Papers by Keyword: Drag

Abstract: The flow past 3D cavity is a common structure, which is located on the surface of the underwater vehicle. The flow mechanism and hydrodynamic characteristics of the cavity have great significance for the design of the underwater vehicle. In this paper, large eddy simulation (LES) is presented to investigate the flow mechanism and hydrodynamic characteristics of the 3D cavity in terms of flow mechanisms, drag and fluctuating pressure. It is found that the motion law of the large vortex inside the cavity, and the drag and fluctuating pressure of the trailing edge is the largest. By the water tunnel experiment, the calculation result agrees with the experiment well, and LES method is verified feasibly.

Abstract: It is critical to understand whether the available drilling assembly could meet the requirements of drilling design during the design and drilling of horizontal wells. This paper pointed out several limitations on horizontal extension capability of horizontal wells and provided judging criteria of the limit of horizontal extension based upon the characteristics of horizontal wells, and set up the gap element model analyzing torque and dragged of whole drill strings in horizontal wells. According to the force analysis of drill strings in bores given the foundation for regularities in the distribution of torque and drag force along the axis, on the basis of those above mentioned models and theories, a software was made to calculate the torque and drag force of a well, which compared with the field data, the average discrepancies of theoretical values are below 20% that could meet the needs in field works.

Abstract: Any aircraft wing is the major component which will play vital role in the generation of lift and at different maneuvering moments throughout the flight. So to maintain this good maneuverability the aircraft wing has to undergo deferent deflections called angle of attack such that the high lift and low drag or vice versa can be settled in the flight. Taking this as the motivation the analysis was carried out on the standard wing airfoil comparing with new designed airfoil. Analyze the numerical simulation values like coefficient of lift, coefficient of Drag, Lift, Drag, and Energy parameters with wind tunnel data to predict accuracy for both the airfoils. Through the selected public literature standard airfoil data and designed airfoil data has been chosen, the geometry was created in the GAMBIT and also the meshing by selecting the suitable c-grid and rectangular grid for the better flow analysis in the FLUENT. The mesh file was imported into the FLUENT software there suitable boundary conditions and operating conditions are given for successful flow convergence. Finally analyzing these results are expecting to be best suitable for good aeromechanical features.

Abstract: This study interest flow control using a new vortex generators (VGs) shape with counter-rotating vortices, obtained by adding a new element to a configuration mostly investigated. The experiments were performed in the aim to determine the VGs answer when placed on the suction face at 10% from the leading edge of an airfoil Naca 0015 in order to improve the lift and drag coefficients. The investigations were accomplished in wind tunnel for two Reynolds numbers and geometrical vortex generators configurations. The obtained results are analyzed according to several parameters such as the VG height, the space between the same VG pair and the additional factor. The results show a profit brought by the passive devices estimated at about 28% of the C_L/C_d ratio.

Abstract: The basic experiment and detailed simulations are carried out to study the aerodynamic characteristics of projectile with deflectable nose. The parameters of computation are revised on the basis of experimental data. Further simulations show that the influence of mach number and deflectable angle on drag, lift, pitching moment and flight trajectory. The drag coefficient increases firstly and then decreases with the change of mach number, while drag coefficient and pitching moment coefficient grows exponentially. It can be seen that the ratio of lift to drag increases consistently, which means the aerodynamic efficiency of projectile would be improved with the increase of deflectable angle and mach number. The range is influenced by the start time of deflection. For the projectile with deflectable angle 10, the maximum range can be obtained if the forehead deflects at 3s.

Abstract: Tubular buckled inside wellbore section of oil or gas wells may cause problems such as: Casing wear/failure, Eliminates the transmission of axial load to the Bit, Drillpipe fatigue, Bit direction change, Severe drag and torque, Tubing seal failure, Connection failure. According to what mentioned above, it would be necessary to make an investigation on the effect of drag and/or torque on buckling of tubular inside horizontal wellbore (the so-called torque-drag-buckling relationship), the study depends mainly on conducting experimental tests and develop Finite Element Model, and utilize the results to predict the tubular behavior under different circumstances of torque and drag, also these results were compared and verified with some of theoretical approaches. Results obtained from this study indicates that torsion load had a little effect on buckling of tubular in horizontal section, this effect increase with decrease in pipe stiffness. Helical buckling tends to increase highly drag force, and thus eliminates transmission of axial load to the bit. Drag force tend to increase with torsion load as a result drag increase helical buckling. For prediction of helical buckling Lubinski and Woods, Gao Deli and Chen et. al provided a good agreement with one-end hinge condition, and Dellinger equation is the best for two-end hinge boundary condition.

Abstract: Laminar flow past a circular cylinder has been studied numerically at low Reynolds number. The upstream and downstream rods have been used as passive control in order to reduce hydrodynamics forces acting on the cylinder. Both the upstream and downstream rods significantly contribute in reduction of drag and fluctuating lift compared to single cylinder without the rods. More detail, the upstream installation rod is more dominant in drag reduction than the downstream one. On the contrary, the downstream rod has suppressed the magnitude of the fluctuating lift almost twice that of the upstream configuration. Placing the two rods together as the upstream and downstream passive control in tandem arrangement has given more hydrodynamics forces reduction than the single rod configurations.Keywords:circular cylinder, passive control, tandem, drag, lift.

Abstract: Aim at the installation of power equipments large size smoke duct of the offshore platform, introducing a improving method which is more easy to operate.

Abstract: The study on the effect of winglet shape in wing design has been a focus of many researchers. Nevertheless, the effect of cant angle on the wing performances at low Reynolds number has not been fully explored. This paper describes the effect of a single semi-circular shaped winglet attached with a rectangular wing model to lower the drag without increasing the span of the wing. Aerodynamic characteristics for the rectangular wing (NACA 65-3-218) with and without semi-circular winglets have been studied using STAR CCM+ 4.0. This numerical analysis is based on Finite Volume Approach. Simulations were carried out on the rectangular wing model with and without winglet at aspect ratio of 2.73 and Reynolds number of 0.16 x 10 ⁶ for various angles of attack. From the numerical analysis, wing performance characteristics in terms of lift coefficient C_L, drag coefficient C_D, and lift-to-drag ratio, C_L/C_D were obtained. It was found that the addition of a semi-circular winglet has resulted in a larger lift curve slope and higher Lift-to-Drag ratio in comparison with the case of a wing without winglet. Further investigation has revealed that a wing with semi-circular winglet with cant angle of 45 degree has produced the best Lift-to-Drag ratio, C_L/C_D.

Abstract: Designing the front grill with the focus on analyzing the flow from outside to the inside of a passenger car bonnet is very important in the automotive industry. This study was done to increase performance of the flow through the analysis on the effect of aerodynamic flow through the front grill by designing different cases of frontal areas of the front grill. Velocity at 34 m/s at steady condition were done to obtain the flow structure around a passenger car as well as the front grill of a passenger car. Analysis was taken inside the wind tunnel as the boundary condition. The grid generation was based on the tetrahedral unstructured meshes. Result obtain was compared with past experiment data. It was found that an appropriate design of frontal area of front grill can improved the stability of a car and the heat surrounding inside the car bonnet. Finally, the aerodynamics of the most suitable design of front grill was introduced and analyzed.