We study the statistics of passive scalars (either temperature or concentration a diffusing substance) at friction Reynolds number ${Re}_{\tau }=1140$ , for turbulent flow within smooth straight pipe circular cross-section, in range Prandtl numbers from ${Pr}=0.00625$ to ${Pr}=16$ using direct numerical simulations (DNS) Navier–Stokes equations. Whereas organization is similar axial velocity fi...