Pub Date : 2019-06-30DOI: 10.3329/jname.v16i1.30548
M. K. Islam, M. Hasanuzzaman, N. Rahim, A. Nahar
Sustainable power generation, energy security, and global warming are the big challenges to the world today. These issues may be addressed through the increased usage of renewable energy resources and concentrated solar energy can play a vital role in this regard. The performance of a parabolic-trough collector’s receiver is here investigated analytically and experimentally using water based and therminol-VP1based CuO, ZnO, Al2O3, TiO2, Cu, Al, and SiC nanofluids. The receiver size has been optimized by a simulation program written in MATLAB. Thus, numerical results have been validated by experimental outcomes under same conditions using the same nanofluids. Increased volumetric concentrations of nanoparticle is found to enhance heat transfer, with heat transfer coefficient the maximum in W-Cu and VP1-SiC, the minimum in W-TiO2 and VP1-ZnO at 0.8 kg/s flow rate. Changing the mass flow rate also affects heat transfer coefficient. It has been observed that heat transfer coefficient reaches its maximum of 23.30% with SiC-water and 23.51% with VP1-SiC when mass-flow rate is increased in laminar flow. Heat transfer enhancement drops during transitions of flow from laminar to turbulent. The maximum heat transfer enhancements of 9.49% and 10.14% were achieved with Cu-water and VP1-SiC nanofluids during turbulent flow. The heat transfer enhancements of nanofluids seem to remain constant when compared with base fluids during either laminar flow or turbulent flow.
{"title":"Effect of nanofluid properties and mass-flow rate on heat transfer of parabolic-trough concentrating solar system","authors":"M. K. Islam, M. Hasanuzzaman, N. Rahim, A. Nahar","doi":"10.3329/jname.v16i1.30548","DOIUrl":"https://doi.org/10.3329/jname.v16i1.30548","url":null,"abstract":"Sustainable power generation, energy security, and global warming are the big challenges to the world today. These issues may be addressed through the increased usage of renewable energy resources and concentrated solar energy can play a vital role in this regard. The performance of a parabolic-trough collector’s receiver is here investigated analytically and experimentally using water based and therminol-VP1based CuO, ZnO, Al2O3, TiO2, Cu, Al, and SiC nanofluids. The receiver size has been optimized by a simulation program written in MATLAB. Thus, numerical results have been validated by experimental outcomes under same conditions using the same nanofluids. Increased volumetric concentrations of nanoparticle is found to enhance heat transfer, with heat transfer coefficient the maximum in W-Cu and VP1-SiC, the minimum in W-TiO2 and VP1-ZnO at 0.8 kg/s flow rate. Changing the mass flow rate also affects heat transfer coefficient. It has been observed that heat transfer coefficient reaches its maximum of 23.30% with SiC-water and 23.51% with VP1-SiC when mass-flow rate is increased in laminar flow. Heat transfer enhancement drops during transitions of flow from laminar to turbulent. The maximum heat transfer enhancements of 9.49% and 10.14% were achieved with Cu-water and VP1-SiC nanofluids during turbulent flow. The heat transfer enhancements of nanofluids seem to remain constant when compared with base fluids during either laminar flow or turbulent flow.","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2019-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3329/jname.v16i1.30548","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42632374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-30DOI: 10.3329/jname.v16i1.39960
R. Persaud, H. Li, J. Leng
Research vessels are commonly used on a daily basis for ocean exploration and payload handling. However, due to unpredictable wave motion on the ship and the flexibility of the cable, the heave of the ship is unavoidable and causes danger during operations, loss of payload, possible damages to expensive equipment and prolong period of downtime. A compensator system is an essential part of operations to mitigate this effect and to ensure safety, reduce down-time of operation and increase efficiency while providing longer and better duration of operation even in harsh conditions. In this article, a passive heave compensator system with cylinder, accumulator and depth compensator connected in series by pressured pipes developed for a scientific research ship with length of 68m and breath of 16m is analyzed along the coast of Guyana, South America. The payload used in this analysis is 200 ton. The working principle of the heave compensation system is described, the parameters affecting the performance of the system are simulated and analyzed using MatLab. A 3D model of the system is built using SolidWorks and schematic drawings are produced from AutoCAD. The compensation rate of the system is higher than 77% under the influence of the input wave and the system has a response of an average setting time of 18s. The point of maximum load exerted is at the splash zone. For a typical most probable extreme significant wave height, Hs= 2.3m, period T= 6s and direction μ= 45° in the operational area, the reduction in heave motion when the vessel is equipped with the heave compensator is approximately 77% compared to 47% reduction when the vessel is without a compensator.
{"title":"Numerical simulation of a passive heave compensator for scientific research ships","authors":"R. Persaud, H. Li, J. Leng","doi":"10.3329/jname.v16i1.39960","DOIUrl":"https://doi.org/10.3329/jname.v16i1.39960","url":null,"abstract":"Research vessels are commonly used on a daily basis for ocean exploration and payload handling. However, due to unpredictable wave motion on the ship and the flexibility of the cable, the heave of the ship is unavoidable and causes danger during operations, loss of payload, possible damages to expensive equipment and prolong period of downtime. A compensator system is an essential part of operations to mitigate this effect and to ensure safety, reduce down-time of operation and increase efficiency while providing longer and better duration of operation even in harsh conditions. In this article, a passive heave compensator system with cylinder, accumulator and depth compensator connected in series by pressured pipes developed for a scientific research ship with length of 68m and breath of 16m is analyzed along the coast of Guyana, South America. The payload used in this analysis is 200 ton. The working principle of the heave compensation system is described, the parameters affecting the performance of the system are simulated and analyzed using MatLab. A 3D model of the system is built using SolidWorks and schematic drawings are produced from AutoCAD. The compensation rate of the system is higher than 77% under the influence of the input wave and the system has a response of an average setting time of 18s. The point of maximum load exerted is at the splash zone. For a typical most probable extreme significant wave height, Hs= 2.3m, period T= 6s and direction μ= 45° in the operational area, the reduction in heave motion when the vessel is equipped with the heave compensator is approximately 77% compared to 47% reduction when the vessel is without a compensator. ","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2019-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3329/jname.v16i1.39960","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48714384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-24DOI: 10.3329/jname.v16i1.34756
M. F. Islam, F. Jahra
This research proposes mesh and domain optimization strategies for a popular Computational Fluid Dynamics (CFD) technique to estimate the open water propulsive characteristics of fixed pitch propellers accurately and time-efficiently based on examining the effect of various mesh and computation domain parameters. It used a Reynolds-Averaged Navier-Stokes (RANS) solver to predict the propulsive performance of a fixed pitch propeller with varied meshing, simulation domain and setup parameters. The optimized mesh and domain size parameters were selected using Design of Experiments (DoE) methods enabling simulations in a limited memory and in a timely manner without compromising the accuracy of results. The predicted thrust and torque for the propeller were compared to the corresponding measurements for determining the prediction accuracy. The authors found that the optimized meshing and setup arrangements reduced the propeller opens simulation time by at least a factor of six as compared to the generally popular CFD parameter setup. In addition, the accuracy of propulsive characteristics was improved by up to 50% as compared to published simulation results. The methodologies presented in this paper can be similarly applied to other simulations such as calm water ship resistance, ship propulsion etc. to systematically derive the optimized meshing arrangement for simulations with minimal simulation time and maximum accuracy. This investigation was carried out using a commercial CFD package; however, the findings can be applied to any RANS solver.
{"title":"Improving accuracy and efficiency of CFD predictions of propeller open water performance","authors":"M. F. Islam, F. Jahra","doi":"10.3329/jname.v16i1.34756","DOIUrl":"https://doi.org/10.3329/jname.v16i1.34756","url":null,"abstract":"This research proposes mesh and domain optimization strategies for a popular Computational Fluid Dynamics (CFD) technique to estimate the open water propulsive characteristics of fixed pitch propellers accurately and time-efficiently based on examining the effect of various mesh and computation domain parameters. It used a Reynolds-Averaged Navier-Stokes (RANS) solver to predict the propulsive performance of a fixed pitch propeller with varied meshing, simulation domain and setup parameters. The optimized mesh and domain size parameters were selected using Design of Experiments (DoE) methods enabling simulations in a limited memory and in a timely manner without compromising the accuracy of results. The predicted thrust and torque for the propeller were compared to the corresponding measurements for determining the prediction accuracy. The authors found that the optimized meshing and setup arrangements reduced the propeller opens simulation time by at least a factor of six as compared to the generally popular CFD parameter setup. In addition, the accuracy of propulsive characteristics was improved by up to 50% as compared to published simulation results. The methodologies presented in this paper can be similarly applied to other simulations such as calm water ship resistance, ship propulsion etc. to systematically derive the optimized meshing arrangement for simulations with minimal simulation time and maximum accuracy. This investigation was carried out using a commercial CFD package; however, the findings can be applied to any RANS solver.","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2019-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43391797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-12-30DOI: 10.3329/JNAME.V15I2.36322
B. Shameem, V. Vincent
The control objective of the Rudder Roll Stabilization (RRS) system is to deploy the rudder, which is primarily a path controlling device, to reduce the roll motion without interference in heading of ship. To achieve the control of both roll and yaw motions, the only control input is the rudder angle and hence the RRS system is referred as a Single Input, Two Output (SITO) system. Rudder roll stabilization is insignificant at low forward speed of the ship, but can give significant control at higher speed when fast rudder movement is applied. This paper presents a closed loop state space model for accurate simulations on rudder roll stabilization in irregular seas considering the 3-degree of freedom motions, i.e., sway, roll and yaw. The computational model is developed to analyze the effect of the rudder movement on sway, roll and yaw in forward speed conditions in irregular sea conditions. The Sea State conditions are modelled as wave perturbation models using the method of shaping filter established by filtered white noise. The control system has been designed using optimal linear quadratic regulator (LQR) method. The control loop contains both the signal for the autopilot action to trigger the heading angle correction as well as the signal for rudder based roll motion control. The simulations are carried out with rudder roll control system ON and OFF mode to analyze the effect of the rudder on steering and motion stabilization. In both cases the autopilot is in active mode to correct deviations in the course heading. The simulations are analyzed for three different ship speeds in two different Seas State conditions with a low and fast rudder movement to show the efficacy of the model. The performance is evaluated and presented based on the RMS value. Since the rudder based roll motion stabilization may also result in unnecessary motions of sway and yaw, besides the desirable roll reduction, the result presents the sway-roll-yaw responses as applicable under the particular speed and Sea State conditions.
{"title":"State space modelling approach for rudder roll stabilization","authors":"B. Shameem, V. Vincent","doi":"10.3329/JNAME.V15I2.36322","DOIUrl":"https://doi.org/10.3329/JNAME.V15I2.36322","url":null,"abstract":"The control objective of the Rudder Roll Stabilization (RRS) system is to deploy the rudder, which is primarily a path controlling device, to reduce the roll motion without interference in heading of ship. To achieve the control of both roll and yaw motions, the only control input is the rudder angle and hence the RRS system is referred as a Single Input, Two Output (SITO) system. Rudder roll stabilization is insignificant at low forward speed of the ship, but can give significant control at higher speed when fast rudder movement is applied. This paper presents a closed loop state space model for accurate simulations on rudder roll stabilization in irregular seas considering the 3-degree of freedom motions, i.e., sway, roll and yaw. The computational model is developed to analyze the effect of the rudder movement on sway, roll and yaw in forward speed conditions in irregular sea conditions. The Sea State conditions are modelled as wave perturbation models using the method of shaping filter established by filtered white noise. The control system has been designed using optimal linear quadratic regulator (LQR) method. The control loop contains both the signal for the autopilot action to trigger the heading angle correction as well as the signal for rudder based roll motion control. The simulations are carried out with rudder roll control system ON and OFF mode to analyze the effect of the rudder on steering and motion stabilization. In both cases the autopilot is in active mode to correct deviations in the course heading. The simulations are analyzed for three different ship speeds in two different Seas State conditions with a low and fast rudder movement to show the efficacy of the model. The performance is evaluated and presented based on the RMS value. Since the rudder based roll motion stabilization may also result in unnecessary motions of sway and yaw, besides the desirable roll reduction, the result presents the sway-roll-yaw responses as applicable under the particular speed and Sea State conditions.","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2018-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3329/JNAME.V15I2.36322","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42690116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-12-29DOI: 10.3329/JNAME.V15I2.36890
K. Shahani, C. Wu, R. Persaud, H. Song
This paper is about Ocean Strider; an Underwater Hybrid Vehicle that is modified with hybrid (manual and autonomous) control system. The aims concerning this Underwater Hybrid Vehicle are to be competent to operate underwater by using remote control via operator and seek out the user interested objects, and in case of autonomously to be smart, to visually follow and manage a secured position comparable to a motionless target, and to visually follow and move behind a moving target and avoid the hindrances for reliable navigation. Vision is a fundamental root that promotes the underwater robot to execute various tasks autonomously. Ocean Strider is intelligent to explicitly identify and locate objects by specifying from distinct color codes and dimension of the objects and respond accordingly. Multiple experiments have been conducted in the laboratory the robot successfully operates manually and grasp the objects underwater, and the robot can locate and track the objects autonomously, secure a fixed distance to the fixed object and travel onward with the object as it moves.
{"title":"Design and control of underwater hybrid vehicle capable of performing numerous tasks","authors":"K. Shahani, C. Wu, R. Persaud, H. Song","doi":"10.3329/JNAME.V15I2.36890","DOIUrl":"https://doi.org/10.3329/JNAME.V15I2.36890","url":null,"abstract":"This paper is about Ocean Strider; an Underwater Hybrid Vehicle that is modified with hybrid (manual and autonomous) control system. The aims concerning this Underwater Hybrid Vehicle are to be competent to operate underwater by using remote control via operator and seek out the user interested objects, and in case of autonomously to be smart, to visually follow and manage a secured position comparable to a motionless target, and to visually follow and move behind a moving target and avoid the hindrances for reliable navigation. Vision is a fundamental root that promotes the underwater robot to execute various tasks autonomously. Ocean Strider is intelligent to explicitly identify and locate objects by specifying from distinct color codes and dimension of the objects and respond accordingly. Multiple experiments have been conducted in the laboratory the robot successfully operates manually and grasp the objects underwater, and the robot can locate and track the objects autonomously, secure a fixed distance to the fixed object and travel onward with the object as it moves. ","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2018-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3329/JNAME.V15I2.36890","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45296429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-12-29DOI: 10.3329/JNAME.V15I2.31314
M. C. Raju, S. H. Reddy, E. K. Reddy
A systematic study has been performed on MHD convective chemically reactive and absorbing fluid along an exponentially accelerated vertical plate with the impact of Hall current by considering ramped temperature. Laplace transform technique is applied to obtain exact solutions of the non-dimensional governing equations for fluid velocity, temperature and concentration. Based on these solutions, the expressions for skin friction coefficient, Nusselt number and Sherwood number are also derived. The consequences of diverse physical parameters on flow quantities are examined thoroughly with graphical representations. The numerical values for skin friction coefficient, rate of heat transfer and rate of mass transfer are recorded and analyzed.
{"title":"Study of ramped temperature influence on MHD convective chemically reactive and absorbing fluid past an exponentially accelerated vertical porous plate","authors":"M. C. Raju, S. H. Reddy, E. K. Reddy","doi":"10.3329/JNAME.V15I2.31314","DOIUrl":"https://doi.org/10.3329/JNAME.V15I2.31314","url":null,"abstract":"A systematic study has been performed on MHD convective chemically reactive and absorbing fluid along an exponentially accelerated vertical plate with the impact of Hall current by considering ramped temperature. Laplace transform technique is applied to obtain exact solutions of the non-dimensional governing equations for fluid velocity, temperature and concentration. Based on these solutions, the expressions for skin friction coefficient, Nusselt number and Sherwood number are also derived. The consequences of diverse physical parameters on flow quantities are examined thoroughly with graphical representations. The numerical values for skin friction coefficient, rate of heat transfer and rate of mass transfer are recorded and analyzed.","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2018-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3329/JNAME.V15I2.31314","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49637665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-12-26DOI: 10.3329/JNAME.V15I2.36225
Prachakon Kaewkhiaw
The realistic flow on each blade of the front and rear propellers with contra-rotating propellers (CRPs) are most complex because that consist the interaction forces with themselves and it affects to the actual efficiency of the propeller blades. The wake of CRPs at the gap between the front and rear propellers have influent to the variation of propeller performance for the front and rear propellers. So, this paper presented the numerical simulation of propeller performance on CRPs with steady method in the first. Second, it is applied to evaluate the propeller performance with unsteady method in time accuracy including investigating the wake on a transverse plane between the front and rear propellers and a transverse plane located downstream of the rear propeller. The wake was analyzed through velocity vector magnitude contours. The numerical simulations were conducted using the Reynolds Averaged Navier-Stokes (RANS). The calculation results have been compared the measurement data.
{"title":"CFD investigation on steady and unsteady performances of contra-rotating propellers","authors":"Prachakon Kaewkhiaw","doi":"10.3329/JNAME.V15I2.36225","DOIUrl":"https://doi.org/10.3329/JNAME.V15I2.36225","url":null,"abstract":"The realistic flow on each blade of the front and rear propellers with contra-rotating propellers (CRPs) are most complex because that consist the interaction forces with themselves and it affects to the actual efficiency of the propeller blades. The wake of CRPs at the gap between the front and rear propellers have influent to the variation of propeller performance for the front and rear propellers. So, this paper presented the numerical simulation of propeller performance on CRPs with steady method in the first. Second, it is applied to evaluate the propeller performance with unsteady method in time accuracy including investigating the wake on a transverse plane between the front and rear propellers and a transverse plane located downstream of the rear propeller. The wake was analyzed through velocity vector magnitude contours. The numerical simulations were conducted using the Reynolds Averaged Navier-Stokes (RANS). The calculation results have been compared the measurement data.","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2018-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3329/JNAME.V15I2.36225","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44715236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-12-25DOI: 10.3329/jname.v15i2.31266
M. S. I. Mallik, Md.Ashraf Uddin
A large eddy simulation (LES) of a plane turbulent channel flow is performed at a Reynolds number Re? = 590 based on the channel half width, ? and wall shear velocity, u? by approximating the near wall region using differential equation wall model (DEWM). The simulation is performed in a computational domain of 2?? x 2? x ??. The computational domain is discretized by staggered grid system with 32 x 30 x 32 grid points. In this domain the governing equations of LES are discretized spatially by second order finite difference formulation, and for temporal discretization the third order low-storage Runge-Kutta method is used. Essential turbulence statistics of the computed flow field based on this LES approach are calculated and compared with the available Direct Numerical Simulation (DNS) and LES data where no wall model was used. Comparing the results throughout the calculation domain we have found that the LES results based on DEWM show closer agreement with the DNS data, especially at the near wall region. That is, the LES approach based on DEWM can capture the effects of near wall structures more accurately. Flow structures in the computed flow field in the 3D turbulent channel have also been discussed and compared with LES data using no wall model.
{"title":"Large eddy simulation of turbulent channel flow using differential equation wall model","authors":"M. S. I. Mallik, Md.Ashraf Uddin","doi":"10.3329/jname.v15i2.31266","DOIUrl":"https://doi.org/10.3329/jname.v15i2.31266","url":null,"abstract":"A large eddy simulation (LES) of a plane turbulent channel flow is performed at a Reynolds number Re? = 590 based on the channel half width, ? and wall shear velocity, u? by approximating the near wall region using differential equation wall model (DEWM). The simulation is performed in a computational domain of 2?? x 2? x ??. The computational domain is discretized by staggered grid system with 32 x 30 x 32 grid points. In this domain the governing equations of LES are discretized spatially by second order finite difference formulation, and for temporal discretization the third order low-storage Runge-Kutta method is used. Essential turbulence statistics of the computed flow field based on this LES approach are calculated and compared with the available Direct Numerical Simulation (DNS) and LES data where no wall model was used. Comparing the results throughout the calculation domain we have found that the LES results based on DEWM show closer agreement with the DNS data, especially at the near wall region. That is, the LES approach based on DEWM can capture the effects of near wall structures more accurately. Flow structures in the computed flow field in the 3D turbulent channel have also been discussed and compared with LES data using no wall model.","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2018-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3329/jname.v15i2.31266","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48172262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-07-04DOI: 10.3329/jname.v18i2.52224
S. Paul
In the field of Naval Architecture, the conventional approach to design any vessel is to follow the classification societies’ rules to ensure adequate strength and structural integrity. Nowadays, owners’ demands and purposes of vessels are changing dramatically. To mitigate these demands, sometimes it is necessary to design new types of structures, but the classification society’s rules are not sufficient to prepare these advanced designs. Moreover, Naval Architects are always eager to minimize the lightweight of a vessel as this is directly related to cost and carrying capacity. Topology optimization has become a powerful tool for designing structures in an optimized way. The concept of topology optimization has been utilized by the automotive and aerospace industry for almost thirty years where problems associated with solutions meant to satisfy maximum stiffness and structural integrity with minimum weight which are of utmost importance. However, in the field of marine and offshore structures, the use of topology optimization is infrequent. As structural optimization aims to design structures under certain constraints to achieve better strength and lower cost, the introduction of this technique in ship structure can be lucrative. In this paper, a methodology to apply structural topology optimization in the field of ship design is presented. An Oil Tanker Bulkhead has been selected for this study. SIMULIA ABAQUS software is used in this regard. Topology optimization has been performed by minimizing the strain energy of the component as the objective function and a target stiffness and material volume of the structure as design constraints. Finally, the results demonstrate the general applicability of the methodology presented for obtaining the geometrical layout of the structure.
{"title":"Topology optimization of an oil tanker bulkhead subjected to hydrostatic loads","authors":"S. Paul","doi":"10.3329/jname.v18i2.52224","DOIUrl":"https://doi.org/10.3329/jname.v18i2.52224","url":null,"abstract":"In the field of Naval Architecture, the conventional approach to design any vessel is to follow the classification societies’ rules to ensure adequate strength and structural integrity. Nowadays, owners’ demands and purposes of vessels are changing dramatically. To mitigate these demands, sometimes it is necessary to design new types of structures, but the classification society’s rules are not sufficient to prepare these advanced designs. Moreover, Naval Architects are always eager to minimize the lightweight of a vessel as this is directly related to cost and carrying capacity. Topology optimization has become a powerful tool for designing structures in an optimized way. The concept of topology optimization has been utilized by the automotive and aerospace industry for almost thirty years where problems associated with solutions meant to satisfy maximum stiffness and structural integrity with minimum weight which are of utmost importance. However, in the field of marine and offshore structures, the use of topology optimization is infrequent. As structural optimization aims to design structures under certain constraints to achieve better strength and lower cost, the introduction of this technique in ship structure can be lucrative. In this paper, a methodology to apply structural topology optimization in the field of ship design is presented. An Oil Tanker Bulkhead has been selected for this study. SIMULIA ABAQUS software is used in this regard. Topology optimization has been performed by minimizing the strain energy of the component as the objective function and a target stiffness and material volume of the structure as design constraints. Finally, the results demonstrate the general applicability of the methodology presented for obtaining the geometrical layout of the structure.","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2018-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47812840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An analysis of the thermal radiation and viscous dissipation effects on an unsteady MHD mixed convection flow of a viscous incompressible fluid past a vertical porous plate, in the presence of variable wall heat flux and heat generation/absorption is presented. The free stream velocity follows an exponentially increasing or decreasing small perturbation law. The governing equations of the flow field are transformed into a system of non-linear ordinary differential equations by perturbation technique and then solved numerically by using the shooting method. The effects of the various parameters on the translation velocity, microrotation and temperature as well as the skin friction coefficient and couple stress coefficient at the wall are prepared with various values of the fluid properties.
{"title":"Internal heat generation effect on radiation heat transfer MHD dissipating flow of a micropolar fluid with variable wall heat flux","authors":"Sreenivasulu Pandikunta, Poornima Tamalapakula, Bhasker Reddy Nandanoor","doi":"10.3329/JNAME.V15I1.19582","DOIUrl":"https://doi.org/10.3329/JNAME.V15I1.19582","url":null,"abstract":"An analysis of the thermal radiation and viscous dissipation effects on an unsteady MHD mixed convection flow of a viscous incompressible fluid past a vertical porous plate, in the presence of variable wall heat flux and heat generation/absorption is presented. The free stream velocity follows an exponentially increasing or decreasing small perturbation law. The governing equations of the flow field are transformed into a system of non-linear ordinary differential equations by perturbation technique and then solved numerically by using the shooting method. The effects of the various parameters on the translation velocity, microrotation and temperature as well as the skin friction coefficient and couple stress coefficient at the wall are prepared with various values of the fluid properties.","PeriodicalId":55961,"journal":{"name":"Journal of Naval Architecture and Marine Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2018-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3329/JNAME.V15I1.19582","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43553453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：