NMX‑LCT‑30 / Rev 00 / naval hydrodynamics & research / circuit · test section · acoustics 2026 · Product Page

NMX-LCT-30 · ENGINEERED TO ORDER — LARGE CAVITATION TUNNEL FACILITIES

Make the water boil on demand. Then watch. Then listen.

Name: Large Cavitation Tunnel Facility
Brand: Neometrix

A fast blade drops the local pressure until water boils cold — cavitation: bubbles whose collapse erodes bronze, breaks down thrust, hammers hulls and broadcasts noise. It obeys the cavitation number σ — so a model at natural pressure runs at the wrong σ and lies politely. The variable-pressure tunnel's trick: lower the pressure until model-scale water boils exactly where full-scale water would. A closed vertical loop — impeller deep, windowed test section high, honeycombs and contraction making the flow glass-smooth — with the vacuum plant setting σ, the degassing plant controlling the nuclei, dynamometry reading thrust and torque, high-speed imaging at the windows and hydrophones listening in a tunnel built quiet. A facility of this class has been quoted against a naval research establishment's large cavitation tunnel facility requirement; no delivered cavitation tunnel is claimed — the class is engineered to order.

Enquire — cavitation tunnels Capability sheet (PDF)

Illustrative of the class — a large vertical closed-circuit water tunnel in a tall clean research hall: a massive fresh light-grey steel flow circuit two storeys high with external ring stiffeners, a long horizontal upper leg carrying the test section with a row of thick circular observation windows, sweeping large-radius corner elbows, heavy support columns, steel access stairs and walkway platforms with fresh yellow railings, clean light floor with a yellow line, no people and no readable markings

Fig · 01 The great loop — test section high in the light, impeller deep where static head keeps its own blades honest

Principle

match σpressure scaled, not just speed

Flow

surveyed uniformhoneycombs · screens · contraction

Watch

high-speed imaginginception to breakdown

Listen

radiated noisequiet-tunnel design

Status

engineered to orderquoted facility class

ISO 9001 / 14001 Engineered to order Facility-class delivery Naval & marine test franchise Noida · India

Overview

Where propellers meet their physics.

Every fast propeller, hydrofoil, rudder and appendage lives with cavitation — and pays for it in eroded bronze, lost thrust, hammered hulls and broadcast noise. The tunnel is where designers see it, measure it and hear it before the ship exists.

Illustrative of the class — close view of a water tunnel test section in a clean research hall: a thick polished circular acrylic observation window in a fresh light-grey steel section, through the window a bronze five-bladed model propeller on a slender polished dynamometer shaft in clear still water, outside the window two professional cameras and a strobe head on dark tripods angled away, neat black cables along the platform, no people and no readable markings

Fig · 02 The window seat — a model propeller, glass-smooth inflow, and the cameras that catch the first bubble

The physics is unforgiving of shortcuts. Cavitation obeys the cavitation number σ = (p − p_v) / (½ρV²) — the margin between local pressure and vapour pressure, scaled by dynamic pressure. Run a model at full atmospheric pressure and the margin is far too generous: the wrong σ, a polite lie. The variable-pressure tunnel exists to remove the lie — its vacuum plant lowers the pressure until model-scale water boils exactly where full-scale water would, and the model starts telling the truth.

The loop is engineered honesty. A lightly loaded axial impeller sits deep in the vertical circuit, where static head suppresses its own cavitation; turning vanes steer the corners; honeycombs and screens erase swirl and turbulence; a contraction accelerates the flow glass-smooth into a windowed, surveyed test section; a diffuser recovers pressure back to the impeller. And the water itself is metrology: inception depends on the nuclei the water carries, so the degassing plant controls dissolved air and water quality is logged with every test.

What runs, runs as it will serve. Model propellers turn on drive-and-dynamometer shafts reading thrust, torque and RPM; hydrofoils, rudders, appendages and pump internals mount in the same surveyed flow; and because a ship's propeller works in the hull's wake rather than open water, wake screens and dummy-hull simulations stand upstream when the behind condition is the question.

A facility of this class has been quoted against a naval research establishment's large cavitation tunnel facility requirement — design, development, supply, commissioning and training as one scope. No delivered cavitation tunnel is claimed: the class is engineered to order, and the record is stated as it stands.

Scaled

The right σ, on demand

Vacuum sets the pressure, the impeller sets the speed — cavitation made to happen exactly where it would at sea.

Surveyed

The tunnel is an instrument

Flow uniformity surveyed, dynamometers calibrated under load, water quality logged with every run.

Quiet

Built silent, to listen

Low-noise impeller, resilient mounts, acoustic isolation — hydrophones are only as honest as the tunnel is quiet.

Architecture

Fill, set σ, run, record.

The schematic follows the test — the water degassed and logged, the cavitation number set, the model run in a surveyed flow, the phenomena watched and heard — and the machine underneath: the circuit and its impeller, the test section and windows, the vacuum and degassing plant, the dynamometry and acoustics.

FIG · 03CAVITATION TUNNEL ARCHITECTURE · CIRCUIT + IMPELLER / TEST SECTION + WINDOWS / VACUUM + DEGASSING / DYNAMOMETRY + ACOUSTICS

Fig · 03 A propeller proven before the ship exists

Arc · 01

Circuit & Impeller

A vertical loop whose geometry is free pressure control — section high, lightly loaded impeller deep, vanes and diffuser shaped for silence.

Arc · 02

Test Section & Windows

Honeycombs, screens and a contraction deliver glass-smooth surveyed flow to a section with serious optical access.

Arc · 03

Vacuum & Degassing

σ on demand; nuclei as metrology — pressure set by plant, air content controlled, water quality on the record.

Arc · 04

Dynamometry & Acoustics

Thrust, torque, pressure pulses and radiated noise — instruments on isolated mounts in a tunnel built quiet.

Planning a hydrodynamic research facility? Send the test envelope, model sizes and measurement scope — a clause-by-clause compliance matrix within two working days · [email protected]

Send tender spec

Specifications

Reference facilities, built to the programme.

The parameters below describe reference facilities. Section size, speed and pressure envelopes, drive power and instrumentation depth all follow from three givens: the model scales the programme runs, the phenomena it must resolve, and the acoustic floor its measurements need.

Illustrative of the class — the machinery floor of a water tunnel facility in a clean plant room: the lower leg of a large fresh-grey flow circuit with a bulged axial impeller housing, a big electric drive motor coupled on a machined baseplate, a vacuum pump skid and a vertical stainless degassing vessel with tidy bright pipework and valves, small dark unreadable gauges, freshly painted pale-grey walls and a clean sealed light floor, no people and no readable markings

Fig · 04 The quiet machinery — a lightly loaded impeller, and the vacuum and degassing plant that make σ and nuclei obey

Where cavitation testing goes wrong

Testing at natural pressure — the wrong σ; the model lies politely. Air content uncontrolled — inception wanders day to day, and designs get slandered or flattered by the water they happened to meet. The tunnel's own turbulence — a dirty inflow masking the phenomena it should reveal. Blockage ignored — a model too big for the section, measuring the tunnel instead of the design. Open-water numbers only — no wake simulation, no service truth. The tunnel's own noise — impeller and vane cavitation contaminating the very acoustics the facility exists to measure. Dynamometers calibrated at standstill — thrust trusted at RPM it was never proven at. Windows fouled — imaging through a lie. And records without water quality — results that cannot be compared across days, let alone across a class's life.

So the discipline runs the other way. The empty section is surveyed before any model sees it; the impeller is sized generously and loaded lightly; σ comes from a calibrated pressure chain; nuclei are controlled and logged as first-class data; blockage and wake simulation are engineered per model, not improvised; dynamometers are calibrated under load and speed; the acoustic floor is proven with the tunnel running clean; and every run leaves with σ, speeds, water quality, imagery and spectra filed together — which is what lets a research programme compare a propeller tested this year with one tested a decade from now.

Full specification — expand

System	Large cavitation tunnel facility — variable-pressure closed-circuit water tunnel with test section, vacuum & degassing plant, dynamometry, imaging & acoustics
Governing Idea	Match σ, not the speed — σ = (p − p_v) / (½ρV²); a model at natural pressure runs at the wrong number and lies politely
The Circuit	Closed vertical loop — test section high, lightly loaded axial impeller deep (static head suppresses its own cavitation), turning vanes, diffuser
Flow Quality	Honeycombs, screens, contraction — swirl and turbulence erased; the empty section surveyed before any model runs
Pressure & σ	Vacuum & pressurisation plant sets the cavitation number on demand, on a calibrated pressure chain
Water as Metrology	Degassing is not a utility — inception depends on nuclei; air content controlled, water quality logged with every test
What Runs	Model propellers on drive-and-dynamometer shafts; hydrofoils, rudders, appendages; pump & valve internals; wake screens / dummy-hull simulation for the behind condition
Inception	The σ at which each phenomenon appears — tip vortex, sheet, bubble, hub vortex — found by eye and by ear
Observation	Stroboscopic & high-speed imaging through serious optical access; developed cavitation recorded to standard
Performance	Thrust breakdown curves as σ falls; pressure pulses on a plate above the model — the hull-vibration source measured directly
Acoustics	Radiated noise on hydrophones — quiet-tunnel engineering (low-noise impeller, resilient mounts, isolation) proven as an acoustic floor
Erosion	Soft-paint & stencil techniques over sustained runs — collapse sites mapped, designs ranked before bronze is cut
The Facility	Multi-storey civil integration — foundations, vibration isolation, model workshops, handling cranes, control room, water treatment — one engineered whole with commissioning and training
The Split	The site's marine propulsion shafting & stern gear carries the propeller's thrust into the hull; this facility proves the propeller's design before the ship exists — different machine, one naval franchise
Scope Boundary	Ours: circuit, vanes, honeycombs, contraction, test section & diffuser, impeller & drive, vacuum/pressurisation & degassing plant, water treatment, windows & optical access, dynamometry integration, wake-simulation hardware, imaging & acoustic instrumentation integration, control & DAQ, isolation & civil-interface engineering, installation, commissioning, documentation, training, spares & AMC — including build to the establishment's specification. Bought-in certified: drive motors & VFDs, vacuum pumps, dynamometers, hydrophones, cameras, DAQ. The customer's: the models, the designs under test, the research programme
Status	Engineered to order — a facility of this class quoted against a naval research establishment's large cavitation tunnel facility requirement; no delivered cavitation tunnel is claimed

PDF · 1 page

Large Cavitation Tunnel Facility — Capability Sheet

Tender Response

Send test envelope, model scales & measurement scope — compliance matrix in two working days

Variants

One physics, four facilities.

What changes is the scale of the loop, the depth of the instrumentation, and whether the tunnel is new or an honest upgrade of one already running.

Var · 01

Large Research Tunnels

Multi-storey vertical loops, variable pressure, quiet-tunnel acoustics — the national-laboratory class, delivered with training.

Var · 02

Medium & University Tunnels

Teaching and industrial research scales — pump, turbine and valve cavitation, hydrofoil studies, compact circuits.

Var · 03

Instrumentation & Retrofit

Dynamometry, imaging, acoustics and degassing onto existing tunnels — the loop is steel; the honesty is instruments.

Var · 04

Models, Wake Simulation & AMC

Wake screens, dummy-hull hardware, calibration regimes, spares, training and support for the facility's working life.

Applications

Wherever water meets a fast blade.

The laboratories that research, and the programmes that sail on the answer.

A · 01Naval research establishments

A · 02Propeller design & qualification programmes

A · 03Shipyards & propulsion integrators

A · 04Pump, turbine & valve manufacturers

A · 05Universities & hydrodynamic laboratories

A · 06Underwater-vehicle developers

FAQ

Common questions.

Plain-language answers from the engineering team.

Q · 01 What is cavitation, and why does it deserve a building?

Water boils at 100 °C only at atmospheric pressure — drop the pressure far enough and it boils cold. A fast blade section does exactly that: the suction side accelerates the flow, local pressure falls below vapour pressure, and vapour cavities appear on the blade. The damage comes when they leave: swept into higher pressure, each bubble collapses in microseconds, focusing energy into a micro-jet that strikes like a hammer. Repeated billions of times, that pits and eats solid bronze — erosion. Grown large, the cavities blanket the blade and thrust falls off a cliff — breakdown. Pulsing rhythmically under the stern, they hammer the hull plating above — the classic source of stern vibration. And collapsing violently, they broadcast broadband noise into the sea — which research navies care about deeply, and which is measured, not guessed, in a facility built quiet enough to hear it. One phenomenon, four expensive consequences — and every one of them is design-dependent: blade sections, skew, tip loading, clearances. That is why serious maritime nations build cavitation tunnels: the propeller is the last thing you want to redesign after the ship is afloat, and the tunnel is where its physics surrenders in advance.

Q · 02 Why must the pressure be variable — what does σ matching mean?

Because cavitation does not care about speed alone — it cares about the ratio of pressure margin to dynamic pressure: σ = (p − p_v) / (½ρV²). At sea, a propeller runs metres below the surface at full-scale speed; its σ is set by depth and ship speed. A model in a laboratory runs smaller and slower — and if the tunnel sits at natural atmospheric pressure, the numerator is far too large for the reduced denominator: the model's σ is several times the ship's, cavitation politely refuses to appear, and the design looks better than it is. The classical answer is beautiful: pull the tunnel's pressure down with the vacuum plant until the model's σ equals the full-scale value, and model-scale water boils exactly where full-scale water would. The same plant also runs the other way — pressurising to suppress cavitation when a clean baseline is wanted. That is the whole reason these facilities exist as a class distinct from ordinary flow loops: speed control gives you Reynolds discipline; pressure control gives you cavitation truth. A tunnel that cannot vary its pressure can measure a propeller's efficiency, but it can never honestly answer the questions cavitation asks.

Q · 03 Why is the loop vertical, and what makes the flow trustworthy?

Because geometry is free pressure control. In a vertical loop the test section rides high and the impeller sits deep — and the water column between them is a permanent, silent gift of static head. At the impeller, metres down, pressure is highest exactly where the machine's own blades work hardest — so a lightly loaded, generously sized axial impeller can drive the circuit for years without cavitating itself; at the test section, metres up, pressure is lowest exactly where the vacuum plant wants leverage. Around the loop, every component serves flow honesty: turning vanes carry the water round the corners without separation; in the settling length, honeycombs straighten it and screens shred its turbulence; then the contraction does the beautiful trick every wind-tunnel engineer knows — accelerating the flow squeezes the same disturbances into a smaller fraction of a faster stream, delivering glass-smooth water to the model. The diffuser downstream recovers pressure gently so the impeller's job stays light. And none of it is taken on faith: the empty section is surveyed — velocity uniformity, turbulence intensity, pressure distribution — before any model is believed, and re-surveyed through the facility's life, because the tunnel is an instrument and instruments get calibrated.

Q · 04 Why does the water itself need a plant — what are nuclei?

Because perfectly clean water is astonishingly reluctant to boil. Cavitation does not start from nothing — it starts from nuclei: microscopic bubbles and gas pockets that act as seeds. Water rich in dissolved and free air cavitates early and enthusiastically; water stripped of its gas holds on far past the textbook σ. Which means the same propeller, in the same tunnel, at the same σ, can test differently on Tuesday and Thursday if the water changed in between — the design slandered by gassy water or flattered by degassed water, with nobody lying except the loop itself. So the water is treated as an instrument. The degassing plant — vacuum towers and circulation — pulls dissolved air down to a controlled level; time under vacuum sweeps free bubbles out; and air content is measured and logged with every test, a first-class data channel beside σ and RPM, so results can be compared across days, programmes and decades. This is the same discipline the site's fluid pages preach — on the metalworking rig it is concentration verified by refractometer; here it is nuclei governed by plant — the hidden variable made visible, so the article gets judged instead of the water.

Q · 05 What does the facility actually measure, run by run?

Four families, one file. Inception: hold speed, walk the pressure down, and record the σ at which each phenomenon first appears — the tip-vortex thread, sheet cavitation spreading from the leading edge, travelling bubbles, the hub vortex — caught by eye at the windows, by stroboscope frozen blade-by-blade, and by ear, because the hydrophones hear inception before the cameras see it. Performance: the dynamometer in the model's drive line reads thrust and torque against RPM while σ falls, tracing the breakdown curve — the exact price, in percent, that cavitation charges. Pulses: pressure transducers in a plate above the model measure the rhythmic hammering a hull would feel, the number a stern-vibration engineer needs years before any stern exists. Acoustics: hydrophones in a facility engineered quiet — low-noise impeller, resilient mounts, isolation — record radiated noise spectra against σ, with the tunnel's own acoustic floor proven so the measurement belongs to the model. Around all four: high-speed video for the analysts, soft-paint erosion mapping over sustained runs, and a record carrying σ, speeds, water quality, imagery and spectra together — because a research programme's real asset is comparability across its whole life.

Q · 06 What do you build, what is bought in — and what is claimed?

Divided honestly. What Neometrix provides: the facility — the circuit with its shell, turning vanes, honeycombs, screens, contraction, test section and diffuser; the impeller and its drive; the vacuum, pressurisation and degassing plant with water treatment; the windows and optical access; the model drive and dynamometry integration; wake-simulation hardware; the imaging and acoustic instrumentation integration on isolated mounts; control and DAQ; the vibration- and acoustic-isolation engineering and the civil interfaces of a multi-storey installation; and installation, commissioning, documentation, training, spares and AMC — the requirement's own scope words, design to training, as one party. What is bought-in certified: drive motors and VFDs, vacuum pumps, dynamometer and hydrophone instruments, cameras and DAQ hardware — proprietary instruments of established makers, integrated rather than imitated. What is the customer's: the models, the designs under test, and the research programme built on the results. And the record, stated plainly: a facility of this class has been quoted against a naval research establishment's large cavitation tunnel facility requirement. No delivered cavitation tunnel is claimed; the class is engineered to order, loop by loop, around the programme it must serve.

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The projects desk replies within two working days with a clause-by-clause compliance matrix and a budgetary quotation. Write to [email protected] or use the form.

Enquire — cavitation tunnels Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 ENGINEERED TO ORDER — LARGE CAVITATION TUNNEL FACILITIES MATCH σ · THE TUNNEL IS AN INSTRUMENT · WATCH, THEN LISTEN ENGINEERED IN NOIDA · INDIA

Make the water boil on demand. Then watch. Then listen.

Where propellers meet their physics.

The right σ, on demand

The tunnel is an instrument

Built silent, to listen

Fill, set σ, run, record.

Circuit & Impeller

Test Section & Windows

Vacuum & Degassing

Dynamometry & Acoustics

Reference facilities, built to the programme.

Where cavitation testing goes wrong

One physics, four facilities.

Large Research Tunnels

Medium & University Tunnels

Instrumentation & Retrofit

Models, Wake Simulation & AMC

Wherever water meets a fast blade.

Common questions.

The naval family from Neometrix.

Marine Propulsion Shafting & Stern Gear

Shipboard Helicopter Traversing & Handling System

Shock Qualification & Shock Test Machines

Send the test envelope
and the model scales.

Similar Products

Share This Page

Make the water boil on demand. Then watch. Then listen.

Where propellers meet their physics.

The right σ, on demand

The tunnel is an instrument

Built silent, to listen

Fill, set σ, run, record.

Circuit & Impeller

Test Section & Windows

Vacuum & Degassing

Dynamometry & Acoustics

Reference facilities, built to the programme.

Where cavitation testing goes wrong

One physics, four facilities.

Large Research Tunnels

Medium & University Tunnels

Instrumentation & Retrofit

Models, Wake Simulation & AMC

Wherever water meets a fast blade.

Common questions.

The naval family from Neometrix.

Marine Propulsion Shafting & Stern Gear

Shipboard Helicopter Traversing & Handling System

Shock Qualification & Shock Test Machines

Send the test envelopeand the model scales.

Similar Products

Share This Page

Send the test envelope
and the model scales.