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In this study, the flow characteristics around two tandem square and equilateral triangle cylinders have been experimentally investigated. Experiments were conducted in an open-circuit subsonic wind tunnel with maximum free-stream turbulence level of 0.3%. Investigations for tandem arrangement were performed by moving the downstream square cylinder along the flow direction at various distances from the upstream triangular cylinder. Measurements were performed using 32-channel pressure transducer, three-component balances and hotwire anemometer. Square cylinder was placed at various distances from the upstream triangular cylinder and the flow Reynolds numbers were chosen to be 26000, 37000, 46000, and 51000. In this study, the mean and fluctuating lift and drag forces were measured for square cylinder at different spacings. Also, the distribution of mean and fluctuating surface pressure on the two-cylinders were measured. The vortex shedding frequency was measured by using both hotwire and surface pressure fluctuations on both cylinders and the results obtained by these two different measurement methods were compared. One of the most important outcome of the present study is the observation of two different flow patterns. It is noticed that the vortex shedding from the upstream cylinder was eliminated for cylinder distances lower than the critical spacing while for distances more than the critical spacing, the vortex shedding occurs from both triangular and square cylinders. The critical distance for this arrangement was obtained to be around three times of the length of the side length of the cylinders. [ABSTRACT FROM AUTHOR]

In the present research aeroacoustic characteristics of flow over a finite height wall mounted square cylinder at different angles of attack is investigated. The aspect ratio of the model and the boundary layer thickness were 7 and훿⁄퐷 = 4.27, respectively. The experiments were done in an acoustically improved aerodynamic wind tunnel. The purpose of this study is to identify correlation between the fluid and the acoustic fields. The flow-induced noise was measured using single microphone. The measured noise is related to aerodynamic characteristics of the flow using a single hot wire. The flowinduced noise of the cylinder is characterized in terms of frequency and magnitude. A sharp peak was observed in the far-field pressure at the vortex shedding frequency which was measured with hot wire anemometer. So, it could be concluded that vortex shedding is a source of aerodynamic noise generation. The Strouhal number obtained from two devices was almost equal to 0.11 which is in agreement with previous studies. Also, maximum vortex shedding frequency was measured for 훼 = 15°. It is observed that sound pressure level is increased with increasing upstream velocity. The overall sound pressure level ranged between 84.2 and 110.95 (dB) for upstream velocities in the range of 5-15 (m/s). The angle of attack has no important effect on overall sound pressure level. [ABSTRACT FROM AUTHOR]

Flow characteristics and sound pressure level in the acoustical far field and on the surface of a square cylinder at incidence are investigated for six angles of attacks. Flow around square cylinder is modeled using large eddy simulation method. The flow simulation is conducted using fluent commercial software. The results of the present study showed good agreement with the available experimental results. The minimum of drag coefficient, mean and root mean squared (rms) value of lift coefficient, and sound pressure level in acoustical far field occurred at 13o angle of attack which is due to the lowest values of fluctuating lift and drag forces at this angle of attack. The induced acoustic field is due to the fluctuating lift force acting on the rod. [ABSTRACT FROM AUTHOR]