원형 관내의 감쇠하는 swirl 유동에서 단일기포 거동에 대한 해석

Abstract

본 연구에서는, 관벽 둘레에서 접선방향의 액체를 주 유동 내로 분사시킴에 의하여 발생된, 감쇠 선회류에 존재하는 단일 기포의 운동에 대한 것으로, 기포 거동을 지배하는 운동식을 유도했고, 이 식들은 이미 발표된 액체의 속도관계 실험식들을 사용하여 수치적으로 풀었다.

축방향 기포운동은, 기포의 초기 위치와 액체의 초기 선회강도에 따라, 하류로 계속 이동하는 것과, 하류로 이동 후, 상류로 이동하는 것의 두 형태로 구분할 수 있다 접선과 반경 방향에서, 기포는 관 중심에 접근할수록 감속한다. 그러나 선회 운동량이 큰 유동에서, 기포는 중심에서 유한한 속도를 가지므로, 관 중심 근처를 진동한다 또한, 기포 크기가 작을수록 단위 체적당의 항력이 증가하므로, 작은 기포일수록 반경방향으로 느리게 이동한다. 한편, 기포가 중심에 도달할 때까지의 기포 축방향 이동거리는 기포가 작아질수록 증가한다.

In this work, the motion of single bubble, in a decaying swirl liquid flow, which was created by tangential liquid injection into main liquid flow at the periphery wall of the tube, was studied. The equations of motion governing the bubble behavior were derived and solved numerically by using experimental relations of liquid velocity published already.

The motions of bubble, in axial direction, can be divided into two patterns ; the one is moving downstream always and the other is moving upstream after some travel to downward, depending on the initial position of bubble and initial swirl intensity of liquid.

In tangential and radial direction, the bubble decelerates as it approaches the center of the tube. But, in the flow with high swirl intensity, the bubble has a finite radial and tangential velocity as it reaches the center, therefore the bubble may oscillate around the center of the tube. And the smaller bubble moves radially slowly due to the larger drag force per unit volume of gas experienced by the smaller bubble, while the axial distance travelled by the bubble before it reaches the center decreases as the bubble size increases.

In this work, the motion of single bubble, in a decaying swirl liquid flow, which was created by tangential liquid injection into main liquid flow at the periphery wall of the tube, was studied. The equations of motion governing the bubble behavior were derived and solved numerically by using experimental relations of liquid velocity published already.

The motions of bubble, in axial direction, can be divided into two patterns ; the one is moving downstream always and the other is moving upstream after some travel to downward, depending on the initial position of bubble and initial swirl intensity of liquid.

In tangential and radial direction, the bubble decelerates as it approaches the center of the tube. But, in the flow with high swirl intensity, the bubble has a finite radial and tangential velocity as it reaches the center, therefore the bubble may oscillate around the center of the tube. And the smaller bubble moves radially slowly due to the larger drag force per unit volume of gas experienced by the smaller bubble, while the axial distance travelled by the bubble before it reaches the center decreases as the bubble size increases.