A Practical Method to Study Over and Under-Pressurizing of Ship Tanks During Ballasting and Deballasting

2008 ◽  
Author(s):  
Manoj Kumar
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Parametric Study ◽  
Pressure Rise ◽  
Practical Method ◽  
Hole Diameter ◽  
Maximum Pressure ◽  
Opening And Closing ◽  
Hull Damage

There have been many incidents of hull damage due to over and under-pressurizing of ship tanks during ballasting and deballasting. A safety relief hole of 6 to 8mm diameter is generally provided in Air-pipes to prevent accidental over and under-pressurizing of ship tanks during ballasting and deballasting. This paper investigates the pressure rise and drop inside the tank assuming the air-pipe to be closed. A practical method based on Computational Fluid Dynamics has been presented to find out the maximum pressure rise or drop. A parametric study, based on varying relief hole diameter, has been carried out. The investigation brings to prospective the extent of pressure rise or drop, and hence the damages that can occur due to poor operation of the Air-pipes during ballasting and deballasting and a need for automated opening and closing of the Air-pipes for a safer ship.

scholarly journals Formation and manipulation of ferrofluid droplets with magnetic fields in a microdevice: a numerical parametric study

Soft Matter ◽  
2020 ◽  
Vol 16 (41) ◽  
pp. 9506-9518 ◽  
Author(s):  
Venoos Amiri Roodan ◽  
Jenifer Gómez-Pastora ◽  
Ioannis H. Karampelas ◽  
Cristina González-Fernández ◽  
Eugenio Bringas ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Magnetic Fields ◽  
Microfluidic Device ◽  
Parametric Study ◽  
Magnetic Force ◽  
Continuous Phase ◽  
Numerical Parametric Study

Integrated computational fluid dynamics and magnetics simulation is employed to analyze the effects of magnetic force on the formation and manipulation of ferrofluid droplets within a flowing non-magnetic continuous phase in a microfluidic device.

Predicting the Treatment Response of Oral Appliances for Obstructive Sleep Apnea Using Computational Fluid Dynamics and Fluid-Structure Interaction Simulations

2013 ◽  
Author(s):  
Moyin Zhao ◽  
Tracie Barber ◽  
Peter Cistulli ◽  
Kate Sutherland ◽  
Gary Rosengarten
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Obstructive Sleep Apnea ◽  
Sleep Apnea ◽  
Pressure Drop ◽  
Treatment Response ◽  
Fluid Structure Interaction ◽  
Maximum Pressure ◽  
Structure Interaction ◽  
Obstructive Sleep

In this study we used computational fluid dynamics (CFD) to analyze the therapeutic effect of an oral device (mandibular advancement splint – MAS, that protrudes the lower jaw during sleep) as a treatment for Obstructive Sleep Apnea (OSA). Anatomically-accurate upper airway (UA) computational models were reconstructed from magnetic resonance images (MRI) of 7 patients with and without a MAS device fitted. CFD simulations of UA airflow were performed at the maximum flow rate during inspiration. The CFD results indicated the lowest pressure often occurs close to the soft palate and the base of the tongue. The airway pressure gradient was estimated as the best indicator for treatment response since the change in the pressure drop forms a linear correlation with the change in patients’ Apnea-Hypopnea Index (AHI). This correlation has the potential to be developed into a model for predicting the outcome of the MAS treatment. However the rigid wall assumption of CFD models is the major uncertainty. To overcome this uncertainty we set up a full fluid-structure interaction model for a typical responder case with a compliant UA wall. The results demonstrated the different UA flow field associated with using MAS alleviated the airway collapse, which was successfully predicted for the untreated patient. We thus show for the first time that FSI is more accurate than CFD with rigid walls for the study of OSA, and can predict treatment response. Comparison of the FSI and CFD results for the UA flow and pressure profiles showed variation between the models. The structural deflection in oropharynx effectively reformed the flow pattern, however, the maximum pressure drops of both results were close. This supports the competence of the CFD method in clinical applications, where maximum pressure drop data can be used to develop a treatment-predicting model.

A New Computational Fluid Dynamics Model To Optimize Sucker Rod Pump Operation and Design

2021 ◽  
pp. 1-9
Author(s):  
Shreyas V. Jalikop ◽  
Bernhard Scheichl ◽  
Stefan J. Eder ◽  
Stefan Hönig
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Operating Conditions ◽  
Valve Closure ◽  
Dynamics Model ◽  
Pump Design ◽  
Pump Operation ◽  
Computational Fluid Dynamics Model ◽  
Sucker Rod ◽  
Opening And Closing

Summary Artificial lift systems are widely used in oil production, of which sucker rod pumps are conceptually among the simpler ones. The reciprocating movement of the plunger triggers the opening and closing of two ball valves, allowing fluid to be pumped to the surface. Their built-in ball valves are subject to long-time erosion and fail as a consequence of this damage mechanism. Understanding the principal damage mechanisms requires a thorough examination of the fluid dynamics during the opening and closing action of these valves. In this article, we present a fluid-structure interaction model that simultaneously computes the fluid flow in the traveling valve (TV), the standing valve (SV), and the chamber of sucker rod pumps during a full pump cycle. The simulations shed light on the causes of valve damage for standard and nonideal operating conditions of the pump. In particular, our simulations based on real pump operating envelopes reveal that the so-called “midcycle valve closure” is likely to occur. Such additional closing and opening events of the valves multiply situations in which the flow conditions are harmful to the individual pump components, leading to efficiency reduction and pump failure. This mechanism, hitherto unreported in the literature, is believed to constitute the primary cause of long-term valve damage. Our finite element method-based computational-fluid-dynamics model can accurately describe the opening and closing cycles of the two valves. For the first time, this approach allows an analysis of real TV speed versus position plots, usually called pump cards. The effects of stroke length, plunger speed, and fluid parameters on the velocity and pressure at any point and time inside the pump can thus be investigated. Identifying the damage-critical flow parameters can help suggest measures to avoid unfavorable operating envelopes in future pump designs. Our flow model may support field operations throughout the entire well life, ranging from improved downhole pump design to optimized pump operation or material selections. It can aid the creation of an ideal interaction between the valves, thus avoiding midcycle valve closure to drastically extend the mean time between failures of sucker rod pumps. Finally, our simulation approach will speed up new pump component development while greatly reducing the necessity for costly laboratory testing.

scholarly journals Revisiting the Simplified Bernoulli Equation

2010 ◽  
Vol 4 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Jeffrey J Heys ◽  
Nicole Holyoak ◽  
Anna M Calleja ◽  
Marek Belohlavek ◽  
Hari P Chaliki
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Dynamics Simulation ◽  
Maximum Pressure ◽  
Bernoulli Equation ◽  
Computational Fluid Dynamics Simulation ◽  
Valvular Stenosis ◽  
Significant Difference

Background: The assessment of the severity of aortic valve stenosis is done by either invasive catheterization or non-invasive Doppler Echocardiography in conjunction with the simplified Bernoulli equation. The catheter measurement is generally considered more accurate, but the procedure is also more likely to have dangerous complications. Objective: The focus here is on examining computational fluid dynamics as an alternative method for analyzing the echo data and determining whether it can provide results similar to the catheter measurement. Methods: An in vitro heart model with a rigid orifice is used as a first step in comparing echocardiographic data, which uses the simplified Bernoulli equation, catheterization, and echocardiographic data, which uses computational fluid dynamics (i.e., the Navier-Stokes equations). Results: For a 0.93cm2 orifice, the maximum pressure gradient predicted by either the simplified Bernoulli equation or computational fluid dynamics was not significantly different from the experimental catheter measurement (p > 0.01). For a smaller 0.52cm2 orifice, there was a small but significant difference (p < 0.01) between the simplified Bernoulli equation and the computational fluid dynamics simulation, with the computational fluid dynamics simulation giving better agreement with experimental data for some turbulence models. Conclusion: For this simplified, in vitro system, the use of computational fluid dynamics provides an improvement over the simplified Bernoulli equation with the biggest improvement being seen at higher valvular stenosis levels.

scholarly journals Aerodynamics analysis of electric car UM body surface using computational fluid dynamics

2018 ◽  
Vol 204 ◽  
pp. 07016
Author(s):  
Mardji ◽  
Andoko ◽  
Dani Prsetiyo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Flow ◽  
Experimental Testing ◽  
Flow Analysis ◽  
Maximum Velocity ◽  
The Body ◽  
Maximum Pressure ◽  
Large Area ◽  
Electric Car

The body shape that is engineered in such a way will produce fluid flow characteristics that very and greatly affect the function of the shape of the body. However, until now researchers have not been able to find the right solution to diagnose and synthesize flow structures, so that it is done directly through experimental testing [3]. One of them by using the help of a software CFD (Computational Fluid Dynamics) is Ansys 18.1. Fluid Flow Analysis on the surface of the body electric car UM produces several characteristics such as fluid flow which has a significant obstacle, especially on the surface that has a wide surface that causes a flow that causes the flow is red which indicates the velocity of air flowing in that large area obtained maximum velocity air results of 21.1885m / s marked with the color red and velocity minimum of 0.03947m / s marked in blue, other than that when the air flows produce a pressure that produces the maximum pressure received by the body of 79.12Pa and the minimum pressure of -316.1Pa and the value of drag coefficient from the car body electric car UM obtained results of 0.46.

scholarly journals Computational fluid dynamics simulation and parametric study of an open channel ultra-violet wastewater disinfection reactor

2014 ◽  
Vol 50 (1) ◽  
pp. 58-71 ◽  
Author(s):  
Rajib Kumar Saha ◽  
Madhumita Ray ◽  
Chao Zhang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Parametric Study ◽  
Open Channel ◽  
Ultra Violet ◽  
Dynamics Simulation ◽  
Inactivation Kinetics ◽  
Cfd Model ◽  
Particle Tracking Method ◽  
Numerical Predictions

The disinfection characteristics of an open channel ultra-violet (UV) disinfection reactor is investigated numerically. The computational fluid dynamics (CFD) model used in this study is based on the volume of fluid (VOF) method to capture the water–air interface. The Lagrangian particle tracking method is used to calculate the microbial particle trajectory and the discrete ordinate (DO) model is used to calculate the UV intensity field inside the reactor. A commercial CFD software package ANSYS FLUENT is used to solve the governing equations. Custom user defined functions (UDFs) are developed to calculate the UV doses. A post-processor is developed in MATLAB to implement the inactivation kinetics of the microbes. The post-processor provides the probabilistic dose distribution and reduction equivalent dose (RED) values achievable in the reactor. The numerical predictions are compared with available experimental data to validate the CFD model. A parametric study is performed to understand the effects of different parameters on disinfection performance of the reactor. The low/high dosed particle trajectories, which can provide an insight for hydraulic and optical characteristics of the reactor for possible design improvements, are identified.

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