c-----------------------------------------------------------------------
      subroutine useric (ix,iy,iz,eg)
      include 'SIZE'
      include 'TOTAL'
      include 'NEKUSE'

      integer e,eg

      common /mydomain/ zlength,pipe_radius

      xr = x/pipe_radius
      yr = y/pipe_radius
      rr = xr*xr + yr*yr
      if (rr.gt.0) rr=sqrt(rr)

      th = atan2(y,x)
      zo = 2*pi*z/zlength

      ux=0.0
      uy=0.0
      uz=0.0
      temp=0

      uz=6.*(1-rr**6)/5.

c     Assign a wiggly shear layer near the wall

      amp_z    = 0.35  ! Fraction of 2pi for z-based phase modification
      freq_z   = 4     ! Number of wiggles in axial- (z-) direction
      freq_t   = 9     ! Frequency of wiggles in azimuthal-direction

      amp_tht  = 5     ! Amplification factor for clipped sine function
      amp_clip = 0.2   ! Clipped amplitude

      blt      = 0.07  ! Fraction of boundary layer with momentum deficit

      phase_z = amp_z*(2*pi)*sin(freq_z*zo)

      arg_tht = freq_t*th + phase_z
      amp_sin = 5*sin(arg_tht)
      if (amp_sin.gt. amp_clip) amp_sin =  amp_clip
      if (amp_sin.lt.-amp_clip) amp_sin = -amp_clip

      if (rr.gt.(1-blt)) uz = uz + amp_sin

c     Quick P-independent randomizer

      big  = 1.e3*eg + 1.e2*ix + 1.e1*iy + 1.e0*iz
      rand = sin(big)
      uz   = uz + .01*rand
      ux   = ux + .05*rand*rand
      uy   = uy + .10*rand*rand*rand

      return
      end
c-----------------------------------------------------------------------