Unsteady impulsive oblique stagnation-point flow impinging axisymmetrically on a vertical circular cylinder with mixed convection heat transfer

For the first time, the problem of impulsive oblique stagnation -point flow on a vertical cylinder along with mixed convection heat transfer due to buoyancy forces has been solved in this study. The fluid at rest with uniform temperature, T-infinity, around the cylinder starts flowing towards it at strength rate of (k) over bar, and the cylinder temperature rises to T-w, at t = 0, simultaneously. The governing equations induced by the impinging flow on the constant-temperature vertical cylinder at any obliqueness angle, a, have been reduced to ODEs by using similarity transformations, and then they have been solved numerically. Considering a sample case of incompressible flow with Re = 1 and Pr = 0.7, the results of Nusselt number and similarity functions of velocity and temperature distributions have been obtained for different values of time and angle, a. At the initial instants of time, the Nusselt number, regardless of a's magnitude, has large values; for example Nu = 5.1 at T = 0.01. As time passes, the value of the Nusselt number reduces intensely within a short period of time (until T approximate to 0.4), and then it changes with a moderate reduction rate, such that in the steady-state situation, its value reaches 0.67, 0.61, and 0.51 for obliqueness angles alpha = 10 degrees, 30 degrees, 60 degrees. (C) 2017 Sharif University of Technology. All rights reserved.