Influence of distributed roughness elements on boundary layer transition for NACA0012 airfoil

2018 ◽  
Vol 32 (29) ◽  
pp. 1850349 ◽  
Author(s):  
Hao Dong ◽  
Shicheng Liu ◽  
Xi Geng ◽  
Kun Zhang ◽  
Keming Cheng
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Wind Tunnel ◽  
Skin Friction Coefficient ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Supersonic Wind Tunnel ◽  
Oil Film ◽  
Naca0012 Airfoil ◽  
Roughness Elements

The influence of distributed cylinder roughness elements on boundary layer transition for NACA0012 airfoil at Ma = 0.6 has been investigated by subsonic/transonic/supersonic wind tunnel experiment with oil-film interferometry. Three different heights and two different distances of cylinder roughness elements on the airfoil model were used, and the skin friction coefficient was measured by the oil-film interferometry. The experimental results show that higher roughness elements promote the transition earlier. In addition, narrower distance of roughness elements can delay the transition compared with the case of wider distance.

Image-based modelling of the skin-friction coefficient in compressible boundary-layer transition

2019 ◽  
Vol 875 ◽  
pp. 1175-1203 ◽  
Author(s):  
Wenjie Zheng ◽  
Shanxin Ruan ◽  
Yue Yang ◽  
Lin He ◽  
Shiyi Chen
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Skin Friction ◽  
Inclination Angle ◽  
Large Scale ◽  
Skin Friction Coefficient ◽  
Boundary Layer Transition ◽  
Small Scale ◽  
Layer Transition ◽  
Scale Structures

We develop a model of the skin-friction coefficient based on scalar images in the compressible, spatially evolving boundary-layer transition. The images are extracted from a passive scalar field by a sliding window filter on the streamwise and wall-normal plane. The multi-scale and multi-directional geometric analysis is applied to characterize the averaged inclination angle of spatially evolving filtered component fields at different scales ranging from a boundary-layer thickness to several viscous length scales. In general, the averaged inclination angles increase along the streamwise direction, and the variation of the angles for large-scale structures is smaller than that for small-scale structures. Inspired by the coincidence of the increasing averaged inclination angle and the rise of the skin-friction coefficient, we propose a simple image-based model of the skin-friction coefficient. The model blends empirical formulae of the skin-friction coefficient in laminar and fully developed turbulent regions using the normalized averaged inclination angle of scalar structures at intermediate and small scales. The model prediction calculated from scalar images is validated by the results from the direct numerical simulation at two Mach numbers, 2.25 and 6, and the relative error can be less than 15 %.

scholarly journals Study on Oil-Film Interferometry Measurement Technique of Hypersonic Boundary Layer Transition

2018 ◽  
Vol 36 (6) ◽  
pp. 1156-1161
Author(s):  
Hao Dong ◽  
Shicheng Liu ◽  
Xi Geng ◽  
Keming Cheng
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Skin Friction ◽  
High Speed ◽  
Smooth Surface ◽  
Roughness Element ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Oil Film ◽  
Hypersonic Wind Tunnel

Prediction of boundary layer transition is important for the design of hypersonic aircrafts. The study of boundary layer transition of hypersonic flow around a flat plate using oil-film interferometry was investigated at Φ500mm traditional hypersonic wind tunnel. In order to measure the skin friction fast and precisely on the hypersonic wind tunnel, the traditional oil-film interferometry technique is improved. A high-speed camera is used to capture the images of fringes and the viscosity of the silicon oil is modified according to the wall temperature measured by thermocouples during the test. The skin frictions of smooth surface and the surface with single square roughness element were measured. For the smooth surface, the boundary layer is laminar. However, the boundary layer transition is promoted by wake vortices induced by the roughness element. Both the results of skin friction with and without the roughness element are in good agreement with the simulation results correspondingly, indicating high accuracy of the oil film interferometry technique.

Infrared thermography of hypersonic boundary layer transition induced by isolated roughness elements

2021 ◽  
Author(s):  
Shicheng Liu ◽  
Meng Wang ◽  
Hao Dong ◽  
Tianyu Xia ◽  
Lin Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Infrared Thermography ◽  
Roughness Element ◽  
Transition Process ◽  
Boundary Layer Transition ◽  
Hypersonic Boundary Layer ◽  
Layer Transition ◽  
Leading Role ◽  
Roughness Elements ◽  
Element Shape

Roughness element induced hypersonic boundary layer transition on a flat plate is investigated using infrared thermography at Ma = 5 and 6 flow condition. Surface Stanton number is acquired to analyze the effect of roughness element shape and height on the transition process. The correlation between the vortex structure induced by roughness element and the wall heat streaks is established. The results indicate that higher roughness element would induce stronger streamwise heat flux streaks, lead to transition advance in streamwise centerline and increase the width of spanwise wake. Moreover, for low roughness element, the effect of the shape is not obvious, and the height plays a leading role in the transition; for tall roughness element, the effect on accelerating transition for the diamond roughness element is the best, the square is the worst, and the shape plays a leading role in the transition.

Boundary-Layer Transition Detection in a Cryogenic Wind Tunnel Using Luminescent Paint

1997 ◽  
Vol 34 (1) ◽  
pp. 34-42 ◽  
Author(s):  
Keisuke Asai ◽  
Hiroshi Kanda ◽  
Tetsuya Kunimasu ◽  
Tianshu Liu ◽  
John P. Sullivan
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Cryogenic Wind Tunnel
Sign in / Sign up

Export Citation Format

Share Document