Unsteady RANS method for surface ship boundary layer and wake and wave field

2001 ◽  
Vol 37 (4) ◽  
pp. 445-478 ◽  
Author(s):  
Shin Hyung Rhee ◽  
Fred Stern
Keyword(s):  
Boundary Layer ◽  
Wave Field ◽  
Surface Ship ◽  
Unsteady Rans ◽  
Rans Method

Unsteady RANS method for ship motions with application to roll for a surface combatant

2006 ◽  
Vol 35 (5) ◽  
pp. 501-524 ◽  
Author(s):  
Robert V. Wilson ◽  
Pablo M. Carrica ◽  
Fred Stern
Keyword(s):  
Ship Motions ◽  
Unsteady Rans ◽  
Surface Combatant ◽  
Rans Method

Scrutiny of buffet mechanisms in transonic flow

2018 ◽  
Vol 28 (5) ◽  
pp. 1031-1046 ◽  
Author(s):  
Antonio Memmolo ◽  
Matteo Bernardini ◽  
Sergio Pirozzoli
Keyword(s):  
Boundary Layer ◽  
Transonic Flow ◽  
Acoustic Waves ◽  
Numerical Experiments ◽  
Large Scale ◽  
Pressure Side ◽  
Trailing Edge ◽  
Content Type ◽  
Unsteady Rans ◽  
Transonic Buffet

Purpose This paper aims to show results of numerical simulations of transonic flow around a supercritical airfoil at chord Reynolds number Rec = 3 × 106, with the aim of elucidating the mechanisms responsible for large-scale shock oscillations, namely, transonic buffet. Design/methodology/approach Unsteady Reynolds-averaged Navier–Stokes simulations and detached-eddy simulations provide a preliminary buffet map, while a high fidelity implicit large-eddy simulation with an upstream laminar boundary layer is used to ascertain the physical feasibility of the various buffet mechanisms. Numerical experiments with unsteady RANS highlight the role of waves travelling on pressure side in the buffet mechanism. Estimates of the propagation velocities of coherent disturbances and of acoustic waves are obtained, to check the validity of popular mechanisms based on acoustic feedback from the trailing edge. Findings Unsteady RANS numerical experiments demonstrate that the pressure side of the airfoil plays a marginal role in the buffet mechanism. Implicit LES data show that the only plausible self-sustaining mechanism involves waves scattered from the trailing edge and penetrating the sonic region from above the suction side shock. An interesting side result of this study is that buffet appears to be more intense in the case that the boundary layer state upstream of the shock is turbulent, rather than laminar. Originality/value The results of the study will be of interest to any researcher involved with transonic buffet.

Phase-Averaged PIV for the Nominal Wake of a Surface Ship in Regular Head Waves

2006 ◽  
Vol 129 (5) ◽  
pp. 524-540 ◽  
Author(s):  
J. Longo ◽  
J. Shao ◽  
M. Irvine ◽  
F. Stern
Keyword(s):  
Boundary Layer ◽  
Incident Wave ◽  
Transverse Velocity ◽  
Diffraction Problem ◽  
Outer Region ◽  
Flow Region ◽  
Random Fluctuation ◽  
Reynolds Stresses ◽  
Surface Ship ◽  
Head Waves

Phase-averaged organized oscillation velocities (U,V,W) and random fluctuation Reynolds stresses (uu¯,vv¯,ww¯,uv¯,uw¯) are presented for the nominal wake of a surface ship advancing in regular head (incident) waves, but restrained from body motions, i.e., the forward-speed diffraction problem. A 3.048×3.048×100m towing tank, plunger wave maker, and towed, 2D particle-image velocimetry (PIV) and servo mechanism wave-probe measurement systems are used. The geometry is DTMB model 5415 (L=3.048m, 1∕46.6 scale), which is an international benchmark for ship hydrodynamics. The conditions are Froude number Fr=0.28, wave steepness Ak=0.025, wavelength λ∕L=1.5, wave frequency f=0.584Hz, and encounter frequency fe=0.922Hz. Innovative data acquisition, reduction, and uncertainty analysis procedures are developed for the phase-averaged PIV. The unsteady nominal wake is explained by interactions between the hull boundary layer and axial vortices and incident wave. There are three primary wave-induced effects: pressure gradients 4%Uc, orbital velocity transport 15%Uc, and unsteady sonar dome lifting wake. In the outer region, the uniform flow, incident wave velocities are recovered within the experimental uncertainties. In the inner, viscous-flow region, the boundary layer undergoes significant time-varying upward contraction and downward expansion in phase with the incident wave crests and troughs, respectively. The zeroth harmonic exceeds the steady-flow amplitudes by 5–20% and 70% for the velocities and Reynolds stresses, respectively. The first-harmonic amplitudes are large and in phase with the incident wave in the bulge region (axial velocity), damped by the hull and boundary layer and mostly in phase with the incident wave (vertical velocity), and small except near the free surface-hull shoulder (transverse velocity). Reynolds stress amplitudes are an order-of-magnitude smaller than for the velocity components showing large values in the thin boundary layer and bulge regions and mostly in phase with the incident wave.

scholarly journals Anisotropic boundary layer mesh generation for reliable 3D unsteady RANS simulations

2020 ◽  
Vol 170 ◽  
pp. 103345
Author(s):  
G. Guiza ◽  
A. Larcher ◽  
A. Goetz ◽  
L. Billon ◽  
P. Meliga ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mesh Generation ◽  
Unsteady Rans ◽  
Rans Simulations ◽  
Boundary Layer Mesh

Prediction of Flow Features in Rotating Cavities With Axial Throughflow by RANS and LES

2009 ◽  
Author(s):  
Qinxue Tan ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flow Structure ◽  
Large Scale ◽  
Scale Model ◽  
Optimized Design ◽  
Flow Features ◽  
Unsteady Rans ◽  
Large Scale Flow ◽  
Rans Method

Rotating cavities with axial throughflow are found inside the compressor rotors of turbomachines. The flow pattern and heat transfer in the cavities are known as sophisticated problems. In this paper, the 3D compressible flow field in a rotating cavity is investigated numerically using a steady RANS method, an unsteady RANS method and LES. The numerical results based on the three methods are analyzed in detail and compared with the available experimental data. For the LES method with a subgrid-scale model, the instantaneous flow structure and the heat transfer can be captured very well. For the unsteady RANS method with an appropriate turbulence model, the large-scale flow structure can be revealed acceptably, and the heat transfer solution agrees with the experimental data with a certain error. For the steady RANS method, a reasonable flow structure cannot be obtained, while the distribution of the heat transfer has a same tendency and uncertain error with the experiments. Therefore, it is suggested that the steady RANS method can still be a numerical tool in the quite preliminary design of the rotating cavities, while the LES is more advanced from an academic view. Moreover, the unsteady RANS method is most appropriate for industry. It should be valuable in the detailed design computations for selecting the optimized design.

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