| 초록 |
The onset of longitudinal vortex rolls due to buoyancy forces in the thermal entrance region of plane Couette flow is investigated theoretically. In the present study, to examine this streamwise roll-type convection, the Boussinesq equations are solved by using the finite volume method. In order to observe the behavior of longitudinal vortex rolls, the local growth rates of the mean fields and fluctuations, r0 and r1 are defined. We suggest that the critical condition of the onset of convective instability would be r1=r0 at x=xc, which is here called the onset distance of intrinsic instability. Also, we define xD where secondary flow can be detected and xm where r1 shows the maximum. The undershoot distance xu where the Nusselt number has the minimum has usually been considered as the onset distance of manifest convection. Here we suggest that xc |
