Open-end Correction for Shock Waves Discharged from the Exit of Various Types of Ducts

초록

On reaching an open end, weak shock waves generate a complex three-dimensional wave pattern in the exit area thereby causing the reflection phenomenon of the expansion waves to delay. The flow does not end at the physical end of the duct and the process of adjustment is subject to constant modification by subsequent incident waves. The reflected wave begins its journey after a small time lag thereby creating an imaginary distance from the duct exit known as open end correction. The aim of the present investigation is to obtain the open end correction values for weak shock waves emitting from the end of diverse duct configurations, a phenomenon commonly encountered in numerous internal flow scenarios. The open end correction values exhibit a negative trend in comparison to a straight duct for a specified range of pressure ratios in the case of the converging area duct. For diverging area ducts, it has been observed that the end correction values indicate an increasing pattern with the change in the area ratio value at the exit. The predicted results of the open end correction in the condition of sudden enlargement duct geometry illustrate an identical pattern to that of the diverging duct scenario. Conversely, in the case of sudden reduction duct, the open end correction value displays a negative trend beyond the pressure ratio value of 2.85 for the area ratio value of 0.3.