Hydrodynamic Test Facilities

High Speed Towing Tank (HSTT)

It is a hydrodynamic test facility recognized by International Towing Tank Conference (ITTC). The tank is fitted with a high speed towing carriage which runs at a maximum speed of 20 m/sec and runs on parallel rails which are fitted to have a tolerance of 0.2 mm over 100 m length and it follow the earth's curvature. It is fitted with a wave generator at one end to simulate random and irregular sea conditions while testing the models. It is also equipped with a model making workshop to make the scale down models of ships and submarines to carry out the model tests for determining the performance characteristics and evaluation of the power plant requirements, etc. The other features of High Speed Towing Tank (HSTT) are given below:

Tank Dimension, m  500 x 8 x 8 
Carriage Speed, m/s  Ahead 20 (max), Astern 3 (max) With accuracy of 0.1% of set speed  
Wave Generator  Dual flap type capable of generating regular and irregular waves (unidirectional) up to wave height of 0.5 m. 
Speed Control  By Ward Leonard System feeding power through current conductors to 8 in number 129 kW DC drive motors.  


The facility is equipped with a Large Amplitude Horizontal Planar Motion Mechanism (LAHPMM) for carrying out planar motion studies of manoeuvring characteristics of surface ships and submerged vehicles in surface condition.

Tests Performed in HSTT

  • Resistance and self propulsion tests to assess speed power characteristics
  • Flow visualization to identify flow separation, if any
  • Open water test to obtain propeller characteristics
  • Wake survey to determine flow velocities
  • Sea-keeping tests for head sea only
  • Dynamic tests for high speed vessels, such as, planning, multi-hulls, hydro-foil, SES, etc. Hydrodynamic performance evaluation of 7m long heavy weight torpedo with PJP through Vertical Planar Motion Mechanism (VPMM) tests

Cavitation Tunnel

The Cavitation Tunnel at NSTL is one of the most modern and the state-of-art facilities in the world. This is used for study of cavitation inception of body profile and propellers. It is also used for the study of Acoustic measurements due to cavitation of propellers

This facility can provide a water flow speed of 15 m/sec and create cavitation numbers 0.03 to 10. In order to design highly efficient propellers for applications to naval ships and platforms it is essential to carry out tests on these propeller models in the cavitation tunnel. The features of cavitation tunnel are given below:

Test Section size,  1.0 x 1.0 x 6.0 m long with an acoustic through positioned below the test section housing 8 in no. B&K hydro-phone array (PULSE) for recording noise signals generated by the raDIATing hull and propeller in the test section  
Drive System  Thyristor controlled 700 kW DC electric motor driving 2.1 m dia fixed pitch 7 bladed axial flow impeller with 9 stator blades.  
Maximum Velocity in Test Section   15 m/s
Pressure Range   10-300 kPa (absolute)  
Minimum Cavitation   0.03 + 10/v2, where v is the flow velocity in test section.  
Back ground noise   90 dB ref 1mPa in 1-100 kHz band, 1/3 Octave scale.  

The tunnel is equipped with an Automatic Control System (ACS) for its operation and control; Data Acquisition & Analysis System (DAAS) for conduct of tests, acquisition of test data, analysis and prediction of results. It is also provided with a stand alone Acoustic Measurement System (AMS) for acoustic measurements, analysis and extrapolation to full scale results. Various types of towing and propulsion dynamometers, component balances, wake rake, hydro-phones pressure transducers, photographic and video recording systems and stroboscopes are also available to conduct model tests


Tests Performed in CT

  • Propeller tests in open water to measure performance characteristics in cavitating and non-cavitating conditions
  • Tests with hull propeller model to measure self propulsion characteristics, propeller working in the wake of the model in cavitating and non-cavitating conditions. Hull propeller interaction.
  • Measurement of forces and moments on surface ships and submerged bodies including their control surfaces.
  • Determination of towing resistance of surface ships and submerged bodies
  • Cavitation tests. Inception and decay
  • Flow visualisation.
  • Wake survey.
  • Measurement of hull pressure fluctuations induced by propeller and cavitation.
  • Measurement of acoustic raDIATion caused by cavitating and non-cavitating propeller and hull.
Wind Tunnel

A wind tunnel to study the aerodynamic characteristics of surface and submerged platforms and underwater weapons has been set up at NSTL with a test section of 1.5 x 1.5 x 4 m. A maximum speed of 60 m/sec can be produced with a 125 kW fan in this wind tunnel. The detailed features are given below

Test Section size ,  1.5 x 1.5 x 4.0 m long  
Plenum Chamber   T4.3 x 4.3 x 4.0 m long  
Contraction Nozzle   Varying from 4.3m x 4.3 m square to 1.5 x 1.5 m square; 4.0 m long
Diffuser   Varying from 1.5 x 1.5 m square to 3.5 m dia; 7.8 m long  
Fan Size   3.04 m dia made of CFRP  
Drive Motor   125 kW DC motor at 750 rpm  
Maximum Speed at Test Section   60 m/s  

The Wind Tunnel is equipped with projection manometers, differential pressure transducers, velocity measuring probes, vertical catheto-meters, hot film anemometers, 48 port Scanivalve traversing gear as well as PC based data acquisition system and analysis software packages.

In order that the Indian Navy crew are battle ready at all times, they need to carry out repeated torpedo firing in quick succession. Use of real torpedo is extremely costly and therefore they need a practice torpedo which exactly simulates a real service torpedo. For this purpose NSTL designed, developed and produced a Drill and Practice torpedo equivalent to an Italian A-244S torpedo, which is in the arsenal of Indian Navy.


Tests Performed in Wind Tunnel

  • Flow visualization and boundary layer studies for underwater vehicles.
  • Pressure and velocity distribution over axi-symetric bodies
  • Estimation of forces and moments on control surfaces of a submerged body, etc.

Acoustic, Shock, Noise and Vibration Test Facilities

Measurement, study, analysis and mitigation of underwater noise generated by ships and submarines are essential requirements to have a healthy and stealthy Naval fleet. Achieving the objective of having a silent ship is possible only if the machinery and equipment fitted on these ships are also silent and their vibrations isolated. This is achieved through proper condition-monitoring of machines and design and development of shock & vibration isolation mounts of appropriate type. The ships and machinery may also be subjected to explosive shock loading due to enemy weapons in the event of a conflict. The design of these ships and equipment should be such that they will withstand such shock and still be operational.

Therefore to understand and design such systems, NSTL has setup several facilities in the field of underwater Shock, Noise and Vibration. An underwater Noise and Degaussing range are installed off Goa coast. The same are described subsequently under field facilities. A Field Shock Testing Platform, a Shock Testing Tank, a Shock Platform and a Vibration Shaker are all established at NSTL. NSTL is the shock qualifying agency for equipments to be fitted on board Naval ships.

Shock Test Facility Measurement, study, analysis and mitigation of underwater noise generated by ships and submarines are essential requirements to have a healthy and stealthy Naval Fleet. Achieving the objective of having a silent ship is possible only if the machinery and the equipment fitted on these ships are also silent and their vibrations isolated. This is achieved through proper condition-monitoring of machines and design and development of shock & vibration mounts of appropriate type. The Ships and machinery may also be subjected to explosive shock loading due to enemy weapons in the event of conflict. The design of these ships and equipment should be such that they will withstand such shock and still be operational. Therefore to understand and design such systems NSTL has set up several facilities in the field of underwater shock, noise and vibration.

Floating Shock Platform:

A field of shock testing facility using floating shock platform and mobile instrumented van for data acquisition are created by NSTL. Using the twin facilities ships main machinery such as the gas turbines, diesel alternators, etc., weighing up to 15 tons can be subjected to the desired shock levels to pass qualifying criterion before installation.

Shock Test Tank:

A double walled steel shock testing tank created at NSTL with a cross section of 15 x 12 x 10 m is capable of handling equipment weighing up to 2.5 tons and can subject them to desired shock loads. The equipment is placed inside an open floating shock barge and an underwater explosion is set off by firing a charge. The behavior of the specimen is recorded through accelerometers placed on its body. The desired shock level can be achieved by varying the quantity of charge, stand off distance and depth.

Shock Testing Machine:

A shock testing machine is also installed at Shock and Vibration centre of NSTL. This micro-processor controlled machine is capable of generating variety of shock pulses such as - half sine, square waves ranging from 2 to 40 m/sec pulse duration. It can generate acceleration of 90 g on pay loads up to 500 kg.

Vibration Shaker:

In order to study the response of equipment and machinery subjected to severe vibration levels, Vibration Excitation Platform is set up at NSTL. This platform with a load capacity of 220 kg can generate vibration in the frequency range of 1 to 5000 Hz varying 'g' values up to 10. This machine is extensively used to test the shock and vibration isolation rubber mounts and various subsystems of torpedoes and mines.


Shock and Vibration Mounts:

The shock and vibration mounts are used to reduce raDIATed noise due to vibration of various machinery and safe-guard the machinery and equipment against underwater explosion. NSTL has developed several types of mounts such as plate, angular and cylindrical types for use with gas turbine engines, reduction gears, diesel engines on board ships. The imported mounts are no longer available for replacement.

The performance of NSTL mounts are superior to those of foreign origin. They can withstand shock loads up to 6 g at the maximum weight of 1.5 tons. Vibration isolation of 20 dB and shock isolation of 15 dB were achieved with these mounts.

Condition Monitoring System:

Vibration signature analysis is an important tool in diagnosing faults on rotating machinery. NSTL has developed Microprocessor based online Condition Monitoring System exclusively for monitoring vibration levels of main propulsion gas turbines and gearing of different classes of ships meeting the Naval Standards. These systems are operational onboard front line ships of Navy.


Acoustic Test Centre:

An Acoustic Test Centre is established at NSTL for noise evaluation and qualification of various types of equipment, machinery, torpedoes, etc. The test centre consists of an Anechoic Room and a Reverberation Room.

Anechoic Room:

It is used to evaluate noise raDIATion characteristics of equipment machinery over a wide frequency range of naval interest. It is basically a room inside room type construction having 1m air gap between inner and outer walls, floor and ceiling. These inner rooms are floating on a heavy duty rubber pads. The dimensions of the inner room are 10 x 10 m and height 6.8 m. The inner walls of the inner room are lined with wedge shaped noise absorbers.

Reverberation Room:

It is used for measuring acoustic properties of material. It is also room inside room type construction having 1 m air gap all around between inner room walls and outer room. The roof height is 5.14 m. The inner room of this reverberation room also is floating or rubber pads. The walls are non parallel, the opposite walls making 5o angle with each other. The roof also makes 5o angle with the floor.

Acoustic Tank Facility:

The Acoustic Tank Facility is also established for calibration of underwater transducers in which near field and far field conditions can be simulated. The tank is of 8m x 8m x 8m size. The transducers operating at frequency of 3 kHz and above can be calibrated.

Field Test Facilities Underwater systems comprise of large number of critical components and subsystems which have to operate in the harsh sea water environment. These are subjected to extreme hydrostatic pressure conditions. It would be unwise to test these sub assemblies etc., straight away at sea as loss of such system during trials would result. Therefore some captive testing is essential in actual field conditions creating nearly the sea conditions and at the same time be capable of recovering the equipment from water even in the event of failure of the test/trial. For this purpose, NSTL created field test facilities such as Lake Test Facility at Nagarjuna Sagar, IN Ship Astravahini and Underwater Ranges off Goa.

NSTL DRDO Lake Test Facility At Nagarjuna Sagar NSTL has setup a field testing facility for testing of the underwater systems and sub assemblies. This facility is setup at Nagarjuna Sagar lake which is a large inland hydro electric reservoir and when full will be able to provide a depth of about 60 m and in the lean season a depth of around 30 m. In this vast reservoir an area of about 10-20 sq. km stretch is available to carryout the underwater testing of torpedoes and mines. The facility is equipped with a Catamaran Launch and Recovery Vessel (CTLRV) and a Gemini boat.

The CTLRV is fitted with echo sounder, a global positioning system (GPS) and with Schottelle Rudders and propellers which can be lifted off water if required.

Under Water Ranges Off Goa Coast:

The measurement of noise and its mitigation and measurement of magnetic signature, etc., are essential to maintain the healthy and stealthy fleet. Therefore all ships and submarines need to be periodically measured for their noise and magnetic signatures and after repair and refit signatures are measured once again. For this purpose underwater Noise and Degaussing Ranges are setup at Goa. The ranges consist of DG ranges for MCMV vessels and Steel Ships and a Noise Range. The Noise Range is configured with series of hydrophones embedded in the sea bottom and connected to the shore recording station through under ground/submarine cables. As ships pass over the range the noise signature is picked up and analysed. The faulty machines/structures causing excessive noise levels can be identified and recommended for repair / refit. Once these are carried out, the test is repeated to see that desired noise levels are maintained.

NSTL Range Test Centre off Goa Coast:

Excessive magnetic signatures of ship and submarines make them vulnerable for detection by enemy through ariel reconnaissance etc. Therefore a magnetic range is also set up at Goa. A series of magnetic sensors are buried in the sea floor and when a ship / submarine passes over it; it will create disturbance in the magnetic field and data is recorded at the shore station. Based on the analysis the ship is advised to degauss by passing suitable current through its degaussing coils. One or two iterations like this brings back the ships magnetic signature to the desired level.

Torpedo Engineering Centre :

For testing and assembly of high precision components like gyros, control and guidance systems, onboard computers, etc., highly dust free and controlled environmental conditions are required. The Torpedo Engineering Centre(TEC) provides these conditions and is equipped with special tools and fixtures for integration of the Torpedoes and Mines.


Electrical Propulsion Test Centre:

The major equipments of this facility are (a) 250 kW high capacity single shaft dynamometers for testing of high-speed torpedo motors, (b) 120 kW contra-rotating dynamometers for testing of present varieties propulsion motors (c) high capacity power supply, from 0-450 V, 0-1500 A DC. The facility will cater for maintenance and over-hauling of propulsion motors and storage and maintenance of propulsion batteries.


High Pressure Test Chambers:

Underwater weapons need to operate at great ambient hydrostatic pressure. Therefore to test the pressure with-standability of these weapons, pressure test chambers are essential. One such Pressure Test Chamber is of 600mm dia and 6500mm long. It can be used for testing the weapons for an external pressure corresponding to several hundred meters of water depth.

As all the major disciplines of engineering and science contribute to the development of a weapon system, several minor test facilities for carrying out different tests are also created in the Nagarjuna Sagar and a ship INS Astravahini are used for evaluation of the sub-systems of underwater weapons and the fully integrated weapons

Prototype Workshop :

Any design and development activity needs high level of internal manufacturing capabilities for producing components which are critical and complex in nature. Normally such unique items can not be manufactured by trade firms. Therefore to have an essential minimum level of capability with in, NSTL created a prototype manufacturing workshop. The workshop is equipped with general purpose machines and high precision machines including CNC machines. Using these machines the workshop produced critical components and sub assemblies for the development of underwater weapons and other hardware such as launchers, targets etc. Highly precise and reliable components/devices equipment needed for Thermal Propulsion system are also fabricated in the workshop. Some of the components developed are combustion device for thermal propulsion, rubber moulding for vibration mounts and static and dynamic 'O' rings/gaskets, recovery aids for weapons and other equipments.


Technical Information Resource Centre:

All Research and Development Organisations require the latest information in the area of its activities. The scientists constantly need to upgrade their knowledge in their respective fields to excel in their profession. For this purpose NSTL is constantly striving to equip its Technical Information Resource Centre. It is equipped with an internet facility to get the latest information and is housing 9000 volumes of technical books, 3800 bound volumes of Journals and 3000 standards in hard copy and CD-ROMs. It is also subscribing to nearly 91 different scientific and technical Journals. The library information is also available to all scientists over the NSTL Local Area Network.