Wake flow past two parallel cylinders at several incidence angles
2020-04-10T07:16:12Z (GMT) by
Data result from careful measurements with hot wires in an aerodynamic channel and from flow visualization in a hydraulic channel to study the wake behavior after pairs of finite cylinders with 25 mm diameter and pitch-to-diameter ratio p/d = 1.26, at several angular positions to the flow, 0o (side-by-side), 2.5o, 5o, 15o, 25o, 35o, 45o, 75o and 90o (tandem). The aerodynamic channel was made of acrylic, with a cross section of 0.147 m x 0.193 m. The flow velocity was 10 m/s, turbulence intensity of about 1%, Reynolds number 1.66x104. The two circular cylinders were made of PVC with a diameter of 25.1 mm, and a blockage ratio of 13% - 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. 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. The cylinders and the probes were numbered as 1 and 2. Cylinder number one is on the left side of the flow stream. At positions different of 0o, cylinder number 2 faced the flow firstly. Flow visualizations were made in a closed-circuit hydraulic channel with the same dimensions as the aerodynamic channel. The Reynolds number was 1.97x10³ (kinematic viscosity of the water at 15 ºC was 1.14 x 106 m²/s), turbulence intensity about 4%. Two ink tanks provided dye, injected by gravity in the flow through 3 mm diameter flexible PVC tubes inside the cylinders. Video resolution was 1080 x 720 pixels at 30 FPS. Each movie was 25 minutes long. A mirror at 45° with the camera allowed simultaneous top and side view. From top view images, a time series of the angle formed between the tangent to the cylinder wall and the deflected flow from the gap between the cylinders was generated with Tracker and Matlab software. Angles were measured at each 200 frames (6.67 s), sampling frequency of 0.15 Hz. Data are in .txt format to be read by almost all software. Excerpts from the movies from the flow visualizations are in .mkv format. Velocity series files: Velocity signals from the hot wire anemometers (m/s) – Time (s); velocity Probe 1; velocity Probe 2 06 Vel 0 deg.txt: Side-by-side cylinders 0o. 11 Vel 2.5 deg.txt: 2.5o. 12 Vel 5 deg.txt: 5o. 13a Vel 15 deg.txt: 15o. 13b Vel 25 deg.txt: 25o. 13c Vel 35 deg.txt: 35o. 15a Vel 45 deg.txt: 45o. 15b Vel 60 deg.txt: 60o. 15c Vel 75 deg.txt: 75o. 15d Vel 90 deg.txt: Tandem 90o. Angular deflection file: 16 Flow deflection angle.txt: Deflection angles from flow visualizations respectively for 0° (side-by-side cylinders), 2.5°, 5°, 15°, 25°, 35°, 45°, 60°, 75° and 90° (tandem). Flow visualization files: Top and side view of flow visualization. Cylinder position is inverted on top view by a mirror. 0deg.mkv: 0° (side-by-side). 2.5deg.mkv: 2.5o. 5deg.mkv: 5o. 15deg.mkv 15o. 25deg.mkv: 25o. 35deg.mkv: 35o. 45deg.mkv: 45o. 60deg.mkv: 60o. 75deg.mkv: 75o. 90deg.mkv: 90o (tandem).