Viscous primary/secondary flow analysis for use with nonorthogonal coordinate systems

1983 ◽  
Author(s):  
R. LEVY ◽  
W. BRILEY ◽  
H. MCDONALD
Keyword(s):  
Secondary Flow ◽  
Flow Analysis ◽  
Coordinate Systems

On the definition of the secondary flow in three-dimensional cascades

2009 ◽  
Vol 223 (6) ◽  
pp. 667-676 ◽  
Author(s):  
G Persico ◽  
P Gaetani ◽  
V Dossena ◽  
G D'Ippolito ◽  
C Osnaghi
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Secondary Flow ◽  
Boundary Layers ◽  
Complex Geometry ◽  
Flow Direction ◽  
Flow Analysis ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Reference Flow

The present article proposes a novel methodology to evaluate secondary flows generated by the annulus boundary layers in complex cascades. Unlike two-dimensional (2D) linear cascades, where the reference flow is commonly defined as that measured at midspan, the problem of the reference flow definition for annular or complex 3D linear cascades does not have a general solution up to the present time. The proposed approach supports secondary flow analysis whenever exit streamwise vorticity produced by inlet endwall boundary layers is of interest. The idea is to compute the reference flow by applying slip boundary conditions at the endwalls in a viscous 3D numerical simulation, in which uniform total pressure is prescribed at the inlet. Thus the reference flow keeps the 3D nature of the actual flow except for the contribution of the endwall boundary layer vorticity. The resulting secondary field is then derived by projecting the 3D flow field (obtained from both an experiment and a fully viscous simulation) along the local reference flow direction; this approach can be proficiently applied to any complex geometry. This method allows the representation of secondary velocity vectors with a better estimation of the vortex extension, since it offers the opportunity to visualize also the region of the vortices, which can be approximated as a potential type. Furthermore, a proficient evaluation of the secondary vorticity and deviation angle effectively induced by the annulus boundary layer is possible. The approach was preliminarily verified against experimental data in linear cascades characterized by cylindrical blades, not reported for the sake of brevity, showing a very good agreement with the standard methodology based only on the experimental midspan flow field. This article presents secondary flows obtained by the application of the proposed methodology on two annular cascades with cylindrical and 3D-designed blades, stressing the differences with other definitions. Both numerical and experimental results are considered.

A Numerical Study of the U-Turn Bend in Return Channel Systems for Multistage Centrifugal Compressors

2005 ◽  
Vol 219 (8) ◽  
pp. 749-756 ◽  
Author(s):  
J. M. Oh ◽  
A Engeda ◽  
M. K. Chung
Keyword(s):  
Velocity Profile ◽  
Secondary Flow ◽  
Numerical Study ◽  
Flow Analysis ◽  
Turbulence Models ◽  
Jet Flow ◽  
Complex Flow ◽  
Centrifugal Compressors ◽  
Return Channel ◽  
Channel Systems

A qualitative numerical study of the flow in the U-turn bend of return channel systems for multistage centrifugal compressors is presented. Calculations have been carried out using the flow analysis program FLUENT. The flow in the U-turn bend is highly three-dimensional and complex. The main cause for this is the circumferential variation of the velocity profile at the inlet of the bend. The circumferential variation of the velocity profile is an unavoidable result from the wake/jet flow at the exit of the impeller. In this article, first the effect of the wake/jet flow coming into the U-turn bend is studied. It is shown that the wake/jet flow develops to form the secondary flow in the U-turn bend. The secondary flow, with the high streamline curvature of the flow in the bend, makes the flow inside the bend highly complex. This complex flow is hard to predict with conventional turbulence models that have been developed on the basis of near homogeneity of flows. Comparing the present result with a study that successfully predicted the loss and flow behaviour in the bend, a discussion is presented on the turbulence and the turbulence models. Also, the loss mechanisms in the U-turn bend are discussed in detail.

The Effects of Wake Mixing on Compressor Aerodynamics

1991 ◽  
Vol 113 (4) ◽  
pp. 600-607 ◽  
Author(s):  
R. P. Dring ◽  
D. A. Spear
Keyword(s):  
Experimental Data ◽  
Secondary Flow ◽  
Flow Analysis ◽  
Strong Impact ◽  
Corner Separation ◽  
Pressure Distributions ◽  
Compressor Aerodynamics ◽  
Airfoil Flow

A methodology based on wake mixing has been developed that enables more accurate predictions of compressor airfoil pressure distributions when the airfoil is operating downstream of an airfoil row that has strong wakes. The methodology has an impact on throughflow analysis, on airfoil-to-airfoil flow analysis, and on the interpretation of experimental data. It is demonstrated that the flow in the endwall region is particularly sensitive to mixing due to the strong wakes caused by the secondary flow and corner separation that commonly occur in this region. It is also demonstrated that wake mixing can have a strong impact on both airfoil incidence and deviation as well as on loading. Differences of up to 13 deg and 30 percent in loading are demonstrated.

Three-dimensional blood flow analysis in a wide-necked internal carotid artery—ophthalmic artery aneurysm

2003 ◽  
Vol 99 (3) ◽  
pp. 526-533 ◽  
Author(s):  
Satoshi Tateshima ◽  
Fernando Viñuela ◽  
J. Pablo Villablanca ◽  
Yuichi Murayama ◽  
Taku Morino ◽  
...  
Keyword(s):  
Blood Flow ◽  
Secondary Flow ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Artery Aneurysm ◽  
Content Type ◽  
Mean Size ◽  
Blood Flow Analysis ◽  
The Mean ◽  
Fine Print

Object. The aim of this study was to evaluate axial and secondary flow structures in a wide-necked internal carotid artery—ophthalmic artery aneurysm, one of the most common locations for endovascular coil placement. Methods. A clear acrylic aneurysm model was manufactured from a three-dimensional computerized tomography angiogram. Intraaneurysm blood flow analysis was conducted using an acrylic aneurysm model together with laser Doppler velocimetry and particle imaging velocimetry. The maximal axial blood flow velocities in the inflow and outflow zones at the aneurysm orifice were noted at the peak systolic phase, measuring 46.8 and 24.9% of that in the parent artery, respectively. The mean size of the inflow zone during one cardiac cycle was 44.3 ± 9.8% (range 35.6–58.7%) the size of the axial section at the aneurysm orifice. In the lower and upper planes of the aneurysm dome, the mean size of inward and outward flow areas were 43.3 ± 6.7% and 43.8 ± 6.8% the size of the axial cross-sectional plane, respectively. The axial flow velocity structures were dynamically altered throughout the cardiac cycle, particularly at the aneurysm orifice. The fastest secondary flow at the opening was also noted at the peak systolic and early diastolic phases. Axial blood flow velocity was slower in the upper axial plane of the aneurysm dome than in the lower one. Conversely, the secondary flow component was faster in the upper plane. Conclusions. The side-wall aneurysm in this study did not demonstrate a simple flow pattern as was previously seen in ideally shaped experimental aneurysms in vitro and in vivo. The flow patterns of inflow and outflow zones were very difficult to predict based on the limited flow information provided on standard digital subtraction angiography, even in an aneurysm with a relatively simple dome shape.

scholarly journals Distribution of primary and secondary currents in sine-generated bends

Water SA ◽  
2018 ◽  
Vol 44 (1 January) ◽  
Author(s):  
Li He
Keyword(s):  
Secondary Flow ◽  
Flow Analysis ◽  
Primary Flow ◽  
Secondary Currents ◽  
Meandering Channel ◽  
Meandering Channels ◽  
Curved Channels ◽  
Mobile Bed ◽  
Using Data ◽  
Curvature Driven

The secondary circulation in a meandering channel redistributes the velocity over the bend. However, the shift of primary flow by secondary currents is not quantitatively understood, due to the difficulty in isolating the role of curvature-driven secondary flow from that of topography-driven secondary flow in bed-deformed meanders. The influences of curvature-driven and topography-driven secondary currents on the redistribution of primary flow in sine-generated meandering channels were examined by CCHE2D. The model is calibrated using data measured in two sets of laboratory experiments including flat-bed flow and mobile-bed flow. Analysis indicated that topography-induced current mainly contributes to the redistribution of primary flow from inner to outer bank in the curved channels, rather than the secondary flow driven by curvature.

Secondary Flow in Repeating Stages of Axial Turbomachines

1995 ◽  
Vol 209 (2) ◽  
pp. 101-110 ◽  
Author(s):  
J H Horlock
Keyword(s):  
Experimental Data ◽  
Secondary Flow ◽  
Flow Analysis ◽  
Axial Flow ◽  
Streamwise Vorticity ◽  
Flow Phenomenon ◽  
Multi Stage ◽  
Axial Velocity Profile ◽  
Flow Through ◽  
Flow Compressor

In a well-designed multi-stage axial flow compressor, the flow settles down to a repeating condition, in which the axial velocity profile does not deteriorate further; it is more or less unchanged between the entry and the exit of a deeply embedded stage. However, experimental data also show that the flow angles repeat, and it is this flow phenomenon that is discussed in the paper. Secondary flow analysis, coupled with empirical data on clearance flows, is used to give a description of the flow in such a repeating stage. The secondary flow at exit from a row involves both the streamwise vorticity generated in that row and the vorticity that exists at entry—the so-called ‘skew’ vorticity due to a non-uniform velocity from a stator being received by a moving rotor (and a similar effect from the rotor to the stator). However, clearance vorticity—shed from the rotor tip (casing) section and the stator root (hub) section—is also present and can be taken into account. Calculations made using the analyses are compared with some limited experimental data drawn from the published literature. Predicted underturning at rotor tip (casing) sections is confirmed by experiments; similarly, predicted underturning at stator tip (casing) sections accords with observations in one compressor but not in another. However, no universal conclusion (on whether underturning or overturning usually occurs) can be drawn for the flow through the rotor and stator root (hub) sections, as either entry or generated secondary vorticity may dominate.

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