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Pump jet is one of the most important propulsion systems for AUVs in high velocities. The critica... more Pump jet is one of the most important propulsion systems for AUVs in high velocities. The critical characteristic of the pump jet is its high efficiency. Pump jets are among the rare propulsion systems which are used non-autonomously in shallow waters. A simple type of pump jet consists of a rotor, a stator and a cylindrical duct covering the rotor and the stator. However, in some cases the propeller with counter rotating direction has been used instead of the stator in some recent applications (like the CRP system). According to the advantages of this propulsion system, it has been widely used in recent years in various naval and military applications. Therefore, there is an essential need to numerical and experimental analysis on these types of propulsion systems. Numerical and experimental analysis conducted on the propulsion systems with ducts, especially the ones with contra rotating propellers, have been done for the purpose of achieving to a configuration with higher efficien...

Contra Rotating Propulsion System (CRP) consists of two propellers with counter rotation directio... more Contra Rotating Propulsion System (CRP) consists of two propellers with counter rotation direction. The main advantage of CRP system is its higher efficiency compared to that of a single propeller system. In this system, propulsion efficiency is increased by removing the radial component of wake flow and changing it into axial propulsive force. Furthermore, the possibility of cavitation occurrence decreases by dividing the load between two propellers. In addition, it is required to balance the propulsion system torque in applications related to AUV (Autonomous underwater vehicle). The AUV body has significant effect on the performance of the propulsion system. The propellers have different performance and higher efficiency due to being located inside the resultant wake. This has led to reanalyzing the propeller alongside the AUV bodies rather than employing the results for standard open water propellers. In order to numerically analyze, computational fluid dynamics method has been u...

Water, Apr 12, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Fluids Engineering

The pressure-time method allows measuring the flowrate in hydraulic turbines, according to IEC 60... more The pressure-time method allows measuring the flowrate in hydraulic turbines, according to IEC 60041 standard. According to this standard, the applicability of the pressure-time method is limited to a straight pipe with a constant cross section with specific limits for length and velocity. However, low-head hydropower plants usually have an intake with a variable cross section and short length making this method difficult to be applied. In this paper, a test rig has been developed to extend the method's applicability. The test rig is designed for developing flows condition and small measurement lengths for pipes with constant and variable cross section, which could be similar to low-head turbine conditions. For pipe with constant cross section, three measuring lengths of 0.5, 1, and 1.5 m can be obtained on this test rig to study the pressure-time method. For pipe with variable cross section, the method is applied across a concentric reducer with a length of 255 mm, i.e., a 9.46...

international journal of advanced design and manufacturing technology, 2017

The present paper numerically discusses the design procedure of marine ducts used for multi-compo... more The present paper numerically discusses the design procedure of marine ducts used for multi-component ducted propulsion systems at the stern of an axisymmetric submerged body. The results are presented in the form of tables showing the effects of dihedral angel as well as camber ratio of the duct as the two most important geometrical parameters on hydrodynamic performance of the propulsion system. Furthermore, a correlation has been extracted between the results of two and three dimensional analysis of ducted propellers. The results show that the design procedure of the duct used for a ducted propulsion system could be performed using some two dimensional analyses. The simulations are performed using a Reynolds averaged Navier Stokes Equations (RANS) based Computational Fluid Dynamics (CFD) tool.

Heat Transfer-Asian Research, 2014

Pump jet is one of the most important propulsion systems for AUVs in high velocities. The critica... more Pump jet is one of the most important propulsion systems for AUVs in high velocities. The critical characteristic of the pump jet is its high efficiency. Pump jets are among the rare propulsion systems which are used non-autonomously in shallow waters. A simple type of pump jet consists of a rotor, a stator and a cylindrical duct covering the rotor and the stator. However, in some cases the propeller with counter rotating direction has been used instead of the stator in some recent applications (like the CRP system). According to the advantages of this propulsion system, it has been widely used in recent years in various naval and military applications. Therefore, there is an essential need to numerical and experimental analysis on these types of propulsion systems. Numerical and experimental analysis conducted on the propulsion systems with ducts, especially the ones with contra rotating propellers, have been done for the purpose of achieving to a configuration with higher efficien...

Contra Rotating Propulsion System (CRP) consists of two propellers with counter rotation directio... more Contra Rotating Propulsion System (CRP) consists of two propellers with counter rotation direction. The main advantage of CRP system is its higher efficiency compared to that of a single propeller system. In this system, propulsion efficiency is increased by removing the radial component of wake flow and changing it into axial propulsive force. Furthermore, the possibility of cavitation occurrence decreases by dividing the load between two propellers. In addition, it is required to balance the propulsion system torque in applications related to AUV (Autonomous underwater vehicle). The AUV body has significant effect on the performance of the propulsion system. The propellers have different performance and higher efficiency due to being located inside the resultant wake. This has led to reanalyzing the propeller alongside the AUV bodies rather than employing the results for standard open water propellers. In order to numerically analyze, computational fluid dynamics method has been u...

Water, Apr 12, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Fluids Engineering

The pressure-time method allows measuring the flowrate in hydraulic turbines, according to IEC 60... more The pressure-time method allows measuring the flowrate in hydraulic turbines, according to IEC 60041 standard. According to this standard, the applicability of the pressure-time method is limited to a straight pipe with a constant cross section with specific limits for length and velocity. However, low-head hydropower plants usually have an intake with a variable cross section and short length making this method difficult to be applied. In this paper, a test rig has been developed to extend the method's applicability. The test rig is designed for developing flows condition and small measurement lengths for pipes with constant and variable cross section, which could be similar to low-head turbine conditions. For pipe with constant cross section, three measuring lengths of 0.5, 1, and 1.5 m can be obtained on this test rig to study the pressure-time method. For pipe with variable cross section, the method is applied across a concentric reducer with a length of 255 mm, i.e., a 9.46...

international journal of advanced design and manufacturing technology, 2017

The present paper numerically discusses the design procedure of marine ducts used for multi-compo... more The present paper numerically discusses the design procedure of marine ducts used for multi-component ducted propulsion systems at the stern of an axisymmetric submerged body. The results are presented in the form of tables showing the effects of dihedral angel as well as camber ratio of the duct as the two most important geometrical parameters on hydrodynamic performance of the propulsion system. Furthermore, a correlation has been extracted between the results of two and three dimensional analysis of ducted propellers. The results show that the design procedure of the duct used for a ducted propulsion system could be performed using some two dimensional analyses. The simulations are performed using a Reynolds averaged Navier Stokes Equations (RANS) based Computational Fluid Dynamics (CFD) tool.

Heat Transfer-Asian Research, 2014