Preliminary airfoil design of an innovative adaptive variable camber compliant wing

In this study, an innovative adaptive variable camber compliant wing, with skin that can change thickness and tailing edge morphing mechanism that is designed based on a new kind of artificial muscles, is designed. Consisted of a compliant base plate and seamless and continuous compliant skin with the artificial muscles embedded in, this trailing edge morphing mechanism is extremely light in weight and efficient in reconfiguration of the wing sectional profile. To demonstrate the feasibility of this design, a simulative experiment of this kind of artificial muscles was designed and carried out. A demonstrative wing section with simulative driving skin mechanism and the compliant skin was manufactured. The demonstration wing section shows that the trailing edge morphing mechanism designed and simulative driving skin work good, with a –30°/+30° trailing edge morphing achieved. Targeting this innovative design, an airfoil design approach, employing CST parametric methodology, XFOIL and Multi-Objective Particle Swarm (MOPS) optimizer, is developed for the preliminary design of this innovative wing. A new selector is introduced to facilitate the searching process and improve the robustness of this method. The results show that this method is capable of designing airfoils for this special wing in a quick and effective way

Numerical investigation on the propulsive performance of flexible flapping fins using CFD/CSD method

A FSI (fluid-structure interaction) numerical simulation was performed to investigate the flow field around a flexible flapping fin using an in-house developed CFD/CSD solver. The three-dimensional fluid-structure interaction of the flapping locomotion was achieved by loosely coupling preconditioned Unsteady Reynolds-Averaged Navier-Stokes (URANS) solutions and non-linear co-rotational structural solutions. The CSD solver was developed specifically for high flexible flapping fins by considering the large geometric nonlinear characteristics. Validation of benchmark tests illustrated the high-fidelity of the developed methodology. Then effect of flexural angles, flexural amplitude and flapping frequency in terms of Strouhal number were evaluated. Results demonstrated that different flexural angles will present different flow fields, and thus significantly varied thrust generation and pressure distribution. The thrust does not increase monotonically with flexural angles. The thrust is also found to increase with increasing Strouhal number while propulsive efficiency peaks within the range of 0.2 <St< 0.4, which lies in the middle of the range observed in nature. The appropriate combination of flexibility and Strouhal number illustrates higher efficiency and gives instruction for further design of flexible flapping fins

Linear Proportional-Integral-Differential-Robustified Continuous-Time Optimal Predictive Control for a Class of Nonlinear Systems

This paper presents a novel robust optimal predictive control approach for a class of nonlinear continuous-time systems perturbed by unknown disturbances. First, a new error state with a linear proportional-integral-differential (PID) structure considering current, accumulative, and derivative tracking errors is defined. Second, prediction of the error state within the predictive periods is expressed by the error state and its high-order derivatives according to the Taylor series expansion. Last, the proposed control law as well as the main result of this paper are derived by minimizing the prediction of the error state. Numerical validation for designing a missile autopilot shows that, due to minimizing the accumulative tracking error included in the PID-structuralized new error state, the proposed approach can generate smaller steady-state tracking errors than two commonly applied continuous-time optimal predictive control approaches whether the disturbances encountered by the missile are constant or time-varying

Functional Polymeric Materials Based on Cellulose

[No abstract available

Numerical study on the flow characteristics of micro air vehicle wings at low Reynolds numbers

The aerodynamic characteristics around a micro air vehicle wing with an inverse-Zimmerman configuration are numerically investigated by an in-house programmed solver particularly dedicated for aircrafts operating in low Reynolds number regime. The complex three-dimensional aerodynamic performance was investigated in terms of force generation and flow structures visualization. Results show that the flow around the low aspect ratio MAV wing is characterized by complex three-dimensional separation-dominated flow. The flow fields exhibit separation, reattachment, secondary separation, secondary reattachment, and strong interaction between the separated boundary layer and wingtip vortices. In addition, the effect of tip-attached vertical stabilizers on flow structure and aerodynamic forces is addressed in this paper. The stabilizers significantly influence both the flow structure and aerodynamic forces via reducing the strength of wingtip vortices and shedding and interacting of wingtip vortices. Eventually, the unsteadiness of the aerodynamics revealed that higher angle of attack will result in stronger unsteady phenomena as demonstrated by the oscillating forces.Aerodynamic