Heat transfer enhancement by Gortler instability

Measurements of mean velocity field and mean temperature field were performed in it concave boundary layer. The growth of the induced Gortler vortices embedded in this boundary layer has been determined in two ways by a criterion based equally on spanwise distortion of velocity or temperature profile. The streamwise and spanwise evolution of hell transfer coefficient has been determined by measurement of wall temperature. It was found that the steady growth of these structures induces a characteristic plateau in the evolution of Stanton number versus Reynolds number. This plateau starts with the enhancement of the amplification criterion and finishes when the transition occurs. (C) 2002 Elsevier Science Inc. All rights reserved

Influence of forced perturbations in the stagnation region on Gortler instability

The growth of forced perturbations gene rated by a wire grid in a concave boundary layer at supercritical Gortler numbers is experimentally investigated. Under certain conditions (sufficiently high wire Reynolds numbers), two pairs of Gortler vortices, instead of the single pair seen in previous experiments (Ajakh, A., Kestoras, M, D,, Peerhossaini, H., and Bahri, F., An Experimental Study of Gortler Vortices, Proceedings of the annual Conference of the French Society of Heat Transfer, Elsevier, Paris, 1995, pp, 272-277), have been observed in the concave boundary layer behind each triggering wire. Two generation mechanisms are examined for these two pairs of vortices associated with Benard-Karman streets and leading-edge vortices. It is shown that whereas the Benard-Karman streets are generated behind the wires, they do not penetrate the boundary layer and, thus, cannot trigger two pairs of Gortler vortices in the unstable boundary layer. The leading-edge vortices, on the contrary, influence the generation of Gortler vortices and control their wavelengths. However, there is a limit to this mechanism: tit very high values of wire Reynolds number Red, the flow behind the wires becomes turbulent, and Gortler vortices cannot be generated. It is also found that the wavelength of Gortler vortices is constant and independent of the diameter of the wire that triggers them

Visualizing shear stress in görtler vortex flow

10.1007/BF03181858Journal of Visualization123195-20

Visualizing Görtler Vortices

10.1007/BF03181550Journal of Visualization84315-32