TRAINING REPORT

TRAINING REPORT

NAVAL SCIENCE & TECHNOLOGICAL LABORATORY (NSTL), VISHAKAPATNAM

Submitted By:Himanshu SharmaVII SemesterRoll No. 14D.O.S.T

INTRODUCTION TO NSTL

In order to meet the requirements of Naval R&D in the field of Underwater Weapons, Warship Technology and Hydrodynamic Research, a decision was taken to set up a major Naval Systems Laboratory at Visakhapatnam. The Naval Science and Technological Laboratory (NSTL) was thus set up on 20th August 1969 in the premises of Andhra University, Visakhapatnam. In these three and half decades this laboratory has grown in strength and performance by making many unique contributions in the fields of Underwater Weapons, Warship Technology Concepts, and Experimental Hydrodynamic Research. Spread over an area of 194 acres on the west of National Highway 5 near Visakhapatnam airport, it has many work centers and facilities for high-end research activities. Keeping pace with rapid growth of technology, the laboratory has also grown manifold in terms of projects, scientific and technological infrastructure development, technical publications and talented human resources. Many products and systems have been delivered to Indian Navy and in the process NSTL has received many national awards for its technological excellence and innovations.

VISION AND MISSION NSTL has established the competence to work towards design and development of underwater weapons and associated systems and structural design of naval platforms. The vision and current mission of the laboratory are as follows:

VISIONTo be a Self Reliant Centre of Excellence in Torpedoes, underwater targets and decoys, ship fire control systems and underwater mines with competitive and cutting edge technologies Hydrodynamics with expertise for supporting indigenous design of marine vehicles and provide comprehensive model test facilities Stealth technology for Naval platforms

MISSION Design, development and evaluation leading to production of torpedoes, mines, targets, decoys, fire control systems and induction into services and also to establish test facilities for the same Establish world class Hydrodynamic test facilities for evolving design criteria through model tests for surface and sub-surface vehicles and torpedoes Develop structural design capabilities and materials for mitigation of radar, infrared, magnetic, acoustic and ELFE signatures leading to stealthier platform

Model AnalysisModels have been used from the beginning of recorded history for visualizing the structure as well as for planning the sequence of construction. In general ship models enjoyed a long and useful history dating back to early Egyptian. Working model became a common usage during the industrial revolution. Modeling of fluid mechanics phenomena started with experiments of Reynold and Froude wherein they developed the criteria for viscous and inertial effects. Structural models have been used for a long time and played a major role in structural engineering and research. In ocean engineering models are playing a major role where the data from the model are used for design or operation of the prototypeIn all fields of engineering model testing has been adopted for various reasons. Some are,1. When a problem cannot be solved by analytical method.2. To obtain empirical coefficients required for the equations predicted.3. To substantiate the results of a new analytical tool.4. To investigate failures.5. To demonstrate visually and with credibility what could happen in extreme conditions.

The Modeling ProcessA successful model study is one that is characterized by careful planning of many diverse steps and stages that goes into modeling process. An experimental study itself is an engineering project and just as in any project logical and careful sequencing is absolutely essential.The following sequence can be employed.1. Define the scope of the problem. Decide what is expected from the model and what is not.2. Decide the required level of reliability or accuracy. 3. Specify similitude requirement for geometry, material, loading and extrapolation of results. Particular attention must be paid to those similitudes which cannot be quantified. For hydrodynamic tests these facts need special attention as dynamic similarity cannot be met completely.4. Decide for the scale factor.5. Select model material. Good workable material should be given due importance, provided it satisfies other similitude requirements.6. Fabricate the models with the help of technicians.7. Test facilities in the case of hydrodynamic testing and loading equipment for structural model tests are both important aspects which influence the selection of scale factor and model tests as a whole.8. Instrumentation is an area where adequate attention should be given. Based on the reliability requirement and the scope of the programme, instrumentation should be planned. In some cases instrumentation has to be installed during the fabrication of the model. 9. Observing model during the tests can reveal many interesting facts which may escape the attention otherwise. Physical model study which has the capability of integrating different natural effects is capable of providing more insight than what is possible in a mathematical tool.10. Analysis of data and preparation of report should receive equal attention. All efforts that go into a model test are useless if the data collected is not analyzed and presented in a comprehensible form. The PC- based data acquisition system can be programmed to provide the results in the required format. Graphical representations of results are easy to understand.

Technical facilitiesIn order to carry out in-house research and support the indigenous efforts in shipbuilding and underwater weapon and platform development programmes of the Navy, NSTL has set up the following test facilities1) High Speed Towing Tank (HSTT)2) Cavitation Tunnel (CT)3) Wind Tunnel (WT)4) Vertical Planar Motion Mechanism (VPMM)5) Large Amplitude Horizontal Planar Motion Mechanism (LAHPMM)

1) 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 mmover100 m length and it follow the earths 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:

a) Tank Dimension, m 500 x 8 x 8

b) Carriage Speed, m/sAhead 20 (max)Astern 3 (max)With accuracy of 0.1% of set speed

c) Wave GeneratorDual flap type capable of generating regular and irregular waves (unidirectional) up to wave height of 0.5 m.

d) Speed ControlBy Ward Leonard System feeding powerthrough currentconductors 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 HSTT1. Resistance and self propulsion tests to assess speed power characteristics2. Flow visualization to identify flow separation, if any3. Open water test to obtain propeller characteristics4. Wake survey to determine flow velocities5. Sea-keeping tests for head sea only6. 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.

Testing of foil catamaran in high speed towing tank

2) Cavitation TunnelThe Cavitation Tunnel at NSTL is one of the most modern and the state-of-artfacilities 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:

a) Test Section size1.0 x 1.0x 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

b) Drive SystemThyristor controlled 700 kW DC electric motor driving 2.1 m diameter fixed pitch 7 bladed axial flow impeller with 9 stator blades.

c) Maximum Velocity in Test Section 15m/s

d) Pressure Range 10-300 kPa (absolute)

e) Minimum Cavitation 0.03 + 10/v2, where v is the flow velocity in test section.

f) Back ground noise< 90 dB ref 1mPa in 1-100 kHz band, 1/3 Octavescale.

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 andpropulsion 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 CT1. Propeller tests in open water to measure performance characteristics in cavitating and non-cavitating conditions. 2. Tests with hull propeller model to measure self propulsion characteristics, propeller working in the wake of the model incavitating and non-cavitating conditions. Hull propeller interaction. 3. Measurement of forces and moments on surface ships and submerged bodies including their control surfaces. 4. Determination of towing resistance of surface ships and submerged bodies. 5. Cavitation tests. Inception and decay. 6. Flow visualisation. 7. Wake survey. 8. Measurement of hull pressure fluctuations induced by propeller and cavitation.9. Measurement of acoustic radiation caused by cavitating and non-cavitating propeller and hull.

Test Section of cavitation Tunnel Cavitation of Torpedo Nose Cone

Tip Vortex Cavitation Testing of contrarotating propeller 3) Wind TunnelA 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 kWfan in this wind tunnel. The detailed features are given below:a) Test Section size1.5 x 1.5 x 4.0 m long

b) Plenum Chamber4.3 x 4.3 x 4.0 m long

c) Contraction NozzleVarying from 4.3m x 4.3 m square to 1.5 x 1.5 m square; 4.0 m long

d) Diffuser Varying from 1.5 x 1.5 m square to 3.5 m diameter; 7.8 m long

e) Fan Size 3.04 m diameter made of CFRP

f) Drive Motor125 kW DC motor at 750 rpm

g) Maximum Speed at Test Section60 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.

Tests Performed in Wind Tunnel 1. Flow visualization and boundary layer studies for underwater vehicles.2. Wake survey and velocity distribution behind a body for propulsor development3. Pressure and velocity distribution over axi-symetric bodies4. Estimation of forces and moments on control surfaces of a submerged body, etc.

Wind tunnel at NSTLWake measurements

Propulsion test for pump jet Aerofoil section in wind tunnelPlanar Motion Mechanism Systems4) Vertical Planar Motion MechanismThe VPMM is used for determining the hydrodynamic coefficients required for prediction of stability and control characteristics of submerged bodies by testing the model in vertical plane. Following are the main components of the VPMM system1. Model Support and Positioning Equipment, consisting of a tilt table, support frame and a pair of towing struts2. Forced Motion Mechanism, mounted on the tilt table. It provides motions with variable amplitude and frequency to the model to undertake dynamic tests3. Forced Rolling Mechanism, produces rolling oscillations to the model about its longitudinal axis4. The motion characteristics of the VPMM in HSTT are as follows:i. Tilt table range: +- 20 deg with 1 deg intervalii. Heave amplitude: 0 to 50 mm Pitch: +- 1.3 deg Roll: +- 2 deg Five discrete frequency for dynamic motion: 0.2 - 0.7 Hziii. Phase angle adjustment: 0 to 360 degiv. Strut spacing adjustment: 1.3 m to 2.3 m

5. Dynamometry includes modular force gauges, roll gauge, rudder torque gauge, model propulsion system, etc.6. Control Equipment and Data Acquisition System, located on board carriage are used for setting the test parameters, remote control of model and data logging

Testing of submerged body model using VPMM5) Large Amplitude Planar Motion MechanismThe equipment is used for study of maneuvering and control effectiveness of surface ship models by determining the complete set of hydrodynamic coefficients essential for formulation of mathematical models of ship motion and to carry out computer simulation of trajectories of the vessels for a wide variety of maneuvers of practical interest. The equipment comprises of the following~ 1. Integrated Towing System, capable of towing 4-7 m long models up to 3000 kg displacement and up to a speed of 3.5 m/sec for 7 m long and 7 m/sec for 4 m long models2. Heel & Roll Mechanism, allows model to be free in heel and roll during test and impartrolling motion as required3. Model Tracking System, consisting of 5 video cameras for on-line recording and displayof 6 motions and course of the model in calm waters and in waves4. Drift Angle Apparatus, to set drift angle upto:t 30 deg at 2 deg intervals e) Sway Apparatus, capable of producing sway amplitude from 0 to 1000 mm 5. Frequency Setting Apparatus, for imparting oscillatory motion of 0.01 - 0.3 Hz to the model6. Yaw Apparatus

7. Rudder Angle Apparatus, for setting rudder angle of:t 45 degrees at increment of 2 degrees8. Control System, all apparatus are controlled by servo motors through power amplifiers containing overload and control switches9. Dynamometry, includes force gauges, model propulsion system and rudder gauges and actuators10. PC based Data Acquisition & Analysis System, includes 20 channel conditioning units foracquiring and processing signals from sensors, all acquisition and on - line / off-line analysis programs

Tests Performed with PMM Systems1. Resistance and self propulsion tests2. Static tests, in vertical plane for submerged bodies using VPMM and in horizontal plane for surface ships using LAHPMM, for estimating forces and moments at different angles of attack drift3. Dynamic tests, in vertical plane using VPMM for submerged models, such as pure pitching, pure rolling, and pure heaving and in horizontal plane using LAHPMM4. Maneuvering tests for high speed crafts subjected to large roll / heel during turning.

Testing of Surface ship model using LAHPMMTypes of Tests

Resistance testResistance experiments are carried out with ship models to determine the resistance of the model and thereby of the ship in a given condition. Such experiments are useful in optimizing the hull form and for predicting the power requirements of ship at a specific speed.

Open Water ExperimentsThe open water experiment is to determine the open water characteristics of a propeller. A geometrically similar model is made of the propeller, the size of the model being governed by the size of the ship model if it is intended to be used to use the model for ship self-propulsion tests also. If only open water tests are to be carried out, when generating propeller methodical series for example, the model propeller is made somewhat larger, its size depending on the capacity of propeller dynamometer available. A major concern is that flow should be sufficiently turbulent. It can be facilitated by:=> making the propeller sufficiently large=>by giving a highly polished propeller surfaceWhen sufficient turbulence (3.2x105 at 0.7R) is not attained turbulence needs to be artificially stimulated by roughening the leading edges of the blades.

The propeller dynamometer measures the thrust and torque of the propeller. The propeller shaft extends a sufficient length from the boat to ensure that the flow around the propeller is not disturbed by the boat. A fairing cap is provided at the forward end of the propeller boss. The open water boat is ballasted so that the propeller shaft is horizontal and its depth below the water surface at least equal to the model propeller diameter.

The open water experiment is conducted by towing the open water boat at a steady speed while running the propeller at a constant revolution rate. The speed of the boat (i.e. speed of advance VA), and the revolution rate n, thrust T and torque Q of the propeller are measured in each run. The speed of advance is varied in steps from zero to the value at which the propeller thrust just becomes negative. The measured thrust and torque are corrected for the idle thrust and torque measured by a dynamometer when the experiment is carried out with a dummy boss of equal weight replacing the propeller.

The open water characteristics of model propeller can be easily calculated from the measured values of VA and n, and corrected values of T and Q. The open water characteristics of the ship propeller will be slightly different because of the difference in Reynolds numbers of the model propeller and ship propeller.

Self Propulsion TestsSelf propulsion experiments are used to determine the performance of the ship hull and propeller taken together. Self propulsion experiments gives:

Delivered power at a given speed of the ship The revolution rate of the ship propeller at a given speed of the ship Wake fraction Thrust deduction fraction Relative rotative efficiency

For a self propulsion test model propeller is fitted in its correct position at the stern of the ship and connected to a propeller dynamometer for measuring the thrust and torque of the propeller at various revolution rates. The ship model should be fitted with all the appendages as possible, particularly those lying in the propeller slipstream, e.g. a rudder. The ship model is fitted to a resistance dynamometer, which in this test measures the force required to make the ship model move at a constant speed with the propeller running. The ship model is accurately ballasted so that it floats at the correct waterline. The model is then towed at steady speed with the propeller running at constant revolution rate, and the thrust and torque of the propeller and the force applied to the ship model through the resistance dynamometer are applied.

HYDROFOIL Hydrofoil craft uses hydrodynamic lift generated by the wings. Surface piercing foils has good stability and submerged hydrofoil with ride control system has good sea keeping qualities can be employed as fast attack craft and transport vessel.Salient features: High Speed power ratio Wide operating range Good maneuvering High endurance, low speed Loss in waves, good sea worthiness

SURFACE EFFECT CATAMARANThis is an advanced hybrid marine vehicle which reduces drag using aerostatic lift, aerodynamic lift and hydrodynamic lift can be used for river and shallow water transportationSalient features: High Speed power ratio Wide operating range Large deck area High stability Large carrying capacity Good stealth features

Foil CatamaranFoil craft is a high hybrid hull from combining features of catamaran, hydrofoil & planning vessels may be used for military and civilian applicationsSalient features: High Speed power ratio High stability Good sea keeping performance Good stealth features Low speed loss in waves

Super Cavitating PropellersPropulsor for high-speed vehicles where subcavitating propellers fail to develop thrust without loss of efficiency and damage of propellerD=250mmRpm 1500Cavitation number 0.3 >60%Speed: > 40KnotsSalient features: Very high-speed cavitation beyond 40 knots Performance under intense cavitating conditions No failure to generate thrust & damage of propeller due to cavitation High efficiency

SURFACE CAVITATING PROPELLERPropeller for high speed vehicles working under partially submerged conditions with ventilated blades and no cavitation and damage of propellerDiameter =250mmRpm 1800No. of blades 4 >60%Speed: > 40KnotsBlade area ratio 0.65Salient features: High efficiency Performance under partially submerged condition with ventilated blades No damage of propellers High-speed application beyond 40 knots

PUMPJET PROPULSORUltra quiet modern propulsor for submarine & torpedo applications with excellent cavitation and stealth featuresSpecifications:Diameter =392mmRpm 1800No. of blades on rotor 17No. of blades on stator 27 80%Speed: 50KnotsPower 310KwSalient features: Very high-speed applications up to 80knots High cavitation inception speeds Nominal wake & turbulence left in slipstream Very high efficiency

Major areas of work at NSTL

Center of excellence for underwater weapon technologies and associated systems. Design, Development, Testing, Evaluation and Leadingto production oftorpedoes, mines,decoys, targets, simulators and launchers. Activities on Warship Technology, Stealth Technology and Hydro-dynamic research services. Development of Materials for Marine Applications. Fleet support activities like Evaluation of machinery for their specified shock resistance, online vibration monitoring and Noise and Magnetic ranging& analysis.