China
Africa
Explore chapters and articles related to this topic
Basic Concepts
Published in Noor A. Ahmed, Coanda Effect, 2019
Transition controls are employed to reduce transitional drag and reduce flow instabilities. Separation controls are employed to reduce viscous effects, thereby reducing drag. On an airfoil, this also leads to increases in the available angle of incidence and thereby contributes to higher lift.
Visual Comfort & Visual Interest
Published in Michael Stiller, Quality Lighting for High Performance Buildings, 2020
As we have discussed, a variety of methods have since been developed to predict whether visual comfort (or discomfort) will be the likely result when using specific fixture types in specific applications. These include the establishment of maximum luminous intensities and luminance values, at certain angles, for lighting fixtures in different work-place scenarios. But to fully evaluate the degree of visual comfort and visual interest we will achieve, we need to consider the overall environment, and all of the surfaces within it, as a collection of luminances. It is, after all, the luminance of the surfaces around us that constitute what we actually see. Unfortunately, luminance calculations are inherently difficult to perform. Add to this the fact that luminance can be difficult to predict where specular surfaces are present, and the task becomes even harder. The behavior of light reflecting off of a specular surface, like a mirror, is significantly different than its behavior with a matte white wall, which while not specular is still very reflective. When dealing with specular surfaces, we need to keep in mind the law of reflection that states for specular reflections the angle of incidence equals the angle of reflection. The angle of incidence is the angle between a ray incident on a surface and a line perpendicular to the surface at the point of incidence. (See Figure 4-2 for an illustration of this law). This means specular, glossy, or mirror-like surfaces will create different luminance values from different viewpoints. (Think of looking at an oil painting in an art museum, and having to move around to find a viewing angle uncompromised by the reflected glare of the lighting fixtures or windows in the room.) This is an extreme example, but the color and finish of each surface, the angle from which it is lit, and the angle at which it is viewed will all work together in a complex way to affect that surface’s luminance, and the viewer’s perceived brightness of it. The variables can quickly multiply, requiring these calculations to be performed hundreds or thousands of times. Thankfully, we now have computer software capable of showing us representations of our lighting designs before they are installed, which can also calculate the illuminances and luminances that will result. With a properly “built” software model that includes the right input to define the reflectance and specularity of the various surfaces, and the proper luminaire data (usually supplied by the manufacturer in the form of a photometric report or an IES file that can be read by the various lighting software packages available today), it is relatively easy to calculate and predict these values for a given environment. And in doing so we can also create a quality rendering that accurately illustrates the resulting interaction of light. (See Figures 4-3 and 6-8 for examples of computer renderings that show the luminance of the surfaces and objects in a particular setting. Figure 4-3 does not account for the specularity of the various surfaces, while the rendering in Figure 6-8 does.)
Aerodynamic Efficiency and Performance Development in an Electric Powered Fixed Wing Unmanned Aerial Vehicle
Published in Electric Power Components and Systems, 2023
Berk Kaynak, Ahmet Yigit Arabul
The relationship between the angle of attack and the lift coefficient is shown in Figure 2(b). The which progresses linearly to a certain degree, shows a gradual improvement according to the difference in the angle of incidence. The increase in the angle of incidence gives a significant advantage for lift coefficient. However, it should be kept at an optimum value as it increases the drag coefficient and stall risk [35].