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FhSim
3.1.0
Marine systems simulation
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FhSim
3.1.0
Marine systems simulation
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Places one analytic porous-disc wake, for a structure that is not simulated.
Collaboration diagram for Porous disc wake source:Placed wake source: one porous-disc wake set up by hand.
The counterpart of a casting structure: a wake for a structure such as an upstream cage in a farm, which is not itself simulated. The SimObject registers one marenv::wake::SourceSetWake with the Environment, under its own name, in FinalSetup, and publishes one elementary source into it, with blend time 0. The wake is the pinned elementary kernel of marenv::wake::ElementaryDeficit (net-hydrodynamics contract C4) for one elementary source of the given area and momentum deficit M, with its surface and seabed images (R53). Above C_T = M / area = 0.96, where the kernel caps C_T, the area is widened to M / 0.96 so the wake carries the whole M, as the casters do (QF6); the widening is logged once at setup (owner ruling R125).
The environment composes the waked current as u = u_amb + d (u_s - u_amb), with deficit d and source velocity u_s; a source with u_s = 0 (the default) is moored, and in still water a moving source drags the water along at d u_s. The wake applies to the current part of the flow only, never to the wave particle velocity.
The source is at Position at the setup time (FinalSetup) and translates with SourceVelocity from then on, its wake with it (owner ruling R125). Its wake axis is either the fixed FlowDirection or, when FlowDirection is absent, the direction of the relative flow at the source, u_amb - u_s, with u_amb from environment::EnvironmentProvider::GetAmbientCurrent (never the waked flow, which would recurse into this wake). The followed direction is re-read once before every major time step, in PreOdeFcn, never in OdeFcn, so every stage of a step sees the same field; the source is published again at that step's time and position, with the seabed image below it. Until the first PreOdeFcn the followed wake is not set and casts nothing, and while the relative flow at the source is below 1 mm/s, or a current field fails there (a status marenv::IsUsable rejects; a clamped current is usable, owner ruling R122), it casts no wake.
None.
None.
| Name | Width | Description |
|---|---|---|
| Position | 3 | Source centroid in the NED frame [x, y, z] [m]. (Default: 0, 0, 0) |
| Area | 1 | The structure's own area [m^2]; the wake footprint is D = sqrt(4 Area / pi). Exactly one of Area and Diameter is required. (Required unless Diameter is given) |
| Diameter | 1 | Footprint diameter D [m], giving Area = pi D^2 / 4. Exactly one of Area and Diameter is required. (Required unless Area is given) |
| MomentumDeficit | 1 | Momentum deficit M = drag / (0.5 rho |U|^2) [m^2], >= 0. Exactly one of MomentumDeficit and ThrustCoefficient is required. (Required unless ThrustCoefficient is given) |
| ThrustCoefficient | 1 | Effective thrust coefficient C_T [-], >= 0, giving MomentumDeficit = C_T Area. Exactly one of MomentumDeficit and ThrustCoefficient is required. (Required unless MomentumDeficit is given) |
| FlowDirection | 3 | Fixed wake axis in the NED frame [-]; normalised on input, so only its direction matters; the zero vector is an error. (Default: absent, the axis follows the relative flow u_amb - u_s at Position) |
| SourceVelocity | 3 | Source velocity u_s in the NED frame [m/s]; the source is at Position at the setup time and translates with it. (Default: 0, 0, 0, a moored structure) |
| WakeExpansion | 1 | Wake expansion rate k in sigma/D = k x/D + epsilon [-]. (Default: 0.05) |
| WakeXStartFactor | 1 | x_start = max(WakeXStartFactor D, 0.02 m): no wake closer than this downstream of the source [-]. (Default: 0.5) |
This SimObject is referred to as PorousDiscWakeSource
1.9.8