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Karbasian, Hamid Reza,Kim, Kyung Chun Elsevier 2016 Ocean engineering Vol.127 No.-
<P><B>Abstract</B></P> <P>This study numerically investigates the behavior of vortices and flow structure in a dynamic stall phenomenon, especially in post-stall where the flow is highly nonlinear. Computational fluid dynamics approaches were used to simulate unsteady flow fields. The Transition SST turbulence model was used to compute the turbulent characteristics, and second-order temporal/spatial schemes were used to reduce dissipation effects. To investigate the behavior of vortices individually, each main vortex core was targeted manually and its strength is computed. It is shown that despite the existence of coherent structures, the interaction of organized vortices is responsible for the complexity of the flow beyond the hydrofoil in post-stall. The primary LEV and primary TEV have the longest lifetime among the LEVs and TEVs, respectively. The Primary LEV loses strength quickly due to counteraction with the TEV and disruption of the energy source provided by the leading edge shear. The secondary LEV plays an important role when dynamic stall occurs and provides a lift peak in post-stall. There are time delays between the maximum circulation of main vortices and corresponding peak of the lift coefficient loop. The general interaction of counter-rotating vortices is responsible for these delays between peaks of the lift coefficient and maximum circulations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrofoil examination in unsteady conditions for energy extraction. </LI> <LI> Investigations on the flow structure in deep dynamic stall of pitching hydrofoil. </LI> <LI> Analysis of vortex behavior by computing its life-time and strength. </LI> <LI> Interaction of major core vortices leads to instability of flow in post stall. </LI> <LI> The major LEVs and TEVs play important role in the dynamic stall. </LI> </UL> </P>
A new method for reducing VOCs formation during crude oil loading process
Karbasian, H. R.,Kim, D. Y.,Yoon, S. Y.,Ahn, J. H.,Kim, K. C. Springer Science + Business Media 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4
<P>This study investigates the process of loading crude oil onto a tanker and the associated formation of Volatile organic compounds (VOCs). The main goal is to find mechanisms for reducing the amount of VOCs formation during the loading process. Different cases with a combination of a swirl unit and a U-bend were examined. Computational fluid dynamics (CFD) method was used to simulate the cavitation phenomenon, fluid flow pattern, and VOCs formation inside a loading pipeline. An experimental study was also done to investigate the accuracy of the numerical approach and to test the designed swirl units. Based on the numerical and experimental studies, a new approach is presented to reduce the VOCs formation notably during the loading process. The proposed approach can reduce the amount of VOCs formation by around 90 %, which can help to reduce the amount of wasted crude oil and also protect the atmosphere from gas emissions.</P>
Designing Reliability Improvement Model Using Design Structure Matrix
Karbasian, Mehdi,Kazemi, Sayed Mohammad,Khayambashi, Bijan,Nilipour, Sayed Akbar Korean Institute of Industrial Engineers 2017 Industrial Engineeering & Management Systems Vol.16 No.4
As an inherent characteristic of any product or system, reliability is one of the parameters of design, construction and operation to be considered and controlled as an important criterion during relevant processes. The need to ensure the continuous and proper functioning of a product has led designers to pay special attention to increasing reliability. Therefore by coordinating all design experts and support groups throughout the implementation of product life cycle, the product development life cycle period can be reduced and value-creation of products increased. As a result, the existence of a comprehensive model is of vital importance. In this study, all industrial engineering techniques effective in improving reliability are first identified and then prioritized in all phases of the product life cycle using multi-criteria decision making method. Finally, using design structure matrix, priority and posteriority of all techniques is determined in each phase and a systematic model is provided to improve equipment reliability.
Numerical visualization of mixing in a circular chamber by two opposite impinging jets
Hamidreza Karbasian(하미드 카바시안),Youngwoo Kim(김영우),In Bum Lee(이인범),Beom Jeong Han(한범정),Yong Chai Jeong(정용채),Kyung Chun Kim(김경천) 한국가시화정보학회 2016 한국가시화정보학회지 Vol.14 No.3
In this study, the mixing process of two distinct flow is numerically investigated. Two flow with different physical properties (resin and hardener) are mixed through the opposing mixing jets. At a high pressure mixing process, the high speed flow is provided by two in-line nozzles. In the case of numerical modeling, Reynolds-Averaged Navier-Stokes Equations (RANS) is conducted to model the flow pattern inside the chamber. Additionally, SST k-omega turbulence model is selected to predict the kinetic energy of flow in impingement zone. The results show that mixing of two distinct flows would be efficient if the velocity of jet is high enough and nozzle diameter is a predominant parameter. Also, this velocity would create higher shear stress between two distinct flows which increases the mixing quality as well as strength of formed vortices. Eventually, the histogram of concentration fraction of resin is examined in order to show the quality of mixing and the range of concentration fractions in the output of chamber.
Designing Reliability Improvement Model Using Design Structure Matrix
Mehdi Karbasian,Sayed Mohammad Kazemi,Bijan Khayambashi,Sayed Akbar Nilipour 대한산업공학회 2017 Industrial Engineeering & Management Systems Vol.16 No.4
As an inherent characteristic of any product or system, reliability is one of the parameters of design, construction and operation to be considered and controlled as an important criterion during relevant processes. The need to ensure the continuous and proper functioning of a product has led designers to pay special attention to increasing reliability. Therefore by coordinating all design experts and support groups throughout the implementation of product life cycle, the product development life cycle period can be reduced and value-creation of products increased. As a result, the existence of a comprehensive model is of vital importance. In this study, all industrial engineering techniques effective in improving reliability are first identified and then prioritized in all phases of the product life cycle using multicriteria decision making method. Finally, using design structure matrix, priority and posteriority of all techniques is determined in each phase and a systematic model is provided to improve equipment reliability.
Unsteady Flow Features over Flapping Foil in Low Reynolds Number
Hamid Reza Karbasian,Kyung Chun Kim(김경천) 한국가시화정보학회 2016 한국가시화정보학회 학술발표대회 논문집 Vol.2016 No.4
This study numerically investigates the behavior of vortices and flow structure in a dynamic stall phenomenon. Computational fluid dynamics approaches were used to simulate unsteady flow fields. the Transition SST turbulence model was used to compute the turbulent characteristics, and second-order temporal/spatial schemes were used to reduce dissipation effects. It is shown that despite the existence of coherent structures, the interaction of organized vortices is responsible for the complexity of the flow beyond the airfoil in post-stall. The Primary LEV loses strength quickly due to counteraction with the TEV and disruption of the energy source provided by the leading edge shear. The secondary LEV plays an important role when dynamic stall occurs and provides a lift peak in post-stall.
The influence of kinematics of blades on the flow structure in deep dynamic stall
Gul Chang,Hamid Reza Karbasian,Shujun Zhang,Yao Yan,Binqi Chen,Kyung Chun Kim 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.7
This study considers the effect of kinematics on the aerodynamic loads and flow structure around moving blades of micro air vehicles (MAVs) in deep dynamic stall. The transversal (pure heaving) and rotational (pure pitching) motions are considered distinctly to investigate the dynamic stall. An equivalent effective angle of the attack profile is given to both motions. This method helps to figure out the influence of kinematics on flow structures when all boundary conditions and effective angles of attack profiles are the same. An experiment is conducted in fully turbulent flow at Re = 1.5×10 4 to avoid any transition regime in the boundary layer, and make the results relatively independent of the flow characteristics. A NACA 0012 airfoil is chosen at high reduced frequencies (k = 0.25 and 0.375) and high angles of attack to reach deep dynamic stall conditions. Additionally, time-resolved particle image velocimetry (PIV) and post-processing are used to compute the aerodynamic loads using a control-volume approach. The flow field is also reconstructed using proper orthogonal decomposition (POD) to separate the flow structures in different modes. It is shown that the kinematics can significantly influence the flow structure and aerodynamic loads. In the pre-stall region, the pure pitching motion usually produces higher lift force, while the pure heaving motion has a higher lift peak. However, in the post-stall region, the pure heaving motion usually has higher lift than the pure pitching motion. The pure heaving motion produced lower drag force than the pure pitching motion. For pure heaving motion, the POD analysis reveals there is a high-energy mode in the flow structure that helps to make the vortices more stable compared to pure pitching motion. Furthermore, the pure heaving motion adds extra kinetic energy to the boundary layer, which decelerates the reversal flow and the transfer of the separation point on suction side of the airfoil.