Insect flight research is propelled by their unmatched flight capabilities. However, complex underlying aerodynamic phenomena make computational modeling of insect-type flapping flight a challenging ...task, limiting our ability in understanding insect flight and producing aerial vehicles exploiting same aerodynamic phenomena. To this end, novel mid-fidelity approach to modeling insect-type flapping vehicles is proposed. The approach is computationally efficient enough to be used within optimal design and optimal control loops, while not requiring experimental data for fitting model parameters, as opposed to widely used quasi-steady aerodynamic models. The proposed algorithm is based on Helmholtz–Hodge decomposition of fluid velocity into curl-free and divergence-free parts. Curl-free flow is used to accurately model added inertia effects (in almost exact manner), while expressing system dynamics by using wing variables only, after employing symplectic reduction of the coupled wing-fluid system at zero level of vorticity (thus reducing out fluid variables in the process). To this end, all terms in the coupled body-fluid system equations of motion are taken into account, including often neglected terms related to the changing nature of the added inertia matrix (opposed to the constant nature of rigid body mass and inertia matrix). On the other hand—in order to model flapping wing system vorticity effects—divergence-free part of the flow is modeled by a wake of point vortices shed from both leading (characteristic for insect flight) and trailing wing edges. The approach is evaluated for a numerical case involving fruit fly hovering, while quasi-steady aerodynamic model is used as benchmark tool with experimentally validated parameters for the selected test case. The results indicate that the proposed approach is capable of mid-fidelity accurate calculation of aerodynamic loads on the insect-type flapping wings.
The angle of attack is one of the most important flight parameters. In the framework of the present study, a flight data recording method was designed to analyze the Valasek angle-of-attack ...estimation method and investigate its applicability for general aviation aircraft. This was performed using two devices characterized by substantially different characteristics. The test flight, and the ground test, i.e., a flight simulator experiment, were conducted. Two flight regimes were analyzed: (a) steady climb and descent with low values of angle of attack, (b) approach to stall with idle power with an increase of the angle of attack to the critical value. A satisfactory angle of attack estimate was obtained for the steady climb and descent regime, while the approach to stall estimate was less accurate but still indicative and considered useful for the pilot. The results indicate that less expensive synthetic sensors may provide acceptable results compared to high-quality certified equipment. A proposed modification of the estimation method enables simplification of the required equipment, while offering important information to the pilot.
The paper describes the use of a rocket's 3D CAD model to determine the effect of nondeterministic manufacturing errors on inertial characteristics of the observed rocket. A case study was performed ...for a chosen unguided rocket with well-known features. For this rocket a 3D model was made, allowing simulation of different manufacturing errors such as misalignment of rocket's components, deviation of mass distribution, shape, etc. The likelihood and the extent of a particular error are gathered either from literature or directly from the manufacturer. The analysis gives a relationship between errors in production and consequent change of the rocket's geometry and inertial characteristics. The observed results are further used to predict the effect of manufacturing errors on the rocket's flight and displacement of impact points. Keywords: unguided rockets; manufacturing errors; 3D CAD model; inertial characteristics; precision.
With the intention of participating in the student aircraft design-build-fly competition, an adaptation to aircraft design methodology was introduced, following the competition rules as requirements ...on the aircraft. The aircraft was dimensioned to match the desirable performance that would lead to the highest points score at the competition. After the preliminary and detailed design, a flight model for the designed aircraft was developed and implemented in the flight simulator in order to subjectively evaluate the design before its production. This allowed for the analysis and validation of the modifications made to the aircraft design that improved the flying qualities. This project was conducted as a students' team project within the Aircraft Design course held at the University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture.
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