Department News
An investigation of the Reynolds-number dependence of the axisymmetric jet mixin
Seminar Date
2001-09-06
Author
손문숙
Date
2001-09-06
Views
1378
1. 제 목 : An investigation of the Reynolds-number dependence of the axisymmetric jet mixing
layer using the 138 hot-wire probe and the POD
2. 연 사 : 정대한 교수
공군사관학교
3. 일 시 : 2001년 9월 19일(수) 17:00 – 18:00
4. 장 소 : 301동 1512호
5. 내 용 : The Proper Orthogonal Decomposition (POD) technique was applied to investigate the effects of Reynolds number and the characteristics of the organized motions or coherent structures as a function of downstream position from x/D=2 to 6 in a turbulent axisymmetric shear layer at Reynolds numbers of 78,400, 117,600, and 156,800. Data were collected simultaneously using the 138 hot-wire probe used by Citriniti and George (2000). The POD was then applied to a double Fourier transform in time and azimuthal direction of the double velocity correlation tensor. The lowest azimuthal mode for all POD modes, which dominated the dynamics at x/D = 3 in the previous experiments, dies off rapidly downstream. This is consistent with a trend toward homogeneity in the downstream evolution, and suggests that some residual value may control the growth rate of the far jet. On the other hand, for the higher azimuthal modes, the peak shifts to lower mode numbers and actually increases with downstream distance. These mixing layer data, normalized by similarity variables for the mixing layer, collapse at all downstream positions and are nearly independent of Reynolds numbers. The presentation will also show dynamic reconstructions of the velocity field at each location (in the manner of Citriniti and George). Most evident by contrast is the diminution with distance downstream of the "volcano"-like events described by them, and an evolution into a more "propeller"-like rotating pattern where the number of "blades" diminishes downstream.
6. 문 의 : 기계항공공학부 최 해 천 교수 (☏ 880-8361)
layer using the 138 hot-wire probe and the POD
2. 연 사 : 정대한 교수
공군사관학교
3. 일 시 : 2001년 9월 19일(수) 17:00 – 18:00
4. 장 소 : 301동 1512호
5. 내 용 : The Proper Orthogonal Decomposition (POD) technique was applied to investigate the effects of Reynolds number and the characteristics of the organized motions or coherent structures as a function of downstream position from x/D=2 to 6 in a turbulent axisymmetric shear layer at Reynolds numbers of 78,400, 117,600, and 156,800. Data were collected simultaneously using the 138 hot-wire probe used by Citriniti and George (2000). The POD was then applied to a double Fourier transform in time and azimuthal direction of the double velocity correlation tensor. The lowest azimuthal mode for all POD modes, which dominated the dynamics at x/D = 3 in the previous experiments, dies off rapidly downstream. This is consistent with a trend toward homogeneity in the downstream evolution, and suggests that some residual value may control the growth rate of the far jet. On the other hand, for the higher azimuthal modes, the peak shifts to lower mode numbers and actually increases with downstream distance. These mixing layer data, normalized by similarity variables for the mixing layer, collapse at all downstream positions and are nearly independent of Reynolds numbers. The presentation will also show dynamic reconstructions of the velocity field at each location (in the manner of Citriniti and George). Most evident by contrast is the diminution with distance downstream of the "volcano"-like events described by them, and an evolution into a more "propeller"-like rotating pattern where the number of "blades" diminishes downstream.
6. 문 의 : 기계항공공학부 최 해 천 교수 (☏ 880-8361)
