dear people

can any one make me clear of whether turbulence is diffusive or dissipative ?

Both.

(1).In cfd and fluid dynamics, the starting point is always the conservation law. (2). At the basic transient equation level, we can only say the the flow has to satisfy the momentum conservation and continuity equations. At this level, everything is transient, and it is expressed in terms of the instantaneous components. (3). If we use Reynolds time average, or ensemble average, and derive the govering equations for the averaged velocity, turbulence kinetic energy, then we can say something about the turbulence in terms of the turbulence kinetic energy. (4). The derived governing equation for the turbulence kinetic energy has the convection term, diffusion term, the production term and the dissipation term, in addition to the transient term. (5). So, it is transient, diffusive, convective, dissipative, and productive. In other words, the turbulence kinetic is produced from the mean flow, at the same time, it will dissipate in time, diffuse in space, and be convected from place to place.