Oscillatory modes of instability for flow between rotating cylinders with a transverse pressure gradient

1971 ◽  
Vol 22 (4) ◽  
pp. 680-690 ◽  
Author(s):  
Donald C. Raney ◽  
Tien S. Chang
Keyword(s):  
Pressure Gradient ◽  
Rotating Cylinders ◽  
Transverse Pressure

Competing 3D Mechanisms in Compressor Flows

2015 ◽  
Author(s):  
James V. Taylor ◽  
Robert J. Miller
Keyword(s):  
Pressure Gradient ◽  
Design Space ◽  
Flow Direction ◽  
Three Dimensional ◽  
Transverse Pressure ◽  
Compressor Design ◽  
Design Systems ◽  
3D Stacking ◽  
Profile Loss ◽  
Different Levels

Even though three-dimensional design is central to all modern compressor design systems, many of these methods still rely, at the their core on a two-dimensional, sectional, view of blade aerodynamics. This paper argues that this view fundamentally limits design by not correctly considering the way in which pressure gradient transverse to the flow direction affects both separation and loss. The first part of the paper details how 3D blade stacking and the transverse pressure gradient fundamentally alters the behaviour of the corner separations and trailing edge separations. By controlling this design parameter it is possible to switch between the two. The transverse pressure gradient is also shown to be responsible for a substantial increase in profile loss. In the second part this understanding is used to explore the uncertainty of the design space by simultaneously varying pitch-chord ratio and 3D stacking. It is shown that the design space is split in half by two different levels of risk.

The Mechanism of the Flow in the Hub Corner and the Control by Tailing Edge Gaps

2018 ◽  
Author(s):  
Wenfeng Zhao ◽  
Bin Jiang ◽  
Yu Duan ◽  
Zhitao Tian ◽  
Qun Zheng
Keyword(s):  
Flow Field ◽  
Pressure Gradient ◽  
Pressure Ratio ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Turn Angle ◽  
Corner Separation ◽  
Transverse Pressure ◽  
Streamwise Pressure Gradient ◽  
Surface Vortex

High-pressure ratio is one of the important characteristics of the sustainable development of the modern aero-engine compressor components. When the fluid flows through the compressor cascade row, it will be influenced by both the streamwise pressure gradient and the transverse pressure gradient, which will cause hub-corner separation or stall. In this paper, different diffusion factors are chosen for the cascades. Each diffusion factor has different turning angles. The formation mechanism of hub-corner separation is studied under the condition of zero angle of attack. Numerical simulation is used to study the influence of pressure gradient on the flow field in the corner. The scale of the concentrated shed vortex forms in the suction surface increases with the increasing of the transverse pressure gradient during the hub-corner separation. When the streamwise pressure gradient increases, the suction surface vortex forms the corner stall. By reasonable design, the two vortexes can cancel out each other. At this time, the loss of cascades is the minimum. Based on the flow mechanism of the corner separation/stall, the trailing gaps are set on three typical turn angle cascades. The results show that the trailing gaps can control the radial development of the suction surface vortex during the stall and improve flow field. The jet cannot blow the suction side boundary layer away during the corner separation, because the gap does not change the static pressure distribution at the root of the cascade. In a word, the trailing edge gaps can not only inhibit the separation in the hub corner but also have the minimum leakage loss at design point. It can be used as an effective and practical compressor design method.

scholarly journals The Oceanography of Chatham Sound, British Columbia

1956 ◽  
Vol 13 (3) ◽  
pp. 385-434 ◽  
Author(s):  
Ronald W. Trites
Keyword(s):  
Pressure Gradient ◽  
Fresh Water ◽  
Coriolis Force ◽  
Coastal Waters ◽  
River Discharge ◽  
Average Data ◽  
Transverse Pressure ◽  
Frictional Forces ◽  
Oceanographic Data ◽  
Synoptic Observations

During May–September, 1948, an oceanographic study was made of Chatham Sound, primarily to determine, if possible, whether there was any obvious characteristic of the water in the region which could be correlated with the known migration of salmon to the spawning grounds up the Nass and Skeena Rivers. A detailed analysis of the oceanographic data is presented.The path taken by the fresh water through the sound is shown to depend on the volume of fresh water being discharged from the rivers. These reach their peak discharge in late May or early June and during this period the amount of fresh water in the sound is three to four times the average. Data obtained at anchor stations occupied for 10 to 40 hours indicate that there is a good correlation between tidal, salinity and temperature cycles.Dynamic calculations have been made of the velocities, total volume and fresh water transports. During normal river conditions, the agreement with observed velocities, and with fresh water discharges determined from gauge readings, suggests that even in these coastal waters there is an approximate balance between the transverse pressure gradient and the Coriolis force. Stations at the mouth of Portland Inlet exhibit an apparent balance at all times which suggests that transverse inertial and frictional forces are slight compared with the transverse pressure gradient and Coriolis force. Evidence of a variation in geopotential slope associated with the tides is proposed.The relatively large tidal amplitudes together with the wide and rapid fluctuations in river discharge make it exceedingly difficult to obtain reliable synoptic observations over the entire sound.

Sinusoidal Excitation of a Free Turbulent Jet With Constant Amplitude Transverse Pressure Gradients Near the Nozzle Exit: Part II: An A-C Fluidic Model for the Jet Gain

1973 ◽  
Vol 95 (2) ◽  
pp. 174-179
Author(s):  
A. K. Stiffler ◽  
J. L. Shearer
Keyword(s):  
Pressure Gradient ◽  
Control Region ◽  
Input Signal ◽  
Nozzle Exit ◽  
Flow Direction ◽  
Turbulent Jet ◽  
Pressure Gradients ◽  
Constant Amplitude ◽  
Transverse Pressure ◽  
Sinusoidal Excitation

A free turbulent jet is perturbed transverse to the flow direction by a sinusoidal pressure gradient near the nozzle exit. An a-c model for the jet gain, based upon the control region dynamics and a uniform deflection of the jet downstream of this region, is generally verified in conjunction with attenuated mean shear velocities. A method is given to experimentally determine the effective amplitude of the input signal at the interface of the jet.

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