2003 Fiscal Year Final Research Report Summary
Experimental and numerical studies for a dynamical coherent structure of the skewed turbulent boundary layer on a rotating cylinder
| Project/Area Number |
14550144
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Fluid engineering
|
|---|
| Research Institution | Gifu University |
|---|
Principal Investigator |
YAMASHITA Shintaro Gifu University, Mathematical & Systems Eng., Professor, 工学部, 教授 (20023236)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
FUKUSHIMA Chiharu Gifu University, Mathematical & Systems Eng., Research Associate, 工学部, 助手 (30262752)
INOUE Yoshihir Gifu University, Mathematical & Systems Eng., Associate Professor, 工学部, 助教授 (00176455)
WATANABE Takashi Nagoya University, Center for Information Media Studies, Professor, 情報メディア教育センター, 教授 (40182927)
|
|---|
| Project Period (FY) |
2002 – 2003
|
| Keywords | Three-dimensional turbulent wall layer / Dynamical coherent structure / Rotating body / Boundary layer / VITA technique / Four-Quadrant method / Wavelet transform / Proper orthogonal decomposition |
|---|
| Research Abstract |
The objective of the present study is to understand a dynamical coherent structure of a turbulent boundary layer. which has skewed velocity profiles, on a rotating cylinder in an axial flow. This is one of the basic models of a three-dimensional. turbulent wall layer, which should be treated as a complicated turbulent flow containing body force and extra strain rate.
This year, the bursting phenomena and the turbulent coherent structure were investigated using VITA technique and four-quadrant method according to the instantaneous time series data obtained the previous year. The results of the VITA analysis exhibit a decrease in amplitude of the fluctuating velocity signal, reduction of the intermittent period and a decrease in the detected frequency of the bursting phenomena. The results of the four-quadrant method exhibit that the contributions of a sweep event in the near wall region become relatively larger than those of the flat plate boundary layer. Continuous and discrete wavelet
… More
transform were also performed to the fluctuating velocity components in the local mean velocity direction within the cylindrical plane, and to the velocity components perpendicular to that plane. The results of the continuous wavelet transform recognized the existence of the peak of wavelet spectra as inherent phenomena. The results of discrete wavelet transform exhibit that there are high-energy spectra in some components of the fluctuating velocity. The velocity components recomposed by high-energy coefficient exhibit distinct. negative correlation.
Two-point space-time correlation and cross-spectra of velocity fluctuations were obtained from time series data at two positions in the azimuthal direction. Then, lateral spectra were obtained from two-point space correlations. The results suggest the existence of large scale helical eddies surrounding the rotating cylinder.
As a first step of numerical analysis, laminar flow analysis considering axisymmetric boundary condition, and turbulent flow analysis based on a k-ε model and algebraic turbulence model, were conducted. The results of turbulent flow analysis show that it is difficult to predict sufficiently both the mean and fluctuating flow filed. At present, we are developing a DNS code for low Reynolds number and verifying it in a channel flow. Less
|
