Drag Resistance Research Articles

Experimental study on the drag reduction of underwater vehicles by drag-reducing agents injection

Underwater vehicles consume much energy to overcome flow resistance; therefore, reducing drag is essential to enhancing its performance. This paper proposes a drag reduction method for underwater vehicles by injecting drag-reducing agents into the turbulent boundary layer of the underwater vehicles and experimentally evaluates its performance based on the scaled suboff model. To this end, the unique injection structure and location are carefully designed to ensure the adherence of the drag-reducing solution on the wall. The polyethyleneoxide (PEO) and ceytltrimethyl ammonium chloride (CTAC) solutions are chosen as the drag-reducing agents. The effects of concentrations, flow rates, and mainstream Reynolds numbers (Re) on the drag reduction performance are investigated by measuring the total drag resistance of the scaled suboff model under different conditions. The results demonstrate that this heterogeneous drag-reducing solution injection strategy performs well in terms of drag reduction for the suboff model. The specially designed injection structure can uniformly distribute the drag-reducing solution to the near-wall region of the suboff model. Under certain conditions, both PEO and CTAC solutions can significantly reduce the total drag resistance and have an optimal concentration at different Re. At their optimal concentrations, the drag reduction of the total resistance can achieve about 59.38% and 48.31% for PEO and CTAC solutions, respectively, at Re = 2.7 × 104. However, with the current design, the drag reduction decreases with the increase of Re due to the difficulty of the drag-reducing agent wrapping around the suboff model effectively. Further work is still necessary to improve the design and the location of the injection structure so that it can adapt to high-Re cases.

The anti-fouling activity of solvothermally synthesized Nb2O5-coated Fe ship strip on optimal interactions at the targeted interfaces of barnacle attachments -An Insilico study

Abstract Fouling is a major issue occurring in water-going vessels, such as ships that cause increased surface roughness and drag resistance. The fouling organisms produce extracellular polymeric substances (EPS), which negatively impact water-going vessels. The settlement-inducing protein complex (SIPC) is a contact pheromone that promotes the gregarious settling of barnacle larvae (cyprids). The SIPC can be found in both adult barnacle cuticles and cyprids as transient adhesive secretions (footprints). The presence of SIPC in the footprints plays a critical role during the initial adhesion, which facilitates further settlement. The adsorption of of SIPC on Iron/Fe ship strip(FSS) surface was often found to be irreversible even after physical treatements. For the antifouling studies, Nb2O5 coated FSS were constructed and simulated to analyze the interaction of barnacles Aacp20K protein. For simulation studies, the homology model of barnacles Aacp20K protein is fabricated using the SWISS automated comparative modeling platform. The result of homology model showed a good 3D secondary structure of Aacp20K protein, especially 7q1y template protein. Adsorption location analysis results illustrate that the surface of the FSS coated with Nb2O5 film disfavour the binding of SIPC inhibiting the binding of barnacle cuticles and cyprids. For validating the simulation results, Nb2O5 nanostructure film was synthesized using a solvothermal process and characterized using XRD,SEM and EDS. Furthermore, the wetting behaviour was studied experimentally. The simulations and experimental results indicate Nb2O5-coated FSS as potent anti-fouling surfaces.

Coulomb Drag in Graphene/h-BN/Graphene Moiré Heterostructures.

We report on the observation of Coulomb drag between graphene-hexagonal boron nitride (h-BN) moiré heterostructure with a moiré wavelength of ∼14 nm and an intrinsic graphene with a lattice constant of ∼0.25 nm. By tuning carrier densities of each graphene layer independently, we find that charge carriers in moiré minibands, i.e., near satellite Dirac point (sDP), can be coupled with massless Fermions near the original Dirac point (oDP), strongly enough to generate a finite drag resistivity. At high temperature (T) and large density (n), the drag resistivities near both oDP and sDP follow a typical n^{-α} (α=1.3-1.7) and T^{2} power law dependence as expected for the momentum transfer process and it also satisfies the layer reciprocity. In contrast, at low T, the layer reciprocity is broken in both oDP-oDP and sDP-oDP coupled regions that suggest dominant energy drag. Furthermore, quantitatively, the drag resistivities near sDPs are smaller than those near oDP and they deviate from T^{2} dependence below ∼100 K. Our work demonstrates that the drag experiment can be used to investigate the coupling between the carriers in moiré minibands and those in original Dirac bands which can be extended to other moiré materials.

Coulomb drag induced non-local resistance in double graphene layers.

We study the effect of Coulomb drag between graphene layers in presence of viscosity term. To do this, we use the simple model of Stokes equations for drift velocities in active and passive layers, known as Pogrebinskii's approach. The solution to these equations allows us to find the potential distribution, and thus the non-local drag resistance of passive layer. It is shown that in viscous regime the non-local resistance may take negative values, in contrast, the ohmic regime results in positive non-local resistance for all drag strengths. Additionally, we discuss the influence of magnetic field on the non-local drag magnetoresistance.

Numerical simulation analysis of turbulent pulsation drag reduction at different intermittent times

The shear stress generated by wall turbulence is the main cause of wall friction resistance in turbulent flow through pipes. This paper investigates the impact of inserting rest periods (regions of constant Reynolds number) within the pulsating operating cycle of velocity on the fully turbulent flow at large time-averaged Reynolds numbers, using the large eddy simulation (LES) method. The study aims to explore the effect of increasing rest periods within pulsations on drag resistance. The dimensionless shear stress and drag reduction rates during different time periods of rest were analyzed. Numerical simulation results indicate that the pulsating velocity operation mode does not necessarily lead to drag reduction; it may even result in increased resistance. Inserting rest periods within the pulsation cycle can achieve drag reduction effects, with the maximum drag reduction rate reaching 21.8%. This paper utilizes large eddy simulation (LES) to compare and validate the feasibility of LES for pipe pulsating operation modes against experimental results and direct numerical simulation (DNS) results from the literature, providing a rationale and proof of concept for further in-depth studies on other pipe pulsating flows.

AERODYNAMIC AND ROLLING RESISTANCES OF HEAVY DUTY VEHICLE. SIMULATION OF ENERGY CONSUMPTION

The main objective of the work was to develop a comprehensive model of energy consumption simulation of heavy duty vehicles using the VECTO simulation tool. The research issue was the impact of aerodynamic drag and rolling resistance on fuel consumption and emissions under various driving conditions described in four driving cycles: Urban Delivery, Regional Delivery, Urban, and Suburban. Each cycle differed in driving time, distance and average speed to represent different operational scenarios. The methodology involved defining vehicle parameters such as weight, aerodynamic coefficients and tyre rolling resistance. The main findings show that the impact of both aerodynamic drag and rolling resistance on fuel consumption can be efficiently modelled. It has been proven that the proposed modifications to aerodynamic drag and rolling resistance can reduce fuel consumption by more than 8%. The lowest fuel consumption was achieved in the Regional Delivery cycle, while the Urban cycle had the highest fuel consumption due to frequent vehicle stops. The results show that optimization of vehicle design and its performance can significantly improve energy efficiency and reduce emissions. A computational modelling tool such as VECTO can contribute to sustainable transport solutions and improve the efficiency of heavy duty vehicle.

COULOMB DRAG RESISTIVITY IN DOUBLE-LAYER GRAPHENE: INHOMOGENEITY EFFECTS

We investigate Coulomb drag resistivity in a double-layer system consisting of two parallel monolayer graphene sheets. In calculations, we employ the random-phase approximation to determine the polarizability functions of the graphene layers and the frequency-dependent dielectric function of the structure, taking into account inhomogeneity effects of the background dielectric. Our numerical calculations reveal that Coulomb drag resistivity in double-layer graphene systems steadily increases with increasing temperature but quickly decreases as the interlayer separation increases. The drag resistivity between the two layers in the case of an inhomogeneous background dielectric is substantially larger than that in the case of a homogeneous one. In addition, both the value and the imbalance in carrier density in the layers lead to noticeable changes in Coulomb drag resistivity in the system. Our study results are useful in graphene-based structure applications.

A durable superhydrophobic surface with bud-particle structure prepared by one-step spray method

Superhydrophobic surfaces play an essential role in numerous applications such as anti-fouling, waterproofing, and drag reduction due to their water-repellent. However, for most fabrication methods, there are high requirements for the preparation process and conditions. Meanwhile, the superhydrophobic surfaces generally have the problem of insufficient durability. In this study, a one-step method to fabricate a stable superhydrophobic surface by spraying is proposed. A new bud-particle structure is obtained by modifying micron and nano Aluminium hydroxide(Al(OH)3) particles, which helps the coated surface to demonstrate excellent superhydrophobicity with the water contact angle ∼157.0° and rolling angle ∼2.0°, and it shows great repellency to water droplet impact. Due to the compatibility of Al(OH)3with the pretreatment substrate and the reinforcing effect of nanoparticles, the coating maintained the superhydrophobicity well in the sandpaper wear and the ultrasonic damage test, which reflects the outstanding robustness of the coating.Moreover,benefiting from the control of the wetting state by micronand nanoparticles doping,the coating showed an excellent underwater drag reduction effect in the rheometer experiment, with a drag reduction rate of ∼67.7 %. The one-step spraying method proposed is a simple and convenient way to create the surface with excellent superhydrophobicity and durability, which has great potential applications in improving metal surface oxidation resistance and underwater reducing drag.

Numerical model of asphaltene deposition in vertical wellbores: Considerations of particle shape and drag force

Asphaltene deposition and plugging are common phenomena during crude oil production, significantly reducing production efficiency. Understanding the deposition behavior of asphaltene particles in vertical wellbores, particularly in relation to drag force interactions and settlement velocity, is imperative to mitigate these issues. Existing empirical models often fail due to their inherent inaccuracies and neglect of asphaltene particles' irregular shapes. This work established a quantitative method to describe irregular geometries of asphaltene particles. Shape coefficient, ∅, and shape coefficient influence factor, θ, are used to assess the impact of particle shape on the drag force coefficient and settling velocity. Experimental results from sedimentation experiments reveal particles with smaller shape coefficients encounter greater flow resistance and higher drag force coefficients. Moreover, the impact of shape coefficient on the drag coefficient gradually decreases as the Reynolds number increases. Based on these experimental findings, distinct models for the drag force coefficient and settling velocity of asphaltene particles are established, achieving a reduction in average error ranging between 2 % ∼ 25 % compared to existing models.

Spin mechanism of drag resistance in strongly correlated electron liquids

Spin mechanism of drag resistance in strongly correlated electron liquids

A novel prediction model of total drag coefficient of an MPV vehicle based on LSA optimization

Abstract Environmental degradation and energy scarcity are caused by the ongoing rise in the number of automobiles. The most efficient way to lower air resistance while driving is to boost vehicle energy efficiency and reduce energy consumption. In this case, a specific MPV model serves as the study subject in this work, and we use CFD simulation to estimate the drag coefficient along with the selection of important factors. Furthermore, to increase prediction accuracy, a lightning search algorithm (LSA)-based BP-neural-network prediction model is created and developed. The results show that the average relative error reduction of 2.83% in the drag resistance model optimized by the lightning search method represents a significant improvement in accuracy. This phenomenon can be explained by the LSA’s ability to resolve the BP neural network’s initial weight and threshold uncertainty as well as the issue of local minima being quickly reached. The high prediction accuracy drag prediction model, obtained herein, is useful for creating and producing automobile shapes with low drag coefficients.

Static analysis and contact angle hysteresis study of bubbles in Chinese space station tank models under different gravity effects

In most space shuttle fuel tanks, a central column is used to secure the Propellant Management Devices. This study focuses on the distribution of fluids in such tanks. Microgravity experiments are conducted on the Chinese Space Station, and annular bubbles surrounding the central column have been observed for the first time. An in-depth study is carried out on the distribution and profile of these bubbles using perturbation methods and the Young–Laplace equation. Theoretical values for the gas–liquid interface morphology of annular bubbles under different gravity levels are obtained and compared with numerical simulation results, showing substantial agreement. The phenomenon of contact angle hysteresis of bubbles under gravity conditions was studied through simulation and theoretical analysis. Detailed analysis of the characteristics of contact angle hysteresis and corresponding drag resistance using the Wenzel model was carried out. Based on this, a numerical calculation program based on the shooting method was developed to obtain the morphology of the same bubble under different gravities. Furthermore, it was found that the theoretical maximum Bond number for circular bubbles suspended on the central column is 2, and it was observed that bubbles with equilibrium contact angles closer to 90° exhibit greater upward displacement of their centroids under varying gravity, providing theoretical support for bubble management in aerospace engineering.

Drag of electron–hole bilayer in silicon-on-insulator metal-oxide-semiconductor field-effect transistor at low temperature

Drag between the electron and the hole layers formed in a silicon-on-insulator MOSFET, with the estimated interlayer distance as small as 18 nm, is investigated. The drag resistance is measured at 10 K and mapped on the plane defined by the electron and hole densities. Analysis shows that the Coulomb drag predominates over the competing virtual-phonon drag. The observed drag resistance is as large as 103-104 Ω, indicating strong Coulomb interaction between the electron and hole layers.

The Effect of Arm Movements on the Dynamics of the Wheelchair Frame during Manual Wheelchair Actuation and Propulsion

Wheelchair propulsion and actuation are influenced by the moving masses of the wheelchair user; however, the extent of this effect is still unclear. The main evidence of this effect is that the speed of the wheelchair frame continues to increase after the end of the push phase. The wheelchair’s speed was measured using IMUs and the duration of the push period was recorded using miniaturised pressure sensors attached to the driver’s middle fingers. The velocity and acceleration were determined for various average stroke cycle speeds to determine the speed dependency of the acceleration. The wheelchair was then mounted on a force plate to measure the inertial forces of the hands moving back and forth. The aerodynamic drag and rolling resistance forces were determined from coast-down experiments. Based on the measured forces, the behaviour of the force and velocity profiles was finally modelled by gradually reducing the mass of the arms and thus their inertial force. The results showed that the wheelchair is accelerated throughout the push phase (except for a temporary deceleration in the middle of the push phase at higher velocities), and that this acceleration continues well after the push phase. In the second half of the recovery phase, the wheelchair decelerates. The horizontal inertial forces measured on the force plate are predominantly negative in the push phase and in the second half of the recovery phase, and positive in the first half of the push phase, and their impulse is zero due to the conservation of momentum. Modelling the wheelchair with moving masses showed that reducing the horizontal inertial forces has no effect on the driver’s propulsive force but reduces the velocity fluctuations. The main conclusion of this research is that the wheelchair user’s power should be calculated only from the pure propulsive force that is required in the push phase to overcome the dissipative forces and that enables the gain or loss in speed per stroke cycle, but not directly from the measured velocity.

Nonlinear dynamics and onset of steady precession of a ring on a vertical rod.

We report on the unexpected precessional motion that occurs when a small, rigid ring is rotated on a vertical smooth rod. Using high-speed imaging, two distinct regimes of motion are observed experimentally. (i) Oscillatory motion when the ring has a single contact with the rod (transient motion). (ii) Steady state (terminal velocity) when the ring has two instantaneously stationary contacts with the rod. These two regimes and the transition between them are analyzed through qualitative, analytical, and numerical means. One key feature of the steady-state motion is energy dissipation through rolling resistance and air drag. Our model predicts that steady-state motion occurs only when certain geometric conditions (the ratio of the radii of a ring and a rod, and the tilt angle) are fulfilled. As the steady-state regime is often found to be the preferred final state, the dynamic stability of the single contact configuration is investigated through bifurcation, phase-space, and linear stability analyses. Our numerical simulation accounts for the stick-slip transition at the contact point, and is in good agreement with experimental data across all experiments. Our findings have potential applications in various engineering fields, such as studying the vibrational detachment of threaded fasteners and developing gravity-driven centrifuges.

Near-field heat transfer and drag resistance in bilayers of composite fermions

Near-field heat transfer and drag resistance in bilayers of composite fermions

Aerodynamic design optimization of locally built FSR Isuzu bus through numerical simulation

Reducing the fuel consumption of commercial vehicles—especially those used for public transportation—has become increasingly important due to advancements in the automotive industry. On the other hand, the main disadvantages of buses and other commercial vehicles are their fuel consumption, exhaust pollutants, and crosswind stability. Most buses built in Ethiopia have aerodynamic rectangular shapes and strong drag resistance forces, which lead to higher fuel consumption. One of the most accessible buses in Ethiopia is the FSR Isuzu Bus; its external body is locally constructed and has a poor aerodynamic shape. The primary goal of this study is to reduce aerodynamic drag force by improving the outer body shape of the current FSR Isuzu Bus. It also aims to examine the impact of roughness (strip) on the overall aerodynamic characteristics of the bus when it encounters crosswinds, thereby reducing fuel consumption, roll moment, and side force. For computational fluid dynamics (CFD) analysis, ANSYS Fluent is used, and Solidwork is used to model the bus body. A comparison is made between the current CFD analysis of the bus body and the modified design at varying speeds. Three separate models are used in the analysis. At an average speed of 100 kmph, 29.58% (4 to 5 liters) of fuel can be saved, and the drag force is reduced by roughly 49.7% when comparing the new concept to the current bus. By utilizing a strip on the bus’s roof, the side force coefficient and the roll moment coefficient are subsequently reduced from model two to model three by 8.76% and 9.01%, respectively. The study’s conclusions indicate that the external body shape changes have reduced drag; and, adding roof strips has decreased drag to acceptable level and enhanced crosswind stability.

Abstract 5971: F3 targeted near-infrared photoimmunotherapy: The ideal therapeutic approach for numerous malignancies

Abstract Introduction: F3 is a cell surface protein that plays a role in blood clotting, but recent research has revealed its implication in cancer proliferation, metastasis, angiogenesis, and immune escape. TCGA cohort analysis has shown that elevated F3 is a common feature of many cancers, and generally correlates with poor patient survival. Therefore, the potential of F3 as a therapeutic target in cancer is worth exploring. Tisotsumab-vedotin, an antibody-drug conjugate (ADC) that targets F3, was approved by the FDA for cervical cancer and is undergoing clinical trials in some solid cancers. However, ADCs may give rise to concerns about drag resistance following cellular internalization. Herein, we developed and tested an F3 targeted near-infrared photoimmunotherapy (NIR-PIT) to overcome some of these resistance mechanisms. Methods: We created a conjugate of tisotumab as an F3 antibody and IR700. The efficacy of F3-targeted NIR-PIT was investigated using multiple cancer cell lines (A431; epidermoid carcinoma, HPAF-II; pancreatic adenocarcinoma, HSC-2; oral carcinoma, HT-1376luc; bladder carcinoma, MDAMB231; breast adenocarcinoma, and SKOV-3; ovarian serous cystadenocarcinoma) in vitro. In vivo, the efficacy of F3-targeted NIR-PIT was evaluated in HPAF-II tumor using xenograft mouse models. In addition, the pathological change after NIR-PIT was also evaluated in A431, HPAF-II, HSC-2, HT-1376luc, MDAMB231, and SKOV-3 tumors. Results: These cell lines showed F3 expression in vitro and in vivo. Additionally, F3 expression was specific to cancer cells in HPAF-II tumor model. In vitro, F3-targeted NIR-PIT damaged the multiple cell lines in an NIR light dose-dependent manner. In vivo, F3-targeted NIR-PIT suppressed tumor growth and improved survival rates compared to the untreated group. Pathologically, A431, HPAF-II, HSC-2, HT1376-luc, MDAMB231 and SKOV-3 tumors after NIR-PIT contain large numbers of necrotic cells that are shown typically less dark nuclei and eosinophilic cytoplasm with some vacuolar degeneration than untreated tumors. Conclusions: F3-targeted NIR-PIT holds the efficacy against multiple cancers expressing F3, regardless of the specific cancer type. Therefore, this modality exhibits significant promise as a potential NIR-PIT option. Citation Format: Seiichiro Takao, Aki Furusawa, Hiroshi Fukushima, Shuhei Okuyama, Makoto Kano, Hiroshi Yamamoto, Peter L. Choyke, Hisataka Kobayashi. F3 targeted near-infrared photoimmunotherapy: The ideal therapeutic approach for numerous malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5971.

Biopolymeric corneal lenticules by digital light processing based bioprinting: a dynamic substitute for corneal transplant

Digital light processing (DLP) technology has gained significant attention for its ability to construct intricate structures for various applications in tissue modeling and regeneration. In this study, we aimed to design corneal lenticules using DLP bioprinting technology, utilizing dual network bioinks to mimic the characteristics of the human cornea. The bioink was prepared using methacrylated hyaluronic acid and methacrylated gelatin, where ruthenium salt and sodium persulfate were included for mediating photo-crosslinking while tartrazine was used as a photoabsorber. The bioprinted lenticules were optically transparent (85.45% ± 0.14%), exhibited adhesive strength (58.67 ± 17.5 kPa), and compressive modulus (535.42 ± 29.05 kPa) sufficient for supporting corneal tissue integration and regeneration. Puncture resistance tests and drag force analysis further confirmed the excellent mechanical performance of the lenticules enabling their application as potential corneal implants. Additionally, the lenticules demonstrated outstanding support for re-epithelialization and stromal regeneration when assessed with human corneal stromal cells. We generated implant ready corneal lenticules while optimizing bioink and bioprinting parameters, providing valuable solution for individuals suffering from various corneal defects and waiting for corneal transplants.

Experimental and CFD investigation on resistance reduction of hydrofoils for amphibious vehicles

ABSTRACT Resistance characteristics of amphibious vehicles are crucial for their sailing speed and battlefield survivability. This study proposes the installation of hydrofoils at the wheel cavity to reduce resistance and enhance performance. Two hydrofoil designs and four shapes are analyzed to determine the optimal drag reduction design. Towing tests and numerical simulations are employed to investigate and evaluate the hydrodynamic performance of amphibious vehicles. The impact of hydrofoils on resistance reduction is analysed and elucidated through a comprehensive analysis of surface pressure distribution, sailing attitude, and energy consumption in the flow field. Results demonstrate that, except for the elongation-hydrofoil, the other three shapes all show significant performance optimisation at medium to high speeds Fr > 0.5 , with improved effectiveness as speed increases. Among the four shapes, the curve-hydrofoil exhibits the best overall drag reduction effect (18%) and resistance peak compression ability (6.68%), owing to its ample lift force and optimal trim capability.