Numerical method for the flow solver: fractional-step method for the
incompressible Navier-Stokes equations.
Spatial derivatives are evaluated using centered differences for all
terms (second-order accurate). Mixed explicit/implicit time advance
(second-order Adams-Bashforth and Crank-Nicholson).
Uniform grid in the streamwise (x) and spanwise (z) directions and a
stretched grid (using a hyperbolic tangent function) in the wall-normal
(y) direction.
Poisson equation for pressure solved using fast transforms.

The domain size is 4*pi*delta in x, 2*delta in y, and 2*pi*delta in z
where delta is the halfwidth.

Grid size is: 128x129x128
Number of particles is: 100,000

Stokes numbers are: 1, 5, 25
Shear Reynolds number is: 150 based on Re_tau

Numerical scheme for integration of the particles: second-order Adams-Bashforth

Fluid velocity interpolation: third-order Lagrange polynomials