Experimental investigation of boundary layer ingesting diffusers of a semi-circular cross section

1998 ◽  
Author(s):  
Amer Anabtawi ◽  
Ron Blackwelder ◽  
Robert Liebeck ◽  
Peter Lissaman
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Cross Section ◽  
Circular Cross Section

Experimental investigation of condensation flows in circular cross-section channel

2018 ◽  
Vol 145 ◽  
pp. 147-154 ◽  
Author(s):  
Georges El Achkar ◽  
Patrick Queeckers ◽  
Carlo Saverio Iorio
Keyword(s):  
Experimental Investigation ◽  
Cross Section ◽  
Circular Cross Section

scholarly journals Pressure Coefficients Acting Upon the Cylinder Obtained by Numerical and Experimental Analysis

2017 ◽  
Vol 13 (2) ◽  
pp. 149-155
Author(s):  
Soňa Medvecká ◽  
Oľga Ivánková ◽  
Marek Macák
Keyword(s):  
Fluid Dynamics ◽  
Boundary Layer ◽  
Cross Section ◽  
Cfd Simulation ◽  
Circular Cross Section ◽  
Wind Pressure ◽  
Wind Flow ◽  
Pressure Coefficients ◽  
High Rise ◽  
Computational Fluid Dynamics Cfd

Abstract Analysis of wind flow acting upon high-rise buildings is a very common topic. This paper deals with experiment in the Boundary Layer Wind Tunnel (BWLT) in Bratislava and comparison with the computational fluid dynamics (CFD) simulation and values given in the Eurocode. The analyzed object was the model of building with circular cross section (cylinder). External wind pressure coefficients were compared in three height levels of model.

Finite amplitude convection cells

1967 ◽  
Vol 30 (3) ◽  
pp. 577-600 ◽  
Author(s):  
J. L. Robinson
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Boundary Conditions ◽  
Boundary Layers ◽  
Cross Section ◽  
Circular Cross Section ◽  
Maximum Heat ◽  
Mean Field Equations

In this paper we consider two-dimensional steady cellular motion in a fluid heated from below at large Rayleigh number and Prandtl number of order unity. This is a boundary-layer problem and has been considered by Weinbaum (1964) for the case of rigid boundaries and circular cross-section. Here we consider cells of rectangular cross-section with three sets of velocity boundary conditions: all boundaries free, rigid horizontal boundaries and free vertical boundaries (referred to here as periodic rigid boundary conditions), and all boundaries rigid; the vertical boundaries of the cells are insulated. It is shown that the geometry of the cell cross-section is important, such steady motion being not possible in the case of free boundaries and circular cross-section; also that the dependence of the variables of the problem on the Rayleigh number is determined by the balances in the vertical boundary layers.We assume only those boundary layers necessary to satisfy the boundary conditions and obtain a Nusselt number dependence $N \sim R^{\frac{1}{3}}$ for free vertical boundaries. For the periodic rigid case, Pillow (1952) has assumed that the buoyancy torque is balanced by the shear stress on the horizontal boundaries; this is equivalent to assuming velocity boundary layers beside the vertical boundaries (rather than the vorticity boundary layers demanded by the boundary conditions) and leads to a Nusselt number dependence N ∼ R¼. If it is assumed that the flow will adjust itself to give the maximum heat flux possible the two models are found to be appropriate for different ranges of the Rayleigh number and there is good agreement with experiment.An error in the application of Rayleigh's method in this paper is noted and the correct method for carrying the boundary-layer solutions round the corners is given. Estimates of the Nusselt numbers for the various boundary conditions are obtained, and these are compared with the computed results of Fromm (1965). The relevance of the present work to the theory of turbulent convection is discussed and it is suggested that neglect of the momentum convection term, as in the mean field equations, leads to a decrease in the heat flux at very high Rayleigh numbers. A physical argument is given to derive Gill's model for convection in a vertical slot from the Batchelor model, which is appropriate in the present work.

Lumped Parameter Description of Thermoviscous Acoustics in Tubes with Equilateral Triangular Cross-Sections

2019 ◽  
Vol 105 (6) ◽  
pp. 1283-1285
Author(s):  
René Christensen
Keyword(s):  
Boundary Layer ◽  
Transmission Line ◽  
Cross Section ◽  
Cross Sections ◽  
Circular Cross Section ◽  
Lumped Parameter Model ◽  
Entire Cross Section ◽  
Lumped Parameter ◽  
Viscous Loss ◽  
Lumped Parameters

An accurate acoustic model of a tube in the millimeter or sub-millimeter size should include the losses that occur due to viscosity and thermal conduction, collectively termed thermoviscous losses. These losses are prominent in a boundary layer near the tube walls. Under the assumption that the boundary layer is thick compared to a characteristic geometry length, such as the radius for a circular cross-section, and fills out the entire cross-section, the tube can be described via a lumped parameter model. The lumped parameters have been known for several decades for a tube with circular cross-section, but the equilateral triangular tube has only been investigated in terms of transmission line parameters. The lumped parameters have here been established for the equilateral triangular tube as a truncated series solution of the transmission line parameters. One result observed is that the lumped parameter model for a triangular tube has 38% more viscous loss than a circular tube for a given area.

Helical Springs of Hollow Circular Cross Section

1959 ◽  
Vol 81 (1) ◽  
pp. 30-35
Author(s):  
C. W. Bert
Keyword(s):  
Experimental Investigation ◽  
Elasticity Theory ◽  
Cross Section ◽  
Circular Cross Section ◽  
Shear Stresses ◽  
Helical Spring ◽  
Circular Section ◽  
Helical Springs ◽  
Elastic Shear ◽  
Theory Solution

A theoretical and experimental investigation of elastic shear stresses and deflection in an axially loaded helical spring having a hollow circular section is reported in this paper. Two analyses are presented: An approximation of the stresses by strength-of-materials theory and a more accurate elasticity-theory solution for stresses and deflection. The results are compared with strain and deflection measurements on an actual tubular spring.

Oscillating Flow in Ducts of Arbitrary Cross Section

1969 ◽  
Vol 73 (706) ◽  
pp. 894-896
Author(s):  
A. M. Abu-Sitta ◽  
D. G. Drake
Keyword(s):  
Boundary Layer ◽  
Viscous Fluid ◽  
Pressure Gradient ◽  
Numerical Solution ◽  
Cross Section ◽  
Circular Cross Section ◽  
Arbitrary Cross Section ◽  
Oscillating Flow ◽  
Elliptic Case ◽  
Uniform Cross Section

The rectilinear flow of an incompressible viscous fluid along a duct of uniform cross section due to an oscillating pressure gradient has been considered by a number of investigators. The duct of circular cross .section has been treated by Richardson and Tyler and Sexl, the elliptic case by Khamrui, and the rectangular case by Drake and Fan and Chao. Recently Jeng has discussed the importance of this type of flow and has given a procedure for calculating a numerical solution for a duct of arbitrary cross-section. An interesting feature of these flows is that, at large frequencies when the flow is of boundary-layer type, the velocity at any instant has its maximum near the walls, the velocity overshooting its almost uniform distribution at the centre of the duct.

A Method for Designing Wind Tunnel Contractions

1951 ◽  
Vol 55 (483) ◽  
pp. 169-180 ◽  
Author(s):  
R. Harrop
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Pressure Gradient ◽  
Cross Section ◽  
Incompressible Flow ◽  
Circular Cross Section ◽  
Flow Theory ◽  
Boundary Layer Separation ◽  
Experimental Results ◽  
Pressure Gradients

SummaryThe contraction of a wind tunnel should be free from adverse pressure gradients, since this might cause boundary layer separation.A wall contour has been designed for a circular cross-section contraction using incompressible flow theory. This gave a favourable pressure gradient at the beginning of the contraction where separation is likely to occur.Appendix I compares the theory with experimental results obtained from a model of a proposed supersonic tunnel of which the contraction is rectangular in cross-section and which has been based on the results obtained in this report.

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