Turbulent flow mechanisms in axially corrugated geometries

• In this study the impact of geometrical expansion on the intrinsic flow structures of corrugated-pipe like geometries is numerically investigated. Two axisymmetric geometrieswith wavy-walls are taken under consideration. The geometries have the same geometric wavelength but differ in their respective corrugation amplitude and mean hydraulic diameter. A Large Eddy Simulation (LES) approach is used to numerically simulate a 3D,incompressible, non pulsatile and turbulent gas flow. Firstly, a solver validation study is performed using experimental data for the periodic hill benchmark case (data set available at http://qnet-ercoftac.cfms.org.uk/w/index.php/Abstr:2D\_Periodic_Hill_Flow). This is followed by a grid resolution study in order to determine an appropriate mesh size. A comparison between the flow profiles and coherent structures as calculated for the two geometries is made. The coherent flow structures are exposedusing a Proper Orthogonal Decomposition (POD) approach and spectral analysis. The POD analysis revealed an asymmetric oscillatory mode for the geometry with the larger mean hydraulic diameter. A similar analysis highlighted axial modes for the geometry withthe smaller mean hydraulic diameter. Subsequent spectral analysis revealed that up to a certain frequency the strongest spectral content appeared in the expansion regions, en-compassing the shear-layer/recirculation bubble, of the geometry. Beyond that frequency the strongest spectral content appeared in a confined region within the shear-layer. For the geometry with larger mean hydraulic diameter the distinguishing frequency was determined to be 500Hz. In the case of the geometry with the smaller mean hydraulic diameter this frequency increased to 1500Hz. Frequency content lower than 100Hz is governed by the dynamics of recirculation bubble whereas higher frequency content is governed by the dynamics of the induced shear-layer.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Strömningsmekanik och akustik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Fluid Mechanics and Acoustics (hsv//eng)

Keyword

Engineering Mechanics

Teknisk mekanik

Publication and Content Type

ref (subject category)

art (subject category)