Dataset for Reynolds number effects on surface-induced secondary flows in turbulent boundary layers

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'Dataset for Reynolds number effects on surface-induced secondary flows in turbulent boundary layers'
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Dataset DOI: 10.5258/soton/d3809

Date of data collection: 03/2023 – 06/2023 (original experiment) and 06/2024 (smooth-wall dataset)

Licence: CC-BY

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Associated publication
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This dataset presents the experimental data described in:

Medjnoun, T., Nilsson-Takeuchi, M. & Ganapathisubramani, B., "Reynolds number effects on surface-induced secondary flows in turbulent boundary layers", Journal of Fluid Mechanics, 2026.

Manuscript DOI: 10.1017/jfm.2026.11216

PLEASE REFER TO THE JOURNAL PAPER WHEN CITING OR USING THIS DATA.

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Overview
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The data provided here correspond to the post-processed
experimental measurements used to generate the figures
presented in the manuscript. All data are provided in MATLAB (.mat) format.

The dataset are made of three subsets. Using the data provided, together with the
normalisation parameters included in the files, the figures in the paper can be reproduced.

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File description and figure mapping
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1. Fig2_DragBalance.mat

This file contains the drag-balance measurements used to
evaluate the skin-friction coefficient and Reynolds-number
scaling presented in Figure 2.

The dataset includes the quantities required to compute the
skin-friction trends and to evaluate equation (3.1) in the
manuscript.

Main quantities include (variable names given in the file):
- Cf Skin-friction coefficient
- Rex Streamwise Reynolds number
- utau Friction velocity
- delta Boundary-layer thickness
- Re_tau Friction Reynolds number

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2. Fig3-12_HotWire_RoughWall.mat

This file contains the post-processed hot-wire anemometry data
for the rough-wall configurations (T50, T100, T200).

The data are sufficient to reproduce Figures 3–12, including:
- inner-scaled mean velocity profiles,
- velocity variance profiles,
- roughness-function trends,
- merging height and roughness height in wall units,
- pre-multiplied energy spectra,
- wavelength- and frequency-scaled spectral representations.

The data are stored in structured arrays indexed by:
- speed case
- surface geometry

Main quantities include:
- y, yplus Wall-normal coordinates
- mean_u, uplus Mean velocity profiles
- var_u Velocity variance
- Cf, utau Skin friction and friction velocity
- Re_tau, Re_theta Reynolds numbers
- Hplus, Lplus Roughness-related wall units
- Psdc Pre-multiplied energy spectra
- Fm, Wavek Frequency and wavelength coordinates
- delta, delta99 Boundary-layer thickness measures

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3. Fig3-12_HotWire_SmoothWall.mat

This file contains the smooth-wall hot-wire baseline data
used for reference and comparison with the rough-wall cases.

The variable naming convention and structure follow those
used in the rough-wall hot-wire dataset, where applicable,
to allow direct comparison.

Main quantities include:
- y, yplus Wall-normal coordinates
- mean_u, uplus Mean velocity profiles
- var_u Velocity variance
- Cf, utau Skin friction and friction velocity
- Re_tau, Re_theta Reynolds numbers
- Psdc Energy spectra
- Fm, Wavek Frequency and wavelength coordinates

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Notes on data usage
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- The data provided are post-processed results derived from
the original experimental measurements.
- The datasets are intended to support figure reproduction,
comparison, and further analysis.
- Raw hot-wire voltage signals and raw drag balance outputs
are not included.

湍流边界层（turbulent boundary layers）内表面诱导二次流的雷诺数（Reynolds number）效应数据集

数据集DOI：10.5258/soton/d3809

数据采集时间：2023年3月—2023年6月（原始实验阶段），2024年6月（光滑壁面数据集阶段）

授权协议：CC-BY

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关联发表论文
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本数据集对应下述论文中的实验数据：
Medjnoun T、Nilsson-Takeuchi M、Ganapathisubramani B，《湍流边界层内表面诱导二次流的雷诺数效应》，《流体力学杂志》，2026年。
论文DOI：10.1017/jfm.2026.11216

引用或使用本数据集时，请标注该期刊论文。

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数据概览
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本数据集提供的均为经后处理的实验测量数据，用于复现论文中的配图。所有数据均以MATLAB（.mat）格式存储。
本数据集包含三个子集。结合提供的数据与文件内附带的归一化参数，即可复现论文中的所有图表。

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文件说明与图表对应关系
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1. Fig2_DragBalance.mat
本文件包含用于计算表面摩擦系数与雷诺数缩放关系的阻力平衡测量数据，对应论文图2。数据集包含计算表面摩擦系数变化趋势以及验证论文中式(3.1)所需的全部物理量。文件内的主要变量包括：
- Cf：表面摩擦系数（Skin-friction coefficient）
- Rex：流向雷诺数（Streamwise Reynolds number）
- utau：摩擦速度（Friction velocity）
- delta：边界层厚度（Boundary-layer thickness）
- Re_tau：摩擦雷诺数（Friction Reynolds number）

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2. Fig3-12_HotWire_RoughWall.mat
本文件包含粗糙壁面配置（T50、T100、T200）的后处理热线风速仪（hot-wire anemometry）数据，可用于复现图3至图12的所有内容，包括：
- 内尺度化平均速度剖面、速度方差剖面、粗糙度函数变化趋势、壁面单位下的融合高度与粗糙度高度、预乘能谱（Pre-multiplied energy spectra）、波长与频率尺度化的频谱表示形式。
数据以结构化数组存储，索引维度包括：
- 来流速度工况、壁面几何构型
文件内的主要变量包括：
- y、yplus：壁面法向坐标（Wall-normal coordinates）
- mean_u、uplus：平均速度剖面（Mean velocity profiles）
- var_u：速度方差（Velocity variance）
- Cf、utau：表面摩擦系数与摩擦速度
- Re_tau、Re_theta：雷诺数（Reynolds numbers）
- Hplus、Lplus：与粗糙度相关的壁面单位
- Psdc：预乘能谱（Pre-multiplied energy spectra）
- Fm、Wavek：频率与波长坐标
- delta、delta99：边界层厚度相关度量

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3. Fig3-12_HotWire_SmoothWall.mat
本文件包含用于参考与对比的光滑壁面热线风速仪基准数据。变量命名规范与数据结构遵循粗糙壁面热线数据集的相关规则，以支持直接对比。
文件内的主要变量包括：
- y、yplus：壁面法向坐标
- mean_u、uplus：平均速度剖面
- var_u：速度方差
- Cf、utau：表面摩擦系数与摩擦速度
- Re_tau、Re_theta：雷诺数
- Psdc：能谱（Energy spectra）
- Fm、Wavek：频率与波长坐标

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数据使用注意事项
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- 本数据集提供的数据均为基于原始实验测量结果经后处理得到的产物。
- 本数据集旨在支持图表复现、对比分析与后续拓展研究。
- 未包含原始热线电压信号与原始阻力平衡输出数据。