Question

The instantaneous stream-wise velocity of a turbulent flow is given as follows:

u(x,y,z,t) =$\bar{u}$(x,y,z,t)+${u}'$ (x,y,z,t)

the time-average of the fluctuating velocity ${u}'$ (x,y,z,t)

      (a) u^’/2                                                                (b)$-\frac{\bar{u}}{2}$

      (c) zero                                                               (d)$\frac{\bar{u}}{2}$