
Power Law ◽  
Perturbation Expansion ◽  
Ice Sheet ◽  
Leading Order ◽  
Plane Flow ◽  
General Law ◽  
Non Linear ◽  
Linear Differential

AbstractSteady plane flow under gravity of a symmetric ice sheet resting on a horizontal rigid bed, subject to surface accumulation and ablation, basal drainage, and basal sliding according to a shear-traction-velocity power law, is treated. The surface accumulation is taken to depend on height, and the drainage and sliding coefficient also depend on the height of overlying ice. The ice is described as a general non-linearly viscous incompressible fluid, with illustrations presented for Glen’s power law, the polynomial law of Colbeck and Evans, and a Newtonian fluid. Uniform temperature is assumed so that effects of a realistic temperature distribution on the ice response are not taken into account. In dimensionless variables a small paramter ν occurs, but the ν = 0 solution corresponds to an unbounded sheet of uniform depth. To obtain a bounded sheet, a horizontal coordinate scaling by a small factor ε(ν) is required, so that the aspect ratio ε of a steady ice sheet is determined by the ice properties, accumulation magnitude, and the magnitude of the central thickness. A perturbation expansion in ε gives simple leading-order terms for the stress and velocity components, and generates a first order non-linear differential equation for the free-surface slope, which is then integrated to determine the profile. The non-linear differential equation can be solved explicitly for a linear sliding law in the Newtonian case. For the general law it is shown that the leading-order approximation is valid both at the margin and in the central zone provided that the power and coefficient in the sliding law satisfy certain restrictions.

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