CAP437 Helideck Turbulence Studies Project Guide

As of version 1.34 (Released January 2020), in addition to the default SST turbulence model, in:Flux is included with a Reynolds Stress Transport Model (RSTM) for performing helideck turbulence studies which can be used for regulations like CAP437 and NORSOK C-004.

The RSTM solves 7 different turbulence equations, rather than the 2-equation SST model used for standard analyses. The additional turbulence equations of the RSTM are used to solve the necessary vertical velocity fluctuations which is the key variable for CAP437 compliance. 

Only when a simulation has been defined using the RSTM  will the post-processing variable, Vertical Fluctuating Velocity, m/s be available. Additionally, a more sensitive mesh adaption will automatically be applied to capture the complex turbulence generation.

The below provides a series of steps for performing a helideck turbulence study. in:Flux's Tutorial 10 also provides visuals to this process. 

Helideck Turbulence Analysis Steps:

1. Import or create 3D CAD geometry model

2. Determine which ventilation cases are needed for your study (wind direction and wind speeds)

3. Setup chosen wind cases to run and set the turbulence model to RSTM, under the advanced options when defining the ventilation cases.

4. Let the simulations complete

5. Review Results of Vertical Fluctuating Velocities with Isosurfaces and contours

6. If needed, define exhausts or other sources to ensure exceedance above 2°C is not present near the helideck (part of CAP 437). The wind cases used when running the exhaust study should use the normal SST 2-equation turbulence model.

7. If needed, review potential gas leak dispersions to ensure permissible gas concentration (10% LFL) is not exceeded (part of CAP 437). The wind cases used when running the dispersion study should use the normal SST 2-equation turbulence model.