二次元ディフューザ流れの数値解析
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概要
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The diffusers are used for converting a part of the excess velocity pressure at inlet of the passage to static pressure by deccelerating the flow in expanding channel. Many types of the diffuser are utilized in piping, turbomachinery and other fluid systems. Such as in the exhaust tube of the internal combustion engine, where pulsating flow exists. In the past, however, the diffuser performance in the pulsating flow has scarcely been investigated because of the fact that a lot of difficulty exist in the experiment as well as in the analysis. Diffuser performance can be improved by the following four effective methods: Converting a part of the excess velocity pressure at diffuser outlet to static pressure by mixing in a constant cross-section added to a diffuser outlet, removing the low energy flow near the wall by suction, installing vanes within a wide angle diffuser, and re-energizing flow near the wall by blowing. As above mentioned, the diffuser performance in steady flow has mainly been studying by means of experiments up to the present, but the numerical method has hardly been conducted. In this paper, a numerical study is conducted to examine a computer simulation method of the steady flow and the pulsating flow in diffusers. The flow is calculated by the finite-difference schemes for solving the Poisson equation of stream function and the vorticity transport equation. First, the results of the numerical analysis show that the former three methods as previously mentioned are effective enough to prevent separation, but the fourth is not, because the blowing calculated is perpendicular to a diffuser wall. The calculated Reynolds numbers of the steady flow are Re=0-100. Next, the pulsating diffuser flows calculated have the dimensionless periods of T=10 and T=50 of sinusoidally oscillated velocity respectively, which are superimposed on the steady flow. In the calculated results, the former gives a flow with accelerated and deccelerated parts having a strong non-linearity and unsteadiness, the latter shows a flow near the steady flow. The calculated timeaveraged Reynolds number of the pulsating flows is Re=80.
- 独立行政法人 海上技術安全研究所の論文
- 1989-05-30
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