Multiple steady solutions and bifurcations in the symmetric driven cavity

The symmetric driven cavity with sinusoidal forcing for two- and three-dimensions is considered. Results are obtained via numerical computations of the Navier Stokes equations with constant density. The numerical integration is a splitting method, using the Crank-Nicholson method for linear terms and the second-order Adams-Bashforth method for the non-linear terms. Spatial derivatives are evaluated with finite differences, and matrix equations are treated with SOR by lines. The results show symmetric solutions for low Reynolds numbers and asymmetric solutions for higher Reynolds numbers. Subcritical bifurcations are observed for two-dimensional flow. Unsteady flow behavior occurs at higher Reynolds number. Three-dimensional simulations for a cube show only one steady solution

Greenhouse Gas Reduction by Utilization of Cold LNG Boil-off Gas

AbstractThis paper present the analysis of utilization the cryogenic temperature of Boil off Gas (BOG) from Liquefied Natural Gas (LNG) to flow air inside insulation space of LNG. Three Dimensional geometry of the tank are model in Computational Fluid Dynamic (CFD) ANSYS Fluent software package using steady state and K-Epsilon turbulence model. Result shows that almost 60% of BOG can be prevented from flared to the atmosphere thus will reduce Greenhouse Gas (GHG) emission and pollution

Boil-off gas formation inside large scale liquefied natural gas (LNG) tank based on specific parameters

Liquefied Natural Gas (LNG) fleets are coasting with various condition and behavior. These variable leads to different type of LNG fleets build every year with unavoidable generated Boil-off Gas (BOG). Estimation of BOG generated inside LNG tank play significant role in determines the ship specification and management method of BOG including venting, propulsion or requalification. Hence, in the present study, the right choices of boundary condition and parameter have been implementing in order to have good estimation amount of BOG evaporates for specific LNG tank. Three dimensional model of cargo with capacity 160000 m3 LNG carrier are simulate using ANSYS Fluent with specific ambient air temperature of 5oC and ambient seawater temperature of 0oC have been chosen as a calculation case, gain the total heat transfer rate and Boiloff Rate (BOR). The result shows that the calculation model and simulation are feasible with typical LNG fleet specification and International Marine Organization (IMO) standard

Estimation of mitral valve degenerative behavior with mitral regurgitation

Degenerative mitral valve prolapse without proper monitoring can cause severe mitral valve failure and occasionally lead to sudden death if the surgical correction is not performed on time. In most cases, mitral valve prolapse would cause mitral regurgitation which in a severe case would lead to left ventricle failure due to hemodynamic burden. The aim of this study is to develop a model to predict the degeneration behaviour of mitral valve which will aid the medical practitioner to estimate the mitral valve condition based on the available mitral regurgitation data by echocardiogram assessment. Minimal hemodynamic model has been adopted with modification to obtain mitral regurgitation severity information. The stress-strain behaviour of mitral leaflet has also been studied to model the degeneration of the mitral valve leaflet. Both models were validated with the previously published data generated using Windkessel and Burkhoff methods. The coupling of both models gave the degenerative behaviour of mitral valve leaflet in relation with mitral regurgitation severity. The mitral valve degeneration was assessed by mitral valve leaflet elasticity properties while the severity of mitral regurgitation was measured by the volume of mitral regurgitation into the left atrium. It was found that the reduction of mitral valve leaflet elasticity would cause an increase of the mitral regurgitation volume into the left atrium. Mitral regurgitation severity was found to be less than 10% of left ventricle stroke volume when the mitral valve leaflet degenerates more than 90%. At this point, even with a slight increase of less than 10% in the degeneration of mitral valve leaflet, the regurgitation volume might increase suddenly from 5% up to 95% of the left ventricle stroke volume

Graphical User Interface (GUI) In MatLab for Solving the Pulsatile Flow in Blood Vessel

Blood flow analysis is a study of measuring the blood pressure and finding its equivalent flow rate, velocity profile and wall shear stress. In this article, the relationship between blood pressure gradient, velocity profile, centreline velocity, volumetric flow rate and wall shear stress is determined analytically through a Graphical User Interface (GUI) developed using MatLab. If one of these time-dependent blood flow properties is known, i.e. pressure gradient, velocity profile, volumetric flow rate or wall shear stress, then the remaining properties can be calculated. A code is developed to solve these blood flow properties. Any time-dependent blood properties can be used as input data. These data are then digitized and saved in this code. Subsequently, these data are curve-fitted using the Fourier series. The corresponding coefficients of Fourier series are then used to calculate the blood property. Once this is obtained, the remaining three other flow properties can be subsequently calculated. This GUI serves as a learning tool for students who wish to pursue his/her knowledge in understanding the relationship of various blood flow properties of pulsatile blood flow as well as the mathematics governing pulsatile flows. (Authors' abstract

Analysis of flow in pulse combustor tailpipe

Pulse combustion is known to have the higher combustion efficiency compared to conventional steady type burner in heating application (Putnam, 1971). However, there are many parameters need for scientific study in designing this kind of combustor. This study intends to model the pulse combustion in order to determine important characteristics that govern the performance of the pulse combustor. The important parameters identified in this study namely frequency, pressure oscillation and pulsating flow inside tailpipe. This study will be useful for predicting the capability of pulse combustor especially in heating application

Non-dimensional distribution pattern analysis of particle transportation in simplified pipeline system

Sustainable preservation of pipeline system that deal with particle transportation is more appealing these days. In petroleum industries for instance, sand transported through the pipelines pose serious problems ranging from blockage, corrosion, abrasion and reduction in pipe efficiency to loss of pipe integrity. Accurate four-dimensional simulation that caters the transient effect of the phenomena is used to promote sustainability in design, evaluation and maintenance procedures. This is employed to minimize conventional practices which are costly and inefficient. This work demonstrates the advantages of applying four-dimensional Splitting Fluid-Particle Solver to simulate particle transportation within a simplified pipeline system. Single-phase fluid with solid sphere particles are the assumptions while drift and gravitational forces are taken into account. Effect of fluid flow rate and particle weight alterations are observed within vertical curled and 2-1-2 segmental pipeline. Flow rate variation on multiple inputs shows that proper simulation is essential in order to predict fluid flow behavior prior to pipeline construction. Particle weight variation shows that simulation can lead to better prediction of potential areas of blockage, corrosion, abrasion and other piping system issues. This work proves that four-dimensional simulation can promote sustainability, cost effectiveness and efficiency of pipeline system management

COMPUTATIONAL INVESTIGATION ON CSF FLOW ANALYSIS IN THE THIRD VENTRICLE AND AQUEDUCT OF SYLVIUS

In this study, a three dimensional (3D) model of the third ventricle and aqueduct of Sylvius derived from MRI scans was constructed by using Computational Fluid Dynamics (CFD) modeling. Cerebrospinal fluid(CSF) can be modeled as a Newtonian Fluid and its flow through the region of interest (ROI) was visualized using Engineering Fluid Dynamics (EFD).The constructed ROI was regarded as rigid walled and only steady state flow was able to be defined due to the limitations of current software. Different flow rate was simulated at the Foramen of Monro and a small stenosis was modeled at the middle of the aqueduct of Sylvius at a fixed location. This was made corresponding to normal patients with variation of CSF flow rate physiologically and abnormal patients with tumor causing obstruction to or within the aqueduct of Sylvius, respectively. Due to the small dimensions of the ROI geometry, gravity and complex external gravity that acted upon it was considered to be neglected. The results show as the flow rate increase, the pressure drop of CSF in the ROI proportionally increased. For normal CSF flow rate, the presence of stenosis in the aqueduct demonstrates a significant increased pressure drop. ABSTRAK-Dalam kajian ini, model tiga dimensi (3D) untuk ventrikel ketiga dan akueduk Sylvius, yang terhasil daripada pengimejan resonans magnetik telah dikonstruksi menggunakan Permodelan Perkomputeran Dinamik Bendalir (Computational Fluid Dynamics (CFD)). Cecair serebrospinal (Cerebrospinal fluid (CSF)) dimodelkan sebagai bendalir Newtonan dan alirannya melalui kawasan kepentingan (region of interest (ROI)) digambarkan menggunakan Dinamik Bendalir Kejuruteraan (Engineering Fluid Dynamics (EFD)). Kawasan kepentingan yang dikonstruksi dianggap sebagai dinding tegar dan hanya aliran keadaan tunak yang dapat ditakrifkan berdasarkan pengehadan perisian komputer terkini. Kadar aliran yang berbeza disimulasikan di foramen monro dan laluan stenosis yang kecil dimodelkan di tengah-tengah akueduk Sylvius di satu lokasi yang telah ditetapkan. Kaedah ini dijalankan terhadap pesakit normal dengan variasi pada kadar aliran CSF, serta pesakit abnormal yang mempunyai tumor, penyebab sekatan terhadap atau melinkungi akueduk Sylvius. Disebabkan oleh ukuran geometri ROI kecil, tarikan graviti dan graviti luar kompleks yang bertindak ke atasnya diabaikan. Keputusan menunjukkan bahawa apabila kadar aliran meningkat, susutan tekanan CSF di dalam ROI meningkat dengan berkadar. Untuk kadar aliran CSF yang normal, kehadiran stenosis di dalam akueduk membuktikan pertambahan susutan tekanan yang ketara

The Effect of Different Reynolds Number On Solid Sphere Using CFD and Its Verification

Aerodynamic behaviour of an object depends on several factors, namely shape, size and flow conditions. Thus, CFD simulations are an effective engineering tools that allows major contribution to understand the flow conditions around an object. This study aims to analyse the effect of two various shapes of spherical models on aerodynamics behaviour for different Reynolds number between 100,000 ≤ Re ≤ 800,000. Geometry models are generated using SolidWorks 2017 and numerical solution is analysed using ANSYS CFX. The numerical results are later compared with experimental data collected from wind tunnel. At the end of the study, the nature flow around spherical models of different Reynolds number are visualized. It is discovered that the flow behaviour around the spherical model changes as the Reynolds number increases. This finding is parallel with past researchers. These forecasts should assist engineers enhance the application of aerodynamic and hydrodynamic design