Card 6y - GPU Radiation Activation

L

L is the code VFRTGPU (or 38)

TOGGLE

TOGGLE specifies whether view factors are calculated.

• TOGGLE = ON (or 4): VFS12, VFSALL, VFS1ALL, VFSENC Cards are processed to calculate view factor requests using the VFRTGPU module. For more information see, Card 6a - View Factor Request.
• TOGGLE = OFF (or 5): View factors are not calculated.

METHODS

METHODS specifies GPU-based calculation methods for radiation exchange to accelerate radiation computation.

• METHOD = 0 uses the GPU-computed view factor method. It computes blackbody (geometric) radiative view factors on the GPU using a Monte Carlo ray-tracing approach. Rays are emitted and terminated at the first surface intersection, with no reflection or secondary bounces. As a result, the method computes pure geometric view factors independent of advanced optical properties. This direct GPU-based view-factor computation is significantly faster than general ray-tracing approaches that model surface reflections.
• METHOD = 1 uses the GPU-computed ray tracing method. It computes ray-traced view factors, radiative couplings, and radiative heat loads. Rays are traced through multiple surface interactions, with energy attenuated according to surface thermo-optical properties. Each ray path is terminated when its remaining energy falls below a predefined threshold, enabling accurate modeling of complex radiative exchange with advanced optical properties.

NRAYS

NRAYS specifies the number of rays that are launched from an element. Depending on the RAY_OPTION flag, the number of rays to be launched to or from an element will be either NRAYS (absolute) or NRAYS per unit area. For view factor requests and radiative source requests, NRAYS specifies the number of rays launched from each element. For environmental heating requests (solar, earth, orbit, or diurnal heating requests), NRAYS specifies the number of rays launched to each element.

RAY_OPTION

RAY_OPTION specifies how rays are launch.

• RAY_OPTION = AREA: NRAYS rays per unit area are launched from or (in the case of environmental heating requests) to the element.
• RAY_OPTION = ABSOLUTE: NRAYS rays are launched per element.

VFTYPE

VFTYPE specifies the method used for computing view factors when METHOD = 1.

• VFTYPE = VF computes view factors using the ray tracing method. Radiative view factors are evaluated using a Monte Carlo ray-tracing approach. The method supports surfaces with advanced optical properties through stochastic secondary ray launching. For enclosure radiation request with GPU computed ray tracing method, only ray-traced view factor calculation is calculated.
• VFTYPE = HTFRAD computes radiative couplings and heat loads directly from the Monte Carlo ray tracing technique. This method uses a stochastic (statistical) secondary ray-launching method for specular and transparent surfaces. View factor requests result in the direct computation of radiative couplings. Heat flux view factor requests and environmental heating requests result in the direct computation of radiative heat loads.

Code example

 $ Radiation(1)                           
 MESH RESET
 VFRTGPU ON 0 666
 VFS12 "Radiation(1) - Region Radiating from Top Side" "Radiation(1) - Region Radiating from Top Side" 0 0 0 SPACE
 VFRTGPU ON 1 150000 ABSOLUTE VF

Notes

To use the VFRTGPU module, you must have supported NVIDIA graphics card.