Comparing Deterministic and Non-deterministic Optimization for Airfoil Shape Design

Transitions in the unsteady wakes and aerodynamic characteristics of the flow past three square cylinders aligned inline

Considering the drag-divergence performance as a constraint, this paper presents a multi-point aero-structural design optimization of wings on a wing-body-tail-engine configuration of long-range dual-aisle civil aircraft by using a gradient-based method based on the discrete adjoint method. Firstly, the accuracy of the coupled aero-structural analysis method used in this paper was validated with DLR-F6 wing-body configuration. Then a wing aero-structural design optimization based on a dual-aisle civil aircraft is offered. The drag coefficient of the optimized configuration in every state decreased, which was reduced by 13.67 counts at the cruise condition, the difference in drag coefficient from Mach 0.85 to Mach 0.87 was decreased from 28.52 counts to 18.98 counts, indicating its drag-divergence performance has been improved undoubtedly. Finally, we compared the performance among the multi-point aero-structural optimized configuration, the single-point aerodynamic optimized configuration and the single-point structural optimized configuration. The results show that the multi-point aero-structural design optimization considering drag-divergence performance has great potential to gain a design configuration with better comprehensive and practical performance compared with a single-point optimization in a single discipline.

Design of adaptive transonic laminar airfoils using the [formula omitted] transition model

Automotive engine downsizing has placed an increased focus on the ability of the turbocharger to provide adequate boost levels across the full engine operating rage. To achieve the desired levels of turbocharger performance the turbine must be capable of operating effectively at the intended design point and also at off-design conditions. Mixed flow turbines (MFTs) provide a potential method to improve performance at off-design conditions and during transient engine operation. A unique feature of a MFT is the spanwise variation of incidence angle at the rotor leading edge. This results in additional flow separation from the blade suction surface near the hub under a wide range of operating conditions. The flow separation generates additional loss and has a detrimental impact on turbine performance. A novel design of turbine volute similar to a conventional twin-entry turbine volute was examined. The novel turbine volutes were designed to produce a spanwise variation in flow conditions at the rotor inlet. The primary objective was to reduce the incidence angle and increase the mass flow rate at the hub side of the passage relative to the shroud side, as it has previously been identified that this can be beneficial for MFT performance. A number of different volute geometries were examined by numerical analysis to determine the impact of key parameters on turbine performance. The results indicated that generating a suitable spanwise flow distribution could produce a moderate improvement in turbine efficiency at off-design operating conditions. The novel volute design also provided a means of achieving a degree of variable geometry operation to further improve off-design performance. Turbine performance was examined under the variable geometry operation and an improvement in turbine power output at low speed, off-design conditions was achieved. This was analogous to operating with a conventional pivoting vane variable geometry system and had the potential to benefit performance during transient engine operation.

The Shell Eco Marathon is a world-class car competition for students. Through this competition, students compete to create innovation and creativity in the development of vehicle technology. The final result of this competition is the birth of vehicles that are economical, environmentally friendly, including a lightweight and aerodynamic body. This study aims to produce an urban concept car body design for racing purposes, with several provisions that comply with the Shell Eco Marathon competition regulations, have a low drag coefficient and turbulence value. This research includes research and development (R&D), using the ADDIE development model (Analysis, Design, Development, Implementation, and Evaluation). The test object is the 3D urban concept body shape design. The development of the urban concept body design uses the Solid work 2018 software with a flow simulation feature to analyze 3D urban concept body shape designs. The results of this research and development are (1) the design of the car body shape has met the competition regulations, (2) the drag coefficient value can be achieved at 0.1965, and (3) the value of turbulence intensity can be achieved at 0.133%. The results showed that the development of the urban concept body shape design was as planned.

New methods for studying the effect of gas injection from the surface of a solid spherical particle on its drag coefficient in the transient and self-similar regimes of flow around the particle have been presented. An advantage of the proposed methods is the ability to isolate in a pure form the effect of the mass flux from the particle surface (without the effect of other factors, for example, particle acceleration) on the drag coefficient. New results of an experimental study of the effect of air flow blowing on the drag coefficient of a solid perforated sphere in the Reynolds number range Re = 133÷9900 have been presented. It has been shown that the drag coefficient decreases when air is blown from the particle surface. As the Reynolds number Re increases, the drag coefficient CD upon gas injection in the transient flow regime decreases to a certain critical value corresponding to the onset of the self-similar regime. At the onset of the selfsimilar regime (reaching the critical value of CD), the drag coefficient increases with an increase in the Reynolds number and asymptotically tends to a constant value CD = 0.44. However, the opposite effect has been found for a small diameter of the particle (D = 1 cm) at a blowing velocity ue ≥ 1.3 m/s: an increase in the drag coefficient of the particle CD at air efflux from the particle surface in comparison with the drag coefficient value in the absence of gas flow injection (ue = 0 m/s). This is apparently associated with a change in the characteristics of the boundary layer of the particle due to the rearrangement of the flow profile near the spherical particle surface caused by a decrease in its size. An empirical dependence of the drag coefficient of a solid sphere on the ratio of the velocity of injection from the surface of the particle to the velocity of blowing CD = 0.15 + (0.44 - 0.15)/ (1 + 9ū/53.8) (with the coefficient of determination R2 = 0.89) has been obtained for a self-similar particle regime flow. Contribution of the authors: the authors contributed equally to this article. The authors declare no conflicts of interests.

Creep Life consumption of the engine components is highly sensitive to variations in operational stresses and temperatures, which are controlled by engine operational conditions that are in turn driven by the mission objectives. Conventional methods of life consumption assessment lack in capturing the variations in the operating conditions and the uncertainties in the governing parameters accurately. The paper describes a method for creep life consumption monitoring of a turbine rotor blade considering the variations in engine operating conditions. Response surface method is applied to develop a functional relationship for the creep life in terms of the influencing variables. Probabilistic creep life prediction model is developed for considering the uncertainty in the input parameters, geometry and material data. A service life consumption assessment method capable of capturing the varying operating conditions with relatively higher accuracy is proposed that enables economic maintenance and withdrawal schedules.

Economic configuration optimization of onboard annual thermoelectric generators under multiple operating conditions

In actual flight, aircraft rarely operate under a single design condition; multiple flight states must be considered to meet performance requirements. With the push for green and low-carbon aviation, there is growing demand for high-performance, fuel-efficient aircraft. This study focuses on the Blended Wing Body (BWB) configuration. To address large-scale design variables and multiple constraints, a discrete adjoint-based aerodynamic optimization method is developed, improving computational efficiency and reducing cost.The optimization results show reduced drag coefficients across various flight conditions and enhanced drag divergence performance. The robustness of the multi-point optimization approach is validated, confirming its ability to improve aircraft performance across different states. The proposed method is practical and provides an effective reference for aerodynamic design of BWB aircraft.

Numerical simulation of flow around a triangular cylinder placed both in left and right position at Reynolds number Re = 80–200 is presented in this study. The single relaxation time lattice Boltzmann method is used. The results are obtained in terms of vorticity contour visualization, drag and lift coefficients, and force statistics. Regular vortex shedding is observed for both cases, but the vortices generated for a triangular cylinder placed in the right position move toward the top downstream position as the range of Reynolds number increases due to effect of pressure (effect of thrust). The drag coefficient is constant, and lift coefficient is containing negative values from Re = 80–150 for that case, but negative Cdmean values are not observed for a triangular cylinder placed in the left position. In that case, it is due to the reason that the effect of thrust diminishes. The maximum value of Cdmean is obtained at Re = 200, that is, 1.5006 for the left triangular cylinder, but the value of the mean drag coefficient for the right triangular cylinder is zero throughout the cases for Re = 80–200. No fluid forces are produced for right triangular case. The Strouhal number (St) values increased by increasing the Reynolds number, i.e., Re = 80–200, for the right triangular cylinder, and it has a mixed trend for the left triangular cylinder. In literature, a lot of work has been found on rectangular and square cylinders, but triangular cylinder has not been studied much.

This paper presents the modified numerical model based on the REMUS simulation model proposed by Timothy Prestero in his paper of MTS/IEEE Conference and Exhibition in 2001 when using it to simulate the “MAUV-III” Mini Autonomous Underwater Vehicle (AUV) of author’s laboratory. In addition, it describes the “MAUV-II” numerical model proposed by Wangbo in his Master thesis of Harbin Engineering University. Because of the inaccuracy of the calculated values of lift and drag coefficients under a series of rudder angles of attack based on the FLUENT software, which is proved by the actual experiment. The calculation method is modified by multiplying by 1.2 as the correction coefficient. After modification, the simulated results are proved to very close match to the experiment data. Based on the corresponding experiments including Circle Maneuver in horizontal plane and diving motion in vertical plane under given operation conditions, these two numerical models are shown to accurately simulate the motion of the “MAUV-III” AUV, especially for the modified REMUS model.

The dynamic resistance of a fluid to a cylinder rolling on an inclined plane in water has been experimentally studied. This creates problems in the form of solid-liquid interactions, which include landslides on the seabed and debris flows on the seabed that cause Tsunamis. The development of flow around a rolling cylinder is described to highlight the implications on the nature of the hydrodynamic force coefficient acting on the cylinder as resistance. The coefficient of drag on the cylinder when rolling on an inclined plane in water is the coefficient of drag that prevents the cylinder from rolling. In addition, other external force coefficients (besides the drag coefficient) also impede the cylinder motion. The equation of motion of the cylinder is solved with experimental data which is used as the most suitable solution to get the drag coefficient value. The movement of the cylinder is also not perfectly linear because there is a force from the side of the track and the cylinder moves slightly zigzag in 1-D motion.
 HIGHLIGHTS
 
 In this study, we present the experimental results of cylindrical drag coefficients of various materials on inclined planes in water as modeling of broader scientific problems, especially the potential for hydrometeorological and sedimentation disasters
 Fluid dynamics of the cylinder drag force on an inclined plane in water were measured experimentally
 The motion of the cylinder on an inclined plane in water is recorded, then the recorded video is processed using Logger Pro to obtain experimental time, speed, and position data which is processed using the appropriate mathematical equations
 
 GRAPHICAL ABSTRACT

The main motivation to pursue this research was to reduce the aerodynamic drag of vehicles so that it may lead to better fuel efficiency. The aim of this research was to investigate the aerodynamic forces on various car models through Computational Fluid Dynamics (CFD) and then validating those results experimentally in a wind tunnel. Two car shapes were chosen based on the commonly found Toyota Corolla EU (2014) and Toyota Land Cruiser 200 (2016). These shapes remodeled with the help of CATIA V5 and Design Modeler. These models were then analyzed using ANSYS FLUENT 14 with different grid sizes until mesh independence was achieved. The results obtained for the drag coefficients were 0.354 and 0.265 for Toyota Land Cruiser 200 and Toyota Corolla respectively. The analysis was done at a wind speed of 20 m/s. The results of the numerical investigation were validated by the already tested values available in the literature, which are 0.35 and 0.27 for Toyota Land Cruiser 200 and Toyota Corolla respectively. For wind tunnel testing, these models were scaled and then 3D printed to be tested in a subsonic wind tunnel. The scale of the models was set to be 1:37 as dictated by the constraints of the wind tunnel. The results obtained during experimentation are comparable only qualitatively nevertheless, a drag coefficient of 0.36 and 0.42 were obtained for Corolla and Land Cruiser 200 by wind tunnel testing. Furthermore, based on our investigation different physical drag reduction techniques were applied to reduce the drag on these models and analysis was performed using CFD. A reduction of 6.26% was observed in the value of drag coefficient by modifications in the Corolla car model.

This paper addresses the problem of multiple operating conditions design, in the context of optimal aircraft mission performance and from the aerodynamic point of view. In particular, the choice of the flight conditions to be included in the optimization problem from desired condition ranges has to be done such that the optimization problem is wellpoised with a minimal computational cost. To this aim, a new method called Gradient Span Analysis is given, based on the analysis of the linear dependencies provided by adjoint sensitivities. A wing-body configuration is presented as test case and optimization results show the interest in terms of computational time savings. Physical interpretation of the method is also given.

The ability to morph the shape of an aircraft wing to optimize performance is widely accepted as a path to improved aircraft efficiency. A simpler approach is to change the wing camber using existing control surfaces. In this work, a Reynolds-averaged Navier–Stokes-based aerodynamic shape optimization methodology is applied to the design of a business jet with variable camber. Variable camber is achieved using the three existing control surfaces on each wing. Multipoint optimization is performed over a range of cruise operating conditions with and without variable camber. Variable camber is found to yield a reduction in drag of approximately 3–11 counts, or 1–5%, over a range of cruise conditions, with the largest reductions seen at lower lift coefficients. The control surface deflections are used to reduce the wing camber at lower lift cruise conditions, leading to an increase in the aircraft angle of attack across most operating points. The increased angles of attack transfer lift to the fuselage, which enables reductions in induced, wave, and trim drag. This additional drag reduction mechanism has not been identified in previous studies and cannot be seen in optimizations that do not include the fuselage and a trim constraint.