This paper presents the behavior of pressure in an air–water shock tube. In this work, high-pressure air (at 100 bar) interacts with water (at 1 atm ∼ 1 bar) through an orifice in a 100 mm constant diameter tube. The experiments are repeated with three different orifice plate diameters of 4, 8, and 15 mm. The variation of pressure during the transient stage is recorded in these experiments and it is found that with increasing orifice diameter, the amplitude of the pressure increases linearly with time when all other conditions are unchanged. The same phenomenon is simulated using the ls-dyna® software using an arbitrary Lagrangian Eulerian (ALE) method to solve the problem numerically. Simulations are made with a range of orifice diameters. The experimental results confirm the validity of the simulations algorithm. The simulations also demonstrated that the pressure behaves linearly with orifice diameter only when orifice diameter is less than 15% of the tube diameter.

No abstract

No abstract

No abstract

In the framework of an optimization study based on a multi-objective optimization formulation, the consideration of optimization parameters such as the actuator location and the outlet design implies a re-meshing procedure that add complexity (even if the actuator is modeled with simple boundary conditions at the jet orifice exit since, locally, the re-mesh is still required). This strongly impacts the global computational cost, in particular if the considered geometry is complex. In this paper we propose an alternative method to model ZNMF synthetic jet actuators through the implementation of volumetric reduced-order models of ZNMF synthetic jet actuators as an additional source terms, in the form of body forces on given local control volumes corresponding to the actual locations of the actuators. This approach is promising as it allows to skip re-meshing procedures (velocity inlet boundaries or full synthetic jet actuator modeling) by directly plugging the volumetric source terms at appropriate locations and, consequently, save a considerable computational time during the optimization process.

No abstract

No abstract

In the "Result" paragraph of section IV.B, the over-prediction of the flow longitudinal momentum is not due to the boundary condition settings but due to the inefficient design of this benchmark actuator that generates a recirculation area in the inner side of the SJA outlet to the outer zones with enhancing of the vorticity that can be seen as a pre-mixing of the emanating jet with the outer quiescent air. This pre-mixing is not present in the ROM case due to the absence of the SJA tube that is not modeled. Thus, the flow efficient section is reduced in the ROM case compared to the SJA one which results in a greater acceleration of the flow in the longitudinal direction for the first case.