Ohad Gur

Optimizing Electric Propulsion Systems for Unmanned Aerial Vehicles

The propeller model and a model of the electric system, together with various optimization schemes, are used to design optimal propulsion systems for a mini unmanned aerial vehicle for various goals and under various constraints. Important design trends are presented, discussed, and explained. Although the first part of the investigation is based on typical characteristics of the electric system, the second part includes a sensitivity study of the influence of variations of these characteristics on the optimal system design.

Full Configuration Drag Estimation

Accurate drag estimation is critical in making computational design studies. Drag may be estimated thousands of times during a multidisciplinary design optimization, and computational fluid dynamics is not yet possible in these studies. The current model has been developed as part of an air-vehicle conceptual-design multidisciplinary design optimization framework. Its use for subsonic and transonic aircraft configurations is presented and validated. We present our parametric geometry definition, followed by the drag model description. The drag model includes induced, friction, wave, and interference drag. The model is compared with subsonic and transonic isolated wings, and a wing/body configuration used previously in drag prediction workshops. The agreement between the predictions of the drag model and test data is good, but lessens at high lift coefficients and high transonic Mach numbers. In some cases the accuracy of this drag estimation method exceeds much more elaborate analyses.

Design Optimization of a Truss-Braced-Wing Transonic Transport Aircraft

the conventional cantilever configuration. One comparison produces a reduction of 45% in the fuel consumption while decreasing the minimum takeoff gross weight by 15%. For a second comparison, the fuel weight is reduced by 33% with a decreased minimum takeoff gross weight of 19%. Very attractive vehicle performance can be achieved without the necessity of decreasing cruise Mach number. The results also indicate that a truss-braced wing has a greater potential for improved aerodynamic performance than other innovative aircraft configurations. Further studieswillconsidertheinclusionofmorecomplextrusstopologiesandotherinnovativetechnologiesthatarejudged to be synergistic with truss-braced-wing configurations.

Aerodynamic Considerations in the Design of Truss-Braced Wing Aircraft

The paper describes a study of the effects of several key aerodynamic considerations on the conceptual design of minimum fuel / emissions, long range transport, truss-braced wing aircraft configurations. This unconventional configuration has a large benefit over conventional cantilever wing configurations. The truss system enables an increased aspect ratio with lower sweep, thickness ratio, and chords, thus exploiting natural laminar flow. The design problem is solved by an MDO process, which takes into account both aerodynamic and structural considerations. The paper contains several studies, each of which investigates the dependency of the design space on a specific aerodynamic parameter such as the extent of laminar flow on the wing, cruise Mach number, maximum cruise twodimensional lift coefficient, the supercritical characteristics of the airfoil, winglet influence, and intersection fairing design. In addition, various fuselage drag reduction technologies are investigated: fuselage relaminarization, surface riblets, tailless arrangements and Goldschmied apparatus. All of these studies illustrate large potential of the truss-braced wing along with additional drag reduction technologies, which may substantially decrease the fuel weight and vehicle emissions. The paper emphasizes the importance of appropriate wing section airfoils, which can satisfy various contradicting criteria of natural laminar flow, supercritical characteristics, high lift coefficient, and low drag coefficient. Finally, these studies illustrate the importance of fuselage drag reduction for a low induced drag, NLF aircraft like a truss-braced wing configuration.

Design of Quiet Propeller for an Electric Mini Unmanned Air Vehicle

Designing a quiet and efficient propeller is a demanding task because these two goals often lead to contradictory design trends. The task becomes even more complicated when additional constraints are introduced. This paper presents a multidisciplinary design optimization process for designing a quiet propeller under various constraints. The acoustic model of the propeller is presented in detail, including its validation. The new process is used to design a quiet propeller for an electric mini unmanned air vehicle. This design is subjected to power, structural, and side constraints. The design variables include blade geometry, blade cone angle, propeller radius, number of blades, and rotational speed. It is shown that the motor characteristics have an important influence on the optimization, and it is therefore important to take them into account during the design process. The influences of the various parameters on the design and propellers characteristics are presented and discussed in detail.

Novel Approach to Axisymmetric Actuator Disk Modeling

Actuator disk models are commonly used for the analysis of rotary wing systems. The blade-element momentum model is probably the most popular one because of its simplicity, efficiency, and good accuracy in many cases. Yet momentum models fail to give satisfactory results in many other cases. The reason is probably the fact that momentum models include a basic assumption that the integral form of the equation of conservation of momentum can be replaced by its differential form. This paper presents a new actuator disk model that does not include the aforementioned assumption. It is assumed that the pressure difference between both sides of each point of the disk is a time average of the pressure difference between both sides of the blade elements that pass through that point. In addition to calculating the axial components of the induced velocity through the disk, the solution procedure also includes calculations of the radial component. The new model includes an iterative solution procedure that converges relatively fast and requires relatively small computing resources and short computing time. The paper describes the new model, presents the solution procedure, and compares the new results with known results from the literature.

Progress Towards Multidisciplinary Design Optimization of Truss Braced Wing Aircraft with Flutter Constraints

on multidisciplinary design optimization (MDO) of truss-braced wing airplanes. The primary focus has been to include utter constraints for structural sizing of the wing. The structural sizing uses a gradient-based optimization procedure along with an analytically calculated response function sensitivity with respect to the thickness design variables. It is shown that using the updated routine leads to lower structural mass in comparison with the fully-stressed structural design procedure used in the previous MDO studies. The primary reasons for the lower mass is that inertial weight relief due to secondary structure is now included in the sizing process, and the buckling analysis is now based on a linearized eigenvalue problem, as opposed to a simple beam Euler buckling criteria used for the previous study which was signicantly conservative. However, the results show that for a wing with lower mass the utter constraint becomes active for both strut-braced and truss-braced wing congurations. Hence, it is important to include those in the MDO studies to maintain feasibility of designs. Two challenges encountered during the process of including structural optimization with the utter constraint within the system-level MDO architecture are discussed along with the strategies devised to overcome them: convergence of structural optimization and the resulting numerical noise. A response surface methodology is used to integrate the structural optimization and system-level MDO and some initial results for the design of a truss-braced wing transonic transport airplane for minimum fuel consumption and emissions are presented.

Optimizing Electric Propulsion Systems for UAV's

Design of an electric propulsion system for an Unmanned Aerial Vehicle (UAV) incorporates various disciplines such as: propeller’s aerodynamic and structural properties, characteristics of the electric system, and characteristics of the vehicle itself. This makes the design of this propulsion system a Multidisciplinary Design Optimization (MDO) task. While the present propeller model is based on previous derivations that are described very briefly, new models of the electric motor and battery pack, which are based on examining existing products on the market, are described in more detail. The propeller model and a model of the electric system, together with various optimization schemes, are used to design optimal propulsion systems for a Mini UAV, for various goals and under various constraints. Important design trends are presented, discussed and explained. While the first part of the investigation is based on typical characteristics of the electric system, the second part includes a sensitivity study of the influence of variations of these characteristics on the optimal system design.