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This study was carried out to investigate the loss mechanism of a blade with a harbor seal whisker structure on the trailing edge under different Mach numbers. The loss of high-pressure turbine blades with four different trailing edge geometries, including a prototype, an elliptical trailing edge (ETE), a sinusoidal trailing edge (STE), and a biomimetic trailing edge (BTE) at Mach numbers of 0.38–1.21 is studied. The delayed detached-eddy simulation method is used to predict the detailed flow of the four cascades. The result shows that, when the Mach number is less than 0.9, the BTE can effectively reduce the energy loss coefficient compared with the other three cases. As the Mach number increases, the three-dimensional characteristics of the wake behind the BTE weaken. The energy loss coefficient of the blade with the BTE is close to that of the blade with the ETE and STE when the Mach number is greater than 0.9. Besides this, by controlling the wake, the BTE can effectively suppress the dynamic movement of shock waves in the cascade at high Mach numbers.

This paper focuses on an aerodynamic noise study of outlet elbow of Continuous Positive Airway Pressure (CPAP) machine by analyzing the wall pressure fluctuations and predicting the far filed sound generated by turbulent flow. A hybrid approach combing the Larger-Eddy Simulation (LES) and Ffcowcs Williams-Hawkings (FW-H) acoustic analogy was used to simulate the flow distribution as well as calculate the flow-induced noise for a three-dimensional elbow pipe. Then, a different elbow structure was designed to form the appropriate structure for the air outlet via considering the sound pressure level of each model. As a result, elbow with guiding plate was demonstrated to be an effective method to reduce the aerodynamic noise strength since this design could weaken the wall pressure fluctuation and vortex magnitude. Furthermore, the decreased magnitude could reach more than 1dB when velocity increased from 5m/s to 9m/s. The results of simulation were a little higher than experimental results since the background noise, elbow vibration and the defect of FW-H equation which couldn't be eliminated thoroughly.

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