Fluid Flow Behavior in the Curved Annular Sector Duct

1994 ◽  
Vol 116 (1) ◽  
pp. 53-60 ◽  
Author(s):  
G. Yang ◽  
M. A. Ebadian
Keyword(s):  
Friction Coefficient ◽  
Pressure Gradient ◽  
Secondary Flow ◽  
Vortex Structure ◽  
Flow Behavior ◽  
Radius Ratio ◽  
Axial Pressure ◽  
Axial Pressure Gradient ◽  
Annular Sector ◽  
Sector Angle

A numerical analysis of the axial and secondary flow behavior in a curved annular sector duct is presented in the paper. The flow is considered to be fully developed laminar flow with constant physical properties. Five parameters have been identified as major variables in controlling the flow behavior. The study indicates that with a moderate Dean number and when the sector angle is smaller than π/2, only two vortices will appear in the cross section of the curved annular sector duct. When the sector angle is larger than π/2, the vortex structure can be very complex, and is often determined by other parameters, especially by the angle between the annular sector duct centerline and the curvature radius direction. The friction coefficient of the curved annular sector duct is affected mainly by the radius ratio, curvature, and axial pressure gradient. The radius ratio of the inner/outer walls can affect the vortex structure only when the radius ratio is very small. When the radius ratio is larger than 0.6, the friction coefficient is only slightly higher than that of a straight annular sector duct. Nevertheless, for the small radius ratio duct, the friction coefficient can be tripled, as compared with a straight annular sector duct. Although the holding pipe curvature and the axial pressure gradient cannot significantly change the vortex structure of the secondary flow, they can however, remarkably increase the friction coefficient by increasing the velocity gradient near the solid boundary.

Slip Flow with Axial Pressure Gradient

1962 ◽  
Vol 29 (11) ◽  
pp. 1393-1394 ◽  
Author(s):  
A. Pozzi ◽  
P. Renno
Keyword(s):  
Pressure Gradient ◽  
Slip Flow ◽  
Axial Pressure ◽  
Axial Pressure Gradient

An Experimental Study of Three-Dimensional Turbulent Boundary Layer and Turbulence Characteristics Inside a Turbomachinery Rotor Passage

1978 ◽  
Vol 100 (4) ◽  
pp. 676-687 ◽  
Author(s):  
A. K. Anand ◽  
B. Lakshminarayana
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Stream Line ◽  
Shear Stresses ◽  
Axial Pressure ◽  
Mean Velocity ◽  
Large Defect ◽  
Axial Pressure Gradient

Three-dimensional boundary layer and turbulence measurements of flow inside a rotating helical channel of a turbomachinery rotor are described. The rotor is a four-bladed axial flow inducer operated at large axial pressure gradient. The mean velocity profiles, turbulence intensities and shear stresses, and limiting stream-line angles are measured at various radial and chordwise locations, using rotating triaxial hot-wire and conventional probes. The radial flows in the rotor channel are found to be higher compared to those at zero or small axial pressure gradient. The radial component of turbulence intensity is found to be higher than the streamwise component due to the effect of rotation. Flow near the annulus wall is found to be highly complex due to the interaction of the blade boundary layers and the annulus wall resulting in an appreciable radial inward flow, and a large defect in the mainstream velocity. Increased level of turbulence intensity and shear stresses near the midpassage are also observed near this radial location.

Axial flow in trailing line vortices

1964 ◽  
Vol 20 (4) ◽  
pp. 645-658 ◽  
Author(s):  
G. K. Batchelor
Keyword(s):  
Pressure Gradient ◽  
Similarity Solution ◽  
Axial Velocity ◽  
Axial Flow ◽  
Radial Pressure ◽  
Axial Pressure ◽  
Line Vortex ◽  
General Terms ◽  
Axial Acceleration ◽  
Axial Pressure Gradient

A characteristic feature of a steady trailing line vortex from one side of a wing, and of other types of line vortex, is the existence of strong axial currents near the axis of symmetry. The purpose of this paper is to account in general terms for this axial flow in trailing line vortices. the link between the azimuthal and axial components of motion in a steady line vortex is provided by the pressure; the radial pressure gradient balances the centrifugal force, and any change in the azimuthal motion with distance x downstream produces an axial pressure gradient and consequently axial acceleration.It is suggested, in a discussion of the evolution of an axisymmetric line vortex out of the vortex sheet shed from one side of a wing, that the two processes of rolling-up of the sheet and of concentration of the vorticity into a smaller cross-section should be distinguished; the former always occurs, whereas the latter seems not to be inevitable.In § 4 there is given a similarity solution for the flow in a trailing vortex far downstream where the departure of the axial velocity from the free stream speed is small. The continual slowing-down of the azimuthal motion by viscosity leads to a positive axial pressure gradient and consequently to continual loss of axial momentum, the asymptotic variation of the axial velocity defect at the centre being as x−1 log x.The concept of the drag associated with the core of a trailing vortex is introduced, and the drag is expressed as an integral over a transverse plane which is independent of x. This drag is related to the arbitrary constant appearing in the above similarity solution.

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