Numerical modeling of rectangular channel with shallow dumbbell dimples based Code Saturne

Numerical study was conducted for rectangular channel with dimples. Developed model was tested for adequacy by simulating of experiment, conducted by Dr. Terekhov, which was found in good agreement. Experimental setup utilized a single spherical dimple which was set at $11$ diameters from inlet. Test simulation was conducted for incompressible fluid (water) in accordance with experiment conditions: inlet velocity $0.43$ m/s, Reynolds for dimple $20000$ and channel length $1.34$ m. A $3\mathrm{D}$ computation domain was meshed for $0.8$ million elements with six viscous layers totalling $3$ mm thick applied to smooth walls. A turbulent flow ($\mathrm{Re} = 31627$) in rectangular channel with shallow dumbbell dimples was modelled with open source Code_Saturne. An ideal gas ($\rho = 1.205$ kg/m$^3$) was considered as working medium. A $3\mathrm{D}$ computation domain was meshed with open source Salome Meca for $0.77$ million elements ranged $0.2…1.0$ mm. Six viscous layers totalling $2$ mm thick were applied to smooth walls. Unsteady flow simulated with k-w SST model utilizing $2$nd order discretization schemes (SOLU) for velocity. $2000$ iterations were calculated so far with pseudo time step of $0.1$ ms. Additionally, impact of mesh quality regarding elements size on computation results was shown. Obtained results showed a strong dependence of flow velocity from inclination of dumbbell towards flow axis. Adjacent dumbbell dimples cause partial flow laminarization. Developed model shows aerodynamic advantage up to $10 \%$ of dumbbell dimples over spherical ones of the same depth ($h = 1.2$ mm) and contact patch area ($S = 59.76$ mm$^2$).