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Aircraft
Published in Milica Kalić, Slavica Dožić, Danica Babić, Introduction to the Air Transport System, 2022
Milica Kalić, Slavica Dožić, Danica Babić
The four forces acting on an aircraft in straight-and-level flight are thrust, drag, lift, and weight (Figure 2.1). Thrust is the force that moves an aircraft in the flight direction, provided by a piston, turboprop, or jet engine. Thrust itself is a force than that can best be described by Newton’s second law. This forward force opposes the force of drag. Drag is the aerodynamic force component parallel to the direction of relative motion. This is a retarding force caused by the disturbance of airflow by the aircraft and its parts. In other words, drag tends to slow the motion of aircraft, and acts opposite to the direction of motion. Lift is a force that is produced by the dynamic effect of the air flow acting on the aerofoil. This force opposes the downward force of weight. Lift represents a component of the aerodynamic force, perpendicular to the direction of aircraft movement through the air, which is equal to or exceeds the weight. Weight is the force that pulls the aircraft downward owing to gravity. When the four forces of flight are balanced, a plane flies in a level direction. The plane climbs if the forces of lift and thrust are greater than gravity and drag. To descend, thrust must be reduced below the level of drag and lift below the level of weight.
Coanda Effect in Aeronautical Applications
Published in Noor A. Ahmed, Coanda Effect, 2019
When a body moves through air, it creates aerodynamic force around it. For convenience of analysis, the aerodynamic force can be resolved into drag and the lift force components. The drag force acts in the direction against the motion of the body, while the lift force acts in the direction perpendicular to the motion of the body. A schematic of forces acting on a moving airfoil is shown in Figure 3.4.
Elementary Aerodynamics
Published in Rama B. Bhat, Principles of Aeroelasticity, 2018
The force acting on a body placed in a flow depends on the relative velocity of the fluid with respect to the body. The aerodynamic force has two parts: the lift, which is normal to the direction of the wind, and the drag force, which is due to the skin friction or the shearing effects and is tangential to the surface of the body while the other drag forces are in the direction of the wind
Airborne dust-induced performance degradation in NREL phase VI wind turbine: a numerical study
Published in International Journal of Green Energy, 2023
J. Zare, S. E. Hosseini, M. R. Rastan
Khakpour et al. (2007) compared the pressure and aerodynamic force coefficients over a 2D section of an S819 airfoil under clean and dusty winds. They varied some parameters individually, such as the sand dimension and sand/air mass flow rate ratio, to get insights into the overall impact of airborne particles on the wind turbine performance. The particle size was determined as a critical parameter in judging the turbine performance in the dusty environment, although no data about the flow field or wake flow were provided. Issues concerning roughness on wind turbine blades were reviewed by Sagol et al. (2013). They discussed how different contaminations, such as dust, dirt, ice, and insects, lead to surface roughness and affect the flow field and power generation. It was emphasized that the turbine performance is a function of the size, location, and density of the elements causing roughness, especially accretion near the leading edge. They speculated that the performance remains stable after a certain level of roughness height.
Crosswind effects on a train-bridge system: wind tunnel tests with a moving vehicle
Published in Structure and Infrastructure Engineering, 2023
In the wind tunnel test, a test of wind pressure distribution on the vehicle-bridge system is challenging for direct access to the three-component coefficient data. To analyse the aerodynamic force coefficients, we used an integral surface method of the model. The calculation formula is as follows where Pi(t) is the wind pressure time-displacement data of the measured points on the bridge model; Fx(t), Fy(t), and M(t) are the drag force, lift force, and overturning moment time-displacement data of the bridge or train model, respectively; li is the length integration; αi is the angle between the normal and horizontal lines; and Xi and Yi are the horizontal and vertical dimensions of the torsional centre in the bridge.
Analysis of variations in annual energy production based on types of suction side erosion at the blade tip of a wind turbine using numerical simulation
Published in International Journal of Green Energy, 2023
Keunseok Lee, Heejeon Im, Jeonghwan Boo, Bumsuk Kim
The influence of suction side erosion on the aerodynamic performance of the airfoil and changes in the output performance and AEP of the wind turbine were analyzed using the SST k-ω γ-Reθ model, which was determined through turbulence model evaluation. Transient 3D CFD simulation was performed to analyze the aerodynamic force of the airfoil according to the four erosion classes. The CFD simulation results were compared through the lift and drag coefficients. At the AOA at which stall occurred, the aerodynamic characteristics were analyzed through streamlines and the pressure coefficient. The blade erosion class (BEC) was also defined to apply the lift and drag coefficients secured by CFD simulation to the aeroelastic parameters. It was classified into four levels by gradually expanding the erosion range from the blade tip. The output curve and AEP of the wind turbine were calculated according to the BEC classified using DNV-Bladed (DNV 2022).