Wake flow past two parallel free-to-rotate cylinders
Description
Data result from careful measurements with hot wires and a high speed camera in an aerodynamic channel with a rectangular cross section of 0.147 m x 0.193 m to study the wake behavior after pairs of finite cylinders made from commercial PVC (Polyvinyl chloride) with 25 mm diameter and pitch-to-diameter ratio p/d = 1.26, assembled on a free-to-rotate table. The cylinder set was submitted to accelerating flows from zero to 5.4 and to10 m/s (ReD = 9.00x103 and 1.66x104) and a turbulence intensity of about 1%. Blockage ratio varied between 13% and 26%, depending on the angular position of the cylinders. Wake flow velocity was measured with a DANTEC StreamLine CTA system with two DANTEC 55P11 probes P1 and P2 (corresponding to velocities u1 and u2) aligned with the cylinders. The behavior of the free-to-rotate cylinders was studied using a high speed camera Phantom V411 – Ametek, with a 50 mm lens AF-S VR Micro-Nikkor, resolution 640 x 480 pixels, 1000 frames per second, corresponding to the 1kHz sampling frequency of the hot wire signal. Camera and data acquisition were synchronized with the CTA by the CTA controller. A 45o inclined mirror on the top of the channel was used to track the rotation angle, generating time series of the angular position (- to ) by means of the free software Tracker (https://physlets.org/tracker/) and of MATLAB® software. 0 rad (0o) corresponds to the position where both cylinders equally face the main flow. At - or , cylinders are aligned to the flow (tandem arrangement). A reference measurement of the bistable flow was firstly made by fixing the cylinder set up at 0o (side-by-side). Data acquisition was performed by a USB 16-bit NI USB-9162 A/D board, sampling frequency 1000 Hz, low pass filter 300 Hz, 131,072 samples, time series 131.072 s long. Time series of angular position were generated separately from velocity series. Data are in .txt format to be read by almost all software. Excerpts from the movies are in .mkv format. Velocity series files, fixed side-by-side cylinders: Re9000_Fixed_Cylinders_Velocity_Signal_(time_u1_u2).txt Velocity and angular position time series files, free-to-rotate side-by-side cylinders, Re=:9.00x103 Re9000_Rotating_Cylinders_Velocity_Signal_(time_u1_u2).txt synchronized with angular position time series Re9000_Rotating_Cylinders_Angular_Position_(time_angpos).txt) Velocity and angular position time series files, free-to-rotate side-by-side cylinders, Re=:1.66x104 Re16000_Rotating_Cylinders_Velocity_Signal_(time_u1_u2).txt synchronized with angular position time series Re16000_Rotating_Cylinders_Angular_Position_(time_angpos).txt) Cylinder rotation visualization files: Excerpt of movies of simultaneous top and side view of rotating cylinders. Cylinder position is inverted on top view by the mirror. Increase velocity for best visualization. Video_Rotating_Cylinders_Re9000.mkv Video_Rotating_Cylinders_Re16000.mkv
Files
Steps to reproduce
Data are in .txt format to be read by almost all software.