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Kareem Khan

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I am working as experimental hydrodynamist at Naval Science and Technological laboratory, Visakhapatnam, India. I am a Naval Architect by educational qualification.

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Papers by Kareem Khan

Measurements of steady manoeuvring forces and moments over an axisymmetric body with appendages in a wind tunnel

Ship Technology Research, Dec 27, 2023

Measurements of steady manoeuvring forces and moments over an axisymmetric body with appendages in a wind tunnel

Steady manoeuvring forces and moments over a generic submarine hull form (SUBOFF) at various angl... more Steady manoeuvring forces and moments over a generic submarine hull form (SUBOFF) at various angles of incidence were investigated through scaled model tests in the Wind Tunnel Facility at the Naval Science and Technological Laboratory, India. Measurements were performed for a range of angles of incidence in angle of attack (±18°) and drift (±18°) including control surface deflections (±15°) on a 1.372 m model at Reynolds number 1.7 × 10 6. The present study at angles of incidence is to gather steady-state force, and moment data and validate such load measurements performed in a Wind Tunnel. The particulars of the SUBOFF model, experimental facility and measurement technique, test results for load measurements and estimated hydrodynamic coefficients are highlighted in the paper. The measurement data generated from the above studies will complement the current research on hydrodynamic characteristics for submerged bodies both computationally and experimentally.

Steady velocity measurements in the stern wake of submarine hull form at high angles of incidence

Ocean Engineering , 2023

Velocity distribution in the stern region over a generic submarine hull form (SUBOFF) at high ang... more Velocity distribution in the stern region over a generic submarine hull form (SUBOFF) at high angles of incidence was investigated through steady velocity measurements in the Wind Tunnel Facility at Naval Science & Technological Laboratory, India. Velocity measurements were performed for a range of angles of incidence in angle of attack (+8 • to-40 •) and drift (0 •-28 •) on 1.372 m model at Reynolds number 1.7 × 10 6. The present study for high angles of incidence is to depict a submarine motion during extreme manoeuvers in case of emergency situations. The particulars of the SUBOFF model, experimental facility and measurement technique, test results for axial, tangential and radial velocity measurements, non-uniformity and circumferential mean velocity, derived quantities for vorticity and circulation are highlighted in the paper. The velocity measurements data generated from the above studies will greatly complement the current research on turbulent flows over submerged bodies both computationally and experimentally.

Design optimization of an AUV for performing depth control maneuver

Ocean Engineering

Manoeuvring Simulations of Autonomous Underwater Vehicle using Quaternion

Defecse Science Journal, 2022

The dynamics of an AUV, which can perform manoeuvres with pitch angles in the range of 90° is inv... more The dynamics of an AUV, which can perform manoeuvres with pitch angles in the range of 90° is investigated in this paper. The purpose of the AUV is to perform a station-keeping manoeuvre at about 90° pitch angle by varying propeller revolution. The AUV is launched in horizontal orientation. Quaternion mathematics, 4 quadrant propeller open water characteristics, and PID controller for propeller revolution are incorporated in manoeuvring mathematical model for this purpose. A procedure for optimizing the gain coefficients for the PID controller is developed using the 7 DoF manoeuvring mathematical model. Two design configurations of the AUV are investigated, positively buoyant and negatively buoyant. The design objective is, the AUV shall travel as far away as possible from the parent vehicle using minimum energy and time. It is shown that both the optimal gain coefficients for the PID controller for propeller revolution and the dynamic response of the AUV is different for each design configuration. The methodology developed in the paper can be used in the design and propeller revolution control system for certain categories of AUVs. The study shows that prime mover torque/ shaft revolution and 7 DoF manoeuvring mathematical model are important in predicting the attitude and trajectory in space and station-keeping manoeuvring capability of an AUV launched from a parent vehicle.

Surface pressure measurements on a generic submarine hull form at high angles of incidence

Journal of Marine Science and Technology, 2022

To investigate the surface pressure distribution at high angles of incidence over a generic subma... more To investigate the surface pressure distribution at high angles of incidence over a generic submarine hull form (SUBOFF), model tests were carried out for pressure measurements in the Wind Tunnel Facility at Naval Science & Technological Laboratory, India. Pressure measurements were performed for a range of high angles of incidence in angle of attack (± 40°) and drift (0 to 40°) on 1.372 m model at Reynolds number 1.7 × 10 6. The particulars of the SUBOFF model, test apparatus, measurement system, test results and observations are presented in the paper. The pressure measurement data generated from the above studies will complement the computational and experimental research on turbulent flows over submerged bodies at wide range of angles of incidence.

SIMULATION STUDIES ON THE EFFECT OF OUT-OF-PLANE LOADS ON SUBMARINE MANOEUVRING

Undersea Defence Technology Conference, 2019

Submarines during manoeuver experienceboth in-plane and out-of-plane loads, especially in the hor... more Submarines during manoeuver experienceboth in-plane and out-of-plane loads, especially in the horizontal plane of motion. The presence of sail, forward planes, deck casing mainly contributes to these loads, as it creates asymmetry in the flowfor manoeuvers involving non-zero angle of drift and yaw rate. Evaluation of these loads though scaled model studies have been well established for small angle of incidence flows. Computational approach is also being considered to capture out-of-plane loads by various authors.In order to simulate the vehicle dynamics for the effect of out-of-plane loads with acceptable level of accuracy, load estimation and subsequent mathematical modeling needs careful understanding. The present paper brings out the effect of out-of-plane loads on submarine manoeuvring through simulations in the view of mathematical treatment.

Roll-induced bifurcation in ship maneuvering under model uncertainty

Journal of Marine Science and Technology, 2016

In this paper, a mathematical model is developed for the maneuvering motion of a naval ship and b... more In this paper, a mathematical model is developed for the maneuvering motion of a naval ship and bifurcations of its equilibrium are identified in roll-coupled motion. The subject ship is a high-speed surface combatant with twin-propeller twin-rudder system. Captive model tests are conducted for the ship using planar motion mechanism. Maneuvering coefficients are calculated by polynomial curve fitting of the test data. Uncertainty distribution in the coefficients is assumed same as that of the curve fitting errors. Uncertainty in the model coefficients is propagated to full-scale simulation results by the stochastic response surface method (SRSM). This method is computationally efficient as compared to standard Monte Carlo simulation technique. The SRSM uses polynomial chaos expansion of orthogonal to fit any probability distribution. Bifurcation analysis of the mathematical model is performed by varying the vertical center of gravity as the bifurcation parameter. Hopf bifurcation is identified. It is found that the bifurcations occur due to the coupling of roll motion with sway, yaw motion and rudder angle. In the presence of wind, roll angle response in bifurcation diagram is discussed.

WIND TUNNEL TESTS FOR HULL WATERJET SYSTEM

Cmde Garg Memorial Educational Lecture, Delhi, Sep 2009., 2009

In the modern world waterjet propulsors have rapidly gained acceptance as the leading means of pr... more In the modern world waterjet propulsors have rapidly gained acceptance as the leading means of propulsion for all types of conventional high speed vehicles like ferries, workboats, patrol crafts, yachts and notably to some unconventional hull forms like Pentamarans, Trimarans and Swaths. Recent advances in waterjet propulsion technology have placed them ahead of conventional propulsion systems in both performance and reliability. Waterjet propulsors manufacturers provide only the performance data of waterjet system and the overall scenario of hull - waterjet system performance in terms interaction may be well away and makes it inconvenient to accept the waterjet performance data alone. Model tests / results in Towing tanks for hull - waterjet system as a whole are very limited and a costly affair to carry out subjected to sufficient and necessary instrumentation. This paper brings out a methodology of testing of hull – waterjet system in wind tunnel and thus transferring useful inputs for hull – waterjet system performance evaluation.

INTERCEPTOR FOR BETTER HYDRODYNAMIC PERFORMANCE OF A PLANING HULL

International Workshop and Conference on Engineering in Marine Applications, IWCEM, Pune, Jan 2010. , 2010

Advances in the field of hydrodynamics have brought out a number of varieties of high speed vesse... more Advances in the field of hydrodynamics have brought out a number of varieties of high speed vessels including advanced hybrid crafts. Yet there is a thirst worldwide in ship building industry/Research & Development organizations to innovate and redefine the hydrodynamic technology for intensifying their performance. There has been a tremendous response for competent hydrodynamic performance technology especially for high speed planing hull forms leading to an innovative idea christened as " Interceptors " which claims to be an effective solution to enhance vessels performance in calm as well as rough waters. The basic Interceptor system offers the high-speed craft to optimise the ship speed and the ride comfort by control of running trim and list. The fundamental working principle of an interceptor is to generate an increase in pressure on the hull bottom plating directly ahead of the transom by intercepting the flow with a blade. Interceptors require less power than any other vertical or horizontal trim tab/ wedge / flap devices. Interceptor concept also offers excellent directional stability when aligned with other thrust producing devices such as waterjets and can operate as a motion damper. The present paper throws light on the performance of interceptors as its application to planing hull form.

HYDRODYNAMIC PERFORMANCE EVALUATION OF HULL - WATERJET SYSTEM USING CFD AND EXPERIMENT

Seventh International conference on High Performance Marine Vehicles (HIPER) , Florida Institute of technology ,USA , Oct 2010., 2010

Waterjet propulsors are successfully used in high speed vessels (HSV). It is efficient both in de... more Waterjet propulsors are successfully used in high speed vessels (HSV). It is efficient both in deep and shallow waters. Recent advances in waterjet propulsion technology have placed them ahead of conventional propulsion systems in both performance and reliability, mainly when used in HSVs. Waterjet propulsion exhibits excellent propulsive performance and maneuverability within a specified speed range which are favorable for high speed applications and also for vessel maneuvers in restricted waters. The waterjet propulsor manufacturers provide only the performance data of waterjet system at a specified operational condition, without the vessel influence effects. But, the overall scenario of the waterjet system interaction effects on the performance of the vessel and that of the hull on the propulsors are neither known nor provided. Several experimental and numerical studies are being carried out worldwide to understand and evaluate the performance of hull -waterjet system as a whole. This paper tries to bring out the interaction between hull and waterjet system numerically using CFD methods based on the RANSE solvers and also the same experimentally based on model tests carried out as part of the present research work. Use of these hydrodynamic interaction parameters go as an input into the design of a more efficient waterjet system for a specific vessel.

TRIMARAN HULL FORM OPTIMISATION USING SHIPFLOW

International conference cum exhibition: Tech Samudra, IMU, Dec 2012., 2012

Trimaran is the most promising hull form for naval vessels because of its excellent performance c... more Trimaran is the most promising hull form for naval vessels because of its excellent performance characteristics notably reduced wave making resistance, larger deck area, good sea keeping and ability to perform optimally in a range of speeds. In its most generic form it consists of a slender centre hull and two side hulls. High slenderness ratio, differential breadth to draft ratios, stagger/separation of the hull forms gives an edge over equivalent monohulls/catamarans in minimising wave making resistance. However by means of advancements to the existing design which can include bulb & wave piercing forms, stern wedge/flap/interceptors, asymmetry in side hull configuration , lifting bodies etc. The present paper investigates the qualitative performance of trimaran hull form modified to various configurations using Shipflow ®. ISSN: 2278 0211 (Online)

Ship Hull Appendages: A Case Study

International conference cum exhibition: Tech Samudra, IMU, Dec 2012., 2012

Hydrodynamic model studies were carried out at Naval Science & Technological Laboratory (NSTL), V... more Hydrodynamic model studies were carried out at Naval Science & Technological Laboratory (NSTL), Vishakhapatnam, India to estimate the resistance contribution of appendages. This paper discusses categorization of ship hull appendages from a hydrodynamic viewpoint. An attempt is made to qualitatively assess the resistance contribution of each of these categories of appendages to the total ship resistance. A relative appraisal of the resistance contribution of appendages on a naval surface combatant, a submarine, a tanker, a container, a dredger and a single screw ship is made to emphasize the large appendage drag on naval ships. Results obtained from hydrodynamic model experiments conducted at High Speed Towing Tank (HSTT) facility at NSTL on a fast displacement hull form used for naval applications (FDHFNA) are discussed at length as a case study. A criterion for rating appendages is proposed. ISSN: 2278 0211 (Online)

THEORETICAL SHIP WAVE PATTERN RESISTANCE EVALUATION USING KOCHIN WAVE AMPLITUDE FUNCTION

International conference cum exhibition: Tech Samudra, IMU, Dec 2012., 2012

Ship wave pattern resistance evaluation has been an important event in the optimization process o... more Ship wave pattern resistance evaluation has been an important event in the optimization process of variety of hull forms ranging from small crafts to fast displacement hull forms including multihull vessels. Several experimental methods for wave pattern analysis like Hogben Matrix Element Method (MEM), Longitudinal & transverse wave cuts involving Landweber Fourier Transform (LFT) and Matrix solution method, theoretical methods like Michell's thin ship theory, Rankine source-sink and Kochin-Fourier method exist today with their merits and limitations. Ship wave pattern resistance is mostly a derived quantity from experiments either as a subset of residuary resistance or when total viscous component is known. In general applying Froude's hypothesis, the residuary resistance coefficient is not subjected to scaling effects from model to prototype and evaluation of total viscous component for surface ships by model experiments is seldom done. Optimization of hull forms through wave pattern studies is a powerful tool and in-house potential flow solvers/experimental evaluation techniques for free surface flows have been developed in many hydrodynamic test facilities. The present paper focuses on ship wave pattern evaluation using Michell's theory (using Kochin wave amplitude function) and its comparison with Shipflow ® & Longitudinal wave cut method (using LFT) on bench mark test model R/V Athena. Matlab ® code development and ship wave pattern resistance evaluation sensitivity for the method chosen is also a part of present discussion.

HYDRODYNAMIC STUDIES ON A TRIMARAN HULL FORM

by Kareem Khan and Praveen PC

The Institution of Engineers, India Sep 2013., 2013

It is expected that, there will be large demand for trimaran hull forms to meet multi-mission def... more It is expected that, there will be large demand for trimaran hull forms to meet multi-mission defense requirements of world in the recent future. Multi-mission requirements include a platform that is fast, agile & versatile with multirole capability such as anti-submarine warfare, surface surveillance, mine countermeasures, littoral and deep sea combat capability with modular mission payloads etc. Hydrodynamically these platforms possess powering and seakeeping advantages, shallow draft operability and excellent maneuverability. Hydrodynamic model tests and CFD studies were carried out to design and evaluate the performance of a 3000 tonne trimaran configuration at NSTL. A brief description of the hydrodynamic activities carried out is highlighted in the present paper.

ESTIMATION OF HULL -PROPELLER SYSTEM PERFORMANCE FOR VARIATION IN PITCH-DIAMETER (P/D) RATIOS

by Kareem Khan and Praveen PC

International conference on Marine Hydrodynamics, MARHY, IIT Madras, Dec 2014., 2014

SUMMARY Performance characteristics assessment of propellers using methodical series has been wel... more SUMMARY Performance characteristics assessment of propellers using methodical series has been well established over decades for variation in geometric parameters of propeller in open water condition. The main geometric parameters for a propeller with specified diameter are P/D ratios, BAR (Blade area ratio) and blade sectional configuration. Although there is a considerable amount of ease in attaining the open water characteristics for a propeller configuration from series charts rather than model tests, the hull-propeller system model test data for a defined displacement condition can only be generated experimentally through self propulsion tests. In the present paper, an attempt is made to employ an approximate method for predicting the hull propeller system data for a range of P/D ratios for a defined hull displacement condition, when the self propulsion data for a single P/D ratio is available.

RESISTANCE CHARACTERISITCS OF A TRIMARAN FOR DIFFERENT SIDE HULL CONFIGURATIONS

by Kareem Khan and Praveen PC

International conference on ship and offshore technology, IIT Kharagpur, Dec 2013., 2013

SUMMARY Trimaran platforms have gained increasing importance in the recent past and over a decade... more SUMMARY Trimaran platforms have gained increasing importance in the recent past and over a decade because of their superiority over monohulls in several hydrodynamic aspects like stability, powering & seakeeping. Trimarans also offer numerous benefits such as larger payload & deck area, flexible layout, shallow draft operability and efficient fuel consumption in terms of weight to power relationships. Commercially trimarans seen today are used as passenger ferries, Ro-Ro vessels and pleasure boats where as naval applications focus on multirole and littoral combat vessels. Presently a research program is underway at High Speed Towing Tank, Naval Science & Technological Laboratory (NSTL) to evaluate the resistance characteristics of a 3000 tonne trimaran configuration through a series model tests and optimization studies in 0.1-0.7 Froude no. range. Present paper deals with the overall effect on trimaran resistance subjected to variation in side hull configuration in terms of its position, length & displacement. Comprehensive comparisons for the series of model test cases are also presented in this paper.

A BRIEF ON HYDRODYNAMIC STUDY OF TRIMARAN WITH WATERJETS

International conference on ship and offshore technology, IIT Kharagpur, Dec 2015., 2015

Future surface combatant designs are focused on multirole mission capabilities and unconventional... more Future surface combatant designs are focused on multirole mission capabilities and unconventional efficient propulsion systems. Concepts in naval design and related systems introduced by several nations in the past two decades shows great amount of advancements from the traditional platform operation criteria such as speed, shock & noise reduction, infrared signature to futuristic demand criteria like flexible mission capability, alternative propulsion architecture, higher degree of stealth, longer duration of loitering capability with smaller crew and cleaner emissions. Few of such platforms are already in operation and many more are under design/construction phase by the world navies. Mission effectiveness of the platform largely depends on two major entities i.e. hull form and propulsor configuration. It has been reviewed that most of advanced marine vehicles rely on unconventional propulsion such as waterjets & podded propulsors for effective platform performance. Studies have been carried out at Naval Science & Technological Laboratory (NSTL), India on a trimaran with waterjet propulsion for hydrodynamic performance evaluation at concept level. The present paper highlights the hydrodynamic studies on trimaran with waterjets carried out at NSTL.

Measurements of steady manoeuvring forces and moments over an axisymmetric body with appendages in a wind tunnel

Ship Technology Research, Dec 27, 2023

Measurements of steady manoeuvring forces and moments over an axisymmetric body with appendages in a wind tunnel

Steady manoeuvring forces and moments over a generic submarine hull form (SUBOFF) at various angl... more Steady manoeuvring forces and moments over a generic submarine hull form (SUBOFF) at various angles of incidence were investigated through scaled model tests in the Wind Tunnel Facility at the Naval Science and Technological Laboratory, India. Measurements were performed for a range of angles of incidence in angle of attack (±18°) and drift (±18°) including control surface deflections (±15°) on a 1.372 m model at Reynolds number 1.7 × 10 6. The present study at angles of incidence is to gather steady-state force, and moment data and validate such load measurements performed in a Wind Tunnel. The particulars of the SUBOFF model, experimental facility and measurement technique, test results for load measurements and estimated hydrodynamic coefficients are highlighted in the paper. The measurement data generated from the above studies will complement the current research on hydrodynamic characteristics for submerged bodies both computationally and experimentally.

Steady velocity measurements in the stern wake of submarine hull form at high angles of incidence

Ocean Engineering , 2023

Velocity distribution in the stern region over a generic submarine hull form (SUBOFF) at high ang... more Velocity distribution in the stern region over a generic submarine hull form (SUBOFF) at high angles of incidence was investigated through steady velocity measurements in the Wind Tunnel Facility at Naval Science & Technological Laboratory, India. Velocity measurements were performed for a range of angles of incidence in angle of attack (+8 • to-40 •) and drift (0 •-28 •) on 1.372 m model at Reynolds number 1.7 × 10 6. The present study for high angles of incidence is to depict a submarine motion during extreme manoeuvers in case of emergency situations. The particulars of the SUBOFF model, experimental facility and measurement technique, test results for axial, tangential and radial velocity measurements, non-uniformity and circumferential mean velocity, derived quantities for vorticity and circulation are highlighted in the paper. The velocity measurements data generated from the above studies will greatly complement the current research on turbulent flows over submerged bodies both computationally and experimentally.

Design optimization of an AUV for performing depth control maneuver

Ocean Engineering

Manoeuvring Simulations of Autonomous Underwater Vehicle using Quaternion

Defecse Science Journal, 2022

The dynamics of an AUV, which can perform manoeuvres with pitch angles in the range of 90° is inv... more The dynamics of an AUV, which can perform manoeuvres with pitch angles in the range of 90° is investigated in this paper. The purpose of the AUV is to perform a station-keeping manoeuvre at about 90° pitch angle by varying propeller revolution. The AUV is launched in horizontal orientation. Quaternion mathematics, 4 quadrant propeller open water characteristics, and PID controller for propeller revolution are incorporated in manoeuvring mathematical model for this purpose. A procedure for optimizing the gain coefficients for the PID controller is developed using the 7 DoF manoeuvring mathematical model. Two design configurations of the AUV are investigated, positively buoyant and negatively buoyant. The design objective is, the AUV shall travel as far away as possible from the parent vehicle using minimum energy and time. It is shown that both the optimal gain coefficients for the PID controller for propeller revolution and the dynamic response of the AUV is different for each design configuration. The methodology developed in the paper can be used in the design and propeller revolution control system for certain categories of AUVs. The study shows that prime mover torque/ shaft revolution and 7 DoF manoeuvring mathematical model are important in predicting the attitude and trajectory in space and station-keeping manoeuvring capability of an AUV launched from a parent vehicle.

Surface pressure measurements on a generic submarine hull form at high angles of incidence

Journal of Marine Science and Technology, 2022

To investigate the surface pressure distribution at high angles of incidence over a generic subma... more To investigate the surface pressure distribution at high angles of incidence over a generic submarine hull form (SUBOFF), model tests were carried out for pressure measurements in the Wind Tunnel Facility at Naval Science & Technological Laboratory, India. Pressure measurements were performed for a range of high angles of incidence in angle of attack (± 40°) and drift (0 to 40°) on 1.372 m model at Reynolds number 1.7 × 10 6. The particulars of the SUBOFF model, test apparatus, measurement system, test results and observations are presented in the paper. The pressure measurement data generated from the above studies will complement the computational and experimental research on turbulent flows over submerged bodies at wide range of angles of incidence.

SIMULATION STUDIES ON THE EFFECT OF OUT-OF-PLANE LOADS ON SUBMARINE MANOEUVRING

Undersea Defence Technology Conference, 2019

Submarines during manoeuver experienceboth in-plane and out-of-plane loads, especially in the hor... more Submarines during manoeuver experienceboth in-plane and out-of-plane loads, especially in the horizontal plane of motion. The presence of sail, forward planes, deck casing mainly contributes to these loads, as it creates asymmetry in the flowfor manoeuvers involving non-zero angle of drift and yaw rate. Evaluation of these loads though scaled model studies have been well established for small angle of incidence flows. Computational approach is also being considered to capture out-of-plane loads by various authors.In order to simulate the vehicle dynamics for the effect of out-of-plane loads with acceptable level of accuracy, load estimation and subsequent mathematical modeling needs careful understanding. The present paper brings out the effect of out-of-plane loads on submarine manoeuvring through simulations in the view of mathematical treatment.

Roll-induced bifurcation in ship maneuvering under model uncertainty

Journal of Marine Science and Technology, 2016

In this paper, a mathematical model is developed for the maneuvering motion of a naval ship and b... more In this paper, a mathematical model is developed for the maneuvering motion of a naval ship and bifurcations of its equilibrium are identified in roll-coupled motion. The subject ship is a high-speed surface combatant with twin-propeller twin-rudder system. Captive model tests are conducted for the ship using planar motion mechanism. Maneuvering coefficients are calculated by polynomial curve fitting of the test data. Uncertainty distribution in the coefficients is assumed same as that of the curve fitting errors. Uncertainty in the model coefficients is propagated to full-scale simulation results by the stochastic response surface method (SRSM). This method is computationally efficient as compared to standard Monte Carlo simulation technique. The SRSM uses polynomial chaos expansion of orthogonal to fit any probability distribution. Bifurcation analysis of the mathematical model is performed by varying the vertical center of gravity as the bifurcation parameter. Hopf bifurcation is identified. It is found that the bifurcations occur due to the coupling of roll motion with sway, yaw motion and rudder angle. In the presence of wind, roll angle response in bifurcation diagram is discussed.

WIND TUNNEL TESTS FOR HULL WATERJET SYSTEM

Cmde Garg Memorial Educational Lecture, Delhi, Sep 2009., 2009

In the modern world waterjet propulsors have rapidly gained acceptance as the leading means of pr... more In the modern world waterjet propulsors have rapidly gained acceptance as the leading means of propulsion for all types of conventional high speed vehicles like ferries, workboats, patrol crafts, yachts and notably to some unconventional hull forms like Pentamarans, Trimarans and Swaths. Recent advances in waterjet propulsion technology have placed them ahead of conventional propulsion systems in both performance and reliability. Waterjet propulsors manufacturers provide only the performance data of waterjet system and the overall scenario of hull - waterjet system performance in terms interaction may be well away and makes it inconvenient to accept the waterjet performance data alone. Model tests / results in Towing tanks for hull - waterjet system as a whole are very limited and a costly affair to carry out subjected to sufficient and necessary instrumentation. This paper brings out a methodology of testing of hull – waterjet system in wind tunnel and thus transferring useful inputs for hull – waterjet system performance evaluation.

INTERCEPTOR FOR BETTER HYDRODYNAMIC PERFORMANCE OF A PLANING HULL

International Workshop and Conference on Engineering in Marine Applications, IWCEM, Pune, Jan 2010. , 2010

Advances in the field of hydrodynamics have brought out a number of varieties of high speed vesse... more Advances in the field of hydrodynamics have brought out a number of varieties of high speed vessels including advanced hybrid crafts. Yet there is a thirst worldwide in ship building industry/Research & Development organizations to innovate and redefine the hydrodynamic technology for intensifying their performance. There has been a tremendous response for competent hydrodynamic performance technology especially for high speed planing hull forms leading to an innovative idea christened as " Interceptors " which claims to be an effective solution to enhance vessels performance in calm as well as rough waters. The basic Interceptor system offers the high-speed craft to optimise the ship speed and the ride comfort by control of running trim and list. The fundamental working principle of an interceptor is to generate an increase in pressure on the hull bottom plating directly ahead of the transom by intercepting the flow with a blade. Interceptors require less power than any other vertical or horizontal trim tab/ wedge / flap devices. Interceptor concept also offers excellent directional stability when aligned with other thrust producing devices such as waterjets and can operate as a motion damper. The present paper throws light on the performance of interceptors as its application to planing hull form.

HYDRODYNAMIC PERFORMANCE EVALUATION OF HULL - WATERJET SYSTEM USING CFD AND EXPERIMENT

Seventh International conference on High Performance Marine Vehicles (HIPER) , Florida Institute of technology ,USA , Oct 2010., 2010

Waterjet propulsors are successfully used in high speed vessels (HSV). It is efficient both in de... more Waterjet propulsors are successfully used in high speed vessels (HSV). It is efficient both in deep and shallow waters. Recent advances in waterjet propulsion technology have placed them ahead of conventional propulsion systems in both performance and reliability, mainly when used in HSVs. Waterjet propulsion exhibits excellent propulsive performance and maneuverability within a specified speed range which are favorable for high speed applications and also for vessel maneuvers in restricted waters. The waterjet propulsor manufacturers provide only the performance data of waterjet system at a specified operational condition, without the vessel influence effects. But, the overall scenario of the waterjet system interaction effects on the performance of the vessel and that of the hull on the propulsors are neither known nor provided. Several experimental and numerical studies are being carried out worldwide to understand and evaluate the performance of hull -waterjet system as a whole. This paper tries to bring out the interaction between hull and waterjet system numerically using CFD methods based on the RANSE solvers and also the same experimentally based on model tests carried out as part of the present research work. Use of these hydrodynamic interaction parameters go as an input into the design of a more efficient waterjet system for a specific vessel.

TRIMARAN HULL FORM OPTIMISATION USING SHIPFLOW

International conference cum exhibition: Tech Samudra, IMU, Dec 2012., 2012

Trimaran is the most promising hull form for naval vessels because of its excellent performance c... more Trimaran is the most promising hull form for naval vessels because of its excellent performance characteristics notably reduced wave making resistance, larger deck area, good sea keeping and ability to perform optimally in a range of speeds. In its most generic form it consists of a slender centre hull and two side hulls. High slenderness ratio, differential breadth to draft ratios, stagger/separation of the hull forms gives an edge over equivalent monohulls/catamarans in minimising wave making resistance. However by means of advancements to the existing design which can include bulb & wave piercing forms, stern wedge/flap/interceptors, asymmetry in side hull configuration , lifting bodies etc. The present paper investigates the qualitative performance of trimaran hull form modified to various configurations using Shipflow ®. ISSN: 2278 0211 (Online)

Ship Hull Appendages: A Case Study

International conference cum exhibition: Tech Samudra, IMU, Dec 2012., 2012

Hydrodynamic model studies were carried out at Naval Science & Technological Laboratory (NSTL), V... more Hydrodynamic model studies were carried out at Naval Science & Technological Laboratory (NSTL), Vishakhapatnam, India to estimate the resistance contribution of appendages. This paper discusses categorization of ship hull appendages from a hydrodynamic viewpoint. An attempt is made to qualitatively assess the resistance contribution of each of these categories of appendages to the total ship resistance. A relative appraisal of the resistance contribution of appendages on a naval surface combatant, a submarine, a tanker, a container, a dredger and a single screw ship is made to emphasize the large appendage drag on naval ships. Results obtained from hydrodynamic model experiments conducted at High Speed Towing Tank (HSTT) facility at NSTL on a fast displacement hull form used for naval applications (FDHFNA) are discussed at length as a case study. A criterion for rating appendages is proposed. ISSN: 2278 0211 (Online)

THEORETICAL SHIP WAVE PATTERN RESISTANCE EVALUATION USING KOCHIN WAVE AMPLITUDE FUNCTION

International conference cum exhibition: Tech Samudra, IMU, Dec 2012., 2012

Ship wave pattern resistance evaluation has been an important event in the optimization process o... more Ship wave pattern resistance evaluation has been an important event in the optimization process of variety of hull forms ranging from small crafts to fast displacement hull forms including multihull vessels. Several experimental methods for wave pattern analysis like Hogben Matrix Element Method (MEM), Longitudinal & transverse wave cuts involving Landweber Fourier Transform (LFT) and Matrix solution method, theoretical methods like Michell's thin ship theory, Rankine source-sink and Kochin-Fourier method exist today with their merits and limitations. Ship wave pattern resistance is mostly a derived quantity from experiments either as a subset of residuary resistance or when total viscous component is known. In general applying Froude's hypothesis, the residuary resistance coefficient is not subjected to scaling effects from model to prototype and evaluation of total viscous component for surface ships by model experiments is seldom done. Optimization of hull forms through wave pattern studies is a powerful tool and in-house potential flow solvers/experimental evaluation techniques for free surface flows have been developed in many hydrodynamic test facilities. The present paper focuses on ship wave pattern evaluation using Michell's theory (using Kochin wave amplitude function) and its comparison with Shipflow ® & Longitudinal wave cut method (using LFT) on bench mark test model R/V Athena. Matlab ® code development and ship wave pattern resistance evaluation sensitivity for the method chosen is also a part of present discussion.

HYDRODYNAMIC STUDIES ON A TRIMARAN HULL FORM

by Kareem Khan and Praveen PC

The Institution of Engineers, India Sep 2013., 2013

It is expected that, there will be large demand for trimaran hull forms to meet multi-mission def... more It is expected that, there will be large demand for trimaran hull forms to meet multi-mission defense requirements of world in the recent future. Multi-mission requirements include a platform that is fast, agile & versatile with multirole capability such as anti-submarine warfare, surface surveillance, mine countermeasures, littoral and deep sea combat capability with modular mission payloads etc. Hydrodynamically these platforms possess powering and seakeeping advantages, shallow draft operability and excellent maneuverability. Hydrodynamic model tests and CFD studies were carried out to design and evaluate the performance of a 3000 tonne trimaran configuration at NSTL. A brief description of the hydrodynamic activities carried out is highlighted in the present paper.

ESTIMATION OF HULL -PROPELLER SYSTEM PERFORMANCE FOR VARIATION IN PITCH-DIAMETER (P/D) RATIOS

by Kareem Khan and Praveen PC

International conference on Marine Hydrodynamics, MARHY, IIT Madras, Dec 2014., 2014

SUMMARY Performance characteristics assessment of propellers using methodical series has been wel... more SUMMARY Performance characteristics assessment of propellers using methodical series has been well established over decades for variation in geometric parameters of propeller in open water condition. The main geometric parameters for a propeller with specified diameter are P/D ratios, BAR (Blade area ratio) and blade sectional configuration. Although there is a considerable amount of ease in attaining the open water characteristics for a propeller configuration from series charts rather than model tests, the hull-propeller system model test data for a defined displacement condition can only be generated experimentally through self propulsion tests. In the present paper, an attempt is made to employ an approximate method for predicting the hull propeller system data for a range of P/D ratios for a defined hull displacement condition, when the self propulsion data for a single P/D ratio is available.

RESISTANCE CHARACTERISITCS OF A TRIMARAN FOR DIFFERENT SIDE HULL CONFIGURATIONS

by Kareem Khan and Praveen PC

International conference on ship and offshore technology, IIT Kharagpur, Dec 2013., 2013

SUMMARY Trimaran platforms have gained increasing importance in the recent past and over a decade... more SUMMARY Trimaran platforms have gained increasing importance in the recent past and over a decade because of their superiority over monohulls in several hydrodynamic aspects like stability, powering & seakeeping. Trimarans also offer numerous benefits such as larger payload & deck area, flexible layout, shallow draft operability and efficient fuel consumption in terms of weight to power relationships. Commercially trimarans seen today are used as passenger ferries, Ro-Ro vessels and pleasure boats where as naval applications focus on multirole and littoral combat vessels. Presently a research program is underway at High Speed Towing Tank, Naval Science & Technological Laboratory (NSTL) to evaluate the resistance characteristics of a 3000 tonne trimaran configuration through a series model tests and optimization studies in 0.1-0.7 Froude no. range. Present paper deals with the overall effect on trimaran resistance subjected to variation in side hull configuration in terms of its position, length & displacement. Comprehensive comparisons for the series of model test cases are also presented in this paper.

A BRIEF ON HYDRODYNAMIC STUDY OF TRIMARAN WITH WATERJETS

International conference on ship and offshore technology, IIT Kharagpur, Dec 2015., 2015

Future surface combatant designs are focused on multirole mission capabilities and unconventional... more Future surface combatant designs are focused on multirole mission capabilities and unconventional efficient propulsion systems. Concepts in naval design and related systems introduced by several nations in the past two decades shows great amount of advancements from the traditional platform operation criteria such as speed, shock & noise reduction, infrared signature to futuristic demand criteria like flexible mission capability, alternative propulsion architecture, higher degree of stealth, longer duration of loitering capability with smaller crew and cleaner emissions. Few of such platforms are already in operation and many more are under design/construction phase by the world navies. Mission effectiveness of the platform largely depends on two major entities i.e. hull form and propulsor configuration. It has been reviewed that most of advanced marine vehicles rely on unconventional propulsion such as waterjets & podded propulsors for effective platform performance. Studies have been carried out at Naval Science & Technological Laboratory (NSTL), India on a trimaran with waterjet propulsion for hydrodynamic performance evaluation at concept level. The present paper highlights the hydrodynamic studies on trimaran with waterjets carried out at NSTL.