# The Resolution and Structure of High Reynolds Number Turbulent Boundary Layers Over Rough and Smooth Walls in Pressure Gradient

This dataset contains mean profiles for velocity, Reynolds stress, coefficients of pressure (Cp), and mean boundary layer parameters for a systematic varying family of high Reynolds number (11,000 < Re_theta < 83,000), low Mach number (0.08 < M < 0.20), turbulent boundary layer flows over smooth and very rough (300 < k+ < 900) surfaces in continually varying mild adverse and favorable pressure gradients (-0.91 < beta < 0.71).

The mean velocity and turbulence stress profiles were measured using particle image velocimetry (PIV), which were acquired at a sampling rate of 1 kHz and were ensemble averaged from 24,839 realizations. The PIV data were measured using two lens magnifications (a baseline and 2x magnified) and the provided data are produced by concatenating the profiles from the two resolutions. The pressure gradient (PG) family was generated on a wind tunnel test section wall by a 0.914-m chord NACA 0012 airfoil. The PG family for each wall-normal profile is denoted by the airfoil angle of attack and the streamwise location (in meters), which are both specified in the title of each file. All provided mean velocity and turbulence data were measured at a Reynolds number per meter of 2.18 million, based on freestream edge velocity, at three pressure gradient cases where the airfoil was at -10, 0, and +12 degrees, at three streamwise positions measured from the coordinate origin at x ~= 2.74 m, x~= 3.31 m, and x ~= 3.94 m, and for two surface conditions, rough and smooth. Provided for each condition are, the streamwise station of measurement (x), skin friction (Cf), boundary layer thickness (delta), displacement thickness (deltaS), momentum thickness (theta), local edge velocity (Ue), streamwise mean velocity profiles, and wall-normal, streamwise, and shear component Reynolds stress profiles in inner and outer coordinates, and uncertainty estimates (averaging and PIV bias) for the mean velocity and stress profiles also in inner and outer coordinates. The velocity components in the streamwise and wall-normal directions are denoted as u and v respectively. The spatial components in the streamwise, wall-normal, and spanwise directions are denoted as x, y, and z respectively. Inner coordinate normalizations of the mean profiles are done based on the shear velocity (ut) and the kinematic viscosity (nu). Outer coordinate normalizations of the the mean profiles are done based on the boundary layer thickness (delta) and the freestream edge velocity (Ue).

Also included in this database are the streamwise varying mean Cp distributions at two Reynolds numbers per meter of 2.18 million and 3.83 million, for twelve pressure gradient distributions generated by the airfoil at angles of attack varying between -10 to +12 degrees in increments of 2 degrees. These mean pressures were measured using both DTC Initium and Esterline 9818/98RK pressure scanners, with varying ranges, and static pressure taps that were installed on the research test wall and connected.

Further information regarding the acquisition parameters and instrumentation used to measure the mean turbulence statistics and pressure distributions can be found in the dissertation titled “The Resolution and Structure of High Reynolds Number Turbulent Boundary Layers Over Rough and Smooth Surfaces in Pressure Gradient.” The mathematical and physical definitions for these variables are also provided in the dissertation. These data are presented in two papers submitted for peer-review and are available as pre-prints (at the time of this data release). The papers are entitled “Spatial Resolution Limitations of Particle Image Velocimetry in High Reynolds Number Turbulent Boundary Layers,” and “History Effects and Wall-Similarity of Non-Equilibrium Turbulent Boundary Layers in Varying Pressure Gradient Over Rough and Smooth Surfaces”. The present data are also companion to the fluctuating pressure and other mean velocity characteristics released in the data repository as part of the dissertation entitled, “Surface Pressure Spectra Beneath High Reynolds Number Smooth and Rough Wall Boundary Layers in Pressure Gradient.”

**Related resource -**

**Title: **The Resolution and Structure of High Reynolds Number Turbulent Boundary Layers Over Rough and Smooth Walls in Pressure Gradient

**URI: **http://hdl.handle.net/10919/113290

**Group: **Center for Research and Engineering in Aero/hydrodynamic Technologies (CREATe), Kevin T. Crofton Department of Aerospace and Ocean Engineering

**Other References:**

Vishwanathan, V. "The Resolution and Structure of High Reynolds Number Turbulent Boundary Layers Over Rough and Smooth Walls in Pressure Gradient." Virginia Tech, 2023.

Vishwanathan, V., Fritsch, D. J., Lowe, K. T., and Devenport, W. J. "Spatial Resolution Limitations of Particle Image Velocimetry in High Reynolds Number Turbulent Boundary Layers." Experiments in Fluids.* In-Review*

Vishwanathan, V., Fritsch, D. J., Lowe, K. T., and Devenport, W. J. "History effects and wall similarity of non-equilibrium turbulent boundary layers in varying pressure gradient over rough and smooth surfaces," *12th International symposium on turbulence and shear flow phenomena (TSFP12), Osaka, Japan (19-22 July, 2022)*. 2022.

Vishwanathan, V., Fritsch, D. J., Lowe, K. T., and Devenport, W. J. “History Effects and Wall-Similarity of Non-Equilibrium Turbulent Boundary Layers in Varying Pressure Gradient Over Rough and Smooth Surfaces.” International Journal of Heat and Fluid Flow. *In-Review*