Welcome to the homepage of IITM-RANS3D. It is an in-house CFD code developed at the Department of Ocean Engineering, IIT Madras. The code has been developed with the aim of handling complex wave-structure interaction simulations in large domains over a long period of time.

IITM-RANS3D is a multiphase code based on the single-fluid formulation of the incompressible Navier-Stokes equations. The Navier-Stokes equations are solved using a semi-explicit solver over a Cartesian staggered mesh. Multiphase treatment is achieved using the VOF method. Waves are generated through a Dirichlet input from the in-house fully non-linear potential theory (FNPT) code IITM-FNPT2D. Turbulence effects are modeled using the RANS philosophy. Structures are modeled using the fictitious-domain method.

Key Features and Strengths:

  1. Strong pressure-velocity coupling realized through the staggered mesh.
  2. CICSAM scheme optimized for speed on Cartesian meshes through operator-splitting.
  3. One-way coupled with IITM-FNPT2D thus enabling very high fidelity generation of a wide range of waves.
  4. One-way coupling with IITM-FNPT2D allows for truncation of the RANS domain to the near-field of the structure. This saves computational effort by delegating the inviscid wave simulations to FNPT.
  5. Wave simulations are energy preserving even for large domains (say GWK: 350m x 5m x 7m) and for long time (say >~100 s).
  6. Turbulence effects characterizing wave-structure interaction modeled using the standard k-ε model.
  7. Fictitious-domain modeling of the structure precludes modifying the mesh topology in the vicinity of the structure thus enabling the use of Cartesian meshes even for complex structures.
  8. Parallelized using MPI. Capable of fully utilizing the computational resources offered by multi-core standalone compute nodes (SMA-shared memory architecture) as well as the VSR group server and IITM’s AQUA cluster (DMA-distributed memory architecture).
  9. Option for importing structure geometries through *.STL files.
  10. Capable of simulating forward speed problems.

Limitations (general):

  1. RANS as well as VOF formulation only applicable to Cartesian meshes.
  2. Diffuse interface treatment of the solid region ; implicit imposition of the slip boundary condition.
  3. Algebraic VOF scheme-based estimation of the interface location ; interface placement is not geometric.

Limitations (specific to release 1.0):

  1. No turbulence modeling ; laminar solver.
  2. Time discretization is first order forward Euler ; pressure and diffusion terms treatment is second-order.
  3. Two-phase Navier-Stokes formulation is non-conservative.
  4. Capable of handling complex albeit fixed structures.
  5. FNPT-RANS coupling is one-way. IITM-RANS3D_updated

Work in progress and future updates:

  1. 6-DoF rigid solver, mooring lines & coupling for aero elasticity.
  2. Compressible air phase modelling for OWC, entrapped air.

Typical Application problems:

(1) Traditional Green-water loading on a obstacle model
Kleefsman dam-break

(2) Steep solitary wave interacting with a cylinder


(3) Focused waves interacting with a moonpool


(4) Steepness-induced breaking of focusing waves

Focusing wave breaking

(5) Solitary wave (H/d-0.45) breaking over a plane-sloping beach

Li and Raichlen

(6) Steep solitary wave (H/d=0.6) breaking over a sloping ridge

Ridge Soliton

(7) Focusing waves interacting with moving cylinder

Moving Cylinder



(1) N., Hari Ram, Saincher, S. and Sriram, V., 2022.Numerical investigations into wave attenuation characteristics of vegetation belt in terms of vortex shedding due to different arrangement configuration”. IAHR-APD-2022 – Chennai.

(2) Saincher, S. and Sriram, V., 2022.Application of IITM-RANS3D to wave-breaking and wave-structure-interaction problems”. IAHR-APD-2022 – Chennai.

(3) Saincher, S. and Sriram, V., 2022.Comparative assessment of non-conservative and conservative RANS formulations for coastal applications involving breaking waves”. ICCE-2022 – Sydney.

(4) Saincher, S. and Sriram, V., 2022.A three dimensional hybrid fully nonlinear potential flow and Navier Stokes model for wave structure interactions”. Ocean Engineering, 266, 112770.

(5) Saincher, S. and Sriram, V., 2022.An efficient operator-split CICSAM scheme for three-dimensional multiphase-flow problems on Cartesian grids”. Computers & Fluids, 240, 105440.

(6) Harish, S., Saincher, S., Sriram, V., Schüttrumpf, H. and Sannasiraj, S. A., 2022.Numerical investigation of tsunami-like bore induced forces on overtopped buildings”. Oceans-2022 – Chennai.

(7) Saincher, S., Wesly, J., Vineesh, P. and Sriram, V., 2021.Experimental and FNPT-RANS investigations into gap-excitation and vortex dynamics in a rectangular moonpool interacting with focused waves”. OMAE-2021 – Virtual.

(8) Saincher, S., Sriram, V. and Didenkulova, I., 2021.Run-up of breaking focused waves on a beach studied experimentally in a large scale facility and numerically using hybrid FNPT-RANS model”. EGU (European Geosciences Union) General Assembly Conference Abstracts (vEGU21).


IITM – RANS3D is an open source code. We welcome researchers to either use it or change it according to your needs.

Any clarification and suggestions you may reach us: Dr. Shaswat Saincher: shaswat.saincher@gmail.com or Myself: vsriram@iitm.ac.in

Version 1.1: IITM-RANS3D_v1.1 (Conservative Laminar Solver) – released Dec. 2022

Version 1.0: IITM-RANS3D_v1.0 (Non Conservative Laminar Solver) – released Oct. 2021

Developed and tested by:

Dr. Shaswat Saincher (PostDoc)

Mr. Hari Ram N. (Ph.D) – Wave-rigid vegetation interaction

Mr. Harish Selvam (Ph.D) – Tsunami-induced overtopping over buildings

Ms. Shrushti Shirsat (M.Tech) – Aero-hydrodynamics of bottom-profiled OWC chambers

Mr. John Wesly (M.S) and Mr. Kartik Ruikar (B.Tech) – Gap resonance in moonpools

Mr. Manish Verma (Ph.D) – Wave-current loads on ships

Ms. Golda Percy (Ph.D) and Ms. Praba Nageswaran (Ph.D) and Mr. Sakthi Vasanth (Ph.D) – Buffer blocks for coastal protection (dam-break waves ; solitons ; undular bores)

Mr. Vineesh P. (Ph.D) – Twin floating-body dynamics

Dr. Jemi Jeya (Ph.D) – Regular waves interacting with pile-supported caisson