Effects of Nonuniform Inlet Velocity Profiles on Flow Regimes and Performance in Two-Dimensional Diffusers

1969 ◽  
Vol 91 (3) ◽  
pp. 462-474 ◽  
Author(s):  
S. Wolf ◽  
J. P. Johnston
Keyword(s):  
Shear Flows ◽  
Prediction Method ◽  
Flow Regimes ◽  
Velocity Profiles ◽  
Two Dimensional ◽  
Rotational Model ◽  
Inlet Velocity ◽  
The Core ◽  
Uniform Shear ◽  
And Performance

An analytical and experimental study on the effects of large distortions of inlet velocity profiles on flow regimes and performance in diffusers is reported. Experiments are restricted to flow in straight, two-dimensional diffusers with turbulent boundary layers. Systematic data are obtained for two general types of inlet flows: (1) simple, uniform shear flows in the core, and (2) severely nonuniform shear flows of the wake, jet, and step-shear type. For uniform shear flows a first order prediction method based on inviscid rotational flow and the boundary layer blockage concept is developed and verified for diffusers operating in the unstalled flow regime. For nonuniform shear flows the inviscid rotational model is shown to predict performance trends better than the irrotational model; however, the inviscid rotational model is inadequate as a precise prediction method because no account is taken of mixing in the core region. Geometry and performance correlations for peak pressure recovery (at constant N/W1) are also established.

Effects of Wall Shape on Flow Regimes and Performance in Straight, Two-Dimensional Diffusers

1967 ◽  
Vol 89 (1) ◽  
pp. 151-159 ◽  
Author(s):  
J. J. Carlson ◽  
J. P. Johnston ◽  
C. J. Sagi
Keyword(s):  
Flow Regime ◽  
Performance Prediction ◽  
Prediction Method ◽  
Flow Regimes ◽  
Two Dimensional ◽  
Simple Class ◽  
And Performance

Three diffuser sets (N/W1, held constant in each set) were built and tested for performance and flow regime over a range of total area ratios, AR, which yielded unstalled and stalled flows. At each AR and N/W1, a simple class of convex-inward (trumpet-shaped), straight, and convex-outward (bell-shaped) wall shapes were tested. It is concluded that there is little advantage to be gained by contouring the walls of two-dimensional diffusers. A corollary result shows that the performance prediction method of reference [1] gives good results for unstalled diffusers.

scholarly journals Investigation of Flows in Rectangular Diffusers With Inlet Flow Distortion

1982 ◽  
Author(s):  
M. M. Al-Mudhafar ◽  
M. Ilyas ◽  
F. S. Bhinder
Keyword(s):  
Experimental Study ◽  
Velocity Profiles ◽  
Pressure Recovery ◽  
Two Dimensional ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Inlet Velocity ◽  
Inlet Distortion ◽  
Mach Numbers ◽  
Inlet Flow Distortion

The results of an experimental study on the influence of severely distorted velocity profiles on the performance of a straight two-dimensional diffuser are reported. The data cover entry Mach numbers ranging from 0.1 to 0.6 and several inlet distortion levels. The pressure recovery progressively deteriorates as the inlet velocity is distorted.

Mycielski Based 2d-Predictive Image Coding Algorithm

2016 ◽  
Vol 850 ◽  
pp. 144-151 ◽  
Author(s):  
Mehmet Fidan ◽  
Ömer Nezih Gerek
Keyword(s):  
Image Coding ◽  
Predictive Coding ◽  
Prediction Method ◽  
Physical Distance ◽  
Prediction Algorithm ◽  
Two Dimensional ◽  
Two Dimensional Image ◽  
Past Data ◽  
And Performance ◽  
Definition Of

The Mycielski method is a prospering prediction algorithm which is based on searching and finding largest repeated binary patterns. It uses infinite-past data to devise a rule based prediction method on a time series. In this work, a novel two-dimensional (image processing) version of the Mycielski algorithm is proposed. Since the dimensionality definition of “past” data increases in two-dimensional signals, the proposed algorithm also needs to handle how the boundaries of the pixel cliques are iteratively extended in the neighborhood of a current pixel. The clique extension invokes novel similarity search strategies that depend on the chosen physical distance metric. The proposed prediction algorithm is used for predictive image compression and performance comparisons with other predictive coding methods are presented.

The generation of symmetrical duct velocity profiles of high uniform shear

1964 ◽  
Vol 20 (2) ◽  
pp. 201-208 ◽  
Author(s):  
J. L. Livesey ◽  
J. T. Turner
Keyword(s):  
Boundary Layer ◽  
Design Method ◽  
Slight Modification ◽  
Velocity Profiles ◽  
Two Dimensional ◽  
Grid Spacing ◽  
Uniform Shear ◽  
Linear Shear ◽  
Logical Design ◽  
Upstream Flow

The logical design method of Owen & Zienkiewicz (1957), for the generation of linear shear flow, is successfully applied to the case of symmetrical velocity profiles in a two-dimensional duct. Shear parameters as high as 0·8 (corresponding to $\hat{V}| \overline {V} = 1\cdot4$) are obtained experimentally. Some slight modification to the theoretical grid spacing is required because of the non-uniformity of the upstream flow.The decay of the profiles is confined to that due to the developing boundary layer and to the breakdown of the physically impossible condition at the centre, where symmetry implies a change in sign of the uniform shear.

Effect of Inlet Flow Distortion on Performance of Vortex Controlled Diffusers

1992 ◽  
Vol 114 (2) ◽  
pp. 191-197 ◽  
Author(s):  
R. K. Sullerey ◽  
V. Ashok ◽  
K. V. Shantharam
Keyword(s):  
Reynolds Number ◽  
High Pressure ◽  
Velocity Profiles ◽  
Short Length ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Flow Distortion ◽  
Exit Velocity ◽  
Inlet Velocity ◽  
Vortex Control

The present experimental investigations are concerned with diffusers employing the concept of vortex control to achieve high pressure recovery in a short length. Two types of two-dimensional diffusers have been studied, namely, vortex controlled and hybrid diffusers. Investigations have been carried out on such short diffusers with symmetrically and asymmetrically distorted inlet velocity profiles for area ratios 2.0 and 2.5 and divergence angle of 30 and 45 deg at a Reynolds number of 105. For each of the above configurations, experiments have been carried out for a range of fence subtended angles and bleed rates. The results indicate improvement in diffuser effectiveness up to a particular bleed off for both types of diffusers. It was observed that the nature of exit velocity profiles could be controlled by differential bleed.

scholarly journals Eigenvalues in trailing edge flows

1975 ◽  
Vol 19 (2) ◽  
pp. 210-221
Author(s):  
K. Capell
Keyword(s):  
Asymptotic Formula ◽  
Flat Plate ◽  
Similarity Solution ◽  
Shear Flows ◽  
Two Dimensional ◽  
Trailing Edge ◽  
Uniform Shear

Abstract A wake similarity solution for symmetric uniform shear flows merging at the trailing edge of a flat plate has associated with it an eigenfunction problem which was overlooked by Hakkinen and O'Neil (1967). An asymptotic formula for large eigenvalues is obtained and compared with another such formula related to both the Goldstein (1930) inner wake solution and Tillett's (1968) similarity solution for a jet emerging from a two-dimensional channel.

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