scholarly journals Application of non-linear k-e turbulence model in flow simulation over underwater axisymmetric hull at higher angle of attack

2011 ◽  
Vol 8 (2) ◽  
pp. 149-163 ◽  
Author(s):  
R Sakthivel ◽  
S Vengadesan ◽  
S K Bhattacharyya
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Autonomous Underwater Vehicle ◽  
Angle Of Attack ◽  
Cross Flow ◽  
Flow Simulation ◽  
Underwater Vehicle ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Non Linear

This paper addresses the Computational Fluid Dynamics Approach (CFD) to simulate the flow over underwater axisymmetric bodies at higher angle of attacks.  Three Dimensional (3D) flow simulation is carried out over MAYA Autonomous Underwater Vehicle (AUV) at a Reynolds number (Re) of 2.09×106. These 3D flows are complex due to cross flow interaction with hull which produces nonlinearity in the flow. Cross flow interaction between pressure side and suction side is studied in the presence of angle of attack. For the present study standard k-ε model, non-linear k-ε model models of turbulence are used for solving the Reynolds Averaged Navier-Stokes Equation (RANS). The non-linear k-ε turbulence model is validated against DARPA Suboff axisymmetric hull and its applicability for flow simulation over underwater axisymmetric hull is examined. The non-linear k-ε model performs well in 3D complex turbulent flows with flow separation and flow reattachment.  The effect of angle of attack over flow structure, force coefficients and wall related flow variables are discussed in detail. Keywords: Computational Fluid Dynamics (CFD); Autonomous Underwater Vehicle (AUV); Reynolds averaged Navier-Stokes Equation (RANS); non-linear k-ε turbulence modeldoi: http://dx.doi.org/10.3329/jname.v8i2.6984   Journal of Naval Architecture and Marine Engineering 8(2011) 149-163

Translational Added Mass of Axisymmetric Underwater Vehicles with Forward Speed Using Computational Fluid Dynamics

2011 ◽  
Vol 55 (03) ◽  
pp. 185-195
Author(s):  
Virag Mishra ◽  
S. Vengadesan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cross Flow ◽  
Added Mass ◽  
Navier Stokes ◽  
Inertia Force ◽  
Mass Coefficient ◽  
Computational Fluid Dynamics Cfd ◽  
Accelerated Flow ◽  
Axisymmetric Bodies

This paper presents a computational fluid dynamics (CFD) approach to the calculation of translational added mass coefficient of axisymmetric underwater bodies in both longitudinal and transverse directions. The proposed method involves CFD simulations of accelerated as well as uniform flows past axisymmetric bodies based on Reynolds averaged Navier-Stokes (RANS) equations and makes use of the results of these simulations to obtain the inertia force acting on a body as a function of time. The translational added mass can be obtained from this inertia force history. Validation of the methodology is presented for the benchmark case of accelerated flow past sphere and infinitely long circular cylinder in cross-flow for which analytical solutions of the added mass problem are well known.

scholarly journals What does computational fluid dynamics tell us about intracranial aneurysms? A meta-analysis and critical review

2019 ◽  
Vol 40 (5) ◽  
pp. 1021-1039 ◽  
Author(s):  
Khalid M Saqr ◽  
Sherif Rashad ◽  
Simon Tupin ◽  
Kuniyasu Niizuma ◽  
Tamer Hassan ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Intracranial Aneurysms ◽  
Meta Analysis ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Fundamental Properties ◽  
Cfd Models ◽  
Computational Fluid Dynamics Cfd ◽  
Supplementary Material

Despite the plethora of published studies on intracranial aneurysms (IAs) hemodynamic using computational fluid dynamics (CFD), limited progress has been made towards understanding the complex physics and biology underlying IA pathophysiology. Guided by 1733 published papers, we review and discuss the contemporary IA hemodynamics paradigm established through two decades of IA CFD simulations. We have traced the historical origins of simplified CFD models which impede the progress of comprehending IA pathology. We also delve into the debate concerning the Newtonian fluid assumption used to represent blood flow computationally. We evidently demonstrate that the Newtonian assumption, used in almost 90% of studies, might be insufficient to describe IA hemodynamics. In addition, some fundamental properties of the Navier–Stokes equation are revisited in supplementary material to highlight some widely spread misconceptions regarding wall shear stress (WSS) and its derivatives. Conclusively, our study draws a roadmap for next-generation IA CFD models to help researchers investigate the pathophysiology of IAs.

scholarly journals Numerical Investigation of Hydrodynamics Induced by a Pitched Blade Turbine: Effect of the Shape of Vessel Base

Mechanika ◽  
2019 ◽  
Vol 25 (5) ◽  
pp. 370-376 ◽  
Author(s):  
BELHANAFI Abdelghani
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Turbulent Model ◽  
Stirred Tanks ◽  
Navier Stokes Equation ◽  
Stirred Vessel ◽  
Pitched Blade Turbine ◽  
Hydrodynamic Structure

This paper presents an numerical analysis influence of bottom shape on the hydrodynamic structure for cylindrical stirred vessel with bump. The turbulent flow generated in stirred tanks is numerically predicted by the resolution of the Navier-Stokes equation using standard k-ε turbulent model. Several parameters on the mixture efficiency has been investigated. Particularly, we have studied the bottom shape of the tank, which is the distance between the bump-turbine with down pumping direction  and impeller diameter.  The numerical obtained results of the CFD (computational fluid dynamics) code CFX V13.0 with the MRF (Multi Reference Frame) are presented in order to understand the flow structure. The three components velocity profiles and the turbulent kinetic energy dimensionless distributions obtained at bottom tanks with three different heights are analyzed and discussed. From these results, we can confirm that including a bump at the bottom center of the tank closer to the turbine improves significantly the operating conditions of stirring and mixing. Predictions have been compared with literature data and a satisfactory agreement has been found.

scholarly journals Mixing Performance of Counter-Axial Flow Impeller using Computational Fluid Dynamics

2018 ◽  
Vol 8 (02) ◽  
Author(s):  
Ian Torotwa ◽  
Changying Ji
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Axial Flow ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Rushton Turbine ◽  
Mixing Performance ◽  
Computational Fluid Dynamics Cfd

In this study, turbulent flow fields in a baffled vessel stirred by counter-axial flow impeller have been investigated in comparison to the Rushton turbine. The resultant turbulence was numerically predicted using computational fluid dynamics (CFD). Turbulence models were developed in ANSYS Fluent 18.1 solver using the Navier-Stokes equation with the standard k-ε turbulence model. The Multiple Reference Frame (MRF) approach was used to simulate the impeller action in the vertical and horizontal planes of the stirred fluid volume. Velocity profiles generated from the simulations were used to predict and compare the performance of the two designs. To validate the CFD model, the simulation results were compared with experimental results from existing work and a satisfactory agreement was established. It was concluded that the counter-axial flow impeller could provide better turbulence characteristics that would improve the quality of mixing systems.

Robotic Fish

2014 ◽  
Vol 26 (3) ◽  
pp. 391-393
Author(s):  
Yogo Takada ◽  
◽  
Keisuke Koyama ◽  
Takahiro Usami
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Autonomous Underwater Vehicle ◽  
Underwater Vehicle ◽  
Robotic Fish ◽  
Remotely Operated Vehicle ◽  
Gate Arrays ◽  
Propulsion Performance ◽  
Entertainment Robot ◽  
Computational Fluid Dynamics Cfd

<div class=""abs_img""><img src=""[disp_template_path]/JRM/abst-image/00260003/13.jpg"" width=""300"" />Structure of BREAM </span></div> Based on our robotic fish studies since 2003, this paper introduces a FPGA offline control underwater searcher (FOCUS) and a bream robot equipped with advanced mechanism (BREAM). The performance of the first FOCUS prototype, built in 2011, is now being improved. FOCUS has 2 cameras and fieldprogrammable gate arrays (FPGAs) with high arithmetic processing capabilities. The appearance of the FOCUS is so cute. The two FOCUS types now available are an autonomous underwater vehicle (AUV) and a remotely operated vehicle (ROV). BREAM, in contrast, is an entertainment robot prototype designed for Asutamuland Tokushima exhibition. BREAM has four joints based on analytical computational fluid dynamics (CFD) results showing that robotic fish with multiple joints achieve better propulsion performance than that with single joint. Two of the four joints are used for propulsion and two are used for turning the prototype. RC-FOCUS is also exhibited at Asutamuland Tokushima, together with BREAM. </span>

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