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In aerodynamics, the normal shock tables are a series of tabulated data listing the various properties before and after the occurrence of a normal shock wave. [1] With a given upstream Mach number , the post-shock Mach number can be calculated along with the pressure , density , temperature , and stagnation pressure ratios.
[6]: 92 If the center of gravity is forward of the neutral point, the static margin is positive. [7]: 8 If the center of gravity is aft of the neutral point, the static margin is negative. The greater the static margin, the more stable the aircraft will be.
The stiffness does not only depend on the static stability term , it also contains a term which effectively determines the angle of attack due to the body rotation. The distance of the center of lift, including this term, ahead of the centre of gravity is called the maneuver margin. It must be negative for stability.
A static balance (sometimes called a force balance [2] [3]) occurs when the inertial axis of a rotating mass is displaced from and parallel to the axis of rotation.Static unbalances can occur more frequently in disk-shaped rotors because the thin geometric profile of the disk allows for an uneven distribution of mass with an inertial axis that is nearly parallel to the axis of rotation.
It is also known as the stiffness to weight ratio or specific stiffness. High specific modulus materials find wide application in aerospace applications where minimum structural weight is required. The dimensional analysis yields units of distance squared per time squared.
For input frequencies much lower than corner, the ratio / is small, and therefore the phase angle is close to zero. As the ratio increases, the absolute value of the phase increases and becomes −45° when =. As the ratio increases for input frequencies much greater than the corner frequency, the phase angle asymptotically approaches −90°.
Phase margin and gain margin are two measures of stability for a feedback control system. They indicate how much the gain or the phase of the system can vary before it becomes unstable. Phase margin is the difference (expressed as a positive number) between 180° and the phase shift where the magnitude of the loop transfer function is 0 dB.
Stagnation pressure is the static pressure a gas retains when brought to rest isentropically from Mach number M. [6]= (+) or, assuming an isentropic process, the stagnation pressure can be calculated from the ratio of stagnation temperature to static temperature: