Bifurcation of vortex turbulent flow and intensification of heat transfer in a hollow

Comparative Analysis of the Vortex Heat Exchange in Turbulent Flows around a Spherical Hole and a Two-Dimensional Trench on a Plane Wall

“…It has been established in the present work, as also in earlier works [3,4,8], that in a flow around a deep hole (∆ of the order of 0.2) there arise single-vortex structures (Fig. 6b and d) transporting the fluid in the transverse direction with a maximum velocity of the order of 0.2.…”

“…The determining linear sizes -the depth of the hole (trench) ∆, the radius of the rounding of the sharp-pointed edge r, the initial thickness of the boundary layer δ, and the sizes of the computational region -were determined in fractions of d. The velocity of an incompressible viscous fluid flowing uniformly at a distance from the wall U was taken as the scale of de-dimension of the parameters. The Reynolds number determined by U and d in the process of parametric investigation of the effect of ∆ was equal to 4⋅10 4 , which corresponds to the experimental value of Re determined in [19]. The Prandtl number for air was taken to be 0.7, and the turbulent Prandtl number was taken to be 0.9.…”

Numerical simulation of the turbulent air flow in the narrow channel with a heated wall and a spherical dimple placed on it for vortex heat transfer enhancement depending on the dimple depth

“…(3) One of the remarkable numerical modeling results is associated with changing the separated flow structure to the symmetric monotornado-like one when increasing the depth of the spherical dimple that causes heat transfer to enhance spasmodically inside the dimple and in its wake. Bifurcation of a vortex structure is stipulated by a level of disturbances [36,[40][41][42][43]. (4) The 3D flow in the dimple wake defines higher rates of heat transfer enhancement in comparison with a trench [44].…”

Reconstruction of the Vortex-Jet Structure of the Separation Turbulent Flow in a Spherical Dimple on the Wall of a Narrow Channel with Increase in the Depth of the Dimple and Intensification of the Secondary Flow in It

“…The identifi cation of the vortex-jet structures in the three-dimensional separation zones of the turbulent fl ows of an incompressible viscous fl uid around dimples made on the plane walls of such channels is an effi cient method of investigation of the physical mechanism of vortex intensifi cation of these fl ows. In the pioneer work [1] devoted to the computer visualization of the fl ow in a dimple of depth Δ = 0.22 (in fractions of the dimple-spot diameter) with an edge of rounding radius 0.1 in a plane in the case where the Reynolds number of the incident fl ow is equal to 2.3·10 4 and the thickness of the boundary layer is δ = 0.175, it was shown that the side deformation of the simple with change of its circular contour to the elliptic one leads to the formation of an asymmetric fl ow around the dimple and a multivortex structure inclined at an angle of 45 o to the plane and to the intensifi cation of the reverse fl ow in the dimple.In [2], it was established that the structure of a nondisturbed fl ow in a spherical dimple on a plane, identical in depth and edge rounding to the dimple considered in [1], bifurcates under the conditions [1] where, depending on the mechanism of formation of the fl ow around the dimple, in it there arise two symmetric vortex cells or a single-vortex structure. In [3], on the basis of the visualization of the three-dimensional vortex-jet structure of the fl ow in a dimple of moderate depth (0.13) on a plane at Re = 2.5·10 4 and δ = 0.175 and the comparison of the calculation and experimental data on this fl ow and the heat exchange in the indicated dimple, it was shown that, in this case, in the dimple there arise two vortex cells with separation swirling jet fl ows interacting with the sides of the dimple.…”

“…In [2], it was established that the structure of a nondisturbed fl ow in a spherical dimple on a plane, identical in depth and edge rounding to the dimple considered in [1], bifurcates under the conditions [1] where, depending on the mechanism of formation of the fl ow around the dimple, in it there arise two symmetric vortex cells or a single-vortex structure. In [3], on the basis of the visualization of the three-dimensional vortex-jet structure of the fl ow in a dimple of moderate depth (0.13) on a plane at Re = 2.5·10 4 and δ = 0.175 and the comparison of the calculation and experimental data on this fl ow and the heat exchange in the indicated dimple, it was shown that, in this case, in the dimple there arise two vortex cells with separation swirling jet fl ows interacting with the sides of the dimple.…”