Update README.md

README.md

@@ -2,7 +2,8 @@
  **CP3d** (Channel-Particle 3d) is a comprehensive Euler-Lagrange solver for the direct numerical simulations of particle-laden flows.
 
 * Have the ability to perform **one-way**, **two-way**, **interface-unresolved four-way**, and **interface-resovled four-way** coupling regime.
-* For the fluid sub-solver, both the second-order and four-order finite difference discretization are available, in company with three viscous term treatment approaches: i.e., fully-implicit, partial-implicit, and fully-explicit. Four boundary conditions (BCs) are available in CP3d for the velocity terms, including the periodic, no-slip, slip, and convective outflow conditions. However, only two types of boundary condition are needed for the pressure term: periodic or Neumann BCs (∂p/∂xi=0 for non-periodic directions). 
+* For the fluid sub-solver, both the second-order and four-order finite difference discretization are available, in company with three viscous term treatment approaches: i.e., fully-implicit, partial-implicit, and fully-explicit. 
+* Four boundary conditions (BCs) are available in CP3d for the velocity terms, including the periodic, no-slip, slip, and convective outflow conditions. However, only two types of boundary condition are needed for the pressure term: periodic or Neumann BCs (∂p/∂xi=0 for non-periodic directions). 
 * For the **discrete-element-method (DEM)** solver, both linear and non-linear contact force models can be used, and the collision time can be also adaptive.
 * The **immersed boundary method (IBM)** is used in interface-resolved simulation, and totally three IBM coupling approaches are included.
 * In order to improve the numerical accuracy of the computational **Basset history force**, a third-order exponential approximation method is proposed in interface-unresolved four-way regime.