Abstract: This paper investigates both experimentally and numerically the flow of a viscous fluid around T-profiles, i.e. T-shaped bodies, having different geometries. Of main interest it was the vortex shedding behind the T-profiles with an eye towards its application to flow measurement in open channels. Another purpose of the study was to assess to what extent different numerical models can be used to accurately predict the flow in the vortex street behind T-profiles.
Abstract: The use of active control to get better characteristics of unsteady internal and external flows is the ultimate goal of the research presented in this paper. Usually, unsteady flows are calculated using Euler and/or Navier-Stokes solvers. The efficiency of numerical simulation of an unsteady flow dramatically increases if the unsteady solution is a small perturbation about a steady-state flow, due to disturbances occurring at the boundaries of the flow domain. The main difficulty related to the flow simulation is that any CFD (Computational Fluid Dynamics) technique generates discrete systems with a very large number of states. In order to design an efficient control, the flow solver must be not only accurate and numerically effective, but also it must have a low number of states. The aim of this paper is to present a new method for model reduction of CFD systems using representative governing equations. The focus is on descriptor type systems resulting from the spatial discretization of the CFD governing equations.
Abstract: This paper discusses the mission requirements and design constraints for an Unmanned Martian research aircraft based on a tailor-made classical airplane design methodology. First, the exploration mission is described using the information from previous real-world experiences and the desired payload is proposed accordingly. The environmental conditions that dictate severe constraints to the design space are characterized afterwards. The conventional airplane design cycle is modified to address the lack of statistical data and to define a proper design recycling criteria. Eventually, the outcome is presented in the form of a novel configuration that is well suited to carry out the specified exploration mission, flying low and slow over the Martian surface.
Abstract: Numerical simulations are used to verify the possibility to mitigate the undesired flow self-sustained oscillations of the compressible flows past open cavities. The simple control device proposed in this work consists in a large aspect ratio wing with an non-symmetric thin airfoil mounted in the spanwise direction of the cavity and located immediately upstream with respect the leading edge of the cavity . The results show that this control device is efficient and diminishes the pressure oscillations.
Abstract: The paper emphasizes the theoretical aspects of spherical valve operation, the calculation of hydrodynamic parameters specific to this type of valve and a method of analysis of the influence of the main physical-mechanical parameters of flow simulations using specialized software. It may reveal such power distribution lines for different opening angles of the valve and pressure distribution along the flow speed and hence can express losses coefficients and flow coefficients. Areas with whirlpools and a large cluster of vortex lines characterize significant losses of hydraulic energy along the flow and can lead to structural characteristics that provide optimal design of these valves.
Abstract: Restriction and selection criteria of inertial guidance sensors and system for a small recoverable capsule from onboard a hypersonic, atmospheric reentering rocket vehicle have attracted a specific research on the reentry design and challenges, with emphasize on the overall cost reduction and an optimal balance between the performances and costs under the given exploitation constraints. A simplified method for attitude control is derived that shows an easy accommodation in the capsule, given its high mass constraints, and convenient applicability for the class of small payloads under investigation. The palled experiments and investigating methodology is shown, as the result of the ORVEAL contract research team of ADDA-Association Dedicated to Development in Astronautics research organization, under the sponsorship of Romanian UEFISCDI authority for scientific research.
Abstract: The biological flight involves the movement of a wing (lift surface) in viscous medium and it generates lift and resistance for going forward through friction compared to Reynolds number. The morphing concept is generally based on optimizing the aerodynamic form during the mission so it can execute a maneuver flight. This article desires a short passage through the mathematical aspect in 2D of the morphing profile concept.
Abstract: This paper describes latest results obtained on modeling, simulation and controller design of an insect-like Flapping Wing Micro Air Vehicle (FWMAV). Because of the highly nonlinear and time varying nature of insect flight and the inability to find an equilibrium point, linearization of the model without compromising the accuracy is not possible. Therefore, to address the problem of designing a controller capable of stabilizing and controlling the FWMAV around a hovering point, a metaheuristic optimization approach is proposed, based on the time averaging theorem. The results show that a controller, designed using the proposed method, is capable of stabilizing the FWMAV effectively around its hovering point.
Abstract: System Identification is a key technology for the development and integration of modern engineering systems including unconventional flying vehicles. These systems are highly parametric with complex dynamics and nonlinearities. Ducted fans are special class of these vehicles that can take off vertically, hover and cruise at very low speed. In this paper, an exact equivalent linear system is found from the non-linear dynamic model of a ducted fan by use of frequency response identification. Here, power spectral density analysis is performed, using CIFER software, to evaluate the input-output responses in hover and to derive the transfer functions based on the coherence criterion. Then, PID controllers are designed by utilizing the identified transfer functions and the performance characteristics of the controllers are evaluated in fully non-linear simulation of the system.