The Wall Function for large eddy simulation (LES) proposed by Cabot is extended to the turbulence closure models. Predicted results are discussed and compared with well-documented experimental results. The model with Cabot's Wall Function significantly reduces the computing resources (CPU and storage) required and in most cases improves predicted results.

When air flows through pipe systems that include a corrugated segment, a whistling tone is generated and increases in intensity with increasing flow velocity. This whistling sound is related to the particular geometry of corrugated pipes, which is in the form of alternating cavities. This whistling is an environmental noise problem as well as a possible structural danger because of the resulting induced vibration. This paper studies the whistling behavior of various pipe systems with a combination of smooth and corrugated pipes through a series of experiments. The considered pipe systems consist of two smooth pipes attached at the upstream and downstream ends of a corrugated segment. Experiments with smooth and corrugated pipes, which had inner diameters of 15.25 and 16.5 mm, respectively, and various lengths, were performed for flow velocities of up to approximately 30 m/s. The minimum and maximum Strouhal numbers (St) obtained during our experiments were 0.25 and 0.38, respectively. For all pipe configurations investigated in this study, the lowest Mach number at which whistling was observed was 0.017, and the maximum was 0.093. The lowest frequency at which whistling was detected in our experiments was 650 Hz, and the highest was 3080 Hz. The results presented in the form of different variables and dimensionless parameters, including the frequency, Mach number, Strouhal number, and Helmholtz number. The average mode gap and number of excited acoustic modes were also taken into account for all considered configurations. The pipe systems with longer corrugated segments had broader whistling ranges than did configurations with shorter segments, indicating that the number of cavities inside the corrugated pipe has a direct effect on whistling. Increasing the smooth pipe length (either upstream or downstream) resulted in a decrease in the average mode gap between successive modes. The number of excited acoustic modes was primarily related to the corrugated segment length, but the smooth pipe length also had a pronounced effect on the excited modes for a constant corrugation length. The highest number of excited modes (13) was seen in the case of corrugated length 450 mm and smooth pipe length (either upstream or downstream) 400 mm while the lowest number of excited modes (1) was observed for corrugated length 250 mm and smooth pipe length (downstream) 300 mm and 400 mm.

The Wall Function for large eddy simulation (LES) proposed by Cabot is extended to the turbulence closure models. Predicted results are discussed and compared with well-documented experimental results. Although complete agreement with experiment is not yet achieved for some cases, it shows that the model with Cabot’s Wall Function significantly reduces the computing resources (CPU & storage) required where the first off-wall velocity nodes are located at 60 < y+ < 180; and in most cases improves predicted results.

Abstract. Bluff bodies under the external periodic force vibrate at their own natural or forced frequency. Rectangular bodies or similar structures such as high-rise towers and apartments, and recently a well-cited application -offshore floating bodies, usually needs to reduce these vibrations for stability and the mode control. Therefore, this study is aiming to reduce or control the vibration of a structure by a passive control method, i.e., TLCD (Tuned Liquid Column Damper). Controlling a moving body with a TLCD based on a variety of the orifice shape has been preliminary studied. In order to get a proper control, an optimized study is made on the design of the orifice shape, which has internal plates with the holes. The results show the force acting on the body due to the periodic movement highly depends on the number of holes on the plate and the height of the water level. Therefore, the optimum shape of the orifice and the height of the water level should be confirmed by a series of experiments.