CAVITATION TUNNEL FACILITY DEDICATED TO THE NATION

Dr VK Aatre, SA to RM inaugurating Cavitation Tunnel FacilityDr VK Aatre, Scientific Adviser to Raksha Mantri and Secretary, DRDO, inaugurated the Cavitation Tunnel-a major Hydrodynamic Test Facility established at the Naval Science & Technological Laboratory (NSTL), Visakhapatnam, and dedicated the same to the nation on 7 November 2001. The facility created at a cost of Rs 24.17 crores, is second of its own kind being created as a part of full range hydrodynamic test facilities at NSTL.

 

NSTL has established various hydrodynamic test facilities, viz. high speed towing tank with VPMM; cavitation tunnel and LAHPMM (under installation) for carrying out model tests for surface ships and submerged bodies under controlled conditions.

The cavitation tunnel facility is equipped with various instrumentation, viz. open water propeller dynamometer (OWPD); dummy model propeller dynamometer (dummy model); towing dynamometers; and contrarotating propeller dynamometer (CRPD) for measuring parameters of various tests that can be carried out in the cavitation tunnel, such as forces, moments, pressure fluctuations, velocity distribution, noise, etc.

The facility at NSTL consists of vertical plane, closed re-circulating, variable speed, variable pressure type with automatic control system (ACS), data acquisition and analysis system (DAAS) for operation, control and conduction of tests. It also has a stand-alone acoustic measurement system (AMS) for acoustic data acquisition, analysis and extrapolation. Other features include 5.2 m long acoustic trough, 6.56: 1 contraction nozzle, aeration and de-aeration system, fine filtering system, stainless steel shell, stroboscopy and videography systems and models/dynamometers mounted on large removable test section cover. The tunnel is designed for low turbulence< 0.5 per cent) in the test section and background noise level less than 90 dB at 6m/sec flow over 1-100 kHz band.

Cavitation Tunnel Facility: Specifications

Thyristor controlled 700 KW DC electric motor driving 2.1 m dia, fixed pitch, 7 bladed axial flow impeller with 9 stator blades.

Test section : 1.0 m x 1.0 m x 6.0 m
Total impeller motor power : 700 KW
Working section max. velocity : 15.0 m/s
Pressure range (absolute) : 0.1-3.0 kgf/cm2
Min. cavitation number : 0.03+10/V2, where V indicates flow speed at test section
Tunnel background noise : 90 dB ref. lÁPa in the frequency range, 1-100 kHz, 1/3 Octave

Utility or Cavitation Tunnel Facility:

A view of test section and control room

  • Propeller tests in uniform flow to measure open water characteristics, such as thrust, torque and efficiency in cavitation as well as non-cavitation conditions,

  • Tests with hull-propeller model to measure self-propulsion characteristics behind the wake of the model in non-cavitation and cavitation modes,

  • Determination of hull-propeller interaction factors,

  • Streamline (paint flow) tests,

  • Cavitation and flow visualisation studies of submerged bodies,

  • Measurement of forces and moments on submerged and surface bodies at specified angles of attack,

  • Hydrodynamic wake studies, and

  • Study/analysis of acoustic raDIATion caused by propellers.