Drag Values Research Articles

Turbulent flow and wall forces in staggered square cylinder porous media: An LES Analysis

Abstract The Wall-Modeled-Large Eddy Simulation (WMLES) technique was used to analyze turbulent flow in a porous medium composed of a staggered arrangement of square cylinders. The study focused on a porosity range of 0.3 to 0.8 at a pore Reynolds number of 10×103. The research provides novel information on pressure and shear force distributions around the cylinders and time-averaged values of particle drag and fluctuating lift coefficients. Results indicate that the flow physics are mainly driven by an expansion region in front of the central particle and another in the rear, where the flow is contracted and strongly accelerated. In the first region, velocities, turbulence kinetic energy (k), and its dissipation rate (e) are attenuated by a sudden pressure increase, while in the contraction region, the effect is the opposite. As porosity decreases, flow gradients and the overall levels of k, e, and Reynolds stresses become more significant. Turbulent anisotropy increases as porosity decreases below 0.6. Hydrodynamic stresses in the last interval present relatively uniform levels, which is a unique feature that may be considered in designing dedicated engineering devices with controlled stresses.

Periodic morphing of a NACA6409 aerofoil in ground effect, its wake mechanisms and thrust generation

Abstract The camber morphing of an aerofoil in ground effect was investigated using the FishBAC method and Detached Eddy Simulations with the k-omega SST turbulence model at a Reynolds number of 320,000. The aerofoil was periodically morphed at a start location of 25% chord from the leading edge with a trailing edge deflection range of 0.1% to 3% and morphing frequencies between a Strouhal number of 0.45 to 4 at a constant ground clearance of 10%. Periodically morphing the aerofoil using a sinusoidal function showed that lift and drag increased on the downstroke and decreased on the upstroke in the cycle, resulting in periodic values of lift and drag throughout the cycle. The amplitude of lift and drag increased as the morphing frequency and/or trailing edge deflection increased. It was found that the wake characteristics varied as a function of trailing edge deflection and morphing frequency. For small trailing edge deflections below 0.4% and frequencies below a 2.2 Strouhal number, Kelvin Helmholtz shedding was observed, and above this the wake became chaotic. Large trailing edge deflections showed Von-Karman shedding, where the interaction between the lower counter-clockwise vortex and the ground plane resulted in a jet-like flow that caused forward thrust. For the maximum deflection and morphing frequency tested in this study, reversed Von-Karman shedding was observed, which caused forward thrust from the interaction of the two-shedding counter-rotating vortices. Von-Karman or reversed Von-Karman shedding shows positive thrust generation, however, chaotic shedding should be avoided due to large drag gains. Varying the Reynolds number caused the Strouhal number to change as they depend on the same variables. It was found that the Strouhal number variation had a large effect on the wake, however, the Reynolds number had a minimal effect.

Entropy generation of Williamson hydromagnetic non-linear radiative nanofluid flow near a stagnation point over a porous stretching sheet

Purpose This study aims to analyze the multi-slip effects of entropy generation in steady non-linear magnetohydrodynamics thermal radiation with Williamson nanofluid flow across a porous stretched sheet near a stagnation point. Also, the qualities of viscous dissipation, Cattaneo–Christove heat flux and Arrhenius activation energy are taken into account. Thermophoresis, Brownian motion and Joule heating are also considered. Design/methodology/approach The Navier–Stokes equation, the thermal energy equation and the Solutal concentration equations are the governing mathematical equations that describe the flow and heat and mass transfer phenomena for fluid domains. By using the proper similarity transformations, a set of ordinary differential equationss are retrieved from boundary flow equations. The classical Runge–Kutta fifth-order algorithm along with the shooting technique is implemented to solve the obtained first order differential equations. Findings The study concludes that the temperature distribution boosting for thermal radiation, magnetic field and Eckert number where as the velocity and entropy generation escalate for the Williamson parameter, diffusion parameter and Brinkman number. The skin-friction and heat and mass transfer rate increases with the fluid injection. In addition, tabulated values of friction drag and rate of heat and mass transfer for various values of constraints are provided. Originality/value The comparison of the present results is carried out with the published results and noted a good agreement.

Drag reduction mechanism based on the aerospike-jet composite approach under different incoming dynamic pressures

The drag experienced by the nose of an aircraft varies significantly under different incoming flow conditions. In order to reduce the aerodynamic force on the nose of the (hypersonic) supersonic vehicle, the numerical simulation approach has been used to analyze the drag reduction laws and mechanisms of a blunt-body vehicle with the aerospike-counterflowing jet composite approach under different incoming flow dynamic pressures. The effects of two environments with H = 0.1 km and H = 30 km, as well as the influence of different incoming Mach numbers on the drag reduction at H = 0.1 km were investigated. The research has shown that there exists a minimum overall drag value for the vehicle under different dynamic pressures, while the variation in the wall pressure is related to the actual operating conditions. The recirculation zones at the aerospike and in front of the blunt body are important flow structures that affect the drag reduction. When the jet total pressure ratio increases, the position of the recirculation zone at the head of the drag reduction rod moves away from the central axis of the model. When the incoming flow dynamic pressure is higher, the separation point of the recirculation zone in front of the blunt body is located further downstream, and the reattachment point is related to the incoming flow and jet conditions, aligning with the trend of variation of the position of the maximum pressure on the blunt body wall. As it can effectively push away the shock wave, the enhanced drag reduction effect of the jet is significant when the incoming flow dynamic pressure is higher. However, the high jet pressure resulting from high dynamic pressure needs to be considered in the actual design. Furthermore, the complex turbulent flow field formed by the high dynamic pressure incoming flow and the jet is worthy of further study by means of the large eddy simulation.

Spacing effects on flows around two square cylinders in staggered arrangement via LBM

This study presents a computational analysis of fluid flow characteristics around two staggered arranged square cylinders using the Lattice Boltzmann Method (LBM). With Reynolds number (Re) fixed at 200, numerical simulations explore the influence of varying gap ratios (G) ranging from 0 to 10 times the cylinder size. Emphasis is placed on understanding the impact of cylinders spacing on flow structure mechanisms and induced forces. Investigation of fluid flow parameters includes vorticity behavior, pressure streamlines, and variations in drag and lift coefficients alongside the Strouhal number under different values of G. From the results, four distinct flow patterns emerge: single bluff body flow, flip flopping flow, modulated synchronized flow, and synchronized flow, each exhibiting unique characteristics. This study reveals the strong dependence of fluid forces on G, with low spacing values leading to complex vortex structures and fluctuating forces influenced by jet flow effects. At higher spacing values, proximity effects between cylinders diminish, resulting in a smoother periodic flow. The Strouhal number, average drag force and the rms values of drag and lift force coefficients vary abruptly at narrow gaps and become smooth at higher gap ratios. Unlike the tandem and side-by-side arrangements the staggered cylinders arrangement is found to have significant impact on the pressure variations around both cylinders. Overall, this research could contribute to a comprehensive understanding of staggered cylinder arrangements and their implications for engineering applications.

Reducing Torque and Drag in Extended-Reach Wells Using Thermoplastic Polymers for Protective Sliding Rings

Extended-reach drilling represents an advanced way of drilling and accessing reservoirs that were previously economically not feasible to drain, impossible to reach or in an environmentally sensitive area. One of the main issues that appears while drilling such wells is caused by the high values of friction factor which cause high values of torque and drag. One of the suggested solutions is to use a protective sliding ring made from materials such as POM, Teflon and PA6 in combination with lubricants added to a polymer mud system. First, measurements were conducted on a lubricity tester to choose the best material and, after finishing, a mechanical wear test was conducted on a specially designed device to measure mechanical wear. Results showed that Teflon showed lower values of friction factor in comparison to steel and the mechanical wear was minimal. The lowest value of friction force was recorded for blocks made from Teflon in tested mud systems. It is also noticeable that, in polymer mud with weighting additives and lubricant, the value of the friction force is higher than in polymer mud with lubricant only.

Estimation of Passive Drag in Swimming via Experimental and Computational Means

Discussed is a comparison of computational and experimental evaluations of passive drag during human swimming. Experimentally, ten trials were conducted per athlete at five chosen velocities, using a commercial resistance trainer to record the tension force in a rope during a streamline position tow test. The resistive force recorded was assumed equal to the passive drag force and an average value of passive drag was found across each tow test. Mean passive drag values measured during the tow test were agreed well with existing experimental data across the range of velocities used, varying between 20 N at 1 ms−1 up to 100 N at 2 ms−1. Computationally, using the immersed boundary method in OpenFOAM, basic geometry validation cases and streamline passive drag cases were simulated. Validation cases were completed on 2D cylinders and 3D spheres with the drag coefficient found at low and high Reynolds numbers, using the simpleFoam solver within OpenFOAM. Results tended to be slightly over predictive when compared with existing simulation and experimental data in literature. The accuracy of results could potentially be improved using a finer mesh and better quality geometries. The passive drag was also computed using OpenFOAM over a range of velocities, similar to the experiments, varying from 30 N at 1 ms−1 to 120 N at 2 ms−1. Drag forces computed using simpleFoam were over predictive when compared to existing literature and the completed experiments, likely due to the inaccuracy of the geometry used in the simulations. When results were compared to existing literature for swimmers not in a perfect streamline position, more similar to the geometry used in this study, results were in better agreement. The accuracy of the results could be improved using a better quality geometry in the correct position.

Enhancing hydrodynamic forces through miniaturized control of square cylinders using the lattice Boltzmann method

This study investigates the influence of small control cylinders on the fluid dynamics around a square cylinder using the Lattice Boltzmann Method (LBM). Varying the gaps (L) between the main and control cylinders from 0 to 6, four distinct flow regimes are identified: the solo body regime (SBR), shear layer reattachment (SLR), suppressed fully developed flow (SFDF), and intermittent shedding (IS). The presence of control cylinders results in significant reductions in flow-induced forces, with drag coefficient (CD) and root mean square values of drag and lift coefficients (CDrms and CLrms) decreasing by approximately 31%, 90%, and 81%, respectively. The SFDF flow regime exhibits the lowest fluid forces compared to other regimes. The effects of tiny control cylinders on the fluid flow characteristics of a square cylinder are examined using the Lattice Boltzmann Method (LBM) in this research work. The gaps (L) between the main and control cylinders are varied in the range from 0 to 6. The size of each control cylinder is equal to one-fifth of the primary cylinder. According to the findings, there are four distinct flow regimes as the gap spacing varies: solo body regime (SBR), shear layer reattachment (SLR), suppressed fully developed flow (SFDF), and intermittent shedding (IS) for gap spacing ranges 0 ≤ L ≤ 0.2, 0.3 ≤ L ≤ 0.9, 1 ≤ L ≤ 3, and 3.2 ≤ L ≤ 6, respectively. Additionally, it has been noted that the amplitude of variable lift force is reduced when the gap separation between the main and control cylinders is increased. When compared to solo cylinder values, it is found that the presence of small control cylinders in the flow field results in a considerable reduction of flow-induced forces. The SFDF flow regime was determined to have the lowest fluid forces compared to the other flow regimes studied. Our findings highlight the efficacy of small control cylinders in mitigating flow-induced forces and controlling flow characteristics. The LBM proves to be a valuable computational technique for such fluid flow problems.

CFD Analysis of Counter-Rotating Vane-Type Wing Vortex Generator for Regional Aircraft

Vortex generator is a component that has a significant impact on aircraft performance. The function of the vortex generator is to create vortices that can optimize the aerodynamic performance of aircraft wings by avoiding air flow separation and increasing lift at high angle of attack. Vortex generator can provide increased lift during take-off and landing due to the increased wing angle of attack. Although the use of vortex generator can be carried out using an experimental approach, a computational fluid dynamic approach to determine the influence of geometric parameters and placement of the vortex generator needs to be carried out. The aim of this research is to determine the effect of parameters like placement on the wing chord, height of the boundary layer, length, shape, angle of incidence and distance between pairs on the lift and drag. The model used as a computational fluid dynamic calculation model is the Spalart Allmaras transient model. As a result, vortex generator does not always have a good effect on aerodynamics. All configurations have a negative influence on the lift and drag values, but the flow separation phenomenon can be reduced significantly. Of all the configurations, the best configuration is obtained by exhibiting an ogive shape, positioned at 13.8% of the chord length, set at a 13o angle of incidence. The vortex generator should have a height closely matching the boundary layer, with a length 6.5 times the height and a pair spacing of 6.7 times the height

Analysis and Optimization of Fluid Flow on the Surface of the Prototype Body of Electrical Vehicle Ganesha Diffabilities Using Solidworks Software

Purpose: The aerodynamic aspect is an aspect that takes into account a force caused by the fluid flow shown by the Coefficient of Drag value. This will affect the optimization of performance and energy consumption used. This study aims to modify the standard design of Electrical Ganesha Diffabilities so that a design with a low Coefficient of Drag value considers ergonomic parameters and user comfort to follow the community of people with disabilities. Theoretical Framework: The main theoretical foundation is based on the laws of aerodynamics, which analyze the movement of air around solid objects and its effect on vehicle performance, with a specific emphasis on minimizing drag. The research employs computational fluid dynamics (CFD), a branch of fluid flows. Models and simulations in Solidworks offer a digital environment for improving design aspects to increase aerodynamic efficiency. This theoretical approach focuses on two main objectives: reducing the drag coefficient (CD), which measures resistance caused by shape and surface characteristics, and applying these findings to achieve practical energy savings and enhance vehicle operation specifically designed for individuals with disabilities. The integration of aerodynamic theory and practical application is essential for solving the specific transportation requirements emphasized in the introduction. This alignment with legislation and social objectives aims to provide improved support for the impaired community. Design/Methodology/Approach: This is a numerical method with an R2D2 research model (Reflective, Recursive, Design, and Development) using the 2020 version of Solidworks Software. Solidworks software is known for software that has speed and accuracy in analyzing. Findings: The results of the fluid flow analysis simulation showed that the design of the modified Electrical Ganesha diffabilities vehicle had a Coefficient of Drag value of 0.353 or 35% lower than the standard vehicle value of 0.547. Through expert assessment, the modified design of Electrical Ganesha Diffabilities has received an assessment of 98% with excellent qualifications. Research, Practical & Social implications: The research contributes to the topic of aerodynamic for disability-friendly vehicles, providing a basis for future academic investigations into accessible transportation options. Essentially, the results can immediately impact the development of electric cars that are both more energy-efficient and performance-optimized for those with impairments. This would lead to lower running expenses and improved user-friendliness. From a social perspective, this research emphasizes a dedication to inclusiveness and accessibility, which has the potential to enhance the ability of impaired persons to move around and ultimately enhance their overall well-being. Additionally, it increases awareness among policymakers and manufactures of the significance of incorporating aerodynamic efficiency into the design of assistive devices, hence fostering wider social acceptance and support for this advancement. Originality/Value: The uniqueness and significance of this work stem from its innovative strategy of combining aerodynamic principles with the development of electric cars particularly tailored for those with disabilities-a relatively unexplored field in transportation research. This research examines the E-GADIS vehicle and fills the gap in the current literature on accessible transportation options.

Understanding grain boundary segregation and solute drag using computational and machine learning studies

Grain boundary (GB) solute segregation has been used as a strategy to tailor the properties and processing pathways of a wide range of metallic alloys. GB solute drag results when segregated alloying elements exert a resistive force on migrating GBs hindering their motion. While GB segregation has been the subject of active research, a detailed understanding of solute drag and the migration kinetics of doped boundaries is still lacking, especially in technologically-relevant alloys. Through theoretical analysis, mesoscale modeling, and machine learning studies, we investigate GB segregation and solute drag and establish design maps relating drag effects to relevant alloy and GB properties, i.e., the complete alloy design space. We find that solute drag is dominant in immiscible alloys with far-from-dilute compositions in agreement with experimental observations of GB segregation in metallic alloys. Our analysis reveals that solute–solute interactions within the GB and the degree of segregation asymmetry greatly influence solute drag values. In broad terms, our work provides future avenues to employ GB segregation to control boundary dynamics during materials processing or under service conditions.

NACA 2412 Drag Reduction Using V-Shaped Riblets

This research focuses on addressing a significant concern in the aviation industry, which is drag. The primary objective of this project is to achieve drag reduction through the implementation of riblets on a wing featuring the NACA 2412 aerofoil, operating at subsonic speeds. Riblets, with the flow direction on wing surfaces, have demonstrated the potential to effectively decrease drag in diverse applications. This investigation includes computational analysis within the ANSYS Workbench framework, employing a polyhedral mesh model. The scope of this research encompasses the analysis of both a conventional wing and a modified wing with riblets. A comparative analysis is conducted to assess variations in drag values between the two configurations. Parameters, including geometry, dimensions, and riblet placement at varying angles of attack, are explored to comprehend their impact on drag reduction. Notably, 15.6% and 23% reductions in drag were identified at a 16-degree angle of attack with midspan and three-riblet models, separately. The computational mesh and method were validated using appropriate techniques.

Study on the steady state position of ocean towing cables

A study is conducted on the static equilibrium posture of the towing cable in water under a constant speed state in the towing system. Firstly, the underwater force state of the towing body is calculated and then the posture and tension of the towing cable are analyzed and calculated. As the cable is divided into two states which are above water and below water, a differential equation system is established as the boundary. The initial value of the equation can be transformed by the drag and gravity values of the towing body. The program solves the differential equations using the fourth-order Runge Kutta method and draws the attitude curve. Finally, it verifies the theoretical calculation results through experiments.

Studying Modern Formula 1 Front Wing at Medium Cornering Speeds

A simulation-based study of three different types of front wing designs used in modern Formula 1 cars was done. The study mainly focuses on the aerodynamic forces that a Formula One car generates mainly the Downforce, the Drag force, & the Lateral force at low cornering speeds. These forces were studied in detail & taking a closer look at how they migrate during the dynamic conditions the car is thrown at various Side Slip (Yaw) Angles, these results were compared with the wing Scuderia Ferrari used in the 1998 formula 1 championship to better understand the inherent problems faced in those previous designs. A brief study of the flow field & flow lines was conducted along with the vortex generation for all three wings. Vortex formation and management is a prominent part of research being carried out for a formula 1 car, so a brief study on the phenomenon of vortex generation & Y250 vortex formation was also carried out. The studies were carried out over typical medium-speed corners where the speed ranges between 150-220 KM/Hr. A study on the effect of the flow field of the top element on the lower element was carried out where the 5th element was removed from each of the three wings & the effect on the downforce & drag value was analysed along with the pressure field.
 Keywords: Modern formula 1, Front wing designs, Cornering speeds, aerodynamic forces, Side Slip (Yaw) Angles, Centre of pressure (CoP), Lateral force, CFD, Downforce

Aircraft Performance Simulation of 19-Passenger Commuter Aircraft: A Comparison between Normal and Amphibious Category

This article presents calculating flight performance aspects and simulations of flight characteristics during a flight mission of the 19-passenger commuter aircraft, with a focus on the comparison between the normal and amphibious category aircraft. The objective is to analyse the flight characteristics (warm up, takeoff, cruise, descent, landing) and capabilities of both aircraft configurations. The significant difference between the two aircraft lies in the presence of float components in the 19-passenger Amphibious aircraft. The calculation process, both manual and simulation-based, involves utilizing constraint analysis and mission analysis to determine the weight fraction values for each flight phase. The results of the constraint analysis indicate that the amphibious category aircraft has higher values (35% - 80%) compared to the normal category aircraft. Meanwhile, the calculations using aircraft engine design (AEDsys) software reveal nearly identical reductions in weight fraction for each phase, with the amphibious category aircraft having a significant decrease in the final weight fraction of 0.87836. The fuel weight used is 2129 lb or 965.70 kg (8 barrels) with a range of approximately 372 nm or about 690 km and a flight time of approximately 2.4 hours. The drag polar values obtained using Parametric cycle analysis software at an altitude of 3,048 meters (10,000 ft) show that the normal category aircraft has a smaller coefficient drag (CD) value. Further validation of the findings from this performance simulation study can be conducted through direct experimental validation during flight to be utilized for optimizing aircraft performance.

Experimental investigation of blade-shaped riblets for drag reduction on UAV applications

This study presents an experimental investigation of blade-shaped riblets for drag reduction in unmanned aerial vehicle (UAV) applications. UAVs have gained significant attention since they can perform various missions, including surveillance, reconnaissance, and package delivery. However, their aerodynamic performance, specifically the high drag associated with their exposed surfaces, remains a key challenge for enhancing their efficiency and extending their flight endurance. To address this issue, riblet geometries are proposed as a potential solution, which can reduce the turbulent skin friction drag by up to 8%. The experimental investigation involves wind tunnel testing of blade-shaped riblets, with various spacing-to-height (s/h) ratios and constant groove cross-sectional area (Ag). The riblets are designed for application on the wing, empennage, and fuselage surfaces of a UAV. The investigations are performed on a flat plate for various flow conditions, including different freestream velocities, to evaluate the drag reduction effectiveness of the riblet configuration. The drag force is measured using a force balance system and flow visualization techniques are employed to assess the position where the boundary layer has transitioned to fully turbulent. The results demonstrate the drag-reducing effect of blade-shaped and trapezoidal riblets and the different performances observed for the various s/h ratios. The cases with s/h=1 result in the smallest drag coefficients, while the cases with s/h=2 have significantly increased drag values, compared to the smooth flat plate, due to the increased wetted surface area. These findings highlight the potential of riblets as an effective drag-reduction technique for UAV applications, enabling increased endurance and/or enhanced payload capacity.

Analysis of the wake mechanism in external flow around tandem bluff bodies with different aspect ratios

The interaction mechanism of external flow with two inline rectangular cylinders having different aspect ratios under the impact of gap spacing (G) is the subject of this research. The gap spacing between the cylinders was varied from 0.25 to 20 times their size. Both cylinders were vertically mounted, with the first having a higher aspect ratio than the second. The results revealed five distinct flow patterns under the influence of G: single slender body, shear layer reattachment, intermittent shedding, binary vortex street, and single-row vortex street. The mean pressure on both cylinders was found to vary due to changes in flow patterns. Both cylinders bore the same shedding frequency but had different pressure variations. The second cylinder placed in the wake of first experienced negative average drag force for some spacing values, while the first cylinder had positive average drag values for all chosen G. Due to the change in flow pattern from shear layer reattachment to intermittent shedding flow, the negative drag force on the second cylinder jumped to a positive drag. It was also observed that the rms values of drag and lift force coefficients, as well as their amplitudes for the second cylinder, were mostly higher than corresponding values for the first cylinder at all selected G. This study revealed that G = 4 and 8 are the critical gap spacing values due to sudden changes in fluid force parameters.

Added mass analysis of submersible using computational fluid dynamics

An estimation of the resistance acting on a manned submersible can be performed using computational fluid dynamics (CFD). The resistance force acting on a vehicle can be steady state or transient state drag. Steady state drag comes when a vehicle moves at a constant velocity but drag value increases or decreases when the vehicle accelerates or decelerates. Transient state drag acts on a vehicle when velocity changes. The addition or reduction in drag value is due to the added mass. This paper discusses two CFD approaches to calculate longitudinal added mass. The second CFD method is preferred due to the inaccuracy and assumptions involved in the first method. The preferred CFD method can be used to obtain the added mass for both standard shapes, as well as for complicated geometries like manned submersibles. The drag and added mass of the ellipsoid are calculated using CFD and compared with analytical and experimental results for validation. Additionally, an acceleration sensitivity study indicates that added mass is independent of acceleration. CFD methods proposed here are simple and time-efficient. By using this method, a submersible’s added mass can be calculated without employing expensive experimental methods or other CFD methods. Highlights A vehicle’s steady-state drag develops when moving at constant velocity, but the amount of drag increases or decreases when accelerating or decelerating The CFD method can be used to obtain the added mass of more complicated geometries like manned submersibles and standard shapes like spheres and cylinders An acceleration sensitivity study indicates that added mass is independent of acceleration

Hydrodynamics of pitching hydrofoil in a plane Poiseuille flow

Several advanced medical and engineering tasks, such as microsurgery, drug delivery through arteries, pipe inspection, and sewage cleaning, can be more efficiently handled using micro- and nano-robots. Pressure-driven flows are commonly encountered in these practical scenarios. In our current research, we delve into the hydrodynamics of pitching hydrofoils within narrow channels, which may find their potential applications in designing bio-inspired robots capable of navigating through pressure-driven flows in confined channels. In this paper, we have conducted a numerical investigation into the flow characteristics of a National Advisory Committee for Aeronautics (NACA) 0012 hydrofoil pitching around its leading edge within a plane Poiseuille flow using a graphical processing unit accelerated sharp interface immersed boundary method solver. Our study considers variations of the wall clearance from 20% to 50% of the channel width. We have explored the hydrodynamic features such as instantaneous and time-averaged values of lift, drag, input power, and torque for different wall clearance ratios and oscillation frequencies in the range of Reynolds number 100–200 based on the mean velocity and channel width. We have tried to explain the force, torque, and power variations by examining the flow features in the near wake. While the hydrodynamic coefficients showed significant variations with changes in wall clearance and the Strouhal number (St), we did not observe significant variations with alterations in the Reynolds number (Re).

Chaotic dynamics of two-dimensional flows around a cylinder

We study flow around a cylinder from a dynamics perspective, using drag and lift as indicators. We observe that the mean drag coefficient bifurcates from the steady case when the Karman vortex street emerges. We use standard dynamics metrics to analyze the drag/lift phase diagram. We also find a jump in the dimension of the drag/lift attractor just above Reynolds number of 200, indicating a breakdown of periodicity. We compare the simulated drag values with experimental data obtained over the last hundred years. Although there is substantial agreement, we note a Reynolds number range where there is a substantial, unexplained discrepancy with data from over a hundred years ago. Our simulations suggest that a vibrational resonance in the cylinder would be unlikely for Reynolds numbers greater than 1000, where the drag/lift behavior is fully chaotic.