# Free end flow influence on bistable flow past finite cylinders

## Description

Data result from careful measurements with hot wires in an aerodynamic channel and from flow visualization in a hydraulic to study the bistability phenomenon after pairs of finite cylinders with 25 and 32 mm diameter and aspect ratios of 3 and 4. Measurements were performed in the wake of single and side-by-side finite cylinders, with a sampling frequency of 1000 Hz and a low pass filter at 300 Hz. Each data series has 2^15 elements, corresponding to a time of 32.768 s. Data obtained from digital movies of the flow visualization experiments, used to determine the influence of the flow from the top of the cylinder on the bistable phenomenon, are 159.959 s long, with 160 elements (0.999Hz sampling frequency). Hot wire data are in form of velocity series, movie data in form of distance series. Pitch-to-diameter ratio for side-by-side cylinders was p/d = 1.26. The aerodynamic channel was made of acrylic, with a cross section of 0.147 m x 0.193 m. The flow velocity could be varied from 0 to 15 m/s, with a turbulence intensity of about 1%. The reference velocity, measured with a Pitot tube, and the cylinder diameter, defined the Reynolds number from Red = 2.0×10^4 to Re = 2.5×10^4. DANTEC StreamLine hot wire anemometer with two single hot wire was used. Data acquisition was made with a 16-bit A/D-board (NI 9215-A) with a USB interface using DANTEC StreamWare 3.4 software. Flow visualizations were made in a closed-circuit hydraulic channel with the same dimensions as the aerodynamic channel, with a flow rate from 1.66×10^-6 to 1.93×10^-3 m³/s, velocities of up to 0.068 m/s and turbulence intensity of 4%. The Reynolds number was 2.0×10^3. Data are in .txt format to be read by almost all software. 04-Velocity – non simultaneous 25-3D-25-4D-32-3D-32-4D.txt: Velocity series m/s x time s for : a) 25 mm h/d =3 (253D). b) 25 mm h/d=4 (254D). c) 32 mm h/d =3 (323D). d) 32 mm h/d=4 (324D). 05-Velocity –25-4D-Re25e4.txt: Velocity series m/s x time s for finite cylinder with 25 mm diameter, h/d =4 and Re = 2.5 x 104 Probe 1 – V1. 07-Velocity –25-3D-Re25e4.txt: Velocity series m/s x time s for finite cylinders with 25 mm diameter, h/d=3 and Re = 2.5 x 104 Probe 1 – V1. 10-Distance 25-4D 25-3D.txt: Distance mm x time s for 25 mm diameter cylinders with h/d = 4 (B254D) and 3 (B253D). 11-Velocity –32-4D-Re20e4-P1.txt: Velocity series m/s x time s for 32 mm diameter cylinders finite cylinders with h/d=4 and Re = 2.5 x 104. Probe 1 – V1. 12-Velocity –32-4D-Re20e4-P2.txt: Velocity series m/s x time s for for finite cylinders with h/d=4 and Re = 2.5 x 104 . Probe 2 – V2. . 14-Velocity –32-4D-Re25e4-P1.txt: Velocity series m/s x time s for finite cylinders with h/d=4 and Re = 2.5 x 104. Probe 1 – V1. 15-Velocity –32-4D-Re25e4-P2.txt: Velocity series m/s x time s for finite cylinders with h/d=4 and Re = 2.5 x 104. Probe 2 – V2. 17-Distance 32-4D 32-3D.txt: Series of distance mm x time s for 32 mm diameter cylinders with h/d = 4 (B324D ) and 3 (B323D).