Читать книгу Flow-Induced Vibration Handbook for Nuclear and Process Equipment - Группа авторов - Страница 48

The response to periodic wake shedding must be calculated for any modes that are found to have Strouhal numbers in the range defined in Section 2.4.3. Assuming that the damping is small, peak vibration amplitudes, Y(x), at resonance for the i^th mode may be expressed as:

(2‐49)

where F_L(x^′) is a distributed periodic force formulated by:

(2‐50)

where C_L is the dynamic lift coefficient defined in Section 2.4.3. Equation (2-50) is a generalized form of Eq. (2-35).

Periodic wake shedding can result from very localized flow over a single span. If the velocity distribution has large step changes in velocity, an effective velocity approach like that used for calculating fluidelastic instability may not be appropriate for periodic wake shedding. Regions with nozzles and inlets may have to be assessed separately.