Lifting Surface Research Articles

Aerodynamic shape optimization of non-straight small wind turbine blades

Small wind turbines usually operate in sub-optimal wind conditions in order to satisfy the demand where it is needed. The aerodynamic performance of small horizontal axis wind turbines highly depends on the geometry. In the present study, the geometry of wind turbine blades are optimized not only in terms of the distribution of the chord and twist angle but also with 3-dimensional stacking line. As the blade with 3-dimensional stacking line is given sweep in the plan of rotation and dihedral in the plan containing the blade and rotor axis, the common used blade element momentum method can no longer provide accurate aerodynamic performance solution. A lifting surface method with free wake model is used as the aerodynamic model in the present work. The annual energy production and the starting performance are selected as optimization objective. The starting performance is evaluated based on blade element method. The optimization of the geometry of the non-straight wind turbine blades is carried out by using a micro-genetic algorithm. Results show that the wind turbine blades with properly designed 3-dimensional stacking line can increase the annual energy production and have a better starting behavior compared with 2-dimensional-optimized blade geometries.

A Study on the Hydrodynamic Effect of Biofouling on Marine Propeller

The effect of propeller surface roughness condition on ship performance is very significant even the influence of fouling on propeller performance is not well established compared to biofouling on the hull surface. In present study, predictions of open water efficiency of propeller are made for three different fouling conditions, and its application is given for the 7m full-scale propeller of a medium-size tanker in open water condition. The numerical predictions of propeller efficiency loss due to fouling are based on the results from laboratory-scale drag measurements and boundary layer similarity law analysis presented in Schultz (2007) together with an in-house unsteady lifting surface code which is an appropriate tool to predict the effect of propeller surface roughness on propeller performance. The results of this study indicate that the subject propeller with the small calcareous fouling (ks=0.001) can lead to as high as 15 % loss at the propeller operating condition (J=0.5) and the loss of propeller efficiency due to fouling should be evaluated while the ship is operating.

ワイヤで懸垂された平板のフラッタ実験と解析

This paper deals with the flutter experiments and analysis of a flat plate suspended by wires. In the flutter analysis, Doublet-point method based on unsteady lifting surface theory is used to calculate the unsteady fluid force acting on the plate surface. Moreover, flutter velocity and frequency are examined through the root locus of the flutter determinant of the system with changing flow velocity. These results compared with experimental results. The influence of the suspension angle on the flutter velocity, frequency, and mode are clarified.

非定常揚力面理論に基づく有限幅矩形シートの三次元フラッタ解析と風洞実験

This paper presents a three-dimensional flutter analysis of a rectangular sheet in an axial fluid flow. The unsteady fluid force acting on the sheet surface is calculated using Doublet-point method based on the unsteady lifting surface theory. The equation of motion of the sheet coupled with the fluid flow is derived employing the finite element method. The characteristic roots are obtained from the flutter determinant, and the stability of the system is examined with changing flow velocity. The flutter characteristics are clarified comparing the analytical results with wind-tunnel experiments. Lastly, the local work done by the unsteady fluid force on the sheet surface is shown, and the flutter mechanism is discussed.

ワイヤで支持された矩形シートの三次元フラッタ解析と風洞実験（偏心のフラッタ特性および発生条件への影響）

This paper deals with the flutter analysis of a rectangular sheet supported by a wire in axial flow. In the flutter analysis, Doublet-Point Method based on unsteady lifting surface theory is used to calculate the unsteady fluid force acting on the sheet surface. The equation of motion of the sheet supported by a wire with tension is derived by using the finite element method. Flutter velocity and mode are examined through the root locus of the flutter determinant of the system with changing flow velocity. In this study, experiments are conducted and compared with the analytical results. The flutter velocity, flutter mode and the local work done by the fluid force acting on the sheet surface are determined. Moreover, the influence of eccentricity on the flutter velocity is clarified.

High-Fidelity Hydrodynamic Shape Optimization of a 3-D Hydrofoil

With recent advances in high-performance computing, computational fluid dynamics (CFD) modeling has become an integral part in the engineering analysis and even in the design process of marine vessels and propulsors. In aircraft wing design, CFD has been integrated with numerical optimization and adjoint methods to enable high-fidelity aerodynamic shape optimization with respect to large numbers of design variables. There is a potential to use some of these techniques for maritime applications, but there are new challenges that need to be addressed to realize that potential. This work presents a solution to some of those challenges by developing a CFD-based hydrodynamic shape optimization tool that considers cavitation and a wide range of operating conditions. A previously developed three-dimensional compressible Reynolds-averaged Navier‐Stokes (RANS) solver is extended to solve for nearly incompressible flows, using a low-speed preconditioner. An efficient gradient-based optimizer and the adjoint method are used to carry out the optimization. The modified CFD solver is validated and verified for a tapered NACA 0009 hydrofoil. The need for a large number of design variables is demonstrated by comparing the optimized solution obtained using different number of shape design variables. The results showed that at least 200 design variables are needed to get a converged optimal solution for the hydrofoil considered. The need for a high-fidelity hydrodynamic optimization tool is also demonstrated by comparing RANS-based optimization with Euler-based optimization. The results show that at high lift coefficient (C L) values, the Euler-based optimization leads to a geometry that cannot meet the required lift at the same angle of attack as the original foil due to inability of the Euler solver to predict viscous effects. Single-point optimization studies are conducted for various target C L values and compared with the geometry and performance of the original NACA 0009 hydrofoil, as well as with the results from a multipoint optimization study. A total of 210 design variables are used in the optimization studies. The optimized foil is found to have a much lower negative suction peak, and hence delayed cavitation inception, in addition to higher efficiency, compared to the original foil at the design C L value. The results show significantly different optimal geometry for each C L, which means an active morphing capability was needed to achieve the best possible performance for all conditions. For the single-point optimization, using the highest C L as the design point, the optimized foil yielded the best performance at the design point, but the performance degraded at the off-design C L points compared to the multipoint design. In particular, the foil optimized for the highest C L showed inferior performance even compared to the original foil at the lowest C L condition. On the other hand, the multipoint optimized hydrofoil was found to perform better than the original NACA 0009 hydrofoil over the entire operation profile, where the overall efficiency weighted by the probability of operation at each C L, is improved by 14.4%. For the multipoint optimized foil, the geometry remains fixed throughout the operation profile and the overall efficiency was only 1.5% lower than the hypothetical actively morphed foil with the optimal geometry at each C L. The new methodology presented herein has the potential to improve the design of hydrodynamic lifting surfaces such as propulsors, hydrofoils, and hulls.

High-Fidelity Hydrodynamic Shape Optimization of a 3-D Hydrofoil

With recent advances in high-performance computing, computational fluid dynamics (CFD) modeling has become an integral part in the engineering analysis and even in the design process of marine vessels and propulsors. In aircraft wing design, CFD has been integrated with numerical optimization and adjoint methods to enable high fidelity aerodynamic shape optimization with respect to large numbers of design variables. There is a potential to use some of these techniques for maritime applications, but there are new challenges that need to be addressed to realize that potential. This work presents a solution to some of those challenges by developing a CFD-based hydrodynamic shape optimization tool that considers cavitation and a wide range of operating conditions. A previously developed three-dimensional compressible Reynold saveraged Navier-Stokes (RANS) solver is extended to solve for nearly incompressible flows, using a low-speed preconditioner. An efficient gradient-based optimizer and the adjoint method are used to carry out the optimization. The modified CFD solver is validated and verified for a tapered NACA 0009 hydrofoil. The need for a large number of design variables is demonstrated by comparing the optimized solution obtained using different number of shape design variables. The results showed that at least 200 design variables are needed to get a converged optimal solution for the hydrofoil considered. The need for a high-fidelity hydrodynamic optimization tool is also demonstrated by comparing RANS-based optimization with Euler-based optimization. The results show that at high lift coefficient (CL) values, the Euler-based optimization leads to a geometry that cannot meet the required lift at the same angle of attack as the original foil due to inability of the Euler solver to predict viscous effects. Single-point optimization studies are conducted for various target CL values and compared with the geometry and performance of the original NACA 0009 hydrofoil, as well as with the results from a multipoint optimization study. A total of 210 design variables are used in the optimization studies. The optimized foil is found to have a much lower negative suction peak, and hence delayed cavitation inception, in addition to higher efficiency, compared to the original foil at the design CL value. The results show significantly different optimal geometry for each CL, which means an active morphing capability was needed to achieve the best possible performance for all conditions. For the single-point optimization, using the highest CL as the design point, the optimized foil yielded the best performance at the design point, but the performance degraded at the off-design CL points compared to the multipoint design. In particular, the foil optimized for the highest CL showed inferior performance even compared to the original foil at the lowest CL condition. On the other hand, the multipoint optimized hydrofoil was found to perform better than the original NACA 0009 hydrofoil over the entire operation profile, where the overall efficiency weighted by the probability of operation at each CL, is improved by 14.4%. For the multipoint optimized foil, the geometry remains fixed throughout the operation profile and the overall efficiency was only 1.5% lower than the hypothetical actively morphed foil with the optimal geometry at each CL. The new methodology presented herein has the potential to improve the design of hydrodynamic lifting surfaces such as propulsors, hydrofoils, and hulls.

DETERMINATION OF THE AERODYNAMIC CHARACTERISTICS FOR AGRICULTURAL UAVS IN UNSTEADY FLOW

The purpose of work is estimation of unsteady flow influence on the aerodynamic characteristics of the aircraft with several lifting surfaces. The work presents characteristic features of specialized agricultural aircraft operation based on the specifics of modern agriculture.The most significant factors affecting the efficiency agricultural aircraft were identified.The features of a non-stationary aerodynamics for agricultural aircraft with several supporting surfaces were viewed and the calculation results of aerodynamic characteristics, which depend on the basic parameters of the lifting surfaces, were shown. The mutual influence of lifting surfaces on the aerodynamic characteristics of the aircraft was estimated.To take into account the impact of interference between the bearing surfaces, such as adverse effects of shading one bearing surface by another, used computer panel-symmetric vortex flow modeling method because the nature of pull unsteady flow dissemination around a wing is very similar to the case pull steady flow.For a finding of system parameters, which could provide the best value for the aerodynamic qualities of a multiple bearing surfaces have been used all sorts of variations of these parameters, and then made their linear interpolation.The main parameters, which were considered in this research, of a multi-carrier surfaces system were vertical and horizontal distances between surfaces with forward removal one by one of each wing.The results show, which range of input parameters of multiple bearing surfaces system has the best aerodynamic efficiency.The research was used for design of the UAV to perform aviation chemical works.

Experimental Validation of a Flight Simulation Model for Slightly Flexible Aircraft

The paper presents a methodology for modeling the coupled flight dynamics with aeroelasticity in the time domain. The equations of motion are based on linearized mean-axes formulation. Unsteady, incremental aerodynamics due to elastic deformations are modeled in the time domain, applying the strip theory and a indicial function. The methodology is demonstrated with a prototype of the utility aircraft Stemme S15. Comparisons between the simulation and the flight-test data regarding the added aeroelastic dynamics have indicated that the model is suited for the flight control law and aircraft design, and that care must be taken in modeling the control surface lift slope for low-aspect-ratio lifting surfaces.

Partitioned Time-Domain Substructure Coupling Methodology for Efficient Hypersonic Vehicle Simulation

A partitioned solution framework is developed for time-domain aerothermoelastic simulation of hypersonic vehicles. The motivation for development of such an approach stems from the fact that hypersonic vehicles consist of multiple substructures, each containing different dominant physics. Different model forms are therefore required to capture the main physics of each substructure, and direct coupling of the various substructures of the vehicle is not straightforward. The methodology of this paper is based on a partitioned time-marching formulation, in which individual components of the vehicle are modeled separately, and forces/motion at the interface are exchanged between the systems within each time step. This approach is advantageous in that it does not require direct coupling of the substructures, therefore allowing for the models to be of dissimilar form. The methodology is applied to a representative configuration consisting of an all-movable hypersonic vehicle lifting surface model containing aerothermoelastic effects attached to a single-degree-of-freedom oscillator representing the fuselage. Results from validation cases are first presented. The partitioned solution methodology is then used to investigate the impact of lifting surface–fuselage inertial coupling on overall vehicle dynamics.

Predictions of Fan Broadband Noise Using Lifting Surface Method

This paper adopts the three-dimensional lifting surface method as a new cascade-response function to predict fan broadband interaction noise. The stator is modeled as an annular cascade, and the vanes are assumed to be zero-thickness plates with no stagger angle. The unsteady loading spectrum on the stator vanes is considered under a fully three-dimensional condition rather than calculated by the strip theories that are widely used in the existing analytical broadband fan noise models. The sound power spectrum is calculated in an annular duct using numerical integration weighted by statistical turbulence spectrum. The present theory is verified by calculating the category 4 benchmark problem of the Third Computational Aeroacoustics Workshop for the response function and by comparing the predictions of a benchmark test for the broadband formulations of the sound power spectra. Then, the predictions of the inlet and exhaust sound power spectra for the NASA source diagnostic test are presented, which both show good agreement with the experimental results. The discrepancies indicate the importance of further corrections for stagger and swirling mean flow effects in realistic predictions. In the end, the variation trend of the sound power with different vane numbers is well captured, which indicates that this effect mainly refers to the propagation of cut-on acoustic modes in an annular duct. This model has the capability for further studies on the vane swept or lean effects.

Multi-objective optimization of wind turbine blades using lifting surface method

This paper describes a multi-objective optimization method for the design of horizontal axis wind turbines using the lifting surface method as the performance prediction model. The aerodynamic code for the design method is based on the lifting surface method with a prescribed wake model for the description of the wake. A multi-objective optimization algorithm approach is employed for the optimization of wind turbine blades with 3D stacking line (swept leaned blades). The (NSGA II) Non-dominated sorting genetic algorithm II is used to facilitate the multi-objective optimization and to find the global optima of high-dimensional problems. The scope of the optimization method is to achieve the best trade off of the following objectives: maximum of annual energy production and minimum of blade loads including thrust and blade rood flap-wise moment. To illustrate how the optimization of the blade is carried out the procedure is applied to NREL Phase VI rotor. The result shows the optimization models can provide more efficient designs.

Gas Lift Nodal-Analysis Model Provides Economical Approach to Optimization

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 171345, “Gas Lift Nodal-Analysis Model—Economical Optimization Approach,” by Mustafa Al Lawati, Occidental Petroleum, prepared for the 2014 SPE Artificial Lift Conference and Exhibition—North America, Houston, 6–8 October. The paper has not been peer reviewed. Field X consists of 17 scattered clusters of more than 100 oil wells producing from different reservoirs. Rapid expansion of the network has made the lifting network extremely busy and has resulted in many lowlifting- gas-rate ends. An easy solution is to increase lifting-gas use, but this is expensive. A more economical option is to restructure the gas lift surface pipelines, on the basis of proper engineering, by rerouting the surface network to reduce branching and enhance lifting-gas pressures and rates while maintaining the same level of lifting-gas use. Introduction The main gas lift 4-in. line connects Clusters A through C with the compressor. The main line is branched with 2-in. lines to every well in the cluster to deliver the required gas for lifting. As the number of wells increased dramatically, more low-rate and -pressure branches of the 2-in. lines were built. This was the main reason behind the loss of lifting efficiency. An increase of water cut in these clusters was another reason for loss of vertical-lift efficiency. Considering the operational challenges of the field, the easy yet expensive solution was to increase the volumes of lifting gas, knowing that 30 MMscf/D of gas already was used for lifting. A more-practical and -economical approach was, first, to build a numerical optimization model that could identify the low-pressure and -rate ends in the gas lift network on the basis of nodal analysis. The next step was to modify the gas lift network by rerouting the surface pipelines to help reduce any network branching and enhance lifting-gas pressures and rates accordingly across the network while maintaining the same volume of gas being used. Focusing on the three clusters— A, B, and C—pipeline rerouting and restructuring was implemented to debottleneck constraints at the surface network and to deliver lifting gas to high-productivity- index (PI) wells at optimum rates to optimize gas lift injection depth. Figs. 1 through 3 show the modifications made to these clusters. The main line is a 4-in. gas lift line, and the branched lines are all 2-in. lines. In Cluster A, a new 2-in. line was extended to the high-PI wells. The pipeline is represented in Fig. 1 by a dashed line. This allows for the delivery of higher lifting-gas rates, which helped optimize vertical-lift performance (VLP) of the wells by lifting from a deeper injection point while maintaining the same rate of lifting-gas use. The method of extending a new 2-in. line to high-PI wells was implemented again in Clusters B and C (Figs. 2 and 3, respectively). Methodology Pressure/Volume/Temperature (PVT) Characterization. The fluid PVT model is the first component of the integrated-nodal- analysis model. In this case, a surface fluid sample of Reservoir X from Cluster A was collected from the separator and tested in the laboratory. Later, the sample was modeled and characterized to evaluate the pressure-drop regime the fluid experiences along the production system, from the reservoir to the production separator. The characterization process includes the following: mass- balance calculation, compositional analysis, and entering the PVT laboratory data for matching to the equation of state. Reservoir Material-Balance Model. The reservoir material-balance model is the second component in the integrated model. To perform nodal analysis throughout the gas lift system, defining the production profile and static pressure of the tank (reservoir) from which the gas lift wells in Cluster A are producing is essential because defining an exact reservoir pressure is the starting point of any nodal analysis.

Aircraft Community Noise: The Revenge of a Neglected Problem

Aircraft Community Noise has been for years a simple problem arisen only in the very last moment of the type certification of a new airplane. Just a number to be glued on the airplane, to easily comply with some bored airworthiness rule. The development of new technologies and the always more increasing interest of the local communities toward “green” requirements have moved the aircraft community noise from the desk of few researchers to the wide interest of an increasing number of people even outside the aircraft community. The consolidated reliability and the extremely high level of safety have also addressed the interest of airplane manufacturers to interior noise and comfort perception, key demanding technology issues for the direct impact on customers and community. This paper summarizes some of the activities developed in several years with reference to aircraft noise, with preferred attention to the exterior noise, being it ruled by stringent rules and certification requirements. The long, continuous and successful activity pursued by PIAGGIO Aero Industries for its P180 Avanti II airplane has been the key factor offering the opportunity for a weighted thought to the aircraft community noise problem. PIAGGIO Aero Industries currently designing, manufacturing and certifying his own products, has developed during last year’s relevant experience on both community noise and interior noise, taking advantage of strong cooperation with world-wide research organization (namely DIAS Dept. of Aerospace Design of University of Napoli “Federico II”, INSEAN Italian Institute of Naval Experience, MWL The Marcus Wallenberg Laboratory for Sound and Vibration Research Department of Aeronautic and Vehicle Engineering KTH — The Royal Institute of Technology —, NLR Netherlands National Aerospace Laboratory, DLR Deutschland Aerospace Research Center, SIRE Virtual Reality Simulation Center of University of Savona).The airplane examined is the push-propelled turboprop, three lifting surface aircraft with natural laminar flow wing P180 Avanti II. The paper summarizes numerical aero-acoustic analysis performed as basis for phenomena understanding and for comparison of the aero-acoustic behaviour of P180 novel propeller and engine exhaust design, successfully certified reaching the expected community noise reduction. The time increasing stringency of the Community Noise rules, however, is evidenced by the consideration that the problem is now also affecting small classical configuration airplanes and it cannot be neglected anymore, particularly when expecting large global market acceptance.

Optimization of Aircraft Lifting Surfaces Using a Cellular Division Method

The development of a biologically inspired methodology for topology, shape, sizing, and control surface optimization of aircraft lifting surfaces is presented. The methodology is based on the map L-systems modeling of cellular division to generate the substructure topology. This is combined with variables for aerodynamic shape, structural sizing, and control surfaces (number, size, location, and aeroelastic trimmed settings) and constraints on stiffness, strength, local skin panel buckling, static aeroelastic response (roll performance, pitch rate, trimmed angle of attack), and flutter requirements. A dual-objective function is formulated with weight and and is solved with a bilevel optimization algorithm. The map -system rules that develop the topology are evolved using a genetic algorithm in the outer optimization loop on and weight, which obtains the optimal parameter settings for topology, shape, and control surfaces, whereas the inner loop performs weight minimization with the structural sizing variables. The methodology is demonstrated on the design of a generic fighter aircraft wing.

The New Propeller Design 3 Blades Type on 18o Skew Angle and Testing Cavitation of Tailing Thai Boat

This paper presents to case study the method design of 3-blade type ship propeller. cavitation flow is investigated around ship propellers experimentally. Testing of different types new model propellers and local type propellers are performed in this study. A 3-blades, skew angle 18 degree, developed area 55 and comparison which local type propeller commonly used by Thai fishermen. A practical design method was achieved by combining a vortex lattice lifting method and lifting surface method. The optimum circulation distribution yielding the maximum lift-to-torque ratio was computed for given thrust and chord lengths along the radius of the propeller by dividing the blade into a number of panels extending from hub to tip. The radial distribution of bound circulation could be computed by a set of constant-strength vortex elements. The cavitation phenomenon of new design appeared to be less than local type. Keyword: Cavitation Number(), Skew Angle, Developed Area

The impact of surface dust source exhaustion on the martian dust cycle, dust storms and interannual variability, as simulated by the MarsWRF General Circulation Model

Observations of albedo on Mars suggest a largely invariant long-term mean surface dust distribution, but also reveal variations on shorter (seasonal to annual) timescales, particularly associated with major dust storms. We study the impact of finite surface dust availability on the dust cycle in the MarsWRF General Circulation Model (GCM), which uses radiatively active dust with parameterized ‘dust devil’ and wind stress dust lifting to enable the spontaneous production of dust storms, and tracks budgets of dust lifting, deposition, and total surface dust inventory. We seek a self-consistent, long-term ‘steady state’ dust cycle for present day Mars, consisting of (a) a surface dust distribution that varies from year to year but is constant longer-term and in balance with current dust redistribution processes, and (b) a fixed set of dust lifting parameters that continue to produce major storms for this distribution of surface dust. We relax the GCM’s surface dust inventory toward this steady state using an iterative process, in which dust lifting rate parameters are increased as progressively more surface sites are exhausted of dust. Late in the equilibration process, the GCM exhibits quasi-steady state behavior in which few new surface grid points are exhausted during a 60year period with constant dust lifting parameters. Complex regional-scale dust redistribution occurs on time-scales from less than seasonal to decadal, and the GCM generates regional to global dust storms with many realistic features. These include merging regional storms, cross-equatorial storms, and the timing and location of several storm types, though very early major storms and large amounts of late storm activity are not reproduced. Surface dust availability in key onset and growth source regions appears vital for ‘early’ major storms, with replenishment of these regions required before another large storm can occur, whereas ‘late’ major storms appear primarily dependent on atmospheric variability. For the parameter space explored, no simulation achieves a steady state with continuing major storms lasting longer than 60years when a constant wind stress lifting threshold is used. However, such a long-term steady state is achieved when a variable threshold is introduced, in which the threshold increases as dust is removed. This negative feedback on lifting slows it sufficiently for a balance to be produced between dust removal and re-deposition, even in key source regions for major storms. One concern is that the long-term surface dust distributions produced in these simulations show significant differences to the observed northern hemisphere albedo map, in particular predicting Tharsis and NE Arabia to be relatively dust-free. Although some observed high albedo regions may not have significant mobile dust, others likely have a dust cover several meters thick. The mismatches may reflect deficiencies in the GCM or the iterative process used, or the existence of ancient deep dust deposits formed during a past climate epoch.

Design-Oriented Computational Fluid Dynamics-Based Unsteady Aerodynamics for Flight-Vehicle Aeroelastic Shape Optimization

A design-oriented computational fluid dynamics-based unsteady aerodynamic capability has been developed for the generation of shape sensitivities and approximations of aeroelastic constraints for integration into general flight-vehicle multidisciplinary-design-optimization systems. Complex-variable differentiation was used to convert an Euler unsteady solver with boundary-layer coupling into a design-oriented capability. The resulting shape-sensitivity results have been validated using finite difference method sensitivities on selected lifting surfaces: the AGARD wing, the Cohen wing, and the F-5 wing. Because the complex-variable-differentiation technique is numerically exact, the accuracy of the sensitivity computed by the new capability is step-size independent, whereas that of finite difference methods is highly step-size dependent. The resulting capability is computationally efficient. It covers all flight Mach numbers, including the transonic regime. It is accurate and robust, and interfaces seamlessly with the NASTRAN finite element code, widely used for aircraft design, and with other commercial aeroelastic solvers, such as ZAERO. The present paper focuses on lifting-surface computational fluid dynamics-based unsteady aerodynamics and flutter simulation, and it offers, in addition to the sensitivity-analysis technology described, new insights, not available earlier, regarding the functional dependence of key aeroelastic responses on airplane planform shape, and the accuracy in the cases studied here of Taylor-series-based approximations commonly used in multidisciplinary design optimization.

Structural Optimization of Box Wing Aircraft

Abstract The box wing system is an unconventional way to connect the lifting surfaces that the designers willingly to use in prototypes of new aircrafts. The article present a way to quickly optimize the wing structure of box wing airplane that can be useful during conceptual design. At the beginning, there is presented theory and methods used to code optimization program. Structure analysis is based on FEM beam model, which is sufficient in conceptual design. Optimization is performed using hybrid method, connection of simple iteration and gradient descent methods. Finally, the program is validated by case study.

Research on Modeling of Propeller in a Turboprop Engine

AbstractIn the simulation of engine-propeller integrated control system for a turboprop aircraft, a real-time propeller model with high-accuracy is required. A study is conducted to compare the real-time and precision performance of propeller models based on strip theory and lifting surface theory. The emphasis in modeling by strip theory is focused on three points as follows: First, FLUENT is adopted to calculate the lift and drag coefficients of the propeller. Next, a method to calculate the induced velocity which occurs in the ground rig test is presented. Finally, an approximate method is proposed to obtain the downwash angle of the propeller when the conventional algorithm has no solution. An advanced approximation of the velocities induced by helical horseshoe vortices is applied in the model based on lifting surface theory. This approximate method will reduce computing time and remain good accuracy. Comparison between the two modeling techniques shows that the model based on strip theory which owns more advantage on both real-time and high-accuracy can meet the requirement.