Closure to “Discussion of ‘Effects of Nonuniform Inlet Velocity Profiles on Flow Regimes and Performance in Two-Dimensional Diffusers’” (1969, ASME J. Basic Eng., 91, p. 474)

1969 ◽  
Vol 91 (3) ◽  
pp. 474-474
Author(s):  
S. Wolf ◽  
J. P. Johnston
Keyword(s):  
Flow Regimes ◽  
Velocity Profiles ◽  
Two Dimensional ◽  
Inlet Velocity ◽  
And Performance

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.

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.

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.

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.

On the criteria for reverse transition in a two-dimensional boundary layer flow

1969 ◽  
Vol 35 (2) ◽  
pp. 225-241 ◽  
Author(s):  
M. A. Badri Narayanan ◽  
V. Ramjee
Keyword(s):  
Longitudinal Velocity ◽  
Outer Region ◽  
Transition Process ◽  
Velocity Profiles ◽  
Wall Region ◽  
Two Dimensional ◽  
Mean Velocity ◽  
Law Of The Wall ◽  
Reverse Transition ◽  
Turbulence Decay

Experiments on reverse transition were conducted in two-dimensional accelerated incompressible turbulent boundary layers. Mean velocity profiles, longitudinal velocity fluctuations $\tilde{u}^{\prime}(=(\overline{u^{\prime 2}})^{\frac{1}{2}})$ and the wall-shearing stress (TW) were measured. The mean velocity profiles show that the wall region adjusts itself to laminar conditions earlier than the outer region. During the reverse transition process, increases in the shape parameter (H) are accompanied by a decrease in the skin friction coefficient (Cf). Profiles of turbulent intensity (u’2) exhibit near similarity in the turbulence decay region. The breakdown of the law of the wall is characterized by the parameter \[ \Delta_p (=\nu[dP/dx]/\rho U^{*3}) = - 0.02, \] where U* is the friction velocity. Downstream of this region the decay of $\tilde{u}^{\prime}$ fluctuations occurred when the momentum thickness Reynolds number (R) decreased roughly below 400.

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