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ExamsGATETechnical

The instantaneous stream-wise velocity of a turbulent flow is given by \(u(x,y,z,t)=\bar{u}(x,y,z)+u'(x,y,z,t)\). The time-average of the fluctuating velocity \(u'(x,y,z,t)\) is

  1. u'/2
  2. −\bar{u}/2
  3. zero
  4. \bar{u}/2

Correct answer: zero

Solution

In Reynolds decomposition, the instantaneous velocity is split into a mean part and a fluctuation part. By definition, the time average of the fluctuation is zero.

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