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.

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.

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.

Freestream Flow Effects on Film Effectiveness and Heat Transfer Coefficient Augmentation for Compound Angle Shaped Holes

2017 ◽  
Author(s):  
Joshua B. Anderson ◽  
John W. McClintic ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary Webster
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Layer Thickness ◽  
Film Cooling ◽  
Gas Turbines ◽  
Boundary Layer Thickness ◽  
Adiabatic Effectiveness ◽  
Compound Angle

The use of compound-angled shaped film cooling holes in gas turbines provides a method for cooling regions of extreme curvature on turbine blades or vanes. These configurations have received surprisingly little attention in the film cooling literature. In this study, a row of laid-back fanshaped holes based on an open-literature design, were oriented at a 45-degree compound angle to the approaching freestream flow. In this study, the influence of the approach flow boundary layer thickness and character were experimentally investigated. A trip wire and turbulence generator were used to vary the boundary layer thickness and freestream conditions from a thin laminar boundary layer flow to a fully turbulent boundary layer and freestream at the hole breakout location. Steady-state adiabatic effectiveness and heat transfer coefficient augmentation were measured using high-resolution IR thermography, which allowed the use of an elevated density ratio of DR = 1.20. The results show adiabatic effectiveness was generally lower than for axially-oriented holes of the same geometry, and that boundary layer thickness was an important parameter in predicting effectiveness of the holes. Heat transfer coefficient augmentation was highly dependent on the freestream turbulence levels as well as boundary layer thickness, and significant spatial variations were observed.

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.

Effect of Mainstream Variables on Jets Issuing from a Row of Inclined Round Holes

1979 ◽  
Vol 101 (2) ◽  
pp. 298-304 ◽  
Author(s):  
K. Kadotani ◽  
R. J. Goldstein
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Film Cooling ◽  
Boundary Layer Thickness ◽  
Free Stream ◽  
Source Model ◽  
Mean Velocity ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Eddy Diffusivities

The effects of boundary layer thickness, Reynolds number and free stream turbulence intensity on jets issuing from a row of inclined holes are investigated from the viewpoint of film cooling. The local film cooling effectiveness and mean velocity and mean temperature distributions are measured. The turbulent eddy diffusivities are evaluated from calculations based on a heat source model. The boundary layer thickness and the free stream turbulence significantly influence the jet-mainstream interaction process and consequently the film cooling performance.

Effects of a Source-Type Hypersonic Free Stream on the Flow Field about an Axisymmetric Cone

1966 ◽  
Vol 17 (2) ◽  
pp. 161-176
Author(s):  
Stuart B. Savage
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Layer Thickness ◽  
Surface Pressure ◽  
Shock Layer ◽  
Boundary Layer Thickness ◽  
Free Stream ◽  
Inviscid Flow ◽  
Source Type ◽  
Displacement Thickness

SummaryMost hypervelocity tunnels presently make use of conical or wedge type nozzles which produce source-type flow non-uniformities in the test section. The present paper considers the effects of such free-stream non-uniformities on the flow fields about slender axisymmetric cones. The inviscid flow is considered within the framework of the Newtonian expansion procedure of Cole and simple expressions are obtained for the flow field properties in the shock layer. This inviscid analysis predicts that a free-stream gradient of a magnitude typical of present hypervelocity test facilities can cause sizeable reductions in surface pressure and increased shock-layer thickness at the aft end of long slender conical models. The cone pressure, accounting for the viscous-inviscid interaction, is obtained by applying the inviscid analysis in tangent-cone fashion to the effective body (i.e. physical cone plus boundary-layer displacement thickness). Cheng’s simple equation is used to approximate the hypersonic boundary-layer development. Large increases in the boundary-layer thickness at the aft end of the model are predicted as a consequence of the source flow effects. The analyses agree well with experimental measurements of surface pressure and boundary-layer thickness made on a 5° half-angle cone tested in the Republic 24 inch Longshot I hypervelocity shock tunnel.

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.

Direct Experimental Measurements of Heat Transfer Coefficient Augmentation due to Approach Flow Effects

2018 ◽  
Author(s):  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary Webster
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Layer Thickness ◽  
Film Cooling ◽  
Boundary Layer Thickness ◽  
Experimental Program ◽  
The Heat Transfer Coefficient

The injection of film cooling can have a strong impact on the heat transfer coefficient (HTC) between the overflowing freestream gas and the cooled surface. This study investigated the influence of approach flow characteristics, including the boundary layer thickness and character (laminar and turbulent), as well as the approach flow Reynolds number, on the HTC. The influence of these parameters was previously unreported in the open film cooling literature. The figure of merit for this study was the HTC augmentation, that is the ratio of heat transfer coefficients for a cooled vs. uncooled surface. For this work, a direct measurement of the heat transfer coefficient was made, using a heated foil surface which provided a known wall heat flux. Generally for this type of measurement, a flux foil is placed downstream of the coolant hole. However, for this experimental program a heat flux foil was also placed upstream of the film cooling holes, in order to generate an upstream thermal boundary layer which would be more representative of actual engine conditions. Such a configuration has rarely been seen in published studies. An open-literature shaped-hole design was used, known as the 7-7-7 hole, in order to compare with existing results in the literature. A variety of blowing conditions were tested from M = 0.5–3.0. Two elevated density ratios of DR = 1.20 and DR = 1.80 were used. High-resolution IR thermography was used for these measurements, providing a highly-accurate and spatially-resolved measurement of HTC augmentation. The results indicated that turbulent boundary layer thickness had a modest effect on HTC augmentation, whereas a very high level of augmentation was observed for a laminar approach boundary layer. The presence of upstream heating greatly increased the HTC augmentation in the near-hole region, although these effects died out by 10–15 diameters from the holes.

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.

Sign in / Sign up

Export Citation Format

Share Document