Mostafa Arasteh, Yegane Azargoon and M.H. Djavareshkian
Ground effect is one of the important factors in the enhancement of wing aerodynamic performance. This study aims to investigate the aerodynamic forces and performance of a…
Abstract
Purpose
Ground effect is one of the important factors in the enhancement of wing aerodynamic performance. This study aims to investigate the aerodynamic forces and performance of a flapping wing with the bending deflection angel under the ground effect.
Design/methodology/approach
In this study, the wing and flapping mechanism were designed and manufactured based on the seagull flight and then assembled. It is worth noting that this mechanism is capable of wing bending in the upstroke flight as big birds. Finally, the model was examined at bending deflection angles of 0° and 107° and different distances from the surface, flapping frequencies and velocities in forward flight in a wind tunnel.
Findings
The results revealed that the aerodynamic performance of flapping wings in forward flight improved due to the ground effect. The effect of the bending deflection mechanism on lift generation was escalated when the flapping wing was close to the surface, where the maximum power loading occurred.
Practical implications
Flapping wings have many different applications, such as maintenance, traffic control, pollution monitoring, meteorology and high-risk operations. Unlike fixed-wing micro aerial vehicles, flapping wings are capable of operating in very-low Reynolds-number flow regimes. On the other hand, ground effect poses positive impacts on the provision of aerodynamic forces in the take-off process.
Originality/value
Bending deflection in the flapping motion and ground effect are two influential factors in the enhancement of the aerodynamic performance of flapping wings. The combined effects of these two factors have not been studied yet, which is addressed in this study.
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M.R. Saber and M.H. Djavareshkian
In the present research, the effect of the flexible shells method in unsteady viscous flow around airfoil has been studied. In the presented algorithm, due to the interaction of…
Abstract
Purpose
In the present research, the effect of the flexible shells method in unsteady viscous flow around airfoil has been studied. In the presented algorithm, due to the interaction of the aerodynamic forces and the structural stiffness (fluid-structural interaction), a geometrical deformation as the bump is created in the area where the shock occurs. This bump causes instead of compressive waves, a series of expansion waves that produce less drag and also improve the aerodynamic performance to be formed. The purpose of this paper is to reduce wave drag throughout the flight range. By using this method, we can be more effective than recent methods throughout the flight because if there is a shock, a bump will form in that area, and if the shock does not occur, the shape of the airfoil will not change.
Design/methodology/approach
In this simulation pressure-based procedure to solve the Navier-Stokes equation with collocated finite volume formulation has been developed. For this purpose, a high-resolution scheme for fluid and structure simulation in transonic flows with an arbitrary Lagrangian-Eulerian method is considered. To simulate Navier-Stokes equations large eddy simulation model for compressible flow is used.
Findings
A new concept has been defined to reduce the transonic flow drag. To reduce drag force and increase the performance of airfoil in transonic flow, the shell can be considered flexible in the area of shock on the airfoil surface. This method refers to the use of smart materials in the aircraft wing shell.
Originality/value
The value of the paper is to develop a new approach to improve the aerodynamic performance and reduce drag force and the efficiency of the method throughout the flight. It is noticeable that the new algorithm can detect the shock region automatically; this point was disregarded in the previous studies. It is hoped that this research will open a door to significantly enhance transonic airfoil performance.
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Mahdi Naderinezhad and M.H. Djavareshkian
This study aims to investigate the effectiveness of two types of winglets, multi-tip and raked, on the performance of sinusoidal and simple leading-edge wings and compares it by a…
Abstract
Purpose
This study aims to investigate the effectiveness of two types of winglets, multi-tip and raked, on the performance of sinusoidal and simple leading-edge wings and compares it by a numerical method.
Design/methodology/approach
The wing configuration in this study is rectangular and uses NACA0020 section, and all simulations are performed by a numerical method based on finite volume and base pressure algorithm in Reynolds 2 × [10]^5. In the mentioned numerical method, the flow is considered turbulent, and the k-ω-SST model is used. To calculate the stresses on the wing surface, the mesh is extended to below the viscous layer, and a second-order upstream accuracy is used to calculate the convection flux.
Findings
The use of raked and multi-tip winglets for the sinusoidal edge of the wing improved aerodynamic performance by 5.12 and 2.28%, respectively, and the greatest effect of these two winglets was on increasing the lifting force and reducing the inductive drag, respectively. Also, by examining the distribution of induced vortices around the configurations, it was found that the curvature of the sinusoidal wing tip at the angles of attack before stall reduced the strength of the induced vortices and, the use of winglet during and after stall, caused increased aerodynamic performance of the sinusoidal wing.
Practical implications
The whale is an international species of aquatic animal found in most of the world’s oceans. It has large fin aspect ratios that have a series of bulges at the edge of the attack, which improves the aerodynamic performance near and after stall. Today, one of the fields of research is the use of this idea in the wings of micro air vehicle.
Originality/value
Winglet reduces induced drag in simple wings. So far, the effect of winglets on wings with sinusoidal attack edges has not been investigated.
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Mojtaba Tahani, Mehran Masdari and Ali Bargestan
This paper aims to investigate the aerodynamic characteristics as well as static stability of wing-in-ground effect aircraft. The effect of geometrical characteristics, namely…
Abstract
Purpose
This paper aims to investigate the aerodynamic characteristics as well as static stability of wing-in-ground effect aircraft. The effect of geometrical characteristics, namely, twist angle, dihedral angle, sweep angle and taper ratio are examined.
Design/methodology/approach
A three-dimensional computational fluid dynamic code is developed to investigate the aerodynamic characteristics of the effect. The turbulent model is utilized for characterization of flow over wing surface.
Findings
The numerical results show that the maximum change of the drag coefficient depends on the angle of attack, twist angle and ground clearance, in a decreasing order. Also, it is found that the lift coefficient increases as the ground clearance, twist angle and dihedral angle decrease. On the other hand, the sweep angle does not have a significant effect on the lift coefficient for the considered wing section and Reynolds number. Also, as the aerodynamic characteristics increase, the taper ratio befits in trailing state.
Practical implications
To design an aircraft, the effect of each design parameter needs to be estimated. For this purpose, the sensitivity analysis is used. In this paper, the influence of all parameter against each other including ground clearance, angle of attack, twist angle, dihedral angle and sweep angle for the NACA 6409 are investigated.
Originality/value
As a summary, the contribution of this paper is to predict the aerodynamic performance for the cruise condition. In this study, the sensitivity of the design parameter on aerodynamic performance can be estimated and the effect of geometrical characteristics has been investigated in detail. Also, the best lift to drag coefficient for the NACA 6409 wing section specifies and two types of taper ratios in ground effect are compared.
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Yuan Ma, Hui Tang and Chenglei Wang
This study aims at investigating the heat transfer characteristics of a nonsquare enclosure when hydrodynamic resistance is altered discontinuously along its inner surface…
Abstract
Purpose
This study aims at investigating the heat transfer characteristics of a nonsquare enclosure when hydrodynamic resistance is altered discontinuously along its inner surface. Particularly, it focuses on investigating how several essential factors collaboratively influence the natural convection, including the Rayleigh number (Ra), the aspect ratio (AR), the nanoparticle volume fraction (ϕ) and the locations of changing hydrodynamic resistance.
Design/methodology/approach
To achieve these objectives, an L-shaped enclosure of various AR is adopted, while zero local shear resistance is applied and modeled by stress-free (SF) patches of four distinct arrangements (corresponding to Cases 1–4). The nanofluid is modeled by Buongiorno’s two-phase model. The effects are explored using an in-house numerical framework based on a hybrid lattice Boltzmann-finite difference method with the total variation minimization scheme.
Findings
The results show that when Ra is sufficiently large, i.e. Ra = 105, SF patches can generally enhance the heat transfer performance regardless of other factors. However, the ways of achieving those enhancements are different, which mainly depend on the arrangement of the SF patches and AR but are nearly independent of ϕ. The maximum improvement of heat transfer can be achieved in Case 3 with AR = 0.6, Ra = 105 and ϕ = 0.04, where the averaged Nusselt number is enhanced by 8.89%.
Originality/value
This study presents a new scenario where the SF patches of various arrangements are applied to enhance the nanofluid natural convection of a nonsquared enclosure, and it reveals how the improvement is achieved and cooperatively affected by several important factors.
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Hongwei Ma, Shuai Ren, Junxiang Wang, Hui Ren, Yang Liu and Shusheng Bi
This paper aims to carry out the research on the influence of ground effect on the performance of robotic fish propelled by oscillating paired pectoral fins.
Abstract
Purpose
This paper aims to carry out the research on the influence of ground effect on the performance of robotic fish propelled by oscillating paired pectoral fins.
Design/methodology/approach
The two-dimensional ground effect model of the oscillating pectoral fin without considering flexible deformation is established by introducing a two-dimensional fluid ground effect model. The parameters of the influence of ground effect on the oscillating pectoral fin are analyzed. Finally, the ground effect test platform is built, and a series of hydrodynamic experiments are carried out to study the influence of ground effect on the propulsion performance of the robotic fish propelled by oscillating paired pectoral fins under different motion parameters.
Findings
The thickness of the trailing edge and effective clearance are two important parameters that can change the influence of ground effect on the rigid pectoral fin. The experimental results are consistent with that obtained through theoretical analysis within a certain extent, which indicates that the developed two-dimensional ground effect model in this paper can be used to analyze the influence of ground effect on the propulsion performance of the oscillating pectoral fin. The experiment results show that the average thrust increases with the decreasing distance between the robot fish and the bottom. Meanwhile, with the increase of oscillation frequency and amplitude, the average thrust increases gradually.
Originality/value
The developed two-dimensional ground effect model provides the theoretical basis for the further research on the influence of ground effect on the propulsion performance of the oscillating pectoral fin. It can also be used in the design of the bionic pectoral fins.
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The purpose of this paper is to present a novel approach based on the differential search (DS) algorithm integrated with the adaptive network-based fuzzy inference system (ANFIS…
Abstract
Purpose
The purpose of this paper is to present a novel approach based on the differential search (DS) algorithm integrated with the adaptive network-based fuzzy inference system (ANFIS) for unmanned aerial vehicle (UAV) winglet design.
Design/methodology/approach
The winglet design of UAV, which was produced at Faculty of Aeronautics and Astronautics in Erciyes University, was redesigned using artificial intelligence techniques. This approach proposed for winglet redesign is based on the integration of ANFIS into the DS algorithm. For this purpose, the cant angle (c), the twist angle (t) and taper ratio (λ) of winglet are selected as input parameters; the maximum value of lift/drag ratio (Emax) is selected as the output parameter for ANFIS. For the selected input and output parameters, the optimum ANFIS parameters are determined by the DS algorithm. Then the objective function based on optimum ANFIS structure is integrated with the DS algorithm. With this integration, the input parameters for the Emax value are obtained by the DS algorithm. That is, the DS algorithm is used to obtain both the optimization of the ANFIS structure and the necessary parameters for the winglet design. Thus, the UAV was reshaped and the maximum value of lift/drag ratio was calculated based on new design.
Findings
Considerable improvements on the max E are obtained through winglet redesign on morphing UAVs with artificial intelligence techniques.
Research limitations/implications
It takes a long time to obtain the optimum Emax value by the computational fluid dynamics method.
Practical implications
Using artificial intelligence techniques saves time and reduces cost in maximizing Emax value. The simulation results showed that satisfactory Emax values were obtained, and an optimum winglet design was achieved. Thus, the presented method based on ANFIS and DS algorithm is faster and simpler.
Social implications
The application of artificial intelligence methods could be used in designing more efficient aircrafts.
Originality/value
The study provides a new and efficient method that saves time and reduces cost in redesigning UAV winglets.
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Alireza Rahimi, Abbas Kasaeipoor, Emad Hasani Malekshah, Mohammad Mehdi Rashidi and Abimanyu Purusothaman
This study aims to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with CuO-water nanofluid.
Abstract
Purpose
This study aims to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with CuO-water nanofluid.
Design/methodology/approach
The lattice Boltzmann method is used to solve the problem numerically. Two different multiple relaxation time (MRT) models are used to solve the problem. The D3Q7–MRT model is used to solve the temperature field, and the D3Q19 is used to solve the fluid flow of natural convection within the enclosure.
Findings
The influences of different Rayleigh numbers (103 < Ra < 106) and solid volume fractions (0 < f < 0.04) on the fluid flow, heat transfer, total entropy generation, local heat transfer irreversibility and local fluid friction irreversibility are presented comprehensively. To predict thermo–physical properties, dynamic viscosity and thermal conductivity, of CuO–water nanofluid, the Koo–Kleinstreuer–Li (KKL) model is applied to consider the effect of Brownian motion on nanofluid properties.
Originality/value
The originality of this work is to analyze the three-dimensional natural convection and entropy generation using a new numerical approach of dual-MRT-based lattice Boltzmann method.
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Mojtaba Tahani, Mehran Masdari and Ali Bargestan
The overall performance of an aerial vehicle strongly depends on the specifics of the propulsion system and its position relative to the other components. The purpose of paper is…
Abstract
Purpose
The overall performance of an aerial vehicle strongly depends on the specifics of the propulsion system and its position relative to the other components. The purpose of paper is this factor can be characterized by changing several contributing parameters, such as distance from the ground, fuselage and wing as well as the nacelle outlet velocity and analyzing the aerodynamic performance.
Design/methodology/approach
Navier–Stokes equations are discretized in space using finite volume method. A KW-SST model is implemented to model the turbulence. The flow is assumed steady, single-phase, viscous, Newtonian and compressible. Accordingly, after validation and verification against experimental and numerical results of DLRF6 configuration, the location of the propulsion system relative to configuration body is examined.
Findings
At the nacelle outlet velocity of V/Vinf = 4, the optimal location identified in this study delivers 16% larger lift to drag ratio compared to the baseline configuration.
Practical implications
Altering the position of the propulsion system along the longitudinal direction does not have a noticeable effect on the vehicle performance.
Originality/value
Aerial vehicles including wing-in-ground effect vehicles require thrust to fly. Generating this necessary thrust for motion and acceleration is thoroughly affected by the vehicle aerodynamics. There is a lack of rigorous understanding of such topics owing to the immaturity of science in this area. Complexity and diversity of performance variables for a numerical solution and finding a logical connection between these parameters are among the related challenges.
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Tugrul Oktay, Seda Arik, Ilke Turkmen, Metin Uzun and Harun Celik
The aim of this paper is to redesign of morphing unmanned aerial vehicle (UAV) using neural network for simultaneous improvement of roll stability coefficient and maximum…
Abstract
Purpose
The aim of this paper is to redesign of morphing unmanned aerial vehicle (UAV) using neural network for simultaneous improvement of roll stability coefficient and maximum lift/drag ratio.
Design/methodology/approach
Redesign of a morphing our UAV manufactured in Faculty of Aeronautics and Astronautics, Erciyes University is performed with using artificial intelligence techniques. For this purpose, an objective function based on artificial neural network (ANN) is obtained to get optimum values of roll stability coefficient (Clβ) and maximum lift/drag ratio (Emax). The aim here is to save time and obtain satisfactory errors in the optimization process in which the ANN trained with the selected data is used as the objective function. First, dihedral angle (φ) and taper ratio (λ) are selected as input parameters, C*lβ and Emax are selected as output parameters for ANN. Then, ANN is trained with selected input and output data sets. Training of the ANN is possible by adjusting ANN weights. Here, ANN weights are adjusted with artificial bee colony (ABC) algorithm. After adjusting process, the objective function based on ANN is optimized with ABC algorithm to get better Clβ and Emax, i.e. the ABC algorithm is used for two different purposes.
Findings
By using artificial intelligence methods for redesigning of morphing UAV, the objective function consisting of C*lβ and Emax is maximized.
Research limitations/implications
It takes quite a long time for Emax data to be obtained realistically by using the computational fluid dynamics approach.
Practical implications
Neural network incorporation with the optimization method idea is beneficial for improving Clβ and Emax. By using this approach, low cost, time saving and practicality in applications are achieved.
Social implications
This method based on artificial intelligence methods can be useful for better aircraft design and production.
Originality/value
It is creating a novel method in order to redesign of morphing UAV and improving UAV performance.