Unsteady free-surface wave-induced separation: analysis of turbulent structures using detached eddy simulation and single-phase level set

2007 ◽  
Vol 8 ◽  
pp. N44 ◽  
Author(s):  
Tao Xing ◽  
Mani Kandasamy ◽  
Frederick Stern
Keyword(s):  
Free Surface ◽  
Surface Wave ◽  
Level Set ◽  
Single Phase ◽  
Detached Eddy Simulation ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Free Surface Wave ◽  
Wave Induced

scholarly journals Numerical Simulations of Linearly Stratified Flow Past Submerged Bodies

2018 ◽  
Vol 25 (s3) ◽  
pp. 68-77
Author(s):  
Weizhuang Ma ◽  
Yunbo Li ◽  
Yong Ding ◽  
Kaiye Hu ◽  
Linxin Lan
Keyword(s):  
Free Surface ◽  
Surface Wave ◽  
Density Gradient ◽  
Wave Height ◽  
Near Field ◽  
Turbulence Models ◽  
Stratified Flow ◽  
Stratified Flows ◽  
Detached Eddy Simulation ◽  
Free Surface Wave

Abstract In this study, a methodology was presented to predict density stratified flows in the near-field of submerged bodies. The energy equation in temperature form was solved coupled with momentum and mass conservation equations. Linear stratification was achieved by the definition of the density as a function of temperature. At first, verifications were performed for the stratified flows passing a submerged horizontal circular cylinder, showing excellent agreement with available experimental data. The ability of the method to cope with variable density was demonstrated. Different turbulence models were used for different Re numbers and flow states. Based on the numerical methods proposed in this paper, the stratified flow was studied for the real scale benchmark DAPRA Suboff submarine. The approach used the VOF method for tracing the free surface. Turbulence was implemented with a k − ω based Detached Eddy Simulation (DES) approach. The effects of submarine speed, depth and density gradient on the free surface wave pattern were quantitatively analyzed. It was shown that, with the increasing of the speed of the submarine, the wavelength and wave height of the free surface wave were gradually increasing. The wave height of the free surface wave was gradually reduced as the submarine’s depth increased. Relative to the speed and submarine depth, the changes of the gradient density gradient have negligible effects on the free surface wave field.

Free-Surface Wave-Induced Separation

1996 ◽  
Vol 118 (3) ◽  
pp. 546-554 ◽  
Author(s):  
Z. J. Zhang ◽  
F. Stern
Keyword(s):  
Fluid Dynamics ◽  
Free Surface ◽  
Surface Wave ◽  
Navier Stokes ◽  
Surface Boundary ◽  
Flow Conditions ◽  
Continuity Equations ◽  
Surface Boundary Conditions ◽  
Free Surface Wave ◽  
Wave Induced

Free-surface wave-induced separation is studied for a surface-piercing NACA 0024 foil over a range of Froude numbers (0, .2, .37, .55) through computational fluid dynamics of the unsteady Reynolds-averaged Navier-Stokes and the continuity equations with the Baldwin-Lomax turbulence model, exact nonlinear kinematic and approximate dynamic free-surface boundary conditions, and a body/free-surface conforming grid. The flow conditions and uncertainty analysis are discussed. A topological rule for a surface-piercing body is derived and verified. Steady-flow results are presented and analyzed with regard to the wave and viscous flow and the nature of the separation.

scholarly journals Numerical Analysis of Side-loads Reduction in a Sub-scale Dual-bell Rocket Nozzle

2021 ◽  
Author(s):  
M. Cimini ◽  
E. Martelli ◽  
M. Bernardini
Keyword(s):  
Inflection Point ◽  
Pressure Ratio ◽  
Mean Value ◽  
Detached Eddy Simulation ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Separation Shock ◽  
Delayed Detached Eddy Simulation ◽  
Controlled Flow ◽  
Dual Bell

AbstractA calibrated delayed detached eddy simulation of a sub-scale cold-gas dual-bell nozzle flow at high Reynolds number and in sea-level mode is carried out at nozzle pressure ratio NPR = 45.7. In this regime the over-expanded flow exhibits a symmetric and controlled flow separation at the inflection point, that is the junction between the two bells, leading to the generation of a low content of aerodynamic side loads with respect to conventional bell nozzles. The nozzle wall-pressure signature is analyzed in the frequency domain and compared with the experimental data available in the literature for the same geometry and flow conditions. The Fourier spectra in time and space (azimuthal wavenumber) show the presence of a persistent tone associated to the symmetric shock movement. Asymmetric modes are only slightly excited by the shock and the turbulent structures. The low mean value of the side-loads magnitude is in good agreement with the experiments and confirms that the inflection point dampens the aero-acoustic interaction between the separation-shock and the detached shear layer.

Towed Underwater SPIV Measurement of Flow Fields Around a Surface-Piercing Cylinder With Free Surface Effects

2015 ◽  
Author(s):  
Jeonghwa Seo ◽  
Bumwoo Han ◽  
Shin Hyung Rhee
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Surface Wave ◽  
Flow Field ◽  
Cross Section ◽  
Surface Effects ◽  
Flow Fields ◽  
Two Dimensional ◽  
Two Dimensional Flow ◽  
Wave Induced

Effects of free surface on development of turbulent boundary layer and wake fields were investigated. By measuring flow field around a surface piercing cylinder in various advance speed conditions in a towing tank, free surface effects were identified. A towed underwater Stereoscopic Particle Image Velocimetry (SPIV) system was used to measure the flow field under free surface. The cross section of the test model was water plane shape of the Wigley hull, of which longitudinal length and width were 1.0 m and 100 mm, respectively. With sharp bow shape and slender cross section, flow separation was not expected in two-dimensional flow. Flow fields near the free-surface and in deep location that two-dimensional flow field was expected were measured and compared to identify free-surface effects. Some planes perpendicular to longitudinal direction near the model surface and behind the model were selected to track development of turbulent boundary layer. Froude numbers of the test conditions were from 0.126 to 0.40 and corresponding Reynolds numbers were from 395,000 to 1,250,000. In the lowest Froude number condition, free-surface wave was hardly observed and only free surface effects without surface wave could be identified while violent free-surface behavior due to wave-induced separation dominated the flow fields in the highest Froude number condition. From the instantaneous velocity fields, Time-mean velocity, turbulence kinetic energy, and flow structure derived by proper orthogonal decomposition (POD) were analyzed. As the free-surface effect, development of retarded wake, free-surface waves, and wave-induced separation were mainly observed.

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