SMD eCFE

Subsea SeaJet Controlled Flow Excavator — First-Principles Hydrodynamic, Two-Strata & Berm Modelling Suite

Source of Truth: SMD Manuals (Subsea Operations-CFE, Excavator Assy-CFE, Launch+Recovery-CFE) · SME 185 kW Motor Manual · C3094 FAT · AP4400 (Rev 9) · Gemini NBI (0695-SOM-00005)

1. Tool Geometry, 12° Pin Angles & Motor Power

Active SMD Configuration

Motor Speed & Live Thrust (0–440 RPM) 225 RPM (1.31 Te / 12.8 kN)

Tool Height Above Seabed (Base / Sonar Z) 1.00 m Base / 1.45 m Sonar

Sliding Rail Position (Centreline Pitch)

Outer / Port Pivot Frame Tilt (12° Mechanical Pin Steps) +60°

Inner / Starboard Pivot Frame Tilt (12° Mechanical Pin Steps) +48°

Excavator Fore–Aft Tilt (Y–Z Plane, Config 3 Pin Angle)

Outer / Port Pod Nozzle Type

Inner / Starboard Pod Nozzle Type

Excavated Trench -- --

Created Spoil Berm -- --

Seabed & Horizon Shear -- --

Attitude & Clump Pull -- --

Sonar Look-Window -- --

Excavated Trench (Depth × Width)

Created Spoil Berm (Crest × Width)

Seabed & Interface Shear (τ_b)

Reaction Forces & SME 185 kW Motor

Attitude & Hanging Clump Weight

Gemini NBI Swath & Blind Zone

Effective Nozzle Vectors

Sliding Rail & Table 1 Depth

First-Principles Engineering Analysis — Two-Layer Stratigraphy, Hanging Clump Restraint & AP4400 Sonar Coverage

SMD Standard Thrust Reference (fixed)

Full rated thrust of 2.5 Te (24.5 kN) per excavator (SMD Excavator Assy-CFE manual) is taken at 440 RPM — the top of the 90–440 RPM working range in the SMD C3094 FAT specification (maximum permissible 480 RPM). This matches the FAT spec's maximum rotor torque (4413 Nm) at its nominal 203 kW shaft power: 4413 Nm × 440 RPM ≈ 203 kW. Thrust at other speeds follows T = 2.5 Te × (RPM / 440)².

Methodology & Reference Sources: How RPM → Force, Jet Dissipation & Seabed Scour Are Calculated

Every curve, coordinate, force vector, and seabed scour profile in this simulator is computed strictly from closed-form 1D/2D fluid-mechanics and pendulum-statics equations with zero empirical curve-fitting ("frigging"), parameterised directly by the uploaded SMD & supplier technical manuals:

Physical Stage	Governing First-Principles Equation	Certified Source Document & Verified Constants
1. SME 185 kW Subsea Motor & 836 mm Propeller Thrust	`T_pod(RPM) = T_rated · (RPM / RPM_rated)²` `P_shaft(RPM) = 185 kW · (RPM / RPM_rated)³` `f_VFD = 32 Hz · (RPM / 460)`	SMD Excavator Assembly Manual (REV-1, 18 Apr 2024, p. 8–15): `836 mm` LH/RH counter-rotating propellers (`140 kg`) with static Guide Vanes; `T_rated = 2.5 Te (24.525 kN)` per pod (`5.0 Te / 49.05 kN` total); pod mass `3.0 Te` in air. SME Subsea Motor Manual (ROV228 185kW 8P 4200V 32Hz, p. 15 & 25): `185 kW (250 HP)` shaft output (`213 kW` input @ `86.7%` eff, `38.6 A` FLA, `3854 Nm` torque) at `460 RPM` full-load (`480 RPM` synchronous @ `32 Hz`). SMD C3094 FAT Spec 2.1.2.3 (p. 46): `90–440 RPM` operational working speed range.
2. Nozzle Exit Velocity & Discharge Flow Rate	`A_0 = π · D_0² / 4` `V_0 = η_nozzle · √(T_pod / (ρ_w · A_0))` `Q_0 = A_0 · V_0`, `ṁ_0 = ρ_w · Q_0`	SMD Excavator Assembly Manual Section 3.1 (p. 15): • `730 mm` Primary Nozzle: `A_0 = 0.4185 m²`, `η = 1.00` (`V_0 = 7.56 m/s` @ 2.5 Te). • `630 mm` High-Cutting Nozzle (soils up to `50 kPa`): `A_0 = 0.3117 m²`, `η = 1.00` (`V_0 = 8.76 m/s` @ 2.5 Te). • `Divertor` Nozzle (`730 mm` ID, `+36°` elbow): `A_0 = 0.4185 m²`, `η = 0.94` (`26°` pin + `36°` divertor = `62°` net thrust).
3. Coupled Hanging Clump Weight & Bridle Pendulum Statics	`W_clump,sub = M_clump · 8.535 kN/Te` `F_pull,onset = W_clump,sub · tan(28.5°)` `RPM_onset = RPM_rated · √(F_pull,onset / F_horiz,rated)` `θ_limit = atan2(ΔZ_clump, L_tether)`	SMD Launch & Recovery Manual (REV-1, Figure 3 p. 8 & Section 3.3 p. 19) & C3094 FAT Section 13 (p. 31) / Spec 9.2 (p. 47): • Clump Weight: `3.0–3.3 Te` in air (`0.635 × 0.635 × 1.13 m`) suspended in the water column on a `5 Te` tugger winch wire (`19 mm` wire rope) with a running line to the CFE red tugger lash point. • At `3.0 Te` (`W_sub = 25.61 kN`), pull-in onset is `13.90 kN (1.42 Te)`, corresponding to `~261 RPM` in Config 4A (SMD standard 440 RPM rating). Because the hanging clump weight sits higher than the SeaJet padeye over the `8.0 m` tether, SeaJet tilt climbs with RPM and asymptotically locks near `θ_limit ≈ 10.1°`.
4. Submerged Turbulent Jet Decay & Oblique Wall-Jet Shear	`V_m(s) = V_0 · min(1, s_0 / s)` (`s_0 = 3.85 · D_0`) `b(s) = 0.5 · D_0 + 0.105 · s` `τ_b = ½ · C_f · ρ_w · V_bed²` (`C_f = 0.0021`)	Albertson et al. (1950) submerged axisymmetric turbulent jet entrainment & potential core decay; Rajaratnam (1976) & Beltaos & Rajaratnam (1977) oblique circular jet impingement & radial wall-jet spreading; Soulsby (1997) marine sediment boundary-layer skin friction.
5. Two-Strata Equilibrium Scour & Mass-Conserved Berm	`d_1(x,y) = s_eff · (√(τ_b / τ_crit,1) - 1) · E_1` If `d_1 > h_1` & `τ_int <= τ_crit,2` → arrest at `d = h_1` `A_berm = A_cut · f_ret(w_s, τ_b) · B_bulk`	Hjulström / Shields / Soulsby (1997) critical shear thresholds (strictly ordered: Fine Sand `8.0 Pa` < Medium Sand `14.0 Pa` < Soft Clay `22.0 Pa` < Stiff Clay `42.0 Pa`) and Rouse/Hazen settling retention into the downstream crescent spoil berm with zero artificial depth or width caps.

Searches every outer/inner pin angle (12° steps), fore–aft pin, rail position, nozzle pair, RPM (90–440), stand-off and vessel speed for one pass, with your current strata held fixed and no current. Setups are not limited by the clump: each row shows the clump weight needed to hold station (red if more than your current clump). Each row is the setup that digs the least hole for that berm size. Positions are offsets from the tool track (+ = starboard, the throw side). The current check re-runs each row at 0.25–2 kt in 8 directions and shows the lowest current at which half the berm is lost (— = holds to 2 kt).

Berm (m²/m)	Crest height	Usable berm (m²/m, extent)	Berm position (start → crest → end)	Hole (m²/m)	Trench depth × width	Berm ÷ hole	Vehicle & Tool Setup	Running Parameters	Clump needed	Current check: half berm lost at (kt) by direction

All preset configurations, angular constraints, and structural pitch coordinates below are taken directly from the certified SMD Technical Manuals (Subsea Operations-CFE REV-1, Excavator Assy-CFE, Chassis+Pivot Frame-CFE, CFE Tool Installation) and SMD General Assembly Drawing AP4400 (Rev 9).

SMD Standard Operating Configurations

Config ID	SMD Manual Section & Name	Pivot Frame Tilt (Port & Stbd)	Excavator Tilt (Fore–Aft)	Sliding Rail Position (Pitch)	Nozzle Type	SMD Manual Operating Parameters
Config 1	3.1) Horizontal Orientation (Page 9)	`0°` / `0°` (Vertical motor axes)	`0°`	Inner (`2000 mm`), Centre (`2750 mm`), or Outer (`3500 mm`)	Standard (`630 mm` or `730 mm`)	0.5 m from bottom of tool; up to 100% power
Config 2	3.2) V-Formation (Pages 10–12)	Inwards towards centre: `12°`, `24°`, `36°`, `48°` (60° prohibited)	`0°`	Inner (`2000 mm`), Centre (`2750 mm`), or Outer (`3500 mm`)	Standard (`630 mm` or `730 mm`)	0.5 m from bottom of tool; see Table 1 below for intersection depth
Config 3A	4.1.1) FWD–AFT Tilt – Standard Nozzles (Pages 13–14)	`0°` / `0°`	`39°` recommended (Pin options: 13°, 26°, 39°)	Inner, Centre, or Outer (Parallel twin lanes)	Standard (`630 mm` or `730 mm`)	1.0 m from bottom of tool; 20%–40% full power
Config 3B	4.1.2) FWD–AFT Tilt – Divertor Nozzles (Pages 14–15)	`0°` / `0°`	`26°` Excavator Tilt → `62°` Net Thrust (+36° Divertor)	Inner, Centre, or Outer (Parallel twin lanes)	Divertor Nozzle (+36°) on both pods	1.0 m from bottom of tool; 20%–40% full power
Config 4A	5) Port–Starboard Tilt – Standard Nozzles (Page 16, Fig 13)	Inner (trench-side): `48°` Outer: `60°`	`0°`	Centre (`2750 mm`) ONLY (Clashes with chassis in Inner/Outer)	Standard (`630 mm` or `730 mm`)	1.0 m from bottom of tool; 20%–40% full power
Config 4B	5) Port–Starboard Tilt – Divertor on Outer Pod (Pages 16–17, Fig 14)	Inner: `48°` (Std) Outer: `36°` + Divertor → `72°` Net Thrust	`0°`	Centre (`2750 mm`) ONLY	Inner: Standard Outer: Divertor Nozzle (+36°)	1.0 m from bottom of tool; 20%–40% full power

SMD Manual Table 1 (Page 12) — V-Formation Depth of Jet Intersection Below Bottom of Tool

Pivot Frame Position (Rail Pitch)	Tilt Angle	SMD Manual Table 1 Value	Exact Geometric Calculation	Engineering Note

📐 AP4400 Chassis Dimensions

Overall envelope: 5,140 mm × 2,000 mm × 2,260 mm.
Corner lift points: 4,920 mm × 1,844 mm.
Top padeye height: +2.245 m above base. Lower bumper height: +0.45 m.

📍 Sliding Rail Positions

• Inner Pitch: 2,000 mm (Narrow cut, high energy concentration)
• Centre Pitch: 2,750 mm (Standard deployment, mandatory for Config 4A/4B)
• Outer Pitch: 3,500 mm (Wide swath trench clearance)

All motor parameters, pump thrust ratings, certified dry/submerged weights, and sensor geometry below are extracted from the SME Subsea Motor ROV228 Manual, AP4402/3 Pod Drawings, C3094 FAT Document, and Tritech Gemini NBI Datasheet.

Sub-Assembly / Component	Drawing / Manual Reference	Certified Specification	Engineering & Modelling Role
SME Subsea Electric Motors (×2)	SME Manual `ROV228 185kW 4200V 32Hz` · Drawing `1-010-2367`	`185 kW (250 HP)` shaft output (`213 kW` input @ `86.7%` eff, `38.6 A` FLA) · 8-Pole · `460 RPM` rated full-load speed (`480 RPM` sync @ `32 Hz`; `90–440 RPM` CFE working range) · `3854 Nm` torque · `1073 kg` oil-filled	Drives counter-rotating 836 mm propellers; establishes quadratic thrust `T ∝ RPM²` and cubic shaft power `P ∝ RPM³`
Excavator Assemblies (LH & RH)	`AP4402 Rev 7` (RH) & `AP4403 Rev 8` (LH) · `Excavator Assy-CFE.pdf`	Weight in Air: `3.0 Te` each · Max Thrust: `2.5 Te (24.525 kN)` per pod · Propeller: `836 mm` LH/RH (`140 kg`) + Static Guide Vanes · Ballast: `8 × 28 kg = 224 kg/pod` · Nose Cone: `300 kg` · Bearing Housing `AQ4451`: `160 kg`	Provides `5.0 Te (49.05 kN)` combined thrust; guide vanes remove swirl for coherent axial jet discharge
Outlet Nozzles (730 / 630 / Divertor)	`Excavator Assy-CFE.pdf` Section 3.1 (Page 15)	• `730 mm` Primary Nozzle (`A_0 = 0.4185 m²`) • `630 mm` High-Cutting Nozzle (`A_0 = 0.3117 m²`, soils up to `50 kPa`) • `Divertor` Nozzle (`730 mm` ID, `+36°` elbow → `62°` at `26°` pin)	Determines exit velocity `V_0 = η √(T / (ρ A_0))`, potential core length `s_0 = 3.85 D_0`, and impingement angle
Chassis, Pivot Frames & Measured CFE Mass	`AP4400 Rev 9` · `AP4401 Rev 7` · `AP4405 Rev 3` · C3094 FAT Sec 13	Measured FAT Weight in Air: `9,600 kg (9.60 Te)` (Spec max: `12.0 Te` air / `10.5 Te` submerged) · Chassis: `3.0 Te` (S355) · Pivot Frame: `251 kg` (S690) · Measured Envelope: `5140 × 2000 × 2260 mm` (`4920 × 1844 mm` corner pitch)	Defines exact 1:1 hull geometry in Cross-Section (`4.92 m`) and Side Elevation (`1.844 m`)
Hanging Clump Weight & Tugger Winch LARS	`Launch+Recovery-CFE.pdf` Fig 3 (p. 8) · C3094 FAT Sec 13 & Spec 9.2	Clump Weight in Air: `3.0–3.3 Te` (`0.635 × 0.635 × 1.13 m`) suspended in water column on `5 Te` Tugger Winch wire (`19 mm` wire rope over `5 Te` Outriggers) with Running Line to red Tugger Lash Point	Governs station-keeping pull-in threshold (`13.9 kN` at `3.0 Te`) and collinear bridle-tether tilt lock (`~10.1°`)
AP4400 Sonar Mounting Brackets	Item 14: `AQ1306` · Item 24: `AQ7286` (Qty 2) + `AQ7424` Guard	• Centre Bay `AQ1306`: `X = 0.00 m, Z = +0.45 m` • Stbd/Port End `AQ7286`: `X = ±2.46 m (±0.92 m Y–Z), Z = +0.45 m` • Top Centreline: `X = 0.00 m, Z = +2.245 m`	Positions Tritech Gemini NBI (`620 kHz, 130° × 1.0°`) relative to the excavated trench and spoil berm

Station-keeping equilibrium under hanging clump weight restraint, catenary tilt dynamics, and offshore spoil berm compactness criteria.

⚓ 1. 3.0 Te Hanging Clump Restraint

W_sub = M_air · g · (1 - ρ_water / ρ_steel) ≈ 25.6 kN
H_rxn = T · sin(θ_thrust)
T_pull = W_sub · sin(θ_crit) ≈ 13.9 kN [Onset @ 261 RPM]

Launch+Recovery-CFE.pdf & C3094 FAT Sec 13. When horizontal reaction exceeds 13.9 kN (261 RPM in Config 4A), the clump begins pulling horizontally out of plumb, requiring increased clump mass to maintain station.

📐 2. Tool Pitch & Restoring Tilt Equilibrium

θ_tilt = arctan(H_rxn · Z_padeye / (W_tool,sub · GM_T))
Bridle Tilt Lock: θ_max ≈ 10.1° (Collinear geometric alignment)

Calculates tool pitch deflection under asymmetric lateral or fore–aft thrust, ensuring the excavator remains within safe angular limits during offshore operations.

🏔️ 3. Usable Spoil Berm & Compactness Metric

A_usable = ∫ [h_berm(x) ≥ 0.20 m] dx
Compactness Score = (1.5 · A_usable + A_berm) · H_crest · √(H_crest / W_berm)

Standard Subsea Trench Backfilling Criteria. For post-lay cable or pipeline backfilling, a tight, steep berm mound (height ≥ 0.35 m, narrow footprint) adjacent to the trench shoulder is vastly preferred over a diffuse, shallow 25 m smear. The optimisation engine weights crest steepness and usable depth of cover accordingly.

Peer-Reviewed Literature References

Citation	Publication / Reference	Governing Phenomenon Applied in SeaJet Engine
Albertson, Dai, Jensen & Rouse (1948)	ASCE Transactions 115(1), 639–664	Diffusion of submerged turbulent water jets; potential core length `s_0 = 3.85 D_0` and centerline decay.
Beltaos & Rajaratnam (1974, 1976)	J. Fluid Mech. 60(4) & J. Hydraulic Res. 14(1)	Oblique jet impingement, stagnation pressure, and forward redirection of tangential wall-jet momentum.
Poreh, Tsuei & Cermak (1967)	J. Applied Mechanics 34(4), 457–463	Investigation of turbulent radial wall jets and boundary layer shear stress decay.
Soulsby & Whitehouse (1997)	J. Hydraulic Research 35(5), 689–720	Threshold for incipient sediment motion of non-cohesive and cohesive sediment beds.
van Rhee (2010)	TU Delft Doctoral Dissertation	Fluidisation and dilatancy suction mechanics of dense sand beds under high-velocity water jets.
Mastbergen & van den Berg (2003)	Sedimentology 50(4), 625–637	Breaching and hydraulic erosion of dense sand slopes with dilatancy-controlled suction.
van Rijn (1984)	J. Hydraulic Engineering 110(10), 1431–1456	Sediment pick-up function and bed load transport under high bed shear stress.
Winterwerp & van Kesteren (2004)	Elsevier Oceanographic Series 71	Introduction to the Physics of Cohesive Sediment Dynamics; dynamic mass erosion and hydraulic tearing.

1:1 True-Scale 2D CAD Blueprint — SeaJet, Hanging Clump Weight, Two-Layer Strata & Berm

1:1 Synchronised 2D Overhead Plan View (X–Y Seabed Matrix Z(x,y), Hanging Clump Weight & Radial Plume)

Water-Column Jet Dissipation τ_b(s) vs Soil Thresholds & Parametric RPM Sweep with Clump Pull-Onset (Click Bottom Chart to Set RPM)

First-Principles Engineering Analysis — Two-Layer Stratigraphy, Hanging Clump Restraint & AP4400 Sonar Coverage

SMD Standard Thrust Reference (fixed)

Methodology & Reference Sources: How RPM → Force, Jet Dissipation & Seabed Scour Are Calculated