Shock-tube chemistry. 1. The laminar-to-turbulent boundary layer transition

In the present study, the heat transfer characteristics on the suction and pressure sides of an outlet guide vane (OGV) are investigated by using liquid crystal thermography (LCT) method in a linear cascade. Because the OGV has a complex curved surface, it is necessary to calibrate the LCT by taking into account the effect of viewing angles of the camera. Based on the calibration results, heat transfer measurements of the OGV were conducted. Both on- and off-design conditions were tested, where the incidence angles of the OGV were 25 degrees and −25 degrees, respectively. The Reynolds numbers, based on the axial flow velocity and the chord length, were 300,000 and 450,000. In addition, heat transfer on suction side of the OGV with +40 degrees incidence angle was measured. The results indicate that the Reynolds number and incidence angle have considerable influences upon the heat transfer on both pressure and suction surfaces. For on-design conditions, laminar-turbulent boundary layer transitions are on both sides, but no flow separation occurs; on the contrary, for off-design conditions, the position of laminar-turbulent boundary layer transition is significantly displaced downstream on the suction surface, and a separation occurs from the leading edge on the pressure surface. As expected, larger Reynolds number gives higher heat transfer coefficients on both sides of the OGV.

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Effects of Shock-Tube Cleanliness on Hypersonic Boundary Layer Transition at High Enthalpy

AIAA Journal ◽

10.2514/1.j054897 ◽

2017 ◽

Vol 55 (1) ◽

pp. 332-338 ◽

Cited By ~ 17

Author(s):

Joseph S. Jewell ◽

Nicholaus J. Parziale ◽

Ivett A. Leyva ◽

Joseph E. Shepherd

Keyword(s):

Boundary Layer ◽

Shock Tube ◽

Boundary Layer Transition ◽

Hypersonic Boundary Layer ◽

Layer Transition ◽

High Enthalpy

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Boundary-Layer Transition in Accelerating Flows With Intense Freestream Turbulence: Part 2—The Zone of Intermittent Turbulence

Journal of Fluids Engineering ◽

10.1115/1.2910033 ◽

1992 ◽

Vol 114 (3) ◽

pp. 322-332 ◽

Cited By ~ 13

Author(s):

M. F. Blair

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Boundary Layer Transition ◽

Transitional Region ◽

Freestream Turbulence ◽

Intermittent Turbulence ◽

Adiabatic Wall ◽

Layer Transition ◽

Flow Acceleration ◽

Boundary Layer Turbulence

Hot-wire anemometry was employed to examine the laminar-to-turbulent transition of low-speed, two-dimensional boundary layers for two (moderate) levels of flow acceleration and various levels of grid-generated freestream turbulence. Flows with an adiabatic wall and with uniform-flux heat transfer were explored. Conditional discrimination techniques were employed to examine the zones of flow within the transitional region. This analysis demonstrated that as much as one-half of the streamwise-component unsteadiness, and much of the apparent anisotropy, observed near the wall was produced, not by turbulence, but by the steps in velocity between the turbulent and inter-turbulent zones of flow. Within the turbulent zones u′/v′ ratios were about equal to those expected for equilibrium boundary-layer turbulence. Near transition onset, however, the turbulence kinetic energy within the turbulent zones exceeded fully turbulent boundary-layer levels. Turbulent-zone power-spectral-density measurements indicate that the ratio of dissipation to production increased through transition. This suggests that the generation of the full equilibrium turbulent boundary-layer energy cascade required some time (distance) and may explain the very high TKE levels near onset.

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Evolution of Lagrangian coherent structures in a cylinder-wake disturbed flat plate boundary layer

Journal of Fluid Mechanics ◽

10.1017/jfm.2016.81 ◽

2016 ◽

Vol 792 ◽

pp. 274-306 ◽

Cited By ~ 13

Author(s):

Guo-Sheng He ◽

Chong Pan ◽

Li-Hao Feng ◽

Qi Gao ◽

Jin-Jun Wang

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Coherent Structures ◽

Plate Boundary ◽

Boundary Layer Transition ◽

Lagrangian Coherent Structures ◽

Hydrogen Bubble ◽

Layer Transition ◽

Low Speed Streaks ◽

Flat Plate Boundary Layer

Evolution of Lagrangian coherent structures (LCS) in a flat plate boundary layer transition induced by the wake of a circular cylinder is investigated. Both hydrogen bubble visualization and particle image velocimetry (PIV) techniques are used. It is found that downstream of the cylinder, the disturbance in the boundary layer experiences a fast growth followed by a slow decay in the transition. Lagrangian coherent structures are revealed by qualitative hydrogen bubble visualizations and quantitative finite-time Lyapunov exponents (FTLE) fields derived from the PIV data. The evolution of the LCS is considered from the very beginning of the transition up to when the boundary layer becomes fully developed turbulent flow. The mean convection velocity and average inclination angle of the LCS are first extracted from the FTLE fields. The streamwise length of the low-speed streaks seems to increase, while their spanwise distance decreases in the boundary layer transition. Proper orthogonal decomposition (POD) of the PIV data shows that low-speed streaks associated with the hairpin vortices and hairpin packets are the dominant coherent structures close to the wall in the transitional and turbulent boundary layer. The POD modes also reveal a variety of scales in the turbulent boundary layer. Moreover, it is found that large-scale coherent structures can modulate the amplitude of the small-scale ones.

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Further Experiments on Shock Tube Wall Boundary-Layer Transition

AIAA Journal ◽

10.2514/3.60138 ◽

1983 ◽

Vol 21 (7) ◽

pp. 1046-1048 ◽

Cited By ~ 9

Author(s):

Michael J. Chaney ◽

William J. Cook

Keyword(s):

Boundary Layer ◽

Shock Tube ◽

Tube Wall ◽

Boundary Layer Transition ◽

Layer Transition ◽

Wall Boundary Layer ◽

Wall Boundary

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Further experiments on shock tube wall boundary-layer transition

AIAA Journal ◽

10.2514/3.8198 ◽

1985 ◽

Vol 23 (8) ◽

pp. 1298-1299

Author(s):

William J. Cook ◽

Michael J. Chancy

Keyword(s):

Boundary Layer ◽

Shock Tube ◽

Tube Wall ◽

Boundary Layer Transition ◽

Layer Transition ◽

Wall Boundary Layer ◽

Wall Boundary

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Effect of Tripping Laminar-to-Turbulent Boundary Layer Transition on Tip Vortex Cavitation

Journal of Ship Research ◽

10.5957/jsr.1997.41.1.1 ◽

1997 ◽

Vol 41 (01) ◽

pp. 1-9

Author(s):

T. Pichon ◽

A. Pauchet ◽

A. Astolfi ◽

D. H. Fruman ◽

J-Y. Billard

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Flat Plate ◽

Cross Section ◽

Lift Coefficient ◽

Reynolds Numbers ◽

Boundary Layer Transition ◽

Tip Vortex ◽

Layer Transition ◽

Tip Vortex Cavitation

It is by now well established that, for Reynolds numbers larger than those corresponding to the conditions of laminar-to-turbulent boundary layer transition over a flat plate (≈0.5 × 106) and for a variety of wing shapes and cross sections, desinent cavitation numbers divided by the Reynolds number to the power 0.4 correlate with the square of the lift coefficient. In the case of foils having an NACA 16020 cross section and for Reynolds numbers below or close to those leading to transition over a flat plate, the results are very much different from those obtained for well-developed turbulent boundary layer conditions. Thus, a research program has been conducted in order to investigate the effect of boundary layer manipulation on cavitation occurrence. It consisted in determining the critical cavitation numbers, the lift coefficients, and the velocities in the tip vortex of foils having either a smooth surface or tripping roughness (promoters) near the leading edge. Tests were performed using elliptical foils of NACA 16020 cross section having the promoters extending over 60, 80 and 90 percent of the semi-span. The region near the tip was kept smooth in order to distinguish laminar-to-turbulent transition effects from tip vortex cavitation inhibition effects associated with artificial roughness at the wing tip. Results obtained at very low Reynolds numbers, ≥ 0.24 × 106, with the foil tripped on both the pressure and suction sides collapse rather well with those previously obtained at much larger Reynolds numbers with the smooth foil, and correlate with the square of the lift coefficient. The differences between the tripped and smooth foil results are due to the modification of the lift characteristics through the modification of the wing boundary layer, as shown by flow visualization studies, and as a result of the local tip vortex intensity.

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Transonic Drag Prediction on a DLR-F6 Transport Configuration

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.566.676 ◽

2012 ◽

Vol 566 ◽

pp. 676-679

Author(s):

Qiu Ya Zheng ◽

Jian Hu Feng ◽

Zun Huan Shen

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Transonic Flow ◽

Flow Fields ◽

Boundary Layer Transition ◽

Grid Refinement ◽

Layer Transition ◽

Total Drag ◽

Drag Prediction ◽

Block Structured

The accuracy of the drag prediction is investigated by simulating the transonic flow fields around the DLR-F6 wing-body (WB) and wing-body-nacelle-pylon (WNP) configurations. A series of coarse, medium, and fine density multi-block structured patched grids for both the DLR-F6 WB and WBNP configurations are employed to examine effect of grid on forces and incremental drag by adding the nacelle and pylon. The effect of boundary layer transition specification on the drag and incremental drag are also estimated. The results show that grid refinement decrease WB total drag by 6.8 drag counts, WBNP total drag by 15.3 drag counts. Specifying transition reduce WB total drag by 9.7 drag counts, WBNP total drag by 11 drag counts as compared to fully turbulent boundary layer computations, but transition has little effects on nacelle/pylon incremental drag.

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