![]() We can predict the drag that will be produced under a different set of velocity, density (altitude), and area conditions using the drag equation. When reporting drag coefficient values, it is important to specify the reference area that is used to determine the coefficient. As pointed out on the drag equation slide, the choice of reference area (wing area, frontal area, surface area, …) will affect the actual numerical value of the drag coefficient that is calculated. Through division we arrive at a value for the drag coefficient. In a controlled environment (wind tunnel) we can set the velocity, density, and area and measure the drag produced. This equation gives us a way to determine a value for the drag coefficient. The drag coefficient then expresses the ratio of the drag force to the force produced by the dynamic pressure times the area. The quantity one half the density times the velocity squared is called the dynamic pressure q. The drag coefficient Cd is equal to the drag D divided by the quantity: density r times half the velocity V squared times the reference area A. This equation is simply a rearrangement of the drag equation where we solve for the drag coefficient in terms of the other variables. The drag coefficient is a number that aerodynamicists use to model all of the complex dependencies of shape, inclination, and flow conditions on aircraft drag. ShapeAttributes attrs = new ShapeAttributes() ĪtInteriorColor(new Color(1, 1, 1, 0.5f)) // 50% transparent whiteĮllipse = new Ellipse(new Position(45, -100, 0), 500000, 300000, attrs) ģD Ellipse shapes are also possible: // Create an ellipse with the default attributes, an altitude of 200 km, and a 500km major-radius and a 300kmĮllipse = new Ellipse(new Position(25, -120, 200e3), 500000, 300000) ģD Ellipse shapes have additional configuration possibilities including extrusion and verticals: // Create an ellipse with custom attributes that make the interior 50% transparent and an extruded outline withĪtInteriorColor(new Color(1, 1, 1, 0.Home > Beginners Guide to Aeronautics Drag Coefficient The color of the interior, outline, and line widths can be customized using ShapeAttributes: // Create a surface ellipse with with custom attributes that make the interior 50% transparent and increase the RenderableLayer tutorialLayer = new RenderableLayer() The Ellipse object is now fully configured and ready to be added to the WorldWindow for display on the globe: // Create a layer for the Sightline ellipses are configured with a CLAMP_TO_GROUND altitudeMode and followTerrain set to true.Įllipse ellipse = new Ellipse(new Position(45, -120, 0), 500000, 300000) ĮtAltitudeMode(WorldWind.CLAMP_TO_GROUND) // clamp the ellipse's center position to the terrain surfaceĮtFollowTerrain(true) // cause the ellipse geometry to follow the terrain surface Several Ellipse objects are created, customized with ShapeAttributes, and then added to a RenderableLayer on the WorldWindow.Ĭreating a Surface Ellipse object: // Create a surface ellipse with the default attributes, a 500km major-radius and a 300km minor-radius. The EllipseFragment class extends the BasicGlobeFragment and overrides the createWorldWindow method. The number of points used to build the outline is dynamic and based on the camera distance to the shape. The outline of the ellipse is computed in geographic space using great circle distance. ![]() This tutorial demonstrates how to configure an Ellipse shape and add it to the globe.Įllipse uses the provided major radius, minor radius, heading, and center position to draw an Ellipse on the globe.
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