Abstract. This paper presents the aerodynamic modelling and analysis of surfaces created by a novel deployable mechanism, which is composed of a four-bar linkage and a scissor-structural mechanism (SSM) which contains several scissor-like elements (SLEs). With the help of that mechanism, which is located inside the trailing portion of wing section, continuous adjustment of the airfoil is possible. In order to highlight the advantageous aerodynamic characteristics of newly created airfoil geometries via proposed SSM, several aerodynamic analyses have been performed. The flow characteristics used for the analyses are determined by the flight envelope of an intended generic UAV. Since the maximum speed range of the sample aircraft is well below Mach 0.3, incompressible flow assumption is made throughout the solutions and conservation laws of Reynolds Transport Theorem are employed.

In this paper, the dynamic force analysis of a novel deployable mechanism, called as scissor-structural mechanism (SSM), for active camber and chord morphing have been presented. The mechanism is created via combination of several scissor-like-elements (SLEs). With a novel kinematic synthesis concept, various types of scissor-like-elements are assembled together to provide the desired airfoil geometries. The types (translational, polar), the number of scissor-like-elements, their orientations with respect to centerline of the airfoil and their distribution frequencies over the chord length are the design parameters, which allow designers to achieve all the possible geometric shapes. With the assumption of an existing fullycompliant wing skin, it is possible to adjust the wing profile to various desired airfoil geometries. With the help of developed computer routine, the mechanism is generated which yields the minimum possible design error. After the selection of mechanism, the position, velocity and acceleration analyses of the mechanism have been done. In order to prove aerodynamic efficiency of newly created airfoil geometries and obtain pressure distribution over the airfoil, 2D aerodynamic analyses have been done with the package program XFOIL. The flow characteristics used for the analysis are determined by the flight envelope of a generic UAV. Obtained pressure distribution is applied as the lumped force on the joints. By assigning the approximate link masses and mass centers, the dynamic force analysis of the mechanism has also been performed in order to estimate the required torque to drive the synthesized mechanism.

Optical flow provides an opportunity to elevate the resolution and sensitivity of deflection sensing in background-oriented schlieren (BOS). Despite extensive relevant literature within the field of computer vision, there is a lack of proper quantification of its abilities and limitations with regard to the state-of-the-art BOS experiments. Thus, this study performs an assessment of accuracy and resolution limits in different flow field scenarios utilizing background patterns generated with random dot and wavelet noise distributions. Accordingly, a synthetic assessment over a theoretically generated Prandtl–Meyer expansion fan is conducted with variations introduced in the background patterns and operational parameters of optical flow. A clear superiority of accuracy and resolvable range of density gradient amplitudes over cross-correlation is demonstrated. Moreover, an experimental assessment of supersonic flow features over multiple wind tunnel models is performed. The influence of experimental constraints, limitations and uncertainties related to the application of optical flow in BOS and its comparative performance against the block-matching counterpart is characterized. Graphical abstract

Three-dimensional Lagrangian Particle Tracking measurements with Hellium Filled Soap Bubbles (HFSB) provide quantitative flow visualizations in large measurement volumes up to the cubic metre scale. However, the instantaneously available fluid information density is severely restricted by the finite spatial resolution of the measurements. Therefore, the use of experimental data assimilation approaches are utilized to exploit the temporal information of the flow measurements, along with the governing equations of the fluid motion, to increase the measurement spatial resolution. Nevertheless, only in the last years, attempts to apply data assimilation methods to enhance the Lagrangian particle tracking (LPT) resolution in proximity of solid boundaries have been performed. Thus, in order to handle generic solid body intrusions within the densely interpolated LPT data, two different approaches based on the computational fluid-structure interaction (FSI) frameworks are proposed. The introduced variants of the state of the art physics-driven data assimilation methods are assessed with a high fidelity numerical test case of flow over periodic hills. The accuracy superiority of the flow field reconstructions with the proposed approaches are denoted especially in close proximity of the interaction surface. An experimental application of the introduced methods is demonstrated to compute the pressure distribution over an unsteadily moving elastic membrane surface, revealing the time-resolved interaction between the flow structures and the membrane deformations.