|
|
This is only a preview of the paper
Click here to register and get the full text.
Existing members click here to login
|
|
|
... 0 Abstract
The properties of vortices created by jet engines near ground at varying yaw angles were investigated in the water tunnel located in W. ... The vortices at yaw angles 0°, 30°, 60°, and 90° were visualized using dyes injected through the clear plate. When the pipe was at 0°, two symmetrical vortices were formed, but at any angle greater the two vortices combined to form one dominant vortex. ... This 3-D velocity profile showed that two vortices at 0º, but one was dominant. ... Although these occurrences are rare because of the complexity of the atmospheric and flow variables involved, the vortices themselves are not so uncommon. ... This vorticity appears in the form of small vortices that are generated on the ground and are drawn into the engine inlet [1].
Knowing this, it is interesting to examine the characteristics of such vortices and their effect on the performance and operation of jet engines. These vortices present a potential safety hazard because they can create suction forces strong enough to pick up foreign objects from the runway and inject them into the engine or disrupt the flow ahead of the compressor blades and result in compressor stall [2]. Recreating these vortices in the water tunnel is the first step in producing useful data from such a phenomenon.
Vortices often create stunning visualizations when dye is injected into the flow, and such visualizations can provide valuable insight into the nature of these vortices. By examining the location and size of these vortices at varying yaw angles one can better determine their formation and general characteristics. In addition to dye, a Laser Doppler Anemometer (LDA) can be used to examine the velocity of flow within and around the vortices in all axes. ... The concepts involved in the formation of vortices were used to help describe the profile and explain the data recorded in the lab. ... A common theory suggests the vortices formed as fluid is drawn into the inlet are actually a subset of preexisting ambient vortices that begin from the leading edge of the plate and end within the inlet. These vortices are stretched and amplified as it is drawn into the jet engine. ... The axial stretching of the vortex lines as they enter the siphon increases their vorticity, creating a clear vortex whereas along the surface the vortices have little vorticity and are very miniscule making it hard to observe. ... 7) the line vortices perpendicular to the free stream flow within the boundary layer breaks into two separate vortices as they are drawn into the inlet. ... This flow upstream is caused by the suction of the siphon and results in trailing vortices which can be seen in Figure 6. ... Despite its increasing width downstream, these negative velocities are most likely the flow into the trailing vortices pictured in Figure 6. ... If it were aligned exactly parallel to the flow, there would be two vortices (two regions of high upward velocity), which would be symmetrical across the axis of the intake. ... This concurs in Figure 9, where there are two vortices. As the flow approaches these two vortices, it separates like flow approaching a blunt body and curls around the vortices. This suggests that the two vortices rotate in opposite directions, which is illustrated in Figure 10. ... An interesting phenomenon found was the formation of two symmetrical vortices when the intake was exactly parallel to the flow. In this position, the flow separates ahead of the inlet and forms two vortices and is pictured in Figure 9. Even the slightest deviation from 0º of yaw results in the disappearance of one of the vortices. ... Figure 12b shows the intake parallel to the flow, and two vortices are present. ... These vortices are also created by the jet engines of modern aircraft, and merits study. ... The velocity profile created from the LDA data showed that there were two vortices when the intake was centered parallel to the flow.
Approximate Word count = 3157
Approximate Pages = 12.6
(250 words per page double spaced)
|
|
|
|
|
|