Review: Effects of Inlet Conditions on Conical-Diffuser Performance

1981 ◽  
Vol 103 (2) ◽  
pp. 250-257 ◽  
Author(s):  
A. Klein
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Experimental Evidence ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Shape Parameter ◽  
Conical Diffuser ◽  
Free Discharge ◽  
Inlet Conditions ◽  
Different Sources

The available experimental evidence of the effects of inlet conditions on the performance of conical diffusers with a free discharge is reviewed. The effects of inlet boundary layer thickness blockage, inlet shape parameter, turbulence, and Reynolds number are discussed. It is shown that many of the inconsistencies between different sources of data are the result of nonturbulent approach flows. Graphs are presented as guidelines for diffuser design.

Annulus Wall Boundary-Layer Measurements in a Four-Stage Compressor

1986 ◽  
Vol 108 (1) ◽  
pp. 2-6 ◽  
Author(s):  
N. A. Cumpsty
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Layer Thickness ◽  
Boundary Layers ◽  
Boundary Layer Thickness ◽  
Tip Clearance ◽  
The Other ◽  
Wall Boundary Layer ◽  
Multistage Compressors ◽  
Full Design

There are few available measurements of the boundary layers in multistage compressors when the repeating-stage condition is reached. These tests were performed in a small four-stage compressor; the flow was essentially incompressible and the Reynolds number based on blade chord was about 5 • 104. Two series of tests were performed; in one series the full design number of blades were installed, in the other series half the blades were removed to reduce the solidity and double the staggered spacing. Initially it was wished to examine the hypothesis proposed by Smith [1] that staggered spacing is a particularly important scaling parameter for boundary layer thickness; the results of these tests and those of Hunter and Cumpsty [2] tend to suggest that it is tip clearance which is most potent in determining boundary-layer integral thicknesses. The integral thicknesses agree quite well with those published by Smith.

A Numerical Investigation Into the Sources of Endwall Loss in Axial Flow Turbines

2012 ◽  
Author(s):  
John Denton ◽  
Graham Pullan
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Axial Flow ◽  
Turbine Cascade ◽  
Plane Model ◽  
Blade Row ◽  
Axial Turbines ◽  
Different Sources ◽  
Good Agreement

Endwall loss, often termed “secondary loss”, in axial turbines has been intensively studied for many years, despite this the physical origin of much of the loss is not really understood. This lack of understanding is a serious impediment to our ability to predict the loss and to the development of methods for reducing it. This paper aims to study the origins of the loss by interrogating the results from detailed and validated CFD calculations. The calculation method is first validated by comparing its predictions to detailed measurements in a turbine cascade. Very good agreement between the calculations and the measurements is obtained. The solution is then examined in detail to highlight the sources of entropy generation in the cascade, several different sources of loss are found to be significant. The same blade row is then used to study the effects of the of the inlet boundary layer thickness on the loss. It is found that only the inlet boundary layer loss and the mixing loss vary greatly with inlet boundary layer thickness. Finally a complete 50% reaction stage, with identical stator and rotor blade profiles, is examined using both steady calculations, with a mixing plane model, and the time average of unsteady calculations. It is found that the endwall flow in the rotor is completely different from that in the stator. Because of this it is considered that results from endwall flow and loss measurements in cascades are of limited relevance to the endwall flow in a real turbine. The results are also used to discuss the validity of the mixing plane model.

Improvement of the Performance of Conical Diffusers by Vortex Generators

1974 ◽  
Vol 96 (1) ◽  
pp. 4-10 ◽  
Author(s):  
Y. Senoo ◽  
M. Nishi
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Area Ratio ◽  
Vortex Generators ◽  
Pressure Recovery ◽  
Divergence Angle ◽  
Recovery Coefficient ◽  
Conical Diffuser ◽  
Pressure Recovery Coefficient

Vortex generators, which consist of small blades, are applied to conical diffusers the divergence angles of which are 8, 12, 16, 20, and 30 deg, respectively. The area ratio of each diffuser is four. The experiment covers the influence of various parameters, such as the arrangement of blades, inlet boundary layer thickness, and location of vortex generators relative to the conical diffuser, on the pressure-recovery coefficient. The experiment shows that the vortex generators prevent the flow in a conical diffuser from separating up to a divergence angle of 16 deg, and that the pressure-recovery coefficient is approximately equal to that of conventional best conical diffusers.

Streakline Flow Visualization of Discrete Hole Film Cooling for Gas Turbine Applications

1976 ◽  
Vol 98 (2) ◽  
pp. 245-250 ◽  
Author(s):  
R. S. Colladay ◽  
L. M. Russell
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Flow Field ◽  
Gas Turbine ◽  
Layer Thickness ◽  
Turbulent Mixing ◽  
Film Cooling ◽  
Boundary Layer Thickness ◽  
Hole Diameter ◽  
Neutrally Buoyant

Film injection from discrete holes in a three row staggered array with 5-dia spacing was studied for three hole angles: (1) normal, (2) slanted 30 deg to the surface in the direction of the mainstream, and (3) slanted 30 deg to the surface and 45 deg laterally to the mainstream. The ratio of the boundary layer thickness-to-hole diameter and the Reynolds number were typical of gas turbine film cooling applications. Results from two different injection locations are presented to show the effect of boundary layer thickness on film penetration and mixing. Detailed streaklines showing the turbulent motion of the injected air were obtained by photographing very small neutrally-buoyant helium filled “soap” bubbles which follow the flow field. Unlike smoke, which diffuses rapidly in the high turbulent mixing region associated with discrete hole blowing, the bubble streaklines passing downstream injection locations are clearly identifiable and can be traced back to their point of ejection.

scholarly journals Numerical investigations of flow around subsea covers at high Reynolds numbers

2021 ◽  
Vol 1201 (1) ◽  
pp. 012013
Author(s):  
G Yin ◽  
Y Zhang ◽  
M C Ong
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Numerical Simulations ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Stream Velocity ◽  
Layer Flow ◽  
High Reynolds

Abstract Two-dimensional (2D) numerical simulations of flow over wall-mounted rectangular and trapezoidal ribs subjected to a turbulent boundary layer flow with the normalized boundary layer thickness of δ/D = 0.73,1.96,2.52 (D is the height of the ribs) have been carried out by using the Reynolds-averaged Navier-Stokes (RANS) equations combined with the k – ω SST (Shear Stress Transport) turbulence model. The angles of the two side slopes of trapezoidal rib varies from 0° to 60°. The Reynolds number based on the free-stream velocity U ∞ and D are 1 × 106 and 2 × 106. The results obtained from the present numerical simulations are in good agreement with the published experimental data. Furthermore, the effects of the angle of the two side slopes of the trapezoidal ribs, the Reynolds number and the boundary layer thickness on the hydrodynamic quantities are discussed.

Characteristics of the Flow Past a Wall-Mounted Finite-Length Square Cylinder at Low Reynolds Number With Varying Boundary Layer Thickness

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Sachidananda Behera ◽  
Arun K. Saha
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Flow Field ◽  
Layer Thickness ◽  
Finite Length ◽  
Boundary Layer Thickness ◽  
Square Cylinder ◽  
Near Wake ◽  
Wall Boundary Layer ◽  
Wall Boundary

Direct numerical simulation (DNS) is performed to investigate the modes of shedding of the wake of a wall-mounted finite-length square cylinder with an aspect ratio (AR) of 7 for six different boundary layer thicknesses (0.0–0.30) at a Reynolds number of 250. For all the cases of wall boundary layer considered in this study, two modes of shedding, namely, anti-symmetric and symmetric modes of shedding, were found to coexist in the cylinder wake with symmetric one occurring intermittently for smaller time duration. The phase-averaged flow field revealed that the symmetric modes of shedding occur only during instances when the near wake experiences the maximum strength of upwash/downwash flow. The boundary layer thickness seems to have a significant effect on the area of dominance of both downwash and upwash flow in instantaneous and time-averaged flow field. It is observed that the near-wake topology and the total drag force acting on the cylinder are significantly affected by the bottom-wall boundary layer thickness. The overall drag coefficient is found to decrease with thickening of the wall boundary layer thickness.

Influence of Inlet Flow Conditions and Geometries of Centrifugal Vaneless Diffusers on Critical Flow Angle for Reverse Flow

1977 ◽  
Vol 99 (1) ◽  
pp. 98-102 ◽  
Author(s):  
Yasutoshi Senoo ◽  
Yoshifumi Kinoshita
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Boundary Layer Thickness ◽  
Reverse Flow ◽  
Critical Flow ◽  
Flow Conditions ◽  
Flow Angle ◽  
Inlet Velocity ◽  
Vaneless Diffusers ◽  
Inlet Conditions

The authors’ preceding analysis on centrifugal vaneless diffusers is used to examine the influences of diffuser geometries and of flow inlet conditions on the critical flow angle for reverse flow, and the results are presented in graphs. The diffuser width to radius ratio, the inlet Mach number, and the distortion of the inlet velocity distribution have significant influences on the critical flow angle, while the Reynolds number and the boundary layer thickness at the inlet have minor influences.

Effect of velocity profile on instability of the viscoelastic liquid sheet

2014 ◽  
Vol 229 (11) ◽  
pp. 2031-2044 ◽  
Author(s):  
Runze Duan ◽  
Zhiying Chen ◽  
Liansheng Liu
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Velocity Profile ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Liquid Sheet ◽  
Viscoelastic Liquid ◽  
Rheological Parameters ◽  
Liquid Sheets ◽  
Elasticity Number

A linear analysis method has been used to investigate the instability behavior of the viscoelastic liquid sheets moving in the surrounding ambient gas. The gas boundary layer thickness and the liquid sheet velocity profile were taken into account. The effects of gas and liquid viscosity on the growth rate were revealed. The governing equations were obtained through analysis of the liquid and gas domain and solved using the spectral method. The viscoelastic rheological parameters and some flow parameters have been tested to investigate their influences on the instability of the viscoelastic liquid sheets. The results reveal that the disturbances grow faster for the viscoelastic liquid sheet than Newtonian one with identical viscosity. Moreover, the increases of Weber number, elasticity number, gas Reynolds number, and momentum flux ratio can accelerate the breakup of the viscoelastic liquid sheet. However, the increases of time constant ratio, boundary layer thickness, and liquid Reynolds number have the opposite effects.

Effects of Freestream Mach Number, Reynolds Number, and Boundary Layer Thickness on Film Cooling Effectiveness of Shaped Holes

2016 ◽  
Author(s):  
Joshua B. Anderson ◽  
Ellen K. Wilkes ◽  
John W. McClintic ◽  
David G. Bogard
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Mach Number ◽  
Layer Thickness ◽  
Film Cooling ◽  
Boundary Layer Thickness ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

Film cooling effectiveness can be greatly affected by the characteristics of the upstream approach flow, although the degree of influence that different approach flow parameters exert is not completely clear. While some recent studies have investigated the effect of the approach Mach number, very little data exists that describes the separate effects of approach Mach and Reynolds number. Furthermore, the effect of boundary layer thickness on the effectiveness of shaped holes has not been thoroughly investigated. In this work, a parametric study of these effects was undertaken. This study considered approach flow velocities of Ma∞ = 0.03–0.15, with an independently varied Reynolds number of ReD = 5,500 – 15,500 by utilizing cooling hole diameters of D = 4.0 mm and 9.0 mm. The influence of boundary layer properties, including laminar and turbulent approach boundary layer characteristics, as well as varying boundary layer thickness, was also investigated. This work utilized plenum-fed shaped holes of an open-literature design. Hi-resolution IR thermography measured adiabatic effectiveness downstream of a single row of shaped cooling holes. The experiments were conducted at a density ratio of DR = 1.80 with an ambient temperature approach flow, using blowing ratios varying from M = 1.0 to 3.0. Special attention was paid to the implications of these results for scaling of effectiveness measurements from lower-speed approach flow conditions, as is present in a laboratory, toward higher speed conditions present within a gas turbine engine.

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