Back to articleTop row: Shadowgraph view of a cascade of airfoil shapes. Dark lines on the image would indicate the location of a shock wave, but none are present, showing the flow is subsonic. Adjacent is a graph with time on the x-axis and pressure in kilopascals on the y-axis. The graph shows data from a pressure sensor (Kulite) located near the leading edge of one of the cascade airfoils. The pressure varies slightly about the average pressure level. Middle two rows: These are similar to the top row in composition. The shadowgraph photo this time shows that some airfoils in the cascade have clear shock waves attached to them whereas others do not. It is not totally clear, but it appears that shocks are located on every other airfoil. The pressure sensor data graph shows the sensor measuring a higher pressure for a portion of the time and a lower pressure for the rest. The data show that the pressure stays at one pressure level or the other for varying lengths of time. There does not appear to be a pattern as to which pressure is present. The difference between the two pressure levels is approximately 20 kPa. Bottom row: This is also similar to the top row in composition. The shadowgraph picture clearly shows a similar shock wave pattern on each cascade airfoil. There is an oblique wave off the leading edge followed by a stronger wave normal to the airfoil surface before midchord. The oblique wave terminates above the airfoil surface when it meets the normal wave. The pressure sensor data are similar to the pressure data in the top row in that it the pressure vary slightly about the average pressure level. The average pressure is lower than it is for the subsonic inlet flow.
Last updated: June 2002
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