1999 Fiscal Year Final Research Report Summary
STUDY OF TURBULENT TRANSITION MECHNAISM IN COMPRESSIBLE FLOWS AND PREDICTION OF TRANSITION
| Project/Area Number |
10650163
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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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 Hroshi AT DEPT. F MECHANICAL ENGINEERING AND INTELIGNET SYSTEMS IN UNIVERSITY OF ELECTRO-COMMUNICATIONS, ASSOCIATE PROFESSOR, 電気通信学部, 助教授 (90145459)
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| Co-Investigator(Kenkyū-buntansha) |
前川 博 電気通信大学, 電気通信学部, 助教授 (90145459)
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| Project Period (FY) |
1998 – 1999
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| Keywords | compressible flow / Transition to turbulence / Free shear flow / Boundary layer / Direct Numerical Simulation / Linear stability theory / Critical point theory / Singular point |
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| Research Abstract |
The three-dimensional time-dependent compressible Navier-Stokes equations and a linear stability theory are numerically solved to study plane Poiseuille flows, supersonic boundary layers and supersonic wakes. Navier-Stokes Characteristic Boundary Conditions are used in the non-periodic direction. High order linear/non-linear compact finite difference schemes and a classical Fourier method are employed in the nonperiodic and periodic directions respectively. Unstable disturbances are obtained from the linear stability theory using a Chebyshev/Fourier collocation method. The results regarding transient growth for subsonic Poiseuille flows indicate that disturbances with large amphtudes can create streamwise vortices triggered by streamwise velocity fluctuations of a low frequency. At high Mach number of M = 4.5, the results show that Lambda shock is generated close to the inlet and that acoustic pressure fluctuations appear downstream. Dual vortical structures close to the wall and around the critical layer are also generated downstream in the Poiseuille flow at M = 4.5. The numerical results for supersonic boundary layers at M = 4.5 using non-linear compact schemes indicate the presence of boundary layer instability waves of second mode on the plate after an oblique shock. Finally, the geometry of flow patterns in numerically simulated compressible wakes in a transitional regime has been studied using three-dimensional critical point theory. A statistical robust feature in the tensor invariants of P, Q and R space is explained by the solution trajectories of the three first-order evolution equations of the invariants. Statistics of the right-hand non-linear term of the evolution equations are also studied in this work.
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