Experimental investigation of turbulent boundary layers at high Reynolds number with uniform blowing, part I: statistics

ABSTRACT

Uniform blowing in wall bounded shear flows is well known for its drag reducing effects and has long been investigated ever since. However, many contemporary and former research on this topic has confirmed the drag reducing effect but very less is known regarding how blowing is effecting the Reynolds stresses at high Reynolds number. Therefore, effect of uniform blowing has been experimentally investigated using Stereo Particle Image Velocimetry (SPIV) measurements in a zero pressure gradient turbulent boundary layer (TBL). The data presented in this literature covers a large range of high Reynolds number flow e.g. Re_θ = 7500∼19763 where Reynolds number is based on the momentum thickness. Upstream blowing was varied from 1%∼6% of free stream velocity and measurements were taken downstream after a short interval. Logarithmic and outer region of the TBL was given special attention in terms of investigating statistics and turbulence properties.

KEYWORDS:

• Turbulent boundary layers
• drag reduction
• flow control
• particle image velocimetry
• uniform blowing

Acknowledgments

In particular Dr.-Ing. habil. Holger Nobach for his financial and organisational guidance. The visiting team would like to acknowledge the strong support and friendly atmosphere provided by the Laboratoire de Mécanique des Fluides de Lille (LMFL) group during the whole test campaign. Data presented in this paper can accessed through the following link: https://turbase.cineca.it/init/routes/#/logging/view_dataset/82/tabmeta.

The LMFL equipment used in this presented paper (the wind-tunnel, the PIV equipment and the compressed air regulation and quantification circuit) was funded by the ELSAT2020 project supported by the European Community, the French Ministry of Higher Education and Research and the Hauts de France Regional Council, in the framework of the CNRS Research Foundation on Ground Transport and Mobility.

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

G. Hasanuzzaman  http://orcid.org/0000-0001-8432-1458

Notes

1 In the following description of notations used with $(\cdot {)}^{+}$ are for the parameters normalised with the wall shear velocity ($u_{\tau }$) and corresponding kinematic viscosity (ν). Here, subscript $(\cdot {)}_{SBL}$ indicate measurements over the smooth surface. On the other hand $(\cdot {)}^{\ast }$ are the parameters normalised with the corresponding outer scale factors namely free stream velocity, $U_{\mathrm{\infty }}$ and δ.

2 Design of the holes arrangement was adopted from the Tailored Skin Single Duct (TSSD) design from [83], this was discussed in detail from [84]. The original micro-perforated surface was designed for A340-300 with a hole diameter to to spanwise distance ratio of 1:2. Scale modification was done based on δ for spatially developped thick SBL condition such as LMFL wind tunnel.

3 The laser sheet thickness was computed with laser beam propagation formula (non Gaussian beam with $M^2=1.2$). With the optic used, the half-angle divergence of a Gaussian laser beam (theta) was computed and the light sheet thickness which is then equal to the beam waist diameter $2\times \mathrm{l}\mathrm{a}\mathrm{m}\mathrm{b}\mathrm{d}\mathrm{a}\times M^2/(\pi \times \mathrm{t}\mathrm{h}\mathrm{e}\mathrm{t}\mathrm{a})$, with the laser wavelength, $\mathrm{l}\mathrm{a}\mathrm{m}\mathrm{b}\mathrm{d}\mathrm{a}=532\mathrm{n}\mathrm{m}$. In order to confirm, the result was checked by making some light sheet impact on special paper, therefore, thickness of the light sheet was measured with binocular magnifier with an accuracy of $\pm 0.1\mathrm{m}\mathrm{m}$.

Additional information

Funding

The authors of the present paper would like to acknowledge the financial support of the “European High performance Infrastructures in Turbulence (EuHIT)” project in the frame of its Transnational Access activity. This is a Project coordinated by Max Plank Institute Göttingen and funded by the European Commission under Grant agreement no: 312778, in the frame of the Research Infrastructures Integrating Activity (framework of FP7-INFRASTRUCTURES-2012-1).