scholarly journals Study the Influence of Atmospheric Drag and J2 Effect in a Close-proximity Operation at LEO

2018 ◽  
Vol 7 (4.36) ◽  
pp. 403
Author(s):  
Thangavel Sanjeeviraja ◽  
Santhanakrishnan R ◽  
Lakshmi S
Keyword(s):  
Relative Motion ◽  
Control Strategies ◽  
Tracking Error ◽  
Space Mission ◽  
Atmospheric Drag ◽  
Drag Forces ◽  
J2 Perturbation ◽  
Relative Orbit ◽  
Satellite Relative Motion ◽  
Lift And Drag

In this paper is to assess the mission stability and the influence of J2 effect and aerodynamic forces. To maintain the relative motion of satellites by using a feedback control law for tracking error bound in the presence of J2 perturbation. A constant relative orbit under the effect of earth oblateness and conservative forces is referred as J2 and targeting the presence of atmospheric drag. Although, Schweighart and Sedwick control strategy for satellite relative motion is considering both lift and drag forces. The simulation result shows a better performance with high accuracy than an elliptical orbit under J2 perturbation and atmospheric drag along in-track formation. The algorithm and control strategies is useful tools for analysing a future space mission.   

Satellite formation keeping using differential lift and drag under J2 perturbation

2017 ◽  
Vol 89 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Xiaowei Shao ◽  
Mingxuan Song ◽  
Jihe Wang ◽  
Dexin Zhang ◽  
Junli Chen
Keyword(s):  
Control Strategy ◽  
Tracking Error ◽  
Flat Plates ◽  
Satellite Formation ◽  
Content Type ◽  
Small Satellites ◽  
J2 Perturbation ◽  
Simulation Results ◽  
Lift And Drag ◽  
Formation Keeping

Purpose The purpose of this paper is to present a method to achieve small satellite formation keeping operations by using the differential lift and drag to control the drift caused by J2 perturbation in circular or near-circular low earth orbits (LEOs). Design/methodology/approach Each spacecraft is equipped with five large flat plates, which can be controlled to generate differential accelerations. The aerodynamic lift and drag acting on a flat plate is calculated by the kinetic theory. To maintain the formation within tracking error bounds in the presence of J2 perturbation, a nonlinear Lyapunov-based feedback control law is designed. Findings Simulation results demonstrate that the proposed method is efficient for the satellite formation keeping and better accuracy advantage in comparison with classical approaches via the fixed maximum differential aerodynamic acceleration. Research limitations/implications Because the aerodynamic force will reduce drastically as the orbital altitude increases, the formation keeping control strategy for small satellites presented in this paper should be limited to the scenarios when satellites are in LEO. Practical implications The formation keeping control method in this paper can be applied to solve satellite formation keeping problem for small satellites in LEO. Originality/value This paper proposes a Lyapunov control strategy for satellite formation keeping considering both lift and drag forces, and simulation results show better performance with high accuracy under J2 perturbation.

scholarly journals Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 14
Author(s):  
Gianluca Zitti ◽  
Nico Novelli ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
Offshore Structures ◽  
Fish Farm ◽  
Maximum Displacement ◽  
Drag Forces ◽  
Real Size ◽  
Lift And Drag ◽  
Mesh Grid

Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.

Computational Aerodynamics of a Winston-Cup-Series Race Car

2002 ◽  
Author(s):  
Oktay Baysal ◽  
Terry L. Meek
Keyword(s):  
Present Model ◽  
Pressure Coefficient ◽  
The Body ◽  
Race Car ◽  
Drag Forces ◽  
Surface Pressure Distribution ◽  
Computational Aerodynamics ◽  
Baseline Case ◽  
Quantitative Results ◽  
Lift And Drag

Since the goal of racing is to win and since drag is a force that the vehicle must overcome, a thorough understanding of the drag generating airflow around and through a race car is greatly desired. The external airflow contributes to most of the drag that a car experiences and most of the downforce the vehicle produces. Therefore, an estimate of the vehicle’s performance may be evaluated using a computational fluid dynamics model. First, a computer model of the race car was created from the measurements of the car obtained by using a laser triangulation system. After a computer-aided drafting model of the actual car was developed, the model was simplified by removing the tires, roof strakes, and modification of the spoiler. A mesh refinement study was performed by exploring five cases with different mesh densities. By monitoring the convergence of the computed drag coefficient, the case with 2 million elements was selected as being the baseline case. Results included flow visualization of the pressure and velocity fields and the wake in the form of streamlines and vector plots. Quantitative results included lift and drag, and the body surface pressure distribution to determine the centerline pressure coefficient. When compared with the experimental results, the computed drag forces were comparable but expectedly lower than the experimental data mainly attributable to the differences between the present model and the actual car.

Vibration Excitation Forces in a Normal Triangular Tube Bundle Subjected to Two-Phase Cross Flow

2011 ◽  
Author(s):  
E. S. Perrot ◽  
N. W. Mureithi ◽  
M. J. Pettigrew ◽  
G. Ricciardi
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Random Excitation ◽  
Two Phase ◽  
Constant Frequency ◽  
Fluid Forces ◽  
Drag Forces ◽  
Wide Range ◽  
Drag And Lift ◽  
Lift And Drag

This paper presents test results of vibration forces in a normal triangular tube bundle subjected to air-water cross-flow. The dynamic lift and drag forces were measured with strain gage instrumented cylinders. The array has a pitch-to-diameter ratio of 1.5, and the tube diameter is 38 mm. A wide range of void fraction and fluid velocities were tested. The experiments revealed significant forces in both the drag and lift directions. Constant frequency and quasi-periodic fluid forces were found in addition to random excitation. These forces were analyzed and characterized to understand their origins. The forces were found to be dependent on the position of the cylinder within the bundle. The results are compared with those obtained with flexible cylinders in the same tube bundle and to those for a rotated triangular tube bundle. These comparisons reveal the influence of quasi-periodic forces on tube motions.

scholarly journals Design of Fixed-Wing and Multi-Copter Hybrid Drone System for Human Body Temperature Measurement during COVID-19 Pandemic

2021 ◽  
Vol 20 ◽  
pp. 31-39
Author(s):  
Zayed Almheiri ◽  
Rawan Aleid ◽  
Sharul Sham Dol
Keyword(s):  
Body Temperature ◽  
Temperature Measurement ◽  
Human Body ◽  
Equivalent Strain ◽  
Simulation Software ◽  
Operational Conditions ◽  
Drag Forces ◽  
Human Body Temperature ◽  
Body Temperature Measurement ◽  
Lift And Drag

The purpose of this research is to conduct aerodynamics study and design a hybrid drone system of fixed-wing and multi-copter. The mission of this drone is to measure human body temperature during COVID19 pandemic. The specific aim of the drone is to fly and cover larger industrial areas roughly about 50 km2 with longer flying time than the conventional drone, of about 1.5 hours. The applications of the simulation software such as XFLR5 and ANSYS have a big impact in identifying areas that need to be improved for the drone system. XFLR5 software was used to compare the characteristics of different airfoils with highest lift over drag, L/D ratio. Based on the airfoil selection, it was found that NACA 4412 airfoil produces the highest L/D ratio. The detailed geometry of the drone system includes a fuselage length of 1.9 meters and wingspan of 2 meters. Moreover, 10 sheets of solar panels were placed along the wing for sustainable flight operation to cover wider areas of mission. The structural analysis was done on ANSYS to test the elastic stress, equivalent strain, deformation, factor of safety pressure as well as lift and drag forces under various operational conditions and payloads. The landing gear was analyzed for harsh landing. ANSYS Computational Fluid Dynamics (CFD) was utilized to study the aerodynamics of the drone at different parameters such as the velocities and angles of attack during the operation. This design ensures the stability of the drone during the temperature measurement phase. The best thermal-imaging camera for such purpose would be the Vue Pro R 336, 45° radiometric drone thermal camera with a resolution of 640 x 512 pixels. This camera has the advantage of a permanent continuous out focus that give the ability of taking measurements even if there was changing on the altitude or any kind of vibrations.

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