![]() For slender structures, the 2D aerodynamic theory is applicable. The lift forces, skin friction, and pressure viscous drags are the main sources of the aerodynamic forces for the slender parts of a wind turbine. The aerodynamic forces consist of the lift and drag forces. It is proposed using NS methods to extract airfoil data and applying them in less advanced methods (e.g., BEM theory). The BEM method relies on airfoil data therefore, the results obtained using this method are no better than the input. The advanced BEM theory is fast and gives good accuracy compared to CFD methods. Computational fluid dynamics (CFD) methods are the most accurate, but are very time consuming. Approaches of intermediate complexity, such as the vortex and panel methods, can also be applied. The extended BEM theory can be used to consider advanced and unsteady aerodynamic effects for aero-elastic time domain calculation. The complex methods for calculating the aerodynamics are based on solving the Navier–Stokes (NS) equations for the global compressible flow in addition to accounting for the flow near the blades. The aerodynamic loads are highly nonlinear and result from static and dynamic relative wind flow, dynamic stall, skew inflow, shear effects on the induction, and effects from large deflections. Karimirad, in Comprehensive Renewable Energy, 2012 2.09.4.1 Aerodynamic Loads Often the solution to vibration problems is to change the natural frequency of the system by adding mass (see e.g., Richart et al., 1970). The critical elements here are (i) the machine and foundation mass, as that usually controls the natural frequency and (ii) the operating frequency of the machine. Industrial complexes that involve the operation of heavy machinery (the auto industry) and/or super-sensitive elements sometimes have machine vibration issues. The geotechnical engineer works with geologists and seismologists to develop a suite of design earthquakes for the site and structure, and these motions are used as input to dynamic analyses to assure that the site/structure will perform satisfactorily, and all displacements will be tolerable. Such strength loss can often lead to large uncontrolled deformations. These saturated soils, if not adequately dense, can liquefy and lose strength as a result of earthquake shaking. ![]() The third critical factor is determining the location of the water table as loose saturated sands and silty sands are problematic materials, if subjected to strong shaking. The second critical factor is the presence of loose sands or silty sands. Natural frequency is defined as the frequency at which a system shakes/vibrates or oscillates when not subjected to a continuous or repeated external force. One is depth to rock, as that usually has a significant influence on the natural frequency of the site. From an earthquake engineering point of view, several elements are critical. Earthquake engineering analysis is usually performed on bridges, tall buildings, high retaining walls, and dams where failure would result in substantial loss of life. For the pavement design, the loads are quantified as “Equivalent Single Axel Loads” to allow pavement fatigue and wear to be quantified. In the case of roads and highways, the dynamic loads from vehicle traffic primarily only influence the design of the pavement section. Three subsets of geotechnical engineering that involve dynamic loads are: (i) roads and highways, (ii) earthquake loading issues and (iii) machine vibrations. Most geotechnical engineering issues are controlled by static loads or loads that are assumed to be static. Marcuson III, in Encyclopedia of Geology (Second Edition), 2021 Soil Dynamics
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |