Hele-Shaw flow

About: Hele-Shaw flow is a research topic. Over the lifetime, 5451 publications have been published within this topic receiving 151320 citations.

An experimental investigation into the effect of vortex generators on the near-wake flow of a circular cylinder

Abstract: The effect of the streamwise vortex generators on the near-wake flow structure of a circular cylinder was experimentally investigated. Digital particle image velocimetry (DPIV) measurements were performed in a large circulating water tunnel facility at a Reynolds number of 41,300 where the flow around a bare cylinder was expected to be at the sub-critical flow state. In order to capture various flow properties and to provide a detailed wake flow topology, the DPIV images were analysed with three different but complementary flow field decomposition techniques which are Reynolds averaging, phase averaging and proper orthogonal decomposition (POD). The effect of the vortex generators was clearly demonstrated both in qualitative and in quantitative manner. Various topological features such as vorticity and stress distribution of the flow fields as well as many other key flow characteristics including the length scales and the Strouhal number were discussed in the study. To the best of the authors’ knowledge, the study presents the first DPIV visualization of the near-wake flow of a circular cylinder fitted with the vortex generators in the open literature.

Parallel shear flows of fluids with a pressure-dependent viscosity

Abstract: We consider parallel shear flows of an incompressible Newtonian fluid with a pressure-dependent viscosity. It is proved that pressure driven parallel flow in the plane is possible only if the dependence of the viscosity on the pressure is linear. In this case, a parallel flow exists for a pipe of arbitrary cross-section. For the special case of axisymmetric flow, we identify three cases for which pressure driven parallel flow exists.

Recent Enhancements to USM3D Unstructured Flow Solver for Unsteady Flows

Abstract: The NASA USM3D unstructured flow solver is undergoing extensions to address dynamic flow problems in support of NASA and NAVAIR efforts to study the applicability of Computational Fluid Dynamics tools for the prediction of aircraft stability and control characteristics. The initial extensions reported herein include two second-order time stepping schemes, Detached-Eddy Simulation, and grid motion. This paper reports the initial code verification and validation assessment of the dynamic flow capabilities of USM3D. The cases considered are the classic inviscid shock-tube problem, low Reynolds number wake shedding from a NACA 0012 airfoil, high Reynolds number DES-based wake shedding from a 4-to-1 length-to-diameter cylinder, and forced pitch oscillation of a NACA 0012 airfoil with inviscid and turbulent flow.

Pressure drop in cross flow across tube bundles

Abstract: The commonest methods of calculating the pressure drop in cross flow across tube bundles are discussed, and a new method, which is valid over a wide range of Reynolds numbers, is described. A comparison of the calculated coefficients of the pressure drop with experimental values from the literature shows that these new equations have the smallest deviations.

Stability of flow in a channel with a suddenly expanded part

Abstract: The stability of a two‐dimensional flow in a symmetric channel with a suddenly expanded part is investigated numerically and analyzed by using the method of the nonlinear stability theory. From results of the numerical simulation, it is shown that the flow is steady, symmetric and unique at very low Reynolds numbers, while the symmetric flow loses its stability at a critical Reynolds number resulting in an appearance of asymmetric flow. The transition from the steady symmetric flow to the steady asymmetric one is found to occur due to the symmetry breaking pitchfork bifurcation when the aspect ratio, the ratio of the length of the expanded part to its width, is large. It is also found that the bifurcated flow becomes symmetric again when the Reynolds number is increased and the resultant symmetric flow loses its stability becoming periodic in time as the Reynolds number is further increased. On the other hand, when the aspect ratio is small there occurs no pitchfork bifurcation and the direct transition from the steady symmetric flow to a periodic flow occurs due to a Hopf bifurcation. The critical aspect ratio is found to be about 2.3. The critical Reynolds numbers for these bifurcations are evaluated.