So the frequency can't be simply calculated by the frequency formula of Von Karman vortex street around cylinder because Karman's formula is independent of hydrofoil's attacking angle. 尾流内存在周期性很好的类似卡门涡列的流动现象，其频率与叶片绕流状况有关，随着叶片入流角增加而增大，且属于低频范畴，因此，不能简单地采用圆柱绕流卡门涡街的频率公式进行计算。
He varied the transmission frequency. 他变换了无线电传送的频率。
A unit of frequency equal to one cycle per second. 赫兹频率的单位，等于每秒一周
I'd like to open a credit acrd account. 我想开一个信用卡账户.