Drag Coefficient Research Articles

Numerical Study of Convection Heat Transfer with Confinement Around a Square Cylinder Submerged in a Water-Based Nanofluid

The novelty of this work lies in the comprehensive investigation of Forced convection heat transfer a square cylinder inclined at 45° using CuO nanofluid employing a single phase approach. A heated square cylinder with constant wall temperature boundary condition, subjected to a flowing nanofluid between two parallel walls, undergoes a laminar, steady and two-dimensional flow within a Reynolds number range of 1 < Re > 40. To obtain solutions for the flow and energy transfer, a Finite Element Method (FEM) is employed to numerically solve the governing differential equations and boundary conditions. The objective of this work is to highlight the effects of Reynolds number (Re), confinement ratio (λ), volume concentration (Φ) and diameter of nanoparticles (dnp) on fluid flow and heat transfer characteristics of nanofluid. To capture the effect of Φ and dnp in nanofluid, the thermo-physical-properties of CuO nanofluid are determined experimentally. In the results, at Re = 40, a secondary separation zone (recirculation zone) is observed near the surface of the channel wall. The drag coefficient value rises as the Φ increases and the vdnp decreases, regardless of other factors such as Re and λ. Conversely, as the confinement ratio and volume fraction of nanoparticles increase, the average Nusselt number also rises, while maintaining a constant value of Re and dnp. In contrast, the size of the nanoparticles exhibits an inverse relationship with the average Nusselt number. The study contributes to the understanding of nanofluid behavior and provides practical insights for applications, supported by correlations and Artificial Neural Network predictions (Parrales et al.).

Non-similar bioconvective analysis of magnetized hybrid nanofluid (Ag + TiO2) flow over exponential stretching surface

Scientists have studied fluid flow over a stretching sheet to explore its potential applications in industries. This study investigates the exponential stretching flow of a bioconvective magnetohydrodynamic (MHD) hybrid nanofluid in porous medium taking into consideration thermal radiations, heat genetraion, chemical reaction, porosity, and dissipation. Moreover, microorganisms are present in the fluid, so the fluid is more stable, which is crucial in biotechnology, biomicrosystems, and bio-nano coolant systems. Silver and titanium dioxide in a water-based medium are the prototypical nanoparticles. The present study involves a transformation of the governing system into a set of dimensionless, coupled and nonlinear partial differential equations (PDEs) using nonsimilar techniques. The local non-similarity (LNS) technique is used to truncate these equations to ordinary differential equations (ODEs). This technique is also used to estimate transformed equations numerically until the second level of truncation take place via the bvp4c algorithm, which is a built-in MATLAB solver. Furthermore, tables are provided that presents the drag coefficients, Nusselt numbers, Sherwood numbers, and densities of motile microorganisms. Results show a negative correlation between the velocity and the magnetic field parameter as well as the porosity parameter, as evidenced by a decrease in velocity corresponds to rises in these parameters. The temperature distribution exhibits a positive correlation with the rising values of both radiation parameter and Eckert number. The concentration profiles also exhibits a negative correlation with the increasing values of Lewis and bioconvection Lewis number, chemical reaction parameter, Peclet number and the differences in microbial concentration. This study will improve the future research on hybrid nanofluid regarding industrial applications. There haven't been any previous publications that have investigated the use of this model with the local non-similarity method. The main objective of this article is to enhance the heat transfer performance in a hybrid nanofluid.

The universal two-fifths law of pier scour

Understanding scour at bridge piers is crucial for safeguarding public safety, ensuring infrastructure resilience, and planning effective maintenance. Despite over six decades of extensive studies aiming to develop predictive formulas for the equilibrium scour depth at bridge piers, more than 20 000 highway bridges in the United States have been spotted “scour critical.” The traditional reliance on existing empirical formulas has posed a severe challenge for researchers, hindering to achieve a unified relation for the equilibrium scour depth from a fundamental scientific tenet. This perspective article presents a breakthrough—a universal law governing the equilibrium scour depth at a circular pier embedded in a sediment bed, specifically in clear-water scour condition. Derived from a phenomenological model, the universal law reveals that the equilibrium scour depth to pier diameter ratio obeys a consistent two-fifths scaling law with the introduction of a newly coined pier-scour number. This number accounts for all the key parameters involved in a local scour phenomenon, including the approach mean flow velocity, threshold shear velocity for sediment grain motion, approach flow depth, pier diameter, and sediment grain size. Importantly, the scaling law contains an additional term involving the drag coefficient raised to the power of 2/5, addressing the impact of the pier shape on the equilibrium scour depth. The derived universal law undergoes the validation through an extensive dataset of experimental measurements on circular pier scour.

Effects of Reynolds Number On the Wake Characteristics of a Notchback Ahmed Body

Abstract This paper investigates the effects of Reynolds number on the wake characteristics of a notchback Ahmed body with effective backlight angle, βe = 17.8°. The Reynolds number based on the body height was varied from 5 × 103 to 5 × 104. Prior to the Reynolds number investigation, a Reynolds-Averaged Navier-Stokes (RANS) model assessment was performed using nine turbulence models consisting of one- and two-equation eddy-viscosity models and second moment closure models. The standard Spalart-Allmaras model was the only model that accurately predicted the asymmetric time-averaged wake topology, as reported in previous studies, for the βe = 17.8° notchback Ahmed body at Re = 5 × 104. The drag coefficient decreased with increasing Reynolds number, while the lift coefficient remained constant for Re = 1 × 104. The wake structure exhibited three regimes: symmetric (Re = 1 × 104), transitionally asymmetric (1 × 104< Re = 3.5 × 104) and fully asymmetric (Re ≤ 3.5 × 104) states. The wake asymmetry was attributed to an imbalance in entrainment from the side and asymmetric separation from the roof and the C-pillars of the body. The tilting and stretching terms in the vorticity transport equation were used to provide insight into the source of asymmetry in the vorticity field around the body.

Convolutional Neural Networks-Based For Predicting Aerodynamic Coefficient Of Airfoils At Ultra-Low Reynolds Number

Many applications, including airplane design, wind turbines, and heat transmission, use symmetric or asymmetric airfoils. Engineers employ these airfoil shapes to optimize performance and efficiency. Each airfoil has a unique set of aerodynamic coefficients that must be calculated to maximize the airfoil design. Engineers utilize numerous ways to calculate coefficients, such as lift and drag. One of the methods is the prediction method, which effectively reduces time and cost. This study's training dataset is obtained from particle-based numerical computation using the Lattice Boltzmann Method (LBM). Then, Convolutional Neural Networks (CNN) are used as a prediction method to get the aerodynamic coefficients of airfoils for lift and drag based on two different Reynolds numbers. In CNN, airfoil geometry representation is essential. The Signed Distance Function (SDF) was used to convert airfoil geometry into RGB pictures. On the other hand, the SDF method cannot explain different flow conditions; in this case, it is represented by the Reynolds number (Re). Therefore, we propose a Text-based Watermarking Method (TWM) to differentiate between Re = 500 and Re = 1000. Each airfoil representation was trained and tested to generate each prediction model using a modified LeNet-5. The computation results show that using CNN with TWM on SDF to define the Reynolds numbers could predict the lift and drag coefficients with varying angles of attack. Future research can focus on generalizations to different aerodynamic aspects and practical applications in complex scenarios.

Effects on Aircraft Performance Due to Geometrical Twist of Wing

This paper provides an overview of the effects of Geometric Twist on Aircraft performance by introducing a washout condition in an aircraft wing. This condition results in an effective Angle of Attack at the wingtip that is lower than the Angle of Attack at the wing root. Using CFD analysis, the variation of aircraft performance factors such as lift, drag coefficients, and aerodynamic efficiency is calculated for different Twist angles. A plot of lift and drag coefficients at varying Angle of Attack angles has been generated based on these analyses. These results illustrate the advantages of wing twist variation, particularly at higher angles of attack. One significant advantage of Geometric Twist is that it causes stall conditions to first occur at the wing root, providing a signal to the pilot to control the aircraft before the stall reaches the wingtip. This ensures the effectiveness of control surfaces, such as Ailerons and Flaps, located at the wing trailing edge. A comparison is made between the lift, drag coefficients, and aerodynamic efficiency of twisted wings and untwisted wings with identical parameters. While twisting the wingtip yields favourable results at higher Angles of Attack (AOA) compared to an untwisted wing, the aerodynamic efficiency of the wings decreases at lower AOA. However, applying the twist angle at high angles of attack, such as 10, 12.5, 15, and 20 degrees, leads to an increase in aerodynamic efficiency.

Numerical Simulation of Flows Using the Fourier Pseudospectral Method and the Immersed Boundary Method

The present work proposes the application of a computational methodology based on the coupling of the Fourier Pseudospectral Method (FPSM) and the Immersed Boundary Method (IBM) for conducting flow simulations over slender airfoils. This methodology, termed IMERSPEC, leverages the benefits of both high accuracy and low computational cost inherent in pseudospectral methods, thanks to the utilization of the Fast Fourier Transform algorithm. IBM is employed to impose non-periodic boundary conditions in the Navier–Stokes equations, addressing the requirement of periodicity at boundaries for FPSM convergence and to accurately represent the immersed slender airfoil in the flow. The aerodynamic behavior of the analyzed profiles was assessed by calculating lift and drag coefficients, which were then compared with existing literature results. Consistently favorable outcomes were observed, particularly in flows at lower Reynolds numbers, demonstrating the effectiveness of the IMERSPEC methodology for simulating complex flows computationally. Additionally, weight functions, fundamental to IBM, are employed flexibly for aerodynamic force calculations. Specifically, within the same simulation, a Cubic function is utilized for drag calculation while a Hat function is employed for lift calculation, yielding results more closely aligned with the literature’s findings. This approach offers an alternative to previously proposed methods for IBM implementation.

Implementation of a PAFV turbulence model for airfoil flow simulation on OpenFOAM

To further develop a more effective turbulence model and to improve the calculation accuracy of the flow around airfoil, a new PAFV turbulence model has here been constructed by using a deformation rate tensor and the grouping of an average fluctuation velocity. To evaluate the applicability of the PAFV turbulence model, the numerical calculations of flow around the airfoil have here been implemented, which was based on the OpenFOAM calculation platform. On the basis of grid independence research, the model was used to calculate the low-speed flow-around problem for the plano-convex airfoil NACA4412 and the symmetric airfoil NACA0012. It was also compared with the S-A (Spalart-Allmaras) and SST (Shear Stress Transport) k-ω turbulence models. Firstly, the maximum lift angle-of-attack case of the NACA4412 airfoil was calculated. Thereafter, numerical calculations were performed for the flow around the airfoil in the multi-angle-of-attack case of the NACA0012 airfoil. The results showed that the NACA4412 airfoil had an obviously separated vortex at the trailing edge of the airfoil at the maximum lift angle of attack. Also, there was a certain velocity loss downstream of the trailing edge, which was calculated by all three models. However, the results of the PAFV turbulence model were found to be better than those of the S-A and SST turbulence models. The three turbulence models showed comparable accuracies for the calculations of the surface pressure coefficients of the NACA0012 airfoil. However, the S-A and SST k-ω turbulence models were slightly better for the calculations of the mean velocity profiles of the NACA0012 airfoil. Also, the PAFV turbulence model was more accurate for the calculations of the lift and drag coefficients. In conclusion, the PAFV model can make effective predictions of the airfoil low-speed flow around the problem at hand, which in turn preliminarily verifies the applicability of this turbulence model for the low-speed flow around the airfoil problems.

A Preliminary Evaluation of Morphing Horizontal Tail Design for UAVs

Morphing structures are a relatively new aircraft technology currently being investigated for a variety of applications, from civil to military. Despite the lack of literature maturity and its complexity, morphing wings offer significant aerodynamic benefits over a wide range of flight conditions, enabling reduced aircraft fuel consumption and airframe noise, longer range and higher efficiency. The aim of this study is to investigate the impact of morphing horizontal tail design on aircraft performance and flight mechanics. This study is conducted on a 1:5 scale model of a Preceptor N-3 Pup at its trim condition, of which the longitudinal dynamics is implemented in MATLAB release 2022. Starting from the original horizontal tail airfoil NACA 0012 with the elevator deflected at the trim value, this is modified by using the X-Foil tool to obtain a smooth morphing airfoil trailing edge shape with the same CLα. By comparing both configurations and their influence on the whole aircraft, the resulting improvements are evaluated in terms of stability in the short-period mode, reduction in the parasitic drag coefficient CD0, and increased endurance at various altitudes.

Data-Driven Car Drag Prediction With Depth and Normal Renderings

Abstract Generative artificial intelligence (AI) models have made significant progress in automating the creation of 3D shapes, which has the potential to transform car design. In engineering design and optimization, evaluating engineering metrics is crucial. To make generative models performance-aware and enable them to create high-performing designs, surrogate modeling of these metrics is necessary. However, the currently used representations of 3D shapes either require extensive computational resources to learn or suffer from significant information loss, which impairs their effectiveness in surrogate modeling. To address this issue, we propose a new 2D representation of 3D shapes. We develop a surrogate drag model based on this representation to verify its effectiveness in predicting 3D car drag. We construct a diverse dataset of 4535 high-quality 3D car meshes labeled by drag coefficients computed from computational fluid dynamics simulations to train our model. Our experiments demonstrate that our model can accurately and efficiently evaluate drag coefficients with an R2 value above 0.84 for various car categories. Our model is implemented using deep neural networks, making it compatible with recent AI image generation tools (such as stable diffusion) and a significant step toward the automatic generation of drag-optimized car designs. Moreover, we demonstrate a case study using the proposed surrogate model to guide a diffusion-based deep generative model for drag-optimized car body synthesis.

Numerical investigation of the cavitation effects on the wake dynamics behind a blunt trailing edge hydrofoil

The influence of cavitation on the wake behind a NACA 0009 hydrofoil with a truncated trailing edge has been numerically investigated using a homogeneous mixture model coupled with a controlled decay SST γ-Reθt turbulence model. Using optimal definitions of the inlet turbulent intensity and the empirical condensation and vaporization coefficients of the cavitation model, simulated results have shown a good agreement with experimental data. Notably, the numerical results exhibit negligible deviations of less than 0.7% in vortex shedding frequencies for different cavitation levels. If the size of the vortex cavitation grows, a substantial increase in both lift and drag coefficients on the hydrofoil is observed. Furthermore, the influence of cavitation on the trajectories of vortex centers and the morphology of the primary shedding vortices has been revealed using a vortex identification method. The findings highlight that the cavitation development enhances the advected velocity of the shedding vortices while decreasing the streamwise inter-vortex spacing. Consequently, both factors are found to contribute to the increase of the vortex-shedding frequency behind the NACA 0009 hydrofoil with the truncated trailing edge when cavitation appears and develops.

Hydrodynamic characteristics of rigid net panels for mariculture facilities as determined in flume-tank experiment

Mariculture facilities composed of rigid nets in practical applications gain increasing popularity due to the benefits of high strength and resistance to biofouling. In terms of structural safety and stability, the hydrodynamic characteristics of rigid nets are essential for design optimization and dynamic simulation, yet a comprehensive understanding is currently lacking. Hydrodynamic experiments were thus conducted to investigate four types of rigid net panels in a flume tank. The experiments considered variations in both the angles of attack (ranging from 0° to 90°) and flow velocities (ranging from 0.3 to 1.2 m/s). The results revealed that the drag coefficient of woven net panels exhibited the largest variation range, ranging from 0.13 to 1.26. The tortoise-shell net panels exhibited the lowest drag coefficients when the net panel was normal to the current while the drag coefficients were largest when the net panel was parallel to the current. The maximum lift coefficients, observed when the value of the angle of attack was 50°, were approximately 0.41 for woven net panels, 0.39 for welded net panels, 0.26 for chain-link net panels, and 0.27 for tortoise-shell net panels. Furthermore, hydrodynamic models of rigid net panels with better prediction performances than previous models were proposed. Considering the diverse application scenarios and hydrodynamic differences, utilizing the specific hydrodynamic models to improve prediction accuracy is recommended.

The wake characteristics and hydrodynamic forces of a near-wall circular cylinder with the splitter plate

Flow around a near-wall circular cylinder with the splitter plate is numerically performed at Reynolds number of 500, with the objective of investigating the wake characteristics and hydrodynamic forces. Five gap ratios [Formula: see text] and [Formula: see text] (G is the gap between the lower surface of the cylinder and the wall, D is the diameter of the cylinder) are selected, and the splitter plate length [Formula: see text] ranges from 0 to [Formula: see text]. The flow characteristics of an isolated cylinder with the splitter plate are investigated first for comparison, and four wake flow modes are observed, which include 2S mode ([Formula: see text]), P+S mode ([Formula: see text]), 2S+S mode ([Formula: see text]) and 2P mode ([Formula: see text]). As [Formula: see text] increases from 0 to [Formula: see text], the mean drag coefficient ([Formula: see text]) is decreased, and there is a slight increase of [Formula: see text] for [Formula: see text]. In addition, the cases of [Formula: see text] and [Formula: see text] produce a very significant reduction of drag, and the [Formula: see text] is reduced by as much as [Formula: see text] and [Formula: see text], respectively. The wake characteristics and hydrodynamic forces of a near-wall cylinder with the splitter plate are investigated in detail, and five wake regimes are observed, which include the wake vortex merging regime I, merged vortex attaching regime II, steady flow regime III, wall shear layer elongation regime IV and upper shear layer attaching regime V. For [Formula: see text], the wake vortex shedding is suppressed. For [Formula: see text], the Strouhal number (St) is decreased as [Formula: see text] increases from 0 to 1.0, and there is an increase of St at [Formula: see text]. At [Formula: see text], the St of the near-wall cylinder is larger than that of the isolated cylinder, and the increase in St is affected by the deflected gap flow. What is more, the hydrodynamic characteristics are affected by the wall. For [Formula: see text], the variations of [Formula: see text] with [Formula: see text] are similar to that of the isolated cylinder. It is found that the cases of [Formula: see text] and [Formula: see text] still produce a significant reduction of drag for [Formula: see text], and the [Formula: see text] is increased for all cases of [Formula: see text] as [Formula: see text] increases.

Numerical study on the cavitation instability from the perspectives of pressure change and hydrodynamics evolution in the cavitating flow over a hydrofoil

The objective of this study is to investigate cavitation instability by analyzing the pressure change and hydrodynamics evolution in the cavitating flow over a hydrofoil. Two-dimensional (2D) simulation results indicate that the multi-peak pressure features are influenced by the position on the hydrofoil surface. The increased cavitation number in a certain range aggravates the oscillation of partial cavitation and promotes the cavity change, then leads to the occurrence of higher peak pressure and more complicated fluctuation frequency. The lift coefficient presents a near-linear increasing trend due to the extended low-pressure area on the suction surface and the suppression on the vortex generation in the stable development stage of sheet cavity. The interaction between the vortex with different directions on the trailing edge dominates the fluctuation of lift coefficient. The differences in three-dimensional (3D) cavitating flows with constant velocity inlet and sinusoidal velocity inlet are the flow separation point distribution and vortex changes. More separation points form in the downstream of the hydrofoil due to more cloud cavity reattachment behaviours for sinusoidal velocity inlet. Furthermore, the sinusoidal velocity inlet promotes a more violent cavity detachment and the large-scale vortex formation, which enhances the fluctuations of pressure change, lift and drag coefficient.

Effect of radiation and slip parameter on MHD mixed convective Casson fluid flow along a vertical stretching sheet

The flow behavior of Casson fluids along a vertical stretching sheet is important for a wide range of industrial processes where such fluids are encountered. For example, knowledge of this study might be used in the design of coating processes or in biomedical applications involving blood flow. Aims of this study are the optimization of engineering processes, ensuring efficiency and quality in various applications and analysis of boundary layer along stretching sheet. Mathematical formulation of the problem consists parial differential equations and later on converted to a set of ordinary differential equations (ODEs) with boundary conditions and solved using “Bvp4c solver” in MATLAB. The Bvp4c solver is a numerical technique used to solve boundary value problems (BVPs) for ODEs. For various values of physical parameters the velocity, temperature, and concentration distribution are presented through figures. Skin friction coefficient, Nusselt number, and Sherwood number are tabulated and analyzed through bar graphs. It is noted that for assisting flow [Formula: see text], velocity profile decreases near the sheet while it increases away from the sheet for growing inputs of Casson fluid parameter ([Formula: see text]), while opposite seniro has been observed for Hartmann number ([Formula: see text]). Coefficient of surface drag is lowered with growing inputs of Casson fluid parameter and heat transfer rate is enhanced with increased inputs of Hartmann number in both assisting and opposing flow. The temperature profile enhances for raising inputs of radiation parameter ([Formula: see text]) in both assisting and opposing flow. The concentration profiles also fall, when chemical reaction parameter ([Formula: see text]) and Schmidt number ([Formula: see text]) are enhanced.

A Comparative Analysis of Aerodynamic Performance: Straight Fin and Curved Fin Rockets using Computational Fluid Dynamics (CFD)

This investigation seeks to discern the aerodynamic differentials between rockets featuring straight fins and those with curved fins, focusing on the drag coefficient (cd), lift coefficient (cl), and moment coefficient (cm). Employing the computational fluid dynamics (CFD) methodology within ANSYS Fluent software, the research endeavors to provide comprehensive insights. The rockets under scrutiny share a common cylindrical body configuration, boasting a 70 mm diameter, a conical nose, and four symmetrically positioned fins along the lower body. The CFD analyses encompass subsonic Mach 0.6 and supersonic Mach 1.2 scenarios, with the angle of attack systematically varying from 0° to 25° at 5° intervals for each velocity setting. The outcomes of the simulations reveal notable trends: both cd and cl exhibit an upward trajectory, while cm experiences a decrement with escalating angles of attack and velocities. The culmination of Ansys CFD simulations for both rocket configurations unequivocally indicates superior flight performance for the straight fin rocket. This discernment is grounded in the observed amplification of drag and lift coefficients, coupled with the concomitant reduction in the moment coefficient, thus elucidating the nuanced aerodynamic distinctions between straight fin and curved fin rockets across varying flight conditions.

Flow properties of an Ahmed Body with different passive flow control methods

A numerical simulation by utilizing the FloEFD software was carried out in order to investigate the flow topology formed on slant surface and wake region of an Ahmed Body with and without passive flow control techniques. The effects of those flow controllers on flow at the slant surface and wake region by influencing the flow topology as well as aerodynamic drag coefficient examined carefully. The numerical findings clearly revealed that the best performance in terms of providing the drag reduction obtained when sphere and hemispherical shape flow control techniques were applied at the rear part of slant surface of Ahmed Body. Sphere and hemispherical shape flow controllers positioned at the rear part of slant surface led to have drag reduction of 6% and 7%, respectively. Besides, the results of current study compared with the results obtained from published studies in the literature. It was clearly observed that they are consistent with each other even though they were found by different software.

Effect of topographical pattern on vortex shedding and heat transfer phenomena in power-law fluid flow around a rotating cylinder

The present numerical investigation studies the momentum and heat transfer phenomena from a heated rotating patterned cylinder in the vortex shedding regime. In particular, the effect of surface patterns ( ω , δ ), fluid behavior ( 0.4 ≤ n ≤ 1.6 ), cylinder rotation speed ( 0.5 ≤ α ≤ 2 ), and Prandtl number ( 1 ≤ Pr ≤ 100 ) at Reynolds number 100 on the force coefficients and Nusselt number are studied. Vorticity and isotherm profiles demonstrate the flow dynamics and heat transfer characteristics. According to the findings of this study, the formation of the vortex (including its size, shape, and number of vortices) and the time period during which the vortex shedding pattern repeats itself demonstrates a dependency on the shape of the cylinder, fluid behavior, and rotating speed. It has been noted that a significant decrease in the frequency of vortex shedding occurs on adding topographical patterns. Additionally, it has been noticed that on increasing rotational speed, vortex shedding can be suppressed for all fluid behaviors. Numerical simulation results reveal that the average drag coefficient ( C ¯ D ) for a rotating patterned cylinder decreases with increasing rotational speed ( α ), and it further reduces on increase in pattern frequency ( ω ) and amplitude ( δ ) compared to a smooth circular cylinder. The shear-thinning fluid behavior helps to dissipate the heat from the cylinder to the surrounding fluid. Conversely, shear-thickening fluid behavior exhibits the opposite trend.

Parametric Design Method and Lift/Drag Characteristics Analysis for a Wide-Range, Wing-Morphing Glide Vehicle

The parametric design method is widely utilized in the preliminary design stage for hypersonic vehicles; it ensures the fast iteration of configuration, generation, and optimization. This study proposes a novel parametric method for a wide-range, wing-morphing glide vehicle. The whole configuration, including a waverider fuselage, a rotating wing, a blunt leading edge, rudders, etc., can be easily described using 27 key parameters. In contrast to the typical parametric method, the new method takes internal payloads into consideration during the shape optimization process. That is, the vehicle configuration can be flexibly adjusted depending on the internal payloads; these payloads may be of random amounts and have different shapes. The code for the new parametric design method is developed using the secondary development tools of UG (UG 10.0) commercial software. The lift and drag characteristics over a wide operational range (H = 6–25 km, M = 2.5–8.5, AOA = 0–10°) were numerically investigated, as was the influence of the retracting angle of the morphing wings. It was found that, for the mode of the fully deployed wings, the lift-to-drag ratio (L/D) remained at a high level (≥4.7) over a Mach range of 4.0–8.5 and an AOA range of 4–7°. For the mode of the fully retracted wings, the drag coefficient remained smaller than 0.02 over a Mach range of 4.0–8.5 and an AOA range of 0–5°. A wide L/D of 0.3–4.7 could be achieved by controlling the retracting angle of the wings, thus demonstrating a good potential for flight maneuverability. The flexible change in L/D proved to be a combined result of varying pressure distribution and edge-flow spillage. This will aid in the further optimization of lift/drag characteristics.

Potential of repurposing decommissioned subsea flowlines to dynamically installed anchors

Subsea flowlines are flexible or rigid pipelines that are used in oil and gas fields commonly for transporting production fluids from wells. The majority of the flowlines operating in basins across the world (including e.g. Australia's 1700 km infield flowlines) are approaching the end of their productive life, and will need to be decommissioned over the next 5 decades. This paper, for the first time, investigates the potential of repurposing decommissioned flowlines to dynamically installed anchors for mooring floating facilities. Five shapes of anchor have been developed using segments of flowline. Two series of tests were subsequently carried out on models of those shapes. The first series of tests involved releasing the models in still water to assess free-fall trajectory (i.e. verticality), terminal velocity, and anchor drag coefficient. The second series of tests were carried out at 50 g in clay to investigate the performance of the anchors in terms of tip embedment depth during dynamic installation and capacity under vertical loading. The results confirmed performance similar to conventional dynamically installed anchors, suggesting that there is potential to fabricate offshore anchors using segments of flowline.