Overview

The Resistance CFD Portal provides a fast and affordable way to perform professional CFD (Computational Fluid Dynamics) resistance simulations for marine vessels. This User Guide will walk you through each step of the process — from filling out the online questionnaire to receiving your final CFD study.

How it works

Fill Out the Questionnaire

Provide the key parameters of your project using our intuitive online form.
You’ll be guided through several sections:

Project setup and file upload
- You need to upload file of the CAD of the ship with their appendages in one of the following file formats : stl, iges, igs, step, stp, 3dm. The appendages can be provided in either the same file as the hull or as separate files.
- The hull should be provided as a closed volume with deck and transom surfaces.
- The CAD need to be at the hydrostatic condition of the first displacement with the free surface at z=0.
- The reference frame is :
  - Origin at the transom or AP
  - Vessel bow point towards negative X
  - Z= 0 is at the waterline at the transom or AP
- All data should be provided in this reference frame.
Water and hull characteristics
- You can choose standard salt water at 15 °C, fresh water at 20 °C or enter your own custom water characteristics for the density and dynamic viscosity.
Hull configurations
- You must choose between 3 different hull types: monohull, catamaran or trimaran
- Symmetry condition:
  - Half boat: The computation is performed on the starboard side of the vessel using a half hull mesh. We impose a symmetry condition in the plan Y = 0 m plane. This is the default configuration and is recommended for symmetric vessels without heel or leeway.
  - Entire boat: The computation is performed on the entire vessel with a full hull mesh. We can consider computations with leeway and heel angles. This configuration primarily used for sailing yachts with leeway and heel conditions or asymmetric vessels.
- Number of appendages: You need to indicate the number of appendages included in your CAD. The include bulbous bows, spray rails, keels, skegs, rudders, centreboards, daggerboards, shaft struts, bilge keels, propeller shafts, trim tabs, interceptors, moon pools, foils, stabilizer fins, struts, azipods thrusters, bow/stern thruster, exhaust scallops. For other appendage types not listed, please contact us.
- Waterline length (LWL): This is to compute the Froude number and correctly size the domain.
Simulation conditions
- You can choose 4 types of domain conditions:
  - Deep: Infinite depth without lateral confinement
  - Shallow: Finite depth without lateral confinement. You need to impose the waterway depth.
  - Confined rectangular: Rectangular channel. You need to impose the depth and width characteristics of the channel.
  - Confined trapezoidal: Trapezoidal channel. You need to impose the depth and width characteristics of the channel at the channel bottom and at the free surface.
- Hull roughness: Chose to impose the additional hull roughness corresponding to a clean, recently painted hull instead of a hydrodynamically smooth skin. You can only choose yes or no.
- Trim condition:
  - Fixed trim: The computations are fixed for a user imposed trim angle and free in sinkage. This condition is primarily intended for trim optimization studies or for vessels.
  - Free trim: the computations are free in both trim and sinkage.
- Heel: Give the heel angle in degrees. The heel is positive when heeled to port. Only available when entire boat is simulated.
Displacement and speeds
- Use the “Add Displacement” button to create new displacements.
- Use the “Duplicate” button to save time creating new displacements by copying the displacement values to the new displacement.
- Displacement #
  - Mass: The mass of the entire vessel at the given displacement in kg
  - Center of gravity: The position of the center of gravity in meters. The longitudinal position needs to be negative and the vertical position is with respect to the reference frame.
  - In the menu Speed you can activate Hull resistance or Self-propulsion. You can have both types of computations in the same displacement.
    - Hull resistance: The vessel is towed by a point and with a given initial shaft angle.
      - Shaft angle: Angle of the shaft relative to the horizontal in the reference frame (°)
      - Tow point: coordinate by which the boat is towed (m). For a motor vessel, it is the center of the propeller and for a sailing yacht it is the position of the aerodynamic center
    - Self-propulsion: in the case of self-propulsion computations with an actuator disc we need additional information:
      - Number of actuator: Up to 3 propellers can be specified.
      - Tow point: coordinate of the propeller disk center (m)
      - Shaft angle: Angle of the shaft relative to the horizontal in the reference frame (°)
      - Inner diameter : inner diameter of the propeller (m)
      - Outer diameter: outer diameter of the propeller (m)
      - Thickness: thickness of the propeller (m)
- Speed #: For a displacement you can have several speeds
  - Use the “Add Speed” button to add additional speeds to a given displacement.
  - In the menu Speed you can activate Hull resistance or Self-propulsion by selecting “Actuator disk for speed”.
  - Speed value: You need to enter the speed in knots
  - Lateral speed: Apply a lateral speed in the Y-direction to impose a leeway (m/s). Positive to starboard, negative to port. Only available when entire boat is simulated.
  - Froude number: the value of the Froude number is given
  - Deliverables:
    - Excel file: By default we provide an Excel file. This file contains all of the results of the computations for each speed we have the components of the forces and moments split into pressure and friction parts. The motions of the hull such as sinkage, trim (positive trim means bow up), static and dynamic wetted surface area, ITTC 57 friction force and many other results.
    - Movie: You can choose to have a movie of the free surface and vessel surfaces while the vessel accelerates and achieves a steady running condition.
    - Wake factor: Provide the wake factor (1-w), an image of the propeller disk axial velocities and a text file containing the radial and azimuthal distribution of the axial, radial and tangential velocities. This post-processing is only available for resistance computations. We need the characteristic of the propeller geometry:
      - Propeller inner diameter (m)
      - Propeller outer diameter (m)
    - Forces by section: This post-processing give the evolution of the Fx, Fz along the vessel length. Both pressure and viscous force distributions are given
    - 3D flow filed data file: The flow fields are provided in a format that can be opened using the open source software Paraview. A state file with different common outputs such as the free surface, a cutting plane, and a line of streamlines is provided. These can then be modified by the user. This allows a user to rapidly be able to start using Paraview to analyze a hull’s flow fields. The flow field files are given to the customer through a secure ftp server.

The Price

The price of a study depends on the following:

Hull type (monohull, catamaran, trimaran)
Domain type (deep, shallow, confined)
The use of half-hull or full-hull mesh
The number of appendages

The price of a given displacement depends on the following:

The number of speeds. The first speed is the most expensive because it includes the cost of the mesh. Each additional computation is progressively cheaper.
The number of actuator disks
The desired deliverables

The price of the study is transparently updated as you change the study parameters in the questionnaire. When you click “Submit project” you will receive a quotation by mail which will also be reviewed by the MyCFD team ensure that all inputs are correct with respect to your hull.