Making clear the generation mechanism of fluid dynamic noise is essential to reduce noise deriving from turbomachinery. The analysis of the aerodynamic noise generated from circular cylinder is carried out numerically and experimentally in a low noise wind tunnel. In this study, aerodynamic sound radiated from a circular cylinder in uniform flow is predicted numerically by the following two step method. First, the three-dimensional unsteady incompressible Navier-Stokes equation is solved using the high order accurate upwind scheme. Next, the sound pressure level at the observed point is calculated from the fluctuating surface pressure on the cylinder, based on modified Lighthill-Curl's equation. It is worth to note that the noise generated from the model is reduced rapidly when it is inclined against the mean flow. In other words, the peak level of the radiated noise decreases rapidly with inclination of the circular cylinder. The simulated SPL for the inclined circular cylinder is compared with the measured value, and good agreement is obtained for the peak spectrum frequency of the sound pressure level and tendency of noise reduction. So we expect that the change of flow structures makes reduction of the aerodynamic noise from the inclined models.

We focus on the sound generated from inclined circular cylinder in uniform flow with endplates in order to investigate influence of a aspect ratio that is the ratio of an interval between endplates to cylinder diameter. The analysis of the aerodynamic noise generated from the inclined circular cylinders is carried out numerically and experimentally. In this study, aerodynamic sound radiated from the circular cylinder in uniform flow is predicted numerically by the following two step method. First, the three-dimensional unsteady incompressible Navier-Stokes equations and the continuity equation are solved using the high order accurate upwind scheme. Next, the sound pressure level at the observed point is calculated from the fluctuating pressure on the cylinder surface, based on modified Lighthill-Curle's equation. The numerical simulation results agree with the experimental results qualitatively. It is shown with both experimental results and numerical results that interference between wake and endplates effects on the aerodynamic sound.

No abstract

No abstract

Objective: In Japan, hybrid neurosurgeons who perform both open surgical clipping as well as endovascular embolization for the treatment of intracranial aneurysms are common. Although many Japanese neurosurgeons can perform surgical clipping of middle cerebral artery aneurysms or internal carotid artery—posterior communicating artery aneurysms and coil embolization of cerebral aneurysms using simple techniques—only a limited number of neurosurgeons are able to perform surgical clipping and endovascular procedures for anterior communicating artery aneurysms, paraclinoid, or posterior circulation aneurysms using both treatment modalities equally and safely. Materials and methods: The senior author’s personal experience of more than 500 cases each of surgical clipping and endovascular embolization over the past 25 years included 110 cases of basilar tip aneurysms and 104 cases of paraclinoid internal carotid artery (ICA) aneurysms. Results: The safety and efficacy of both treatments appears to be the same, while the durability of surgical clipping is superior to that of endovascular embolization. Among the 110 basilar tip aneurysms, 18 patients were treated by surgical clipping and 94 were treated by endovascular embolization. The initial results of endovascular therapy seemed to be better than those of surgical clipping, although the rate of retreatment was higher. Among the 104 cases of paraclinoid ICA aneurysm, 23 patients were treated by surgical clipping and 81 were treated by endovascular embolization. The results of both treatments seemed to be same, while surgical clipping had apparently good long-term durability. Over the past 15 years, the frequency of surgical clipping for basilar tip aneurysms has decreased, and the procedure may eventually be abandoned for this type of aneurysm. However, surgical clipping still offers several advantages in the treatment of paraclinoid aneurysms. Conclusions: Hybrid neurosurgeons can make reasonable decisions concerning the choice of treatment for cerebral aneurysms, as they perform both treatments and understand the benefits and drawbacks of each modality.