|Budget Amount *help
¥7,000,000 (Direct Cost : ¥7,000,000)
Fiscal Year 1994 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1993 : ¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1992 : ¥3,700,000 (Direct Cost : ¥3,700,000)
Discussions are presented concering the generation of streaks and fields around them in the wall turbulence using an instaneneoius LES data-base by means of a three dimensional computer graphics.
As a result, it is observed that the phenomena of prpduction, diffusion, redistoribution of Reynolds shear stress appear intermittently in space around streaks, and that Reynolds shear stress is found at places where production and events of turbulence at near wall region produce negative diffusion. Also in the modelling view points, it is shown that velocity-pressure gradient term should not be splitted into pressure diffusion term and pressure-strain one. Furthermore as for regeneration process at near wall region, it is found that quasistreamwise vortices generate new vortices upwardstream of themselves. These vortices are counter-rotating and constitute a sort of chain structure. Regeneration is due to tilting of wall normal vortices and to stretching of itself.
To be confirm the generality
of turbulence structure, it is needed to investigate inhomogeneous flow. Then, we measured a flow in a wavy channel flow, namely channel having a flat plate wall on one side and wavy in the other side. Experimented data, i.e., turbulence intencity, turbulence stresses and skeweness, shows the effect of pressure gradient in the flow field.
DNS code was manufactured for a round jet. As initial conditions nearly axi-symmetric or herical petrubation were assumed and calculations of temporally developing process of turbulent flow were conducted. As a result, in the case of helical peturbation, structure begins to appear earlier and maintains longer-lived coherent structure than in the nearly axi-symmetric peturabation case. It was demonstorated numerically the possibility of turbulence control and aeroacoustics control of jets.
The scheme of analysys of sound source distribution and the possibilty of high resolution analysys of sound souce were also presented by using DNS.It is demonstrated that estimation of the sound source on the surface of a square cylinder by observing the large-scale structure of flow should be careful. Less