scholarly journals Boundary-Layer Transition and Global Skin Friction Measurement with an Oil-Fringe Imaging Technique

1993 ◽  
Author(s):  
Daryl J. Monson ◽  
George G. Mateer ◽  
Florian R. Menter
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Imaging Technique ◽  
Boundary Layer Transition ◽  
Friction Measurement ◽  
Layer Transition

Boundary Layer Transition Under High Free-Stream Turbulence and Strong Acceleration Conditions: Part 1—Mean Flow Results

1997 ◽  
Vol 119 (3) ◽  
pp. 420-426 ◽  
Author(s):  
R. J. Volino ◽  
T. W. Simon
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Free Stream ◽  
Boundary Layer Transition ◽  
Temperature Profiles ◽  
Mean Flow ◽  
Transfer Coefficients ◽  
Mean Velocity ◽  
Layer Transition ◽  
Free Stream Turbulence

Measurements from heated boundary layers along a concave-curved test wall subject to high (initially 8 percent) free-stream turbulence intensity and strong (K = (ν/U∞2) dU∞/dx) as high as 9 × 10−6) acceleration are presented and discussed. Conditions for the experiments were chosen to roughly simulate those present on the downstream half of the pressure side of a gas turbine airfoil. Mean velocity and temperature profiles as well as skin friction and heat transfer coefficients are presented. The transition zone is of extended length in spite of the high free-stream turbulence level. Transitional values of skin friction coefficients and Stanton numbers drop below flat-plate, low-free-stream-turbulence, turbulent flow correlations, but remain well above laminar flow values. The mean velocity and temperature profiles exhibit clear changes in shape as the flow passes through transition. To the authors’ knowledge, this is the first detailed documentation of a high-free-stream-turbulence boundary layer flow in such a strong acceleration field.

Experimental investigations on characteristics of boundary layer and control of transition on an airfoil by AC-DBD

2018 ◽  
Vol 32 (08) ◽  
pp. 1850108 ◽  
Author(s):  
Xi Geng ◽  
Zhiwei Shi ◽  
Keming Cheng ◽  
Hao Dong ◽  
Qun Zhao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Boundary Layer Transition ◽  
Plasma Actuators ◽  
Experimental Investigations ◽  
Dbd Plasma ◽  
Layer Transition ◽  
Piv Measurement ◽  
Induced Flow ◽  
And Control

Plasma-based flow control is one of the most promising techniques for aerodynamic problems, such as delaying the boundary layer transition. The boundary layer’s characteristics induced by AC-DBD plasma actuators and applied by the actuators to delay the boundary layer transition on airfoil at Ma = 0.3 were experimentally investigated. The PIV measurement was used to study the boundary layer’s characteristics induced by the plasma actuators. The measurement plane, which was parallel to the surface of the actuators and 1 mm above the surface, was involved in the test, including the perpendicular plane. The instantaneous results showed that the induced flow field consisted of many small size unsteady vortices which were eliminated by the time average. The subsequent oil-film interferometry skin friction measurement was conducted on a NASA SC(2)-0712 airfoil at Ma = 0.3. The coefficient of skin friction demonstrates that the plasma actuators successfully delay the boundary layer transition and the efficiency is better at higher driven voltage.

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 %.

Boundary Layer Transition Induced by Periodic Wakes

1998 ◽  
Vol 122 (3) ◽  
pp. 442-449 ◽  
Author(s):  
Xiaohua Wu ◽  
Paul A. Durbin
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Direct Numerical Simulation ◽  
Skin Friction ◽  
Plate Boundary ◽  
Boundary Layer Transition ◽  
Bypass Transition ◽  
Layer Transition ◽  
Benchmark Data ◽  
Flat Plate Boundary Layer

Turbulent wakes swept across a flat plate boundary layer simulate the phenomenon of wake-induced bypass transition. Benchmark data from a direct numerical simulation of this process are presented and compared to Reynolds-averaged predictions. The data are phase-averaged skin friction and mean velocities. The predictions and data are found to agree in many important respects. One discrepancy is a failure to reproduce the skin friction overshoot following transition. [S0889-504X(00)00503-1]

Simple Methods for Determining the Virtual Origin of Turbulent Boundary Layers in Hypersonic Flow on Sharp-Edged Flat Plates

1974 ◽  
Vol 41 (3) ◽  
pp. 551-553
Author(s):  
E. J. Hopkins
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Hypersonic Flow ◽  
Boundary Layers ◽  
Turbulent Boundary Layers ◽  
Boundary Layer Transition ◽  
Simple Relationship ◽  
Flat Plates ◽  
Layer Transition ◽  
Virtual Origin

For hypersonic Mach numbers up to about 8, the virtual origin for turbulent skin-friction calculations is shown to be close to the beginning of boundary-layer transition. A simple relationship between the beginning and end of boundary-layer transition is presented.

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.

Flat-Plate Boundary Layers in Accelerated Flow

2016 ◽  
Author(s):  
Pascal Bader ◽  
Manuel Pschernig ◽  
Wolfgang Sanz ◽  
Jakob Woisetschläger ◽  
Franz Heitmeir ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Skin Friction ◽  
Boundary Layers ◽  
Laser Doppler Anemometry ◽  
Plate Boundary ◽  
Boundary Layer Transition ◽  
Test Case ◽  
Transitional Region ◽  
Layer Transition

Flow in turbomachines is generally highly turbulent. The boundary layers, however, often exhibit laminar-to-turbulent transition. But also relaminarization of the turbulent flow may occur. The state of the boundary layer is important, since it strongly influences transport phenomena like skin friction and heat transfer. It is therefore vitally important for the designer to understand the process of boundary layer transition and to determine the position of transition onset and the length of the transitional region. In order to get into the details of transition and relaminarization it is helpful to study simplified test cases first. Therefore, in this paper a relaminarization test case for a simple geometry is investigated: The boundary layer flow along a flat plate is exposed to acceleration with three different acceleration parameters, which is known as a crucial parameter for relaminarization. Measurements were performed for the inlet free-stream velocities of 5 m/s and 9 m/s. Several experimental techniques for detecting transition were tested at the institute before their application. In this work, Laser-Doppler anemometry (LDA) measurements were performed, since this optical technique is non-intrusive and does not disturb the flow. Therefore it can also be used in narrow flow passages where probe blockage can be crucial. As an outcome of this study, an insight into the process of relaminarization is presented. Although the key onset values for relaminarization stated in literature are fulfilled with the test setup, full relaminarization over the whole boundary layer has not been achieved. It seems, that using only the skin friction as indicator for relaminarization is not sufficient.

Sign in / Sign up

Export Citation Format

Share Document