Forces aerodynamic

Other routes to reachieving filament separation have been described and rely on mechanical or aerodynamic forces to affect separation. Figure 4 illustrates one method which utilizes a rotating deflector plane to force the filaments apart while depositing the opened filaments ia overlapping loops (25). After the splayed filaments fall to the deposition surface or forming screen, a suction from below the disposition surface holds the fiber mass in place. 

The use of wind as a renewable energy source involves the conversion of power contained in moving air masses to rotating shaft power. These air masses represent the complex circulation of winds near the surface of Earth caused by Earth s rotation and by convective heating from the sun. The actual conversion process utilizes basic aerodynamic forces, ie, lift or drag, to produce a net positive torque on a rotating shaft, resulting in the production of mechanical power, which can then be used directly or converted to electrical power. 

The Weber number. We, is defined as foUows and represents the ratio of the dismptive aerodynamic forces to the restoring surface tension forces. 

Building Downwash A review must be conducted for each stack to determine if building downwash effec ts need to be considered. Atmospheric flow is disrupted by aerodynamic forces in the immediate vicinity of structures or terrain obstacles. The disrupted flow near either building structures or terrain obstacles can both enhance the vertical dispersion of emissions from the source and reduce the effective height of the emissions from the source, resulting in an increase in the maximum GLC. 

Centrifugal compressors can have problems at the inducer and blade tips. These parts of the blade can be excited by aerodynamic forces. Blade discs can have stresses at the rotor tips, which lead to cracks. To solve this problem, the offending part is removed and a scalloped disc results as seen in Figure 21-20. This type of disc experiences some efficiency loss (about 2 %). 

Another potential problem is due to rotor instability caused by gas dynamic forces. The frequency of this occurrence is non-synchronous. This has been described as aerodynamic forces set up within an impeller when the rotational axis is not coincident with the geometric axis. The verification of a compressor train requires a test at full pressure and speed. Aerodynamic cross-coupling, the interaction of the rotor mechanically with the gas flow in the compressor, can be predicted. A caution flag should be raised at this point because the full-pressure full-speed tests as normally conducted are not Class IASME performance tests. This means the staging probably is mismatched and can lead to other problems [22], It might also be appropriate to caution the reader this test is expensive. 

The aerodynamic force (P) of the main stream and the momentum of the injected air change the X component of the directing jet. The X component of the directing jet can be calculated from... 

The motion of a charged aerosol particle in a gas is governed by the electrostatic force and the aerodynamic forces. The theory dealing with the particle motion has been discussed in several books (see, e.g., Hinds- ). The electrostatic force F caused by the electric field E is given by... 

Impactors utilize aerodynamic forces to separate the various particle size classes. This is consistent with the particles aerodynamic diameter. The operation... 

Aerodynamics deals with the flow of gases, particularly air, and the interaction with objects immersed in the flow. The interaction takes the form of an aerodynamic force and moment exerted on the object by the flow, as well as heat transfer to the object (aerodynamic heating) when the flow velocities exceed several times the speed of sound. 

Resolution of aerodynamic force into lift and drag. 

The pressure (p) and shear stress (tj distributions over an airfoil-shaped body are shown schematically in Figure 1. The pressure and shear stress distributions exerted on the body surface by the moving fluids are the two hands of nature that reach out and grab the body, exerting a net force on the body—the aerodynamic force. 

The net aerodynamic force exerted on a body is illustrated in Figure 2 by the arrow labeled R. The direction and speed of the airflow ahead of the body is denoted by V, called the relative wind. The body is inclined to V . by the angle of attack, a. The resultant aerodynamic force R can be resolved into two components lift, L, perpendicular to V. and drag, D, parallel to V,. In Figure 2, R is shown acting through a point one-quarter of the body length from the nose, the quarter-chord point. Beacuse the aerodynamic... 

The aerodynamic force varies approximately as the square of the flow velocity. This fact was established in the seventeenth centui y—experimentally by Edme Marione in France and Christiaan ITuygens in Holland, and theoretically by Issac Newton. Taking advantage of this fact, dimensionless lift and drag coefficients, and Cj, respectively, are defined as... 

For reentry heat shields, ablator materials are well proven. These materials typically consist of reinforced plastics with a density of 0.5 - 1.0 g/cm3. The high heat loads are consumed by the carbonization or sublimation of the ablator. The carbonized material cannot withstand very high aerodynamical loads. When the aerodynamic forces exceed a specific threshold value, the initial slight erosion on the carbonized layer intensifies until the whole layer splits of. This results in an exponential rise in ablation velocity for the unprotected ablator. 

For steady injection of a liquid through a single nozzle with circular orifice into a quiescent gas (air), the mechanisms of jet breakup are typically classified into four primary regimes (Fig. 3 2)[4°][41][22°][227] according to the relative importance of inertial, surface tension, viscous, and aerodynamic forces. The most commonly quoted criteria for the classification are perhaps those proposed by Ohnesorge)40] Each regime is characterized by the magnitudes of the Reynolds number ReL and a dimensionless number Z ... 

The mechanism is essentially a combination of the deformation of a round liquid jet by aerodynamic forces and the instability of the deformed jet. The liquid jet is first accelerated rapidly in the high speed air stream (Fig. 3.3b). The jet diameter is thus significantly reduced as it interacts with the surrounding air stream. The direction of the thinning capillary liquid jet is influenced by the interaction between the liquid jet and the turbulent structures of the surrounding air stream. The formation of... 

The mechanical breakup mode occurs around the rims of the sheet where the air-liquid relative velocity is low, forming relatively large droplets. At low relative velocities, aerodynamic forces are much smaller than surface tension and inertia forces. Thus, the breakup of the liquid rims is purely mechanical and follows the Rayleigh mechanism for liquid column/jet breakup. For the same air pressure, the droplets detached from the rims become smaller as the liquid flow rate is increased. 

In pressure-swirl atomization, the complex atomization process may be conveniently subdivided into two main stages, as suggested by Lefebvre.12661 In the first stage, surface instabilities are generated as a result of the combined effects of hydrodynamic and aerodynamic forces. In the second stage, surface protuberances are... 

Basic Breakup Modes. Starting from Lenard s investigation of large free-falling drops in still air,12671 drop/droplet breakup has been a subject of extensive theoretical and experimental studies[268] 12851 for a century. Various experimental methods have been developed and used to study droplet breakup, including free fall in towers and stairwells, suspension in vertical wind tunnels keeping droplets stationary, and in shock tubes with supersonic velocities, etc. These theoretical and experimental studies revealed that droplet breakup under the action of aerodynamic forces may occur in various modes, depending on the flow pattern around the droplet, and the physical properties of the gas and liquid involved, i.e., density, viscosity, and interfacial tension. 

Breakup Criteria. Generally, droplet breakup in a flowing stream is governed by its surface tension and viscous forces, and dynamic pressure. For liquids of low viscosities, droplet breakup is primarily controlled by the aerodynamic force and surface tension force, and may begin when a critical condition, i.e., an equilibrium between these two forces, is attained ... 

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