جستجوی مقالات مرتبط با کلیدواژه "trip wire" در نشریات گروه "مکانیک"

Investigating the flow around a circular cylinder is one of the classical problems of fluid mechanics. Unsteady forces formed behind the cylinder are caused by vortices separated from its surface. Controlling the intensity of vortex shedding leads to controlling the intensity of forces caused by vortices. One of equipment that is used to reduce fluctuations caused by vortices is trip wires. Therefore, in the present study, the fluctuating velocities, Reynolds shear stress and drag coefficient around the circular cylinder with the trip wire have been investigated at different Reynolds numbers. For this purpose, the diameter of the circular cylinder is 20 mm and the diameter of the installed trip wires is 0.25, 0.5, 0.75, 1, 1.5 mm. Trip wires are installed at θ=±40 and ±140 positions. The results show that the use of trip wires with a diameter of 0.25mm causes a decrease of 68%, 50% and 55% of fluctuating velocities (u', v', w') and a decrease of 85% Reynolds shear stress compared to the smooth cylinder. Also, the presence of a peak in the fluctuating velocity indicates the presence of large vortices behind the cylinder. Reynolds shear stress has a direct relationship with the diameter of the trip wire.

In this research, the behavior and characteristics of the wake of flow around an elliptic cylinder at zero angle of attack in the presence of a tripping wire were investigated experimentally. An aluminum elliptic cylinder with major axis, minor axis and height of 42.4 mm, 21.2 mm and 390 mm respectively, was used for this purpose. The cylinder model was examined in the test section of a blower type wind tunnel. The Reynolds numbers of the experiment based on major axis are 25700 and 51400 for 10 m/s and 20 m/s speeds, respectively. Tripping wires with the diameter of 0.5 mm, 1 mm, and 1.5 mm are placed symmetrically at both sides of the cylinder, and each are tested at angles of zero, 23.7, and 40.9 degrees with respect to the stagnation point. The drag coefficient of the smooth cylinder for both of the Reynolds numbers is about 0.6. The results indicate that in the best possible case, the drag coefficient for the 0.5 mm wire decreases by 75%. In the best cases, it is also reduced by 56.9% and 65.5% for the 1 mm and the 1.5 mm wires, respectively.

In this research, the behavior and characteristics of the wake of the flow around an elliptic cylinder at zero angle of attack in the presence of a tripping wire of 1 mm diameter were investigated experimentally. An aluminum elliptic cylinder with major axis, minor axis, and height of 42.4 mm, 21.2mm, and 390 mm, respectively, was used for this purpose. The cylinder model was examined in the test section of a blower type wind tunnel. The Reynolds numbers of the experiment, based on major axis were 25700 and 51400 for 10 m/s and 20 m/s speeds, respectively. Tripping wire placed symmetrically at both sides of the cylinder, and each were tested at angles of zero, 23.7, and 40.9 degrees with respect to the stagnation point. The drag coefficient of the smooth cylinder for both of the Reynolds numbers was about 0.6. The results indicate that in the best possible case, the drag coefficient for the 1 mm wire reduces by 56.5% at angle of the 23.7 degree. In the best case, it also reduces by 8.6% for angle of the zero degree, while in the worst case, the drag coefficient for angle of 40. 9 degree increase by 20.7%.