a b s t r a c tIn this study, a pseudospectral s-transformation model is developed to simulate fully nonlinear sloshing waves in a three-dimensional shallow water rectangular tank. The s-transformation maps the physical domain including the water free surface onto a fixed rectangular computational domain. Chebyshev collocation formulae are used to discretize the governing equation and boundary conditions in the computational domain. The numerical model is validated for three well known analytical and numerical sloshing problems. An extensive study is then made of sloshing in a shallow water tank, and the effects of excitation frequency, base aspect ratio, and amplitude of excitation on the wave motions and patterns are considered. Wave regimes and patterns are considerably influenced by the base aspect ratio. In a shallow water tank with a non-square base, different wave regimes are observed during small-amplitude resonant excitation. Also, bores develop during large amplitude resonance excitation.The present study demonstrates that a pseudospectral s-transformation can accurately model nonlinear sloshing waves in a rectangular tank. Also, results show that contrary to the situation in deeper water tanks, sloshing in shallow water strongly depends on the base aspect ratio.

Purpose The purpose of this study is simulation of dynamic stall behavior around the Eppler 387 airfoil in the low Reynolds number flow with a direct-forcing immersed boundary (DFIB) numerical model. Design/methodology/approach A ray-casting method is used to define the airfoil geometry. The governing continuity and Navier–Stokes momentum equations and boundary conditions are solved using the DFIB method. Findings The purposed method is validated against numerical results from alternative schemes and experimental data on static and oscillating airfoil. A base flow regime and different vortices patterns are observed, in accordance with other previously published investigations. Also, the effects of the reduced frequency, the pitch oscillation amplitude and the Reynolds number are studied. The results show that the reduced frequency has a major effect on the flow field and the force coefficients of the airfoil. On the other hand, the Reynolds number of the flow has a little effect on the dynamic stall characteristics of the airfoil at least in the laminar range. Practical implications It is demonstrated that the DFIB model provides an accurate representation of dynamic stall phenomenon. Originality/value The results show that the dynamic stall behavior around the Eppler 387 is different than the general dynamic stall behavior understanding in the shedding phase.

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Purpose The purpose of this study is to the modeling of the dielectric barrier discharge (DBD) actuator on the Eppler 387 (E387) airfoil in low Reynolds number conditions. Design/methodology/approach A validated direct-forcing immersed boundary method is used to solve the governing equations. A linear electric field model is used to simulate the DBD actuator. A ray-casting technique is used to define the geometry. Findings The purposed model is validated against the former studies. Next, the drag and lift coefficients in the static stall of the E387 airfoil are investigated. Results show that when the DBD actuator is on, both of the coefficients are increased. The effects of the location, applied voltage and applied frequency are also studied and find that the leading-edge actuator with higher voltage and frequency has better improvement in the forces. Finally, the dynamic stall of the E387 with the DBD actuator is considered. The simulation shows that generally when the DBD is on, the lift coefficient in the pitch-up section has lower values and in the pitch-down has higher values than the DBD off mode. Practical implications It is demonstrated that using the DBD actuator on E387 in the low Reynolds number condition can increase the lift and drag forces. Therefore, the application of the airfoil must be considered. Originality/value The results show that sometimes the DBD actuator has different effects on E387 airfoil in low Reynolds number mode than the general understanding of this tool.

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