Effect of heat transfer on stability and transition characteristics of boundary-layers
ABSTRACT Stability and transition problems of two dimensional boundary-layers with heated walls have been studied numerically using the linear stability theory. Incompressible stability equations have been modified to account for the variation of temperature dependent fluid properties across the layer. The equations obtained have been solved with an efficient shoot-search technique. Low speed flows of air and water have been analyzed with a wide range of heat transfer rates. In addition to the mean velocity profile characteristics, variable viscosity and density terms in the stability equations also have considerable influence on the results of the stability and transition analysis.
- SourceAvailable from: Serkan Özgen[Show abstract] [Hide abstract]
ABSTRACT: The stability problem of two-dimensional compressible flat-plate boundary layers is handled using the linear stability theory. The stability equations obtained from three-dimensional compressible Navier–Stokes equations are solved simultaneously with two-dimensional mean flow equations, using an efficient shoot-search technique for adiabatic wall condition. In the analysis, a wide range of Mach numbers extending well into the hypersonic range are considered for the mean flow, whereas both two- and three-dimensional disturbances are taken into account for the perturbation flow. All fluid properties, including the Prandtl number, are taken as temperature-dependent. The results of the analysis ascertain the presence of the second mode of instability (Mack mode), in addition to the first mode related to the Tollmien–Schlichting mode present in incompressible flows. The effect of reference temperature on stability characteristics is also studied. The results of the analysis reveal that the stability characteristics remain almost unchanged for the most unstable wave direction for Mach numbers above 4.0. The obtained results are compared with existing numerical and experimental data in the literature, yielding encouraging agreement both qualitatively and quantitatively.Theoretical and Computational Fluid Dynamics 01/2008; 22(1):1-20. DOI:10.1007/s00162-007-0071-0 · 1.75 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Experimental investigation of flow and heat transfer characteristics of a vertical narrow channel with uniform heat flux condition are conducted to analysis the effect of wall heating on the laminar to turbulent transition. The friction factor in the heating condition is compared with that in the adiabatic condition and the results show that wall heating leads to the delay of laminar to turbulent transition. In addition, the heat transfer characteristic indicates that the critical Reynolds number at the point of laminar flow breakdown increases with the increase of fluid temperature difference, and the local Nusselt number at the point of laminar breakdown increases with the increase of the inlet Reynolds number. The analyses of the flow and heat transfer characteristics both indicate that the heating has a stabilizing effect on the water flow at present experimental scale.Annals of Nuclear Energy 09/2012; 47:85–90. DOI:10.1016/j.anucene.2012.04.018 · 1.02 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The stability problem of low-speed plane Couette-Poiseuille flow of air under heat transfer effects is solved numerically using the linear stability theory. Stability equations obtained from two-dimensional equations of motion and their boundary conditions result in an eigenvalue problem that is solved using an efficient shoot-search technique. Variable fluid properties are accounted for both in the basic flow and the perturbation (stability) equations. A parametric study is performed in order to assess the roles of moving wall velocity and heat transfer. It is found that the moving wall velocity and the location of the critical layers play decisive roles in the instability mechanism. The flow becomes unconditionally stable whenever the moving wall velocity exceeds half of the maximum velocity in the channel. With wall heating and Mach number effects included, the flow is stabilized.Heat and Mass Transfer 09/2007; 43(12):1317-1328. DOI:10.1007/s00231-006-0208-5 · 0.93 Impact Factor