University of Minnesota
Aerospace Engineering and Mechanics
Winter 1997 Seminar Series


Turbulence Transport Mechanism in the Stagnation Region of an Axisymmetric Impinging Jet Flow


Professor Koichi Nishino

Yokohama National University



Abstract

Turbulence transport mechanism in the stagnation region of an axisymmetric impinging jet flow was studied from ensemble averaged flow quantities measured with particle tracking velocimetry (PTV). The measurements were made in a submerged water jet facility at a Reynolds number of 13,000 based on the nozzle exit velocity and the nozzle diameter. Both 2-D and 3-D PTV techniques were used for the measurement of highly turbulent flows in the stagnation region. Examination of the axial mean momentum balance revealed that the turbulent normal stress had a significant contribution to the axial mean momentum transport in a sense that it contributed to the increase in the static pressure near the impingement wall. Detailed distributions of the turbulent stresses and the triple correlations of velocity fluctuations were obtained. Examination of the budget equation for the turbulent kinetic energy showed that the net negative production of the turbulent kinetic energy occurred in the vicinity of the wall. This unique feature was analyzed on the basis of the budget equation for each turbulent stress component. It was shown that the turbulence transport in the stagnation region was controlled mostly by the balance between the positive production of turbulence in the decelerating axial velocity component and the negative production in the accelerating radial velocity component (and in the circumferential velocity component as well). Since the turbulence transport between these components was undertaken by the pressure strain terms, their contribution, and therefore, their treatment in turbulence modeling were of high importance, as will be discussed in the seminar.

Friday, January 24, 1997
225 Akerman Hall, 2:30 - 3:30 p.m.


Refreshments served after each seminar in 227 AKERMAN HALL .
Disability accommodations provided upon request.
Contact Leslie Petrus : Secretarial Assistant.

petrus@aem.umn.edu (612) 625-8000.