This paper presents a modified re-entrant honeycomb auxetic structure. The structure is constructed by adding an additional horizontal member between the vertical and re-entrant member of the semi-re-entrant honeycomb model to increase the overall compliance of the structure in order to obtain higher values of negative Poisson’s ratio (NPR). An analytical model of the structure is presented, taking into account the bending, shear, and axial deformations. The model is verified using finite element analysis (FEA) and tensile testing. The results of FEA and tensile testing corroborate the results of the presented mathematical model. The structure is also compared to the existing re-entrant honeycomb structure. The newly added strut has shown a direct effect on the directional properties of the overall structure. With an increase in the newly added strut to re-entrant lengths, NPR was significantly enhanced in the x-direction and reduced in the y-direction loadings. The structure shows an improved Young’s modulus compared to solid material in both loading directions, especially for the low values of the new strut and re-entrant lengths ratio. The structure also shows that high NPR can be achieved for low relative density compared to semi re-entrant honeycomb structure.
The
well-known Shear Stress Transport (SST k–ω)
turbulence model was modified and examined. Two industrially relevant
problems with curved and rotating channels have been selected to assess
the modification potential: a rotating lid in a confined cylinder
and swirling flow through a three-dimensional abrupt expansion pipe.
The postulated amendment simplified the rotation and curvature correction
term that was suggested earlier by Smirnov and Menter [J.
Turbomach.
2009, 131 (4) 041010].
The new formulation avoids the calculation of the complex Lagrangian
derivatives by implementing the Richardson number (Ri) in the applied rotation function. The numerical computations were
performed using OpenFOAM-2.4.x. The results show the expected capability
of the Shear Stress Transport model with Curvature Correction Modification
(SSTCCM) to handle the curvature effects and system rotation. The
paper compares the SSTCCM model with the conventional eddy viscosity
models (EVMs): standard k–ϵ; Re-Normalization
Group (RNG) k–ϵ, and the original SST k–ω.
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