Application of non-linear k-e turbulence model in flow simulation over underwater axisymmetric hull at higher angle of attack
TL;DR: In this paper, the effect of angle of attack over flow structure, force coefficients and wall related flow variables are discussed in detail, and the non-linear k-e turbulence model is validated against DARPA Suboff axisymmetric hull.
Abstract: 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 2.09×10 6 . 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-e model, non-linear k-e model models of turbulence are used for solving the Reynolds Averaged Navier-Stokes Equation (RANS). The non-linear k-e 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-e 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-e turbulence model doi: http://dx.doi.org/10.3329/jname.v8i2.6984 Journal of Naval Architecture and Marine Engineering 8(2011) 149-163
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01 Feb 2021
TL;DR: Autonomous underwater vehicles play an essential role in geophysical data collection, deep water mining, seafloor mapping, ocean exploration, and in many other related activities starting from mili... as mentioned in this paper.
Abstract: Autonomous underwater vehicles play an essential role in geophysical data collection, deep water mining, seafloor mapping, ocean exploration, and in many other related activities starting from mili...
37 citations
TL;DR: In this article, experimental and numerical studies carried out in conjunction, to investigate the hydrodynamic characteristics of AUV hulls at different Reynolds numbers over sloped channel-beds are presented.
Abstract: Improved designs for Autonomous Underwater Vehicles (AUV) are becoming increasingly important due to their utility in academic and industrial applications. However, a majority of such testing and design is carried out under conditions that may not reflect the operating environment of shallow water AUVs. This may lead to imprecise estimations of the AUV's performance and sub-optimal designs. This article presents experimental and numerical studies carried out in conjunction, to investigate the hydrodynamic characteristics of AUV hulls at different Reynolds numbers over sloped channel-beds. We carry out experiments to measure the velocity field and turbulent statistics around the AUV with quantified uncertainty. These are contrasted against corresponding flat bed experiments to gauge the effect of test bed topography on AUV performance. The experimental data was used to validate Reynolds Stress Model predictions. Hydrodynamic parameters such as drag, pressure and skin friction coefficients were predicted from the RSM simulations at different test bed slopes, angles of attack and drift angles of the AUV hull, to analyze the hydrodynamic performance of the AUV. The results presented in this article offer avenues for design improvement of AUVs operating in shallow environments, such as the continental slope and estuaries.
27 citations
TL;DR: In this paper, experimental and numerical studies on the effect of free stream turbulence (FST) on evolution of flow over an AUV hull form at three Reynolds numbers with different submergence depths and angles of attack.
Abstract: This article presents experimental and numerical studies on the effect of free stream turbulence (FST) on evolution of flow over an autonomous underwater vehicle (AUV) hull form at three Reynolds numbers with different submergence depths and angles of attack. The experiments were conducted in a recirculating water tank and the instantaneous velocity profiles were recorded along the AUV using Acoustic Doppler Velocimetry (ADV). The experimental results of stream-wise mean velocity, turbulent kinetic energy (TKE) and Reynolds stresses were used to validate the predictive capability of a Reynolds stress model (RSM) with the wall reflection term of the pressure strain correlation. From the high fidelity RSM based simulations it is observed that in presence of free stream turbulence, the pressure, skin friction, drag and lift coefficients decrease on the AUV hull. The variation of the hydrodynamic coefficients were also plotted along the AUV hull for different values of submergence depth and angle of attack with different levels of free stream turbulence. The conclusions from this experimental and numerical investigation give guidance for improved design paradigms for the design of AUVs.
25 citations
TL;DR: In this paper, the authors investigated the hydrodynamic performance of an AUV, calculate its hydrodynamics coefficients, and consider the flow characteristics of underwater bodies, and conclude that a hull shape with bullet nose and sharp tail with length-to-diameter ratio (LTDR) equal to 7.14 performs better than the SUBOFF model.
Abstract: The main aims of this study are to investigate the hydrodynamic performance of an autonomous underwater vehicle (AUV), calculate its hydrodynamic coefficients, and consider the flow characteristics of underwater bodies. In addition, three important parts of the SUBOFF bare hull, namely the main body, nose, and tail, are modified and redesigned to improve its hydrodynamic performance. A three-dimensional (3D) simulation is carried out using the computational fluid dynamics (CFD) method. To simulate turbulence, the k–ω shear stress transport (SST) model is employed, due to its good prediction capability at reasonable computational cost. Considering the effects of the length-to-diameter ratio (LTDR) and the nose and tail shapes on the hydrodynamic coefficients, it is concluded that a hull shape with bullet nose and sharp tail with LTDR equal to 7.14 performs better than the SUBOFF model. The final proposed model shows lower drag by about 14.9% at u = 1.5 m·s−1. Moreover, it produces 8 times more lift than the SUBOFF model at u = 6.1 m·s−1. These effects are due to the attachment of the fluid flow at the tail area of the hull, which weakens the wake region.
21 citations
TL;DR: In this article, the authors performed calculations on the bare hull DRAPA SUBOFF submarine to investigate the capability of viscous-flow solvers to predict the forces and moments as well as flow field around the body.
Abstract: To estimate the maneuverability of a submarine at the early design stage, an accurate evaluation of the hydrodynamic coefficients is important. In a collaborative exercise, the authors performed calculations on the bare hull DRAPA SUBOFF submarine to investigate the capability of viscous-flow solvers to predict the forces and moments as well as flow field around the body. A typical simulation program was performed for both the steady drift tests and rotating arm tests. The same grid topology based on multi-block mesh strategy was used to discretize the computational domain. A procedure designated drift sweep was implemented to automatically increment the drift angle during the simulation of steady drift tests. The rotating coordinate system was adopted to perform the simulation of rotating arm tests. The Coriolis force and centrifugal force due to the computation in a rotating frame of reference were treated explicitly and added to momentum equations as source terms. Lastly, the computed forces and moment as a function of angles of drift in both conditions are compared with experimental results and literature values. They always show the correct trend. Flow field quantities including pressure coefficients and vorticity and axial velocity contours are also visualized to vividly describe the evolution of flow motions along the hull.
13 citations
References
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TL;DR: In this article, a towing tank-based experimental study on AUV hull form in the vertical plane is presented, where the hydrodynamic forces and moment are measured by an internally mounted multi-component strain gauge type balance.
Abstract: Extensive use of autonomous underwater vehicles (AUVs) in oceanographic applications necessitates investigation into the hydrodynamic forces acting over an AUV hull form operating under deeply submerged condition. This paper presents a towing tank-based experimental study on forces and moment on AUV hull form in the vertical plane. The AUV hull form considered in the present program is a 1:2 model of the standard hull form Afterbody1. The present measurements were carried out at typical speeds of autonomous underwater vehicles (0.4–1.4 m/s) by varying pitch angles (0–15°). The hydrodynamic forces and moment are measured by an internally mounted multi-component strain gauge type balance. The measurements were used to study variation of axial, normal, drag, lift and pitching moment coefficients with Reynolds number ( Re ) and angle of attack. The measurements have also been used to validate results obtained from a CFD code that uses Reynolds Average Navier–Stokes equations (ANSYS™ Fluent). The axial and normal force coefficients are increased by 18% and 195%; drag, lift and pitching moment coefficients are increased by 90%, 182% and 297% on AUV hull form at α =15° and Re v =3.65×10 5 . These results can give better idea for the efficient design of guidance and control systems for AUV.
163 citations
Additional excerpts
...Jagadeesh et al (2009) made a comparative evaluation between experiments and numerical studies....
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TL;DR: In this paper, a method of predicting body drag in subcritical axisymmetric flow is outlined which requires only detailed body shape, free-stream conditions and transition point to be prescribed.
Abstract: A method of predicting body drag in subcritical axisymmetric flow is outlined which requires only detailed body shape, free-stream conditions and transition point to be prescribed. Results of calculations for a range of body shapes are shown essentially to confirm information in Royal Aeronautical Society Data Sheets but clearly demonstrate that fineness ratio alone is not sufficient to characterise body shape. For example, at a fixed fineness ratio of 0.18, detailed changes in body contour are shown to produce 10 per cent changes in drag coefficient.
125 citations
"Application of non-linear k-e turbu..." refers methods in this paper
...The shape of the body is derived from the Myring parameter [Myring (1976)]....
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TL;DR: In this article, a non-linear k-model is adopted as a turbulence model, which can take into account the anisotropy of turbulence with less CPU time and computer memory than RSM or LES.
Abstract: SUMMARY The incompressibleow around blubodies (a square cylinder and a cube) is investigated numerically using turbulence models. A non-linear k - � model, which can take into account the anisotropy of turbulence with less CPU time and computer memory than RSM or LES, is adopted as a turbulence model. In tuning of the model, the model coecients of the non-linear terms are adjusted through the examination of previous experimental studies in simple shearows. For the tuning of the coecient in the eddy viscosity (= C� ), the realizability constraints are derived in three types of basic 2Dow patterns, namely, a simple shearow, �ow around a saddle and a focal point. Cis then determined as a function of the strain and rotation parameters to satisfy the realizability. The turbulence model is �rst applied to a 2Dow around a square cylinder and the model performance for unsteadyows is examined focussing on the period and the amplitude of theow oscillation induced by Karman vortex shedding. The applicability of the model to 3Dows is examined through the computation of theow around a surface-mounted cubic obstacle. The numerical results show that the present model performs satisfactorily to reproduce complex turbulentows around blubodies. Copyright ? 2003 John Wiley & Sons, Ltd.
122 citations
"Application of non-linear k-e turbu..." refers background or methods in this paper
...The model performance for the wall mounted cube is analyzed by Kimura and Hosoda (2003) which is complex three dimensional turbulent flow with flow separation, vortex shedding and flow reattachment....
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...(6) Non-linear terms in the above mentioned equation are reported in Kimura and Hosoda (2003)....
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TL;DR: In this article, the location of three-dimensional crossflow separations is evaluated using several data sets, including oil flow visualization, laser Doppler velocimetry, surface pressure, and surface hot-film skin-friction measurements (magnitude only and directional).
Abstract: Parameters and techniques for detecting the location of three-dimensional crossflow separations are evaluated using several data sets. Several definitions of separations and the physics of the separation process are discussed along with descriptions of the separated flowfield. Measurement techniques that depend on each of these descriptions are then considered, and data are compared and contrasted. The data analyzed here represent a very rare combination of many different measurement techniques applied to the same geometry and apparatus from several different studies, including oil flow visualization, laser Doppler velocimetry, surface pressure, and surface hot-film skin-friction measurements (magnitude only and directional). Pressure is the least sensitive of the indicators of separation, although minima in rms pressure fluctuations correlate well with separation location. Hot-film skin-friction magnitude measurement is one of the easiest and most accurate techniques; local minima correlate well with separation location. Laser Doppler velocimeter measurements provide the most detail about the separation flowfield but at great expense and with the limitation of requiring knowledge of the separation line direction
94 citations
"Application of non-linear k-e turbu..." refers background or methods in this paper
...The typical flow structures around axisymmetric bodies were reported in Wetzel et al (1998) and Pantelatos and Mathioulakis (2004)....
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...Cross flow interaction over prolate spheroid was investigated experimentally by Wetzel et al (1998)....
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TL;DR: Computational Fluid Dynamic (CFD) based on Reynolds Averaged Navier-Stokes equation is used for determining the transverse hydrodynamic damping force and moment coefficients that are needed in the maneuverability study of marine vehicles.
Abstract: Computational Fluid Dynamic (CFD) based on Reynolds Averaged Navier–Stokes equation is used for determining the transverse hydrodynamic damping force and moment coefficients that are needed in the maneuverability study of marine vehicles. Computations are performed for two geometrical shapes representing typical AUVs presently in use. Results are compared with available data on similar geometries and from some of the available semi-empirical relations. It is found that the CFD predictions compares reasonable well with these results. In particular, the CFD predictions of forces and moments are found to be nonlinear with respect to the transverse velocity, and therefore both linear and nonlinear coefficients can be derived. A discussion on the sources of the component forces reveal that the total force and moment variations should in fact be nonlinear.
93 citations
"Application of non-linear k-e turbu..." refers background or methods or result in this paper
...Phillips et al (2007) and Tyagi and Sen (2006) reported the computational approach to predict the lateral hydrodynamic coefficients at various sway velocities....
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...Phillips et al (2007) and Tyagi and Sen (2006) reported the computational approach to predict the lateral hydrodynamic coefficients at various sway velocities. In their studies different numerical strategies such as numerical drift test, rotating arm test were applied to determine the coefficients of underwater hull. De Barros et al (2008) also developed CFD technique to compute the force coefficients of the bare hull for different angles of attack. The results obtained from the CFD approach were compared with the semi-empirical and experimental values. Jagadeesh et al (2009) made a comparative evaluation between experiments and numerical studies....
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...Phillips et al (2007) and Tyagi and Sen (2006) reported the computational approach to predict the lateral hydrodynamic coefficients at various sway velocities. In their studies different numerical strategies such as numerical drift test, rotating arm test were applied to determine the coefficients of underwater hull. De Barros et al (2008) also developed CFD technique to compute the force coefficients of the bare hull for different angles of attack....
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