Study on free shear layrs control by mians of direct numerical simulations.
| Project/Area Number |
03650154
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Fluid engineering
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
MAEKAWA Hiroshi The Univ.Electro-Communications, Dept.Mechanical & Control Eng., Associate Professor, 電気通信学部, 助教授 (90145459)
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| Project Period (FY) |
1991 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1993: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1992: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1991: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Receptivity / Direct Numerical Simulation / Instability Modes / Turbulence Control / Free Shear Flows / Topology / Compressibility / Turbulent Statistics / 乱流散逸 / 伴流 / 混合層 / データベース / 統計(乱流) / 不安定モ-ド / 直接数値シミュレ-ション |
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| Research Abstract |
In the present report, the transition mechanism and the structure evolutions in free shear layrs such as wakes, mixing layrs and jets are studied by means of direct numerical simulations. The free shear layrs are perturbed by temporally/spatially developing instability modes obtained from linear stability theory. The incompressible time-dependent Navier-Stoles equations were solved using pade finite difference approximations and a mapped pseudospectral Fourier method/spectral Galerkin method for spatial discretization. The equations were advanced in time using a compact third-order Runge-Kutta scheme. When a fundamental mode is amplified, the development of a stable vortex street in a plane wake appears downstream. When the inlet flow is forced by a fundamental mode and two subharmonics, a vortex street also appearsm, but the shape of the vorticies is distorted. The phase jitter around the fundamental frequency plays a critical role in generateing vorticies of random shape and spacing downstream. The weak back ground noise has little effect on the evolution, the two-dimensional double rollers are the dominant features of the wake. It is also found that the growth of small wavelength oblique modes leads to the breakdown of the spanwise rollers and counter-rotating streamwise vortical structures appear downstream. Furthermore, the effect of compressibility on the growth of instability modes in free shear layrs was investigated. Numerical results reveal that oblique modes are significant in the mixing layrs at the convective Mach number increases. In plane wakes and jets, two-dimensional instability modes show the most amplification rates for higher Mach numbers. Finally, a study of the geometry of flow patterns in numerically simulated compressible mixing layr was carried out using 3-D critical point methodology. Motions corresponding to high rates of dissipation are found to be characterized by a 3-D rate-of-strain topology of types nustable node/saddle/saddle and u
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Report
(4 results)
Research Products
(20 results)
