scholarly journals Compressibility Effects on Cavity Dynamics behind a Two-Dimensional Wedge

2020 ◽  
Vol 8 (1) ◽  
pp. 39
Author(s):  
Sunho Park ◽  
Woochan Seok ◽  
Sung Taek Park ◽  
Shin Hyung Rhee ◽  
Yohan Choe ◽  
...  
Keyword(s):  
Shear Layer ◽  
Compressible Flow ◽  
Computational Methods ◽  
Computational Studies ◽  
Computational Results ◽  
Two Dimensional ◽  
Compressibility Effect ◽  
Cavitation Tunnel ◽  
Cavity Shedding ◽  
Compressibility Effects

To understand cavity dynamics, many experimental and computational studies have been conducted for many decades. As computational methods, incompressible, isothermal compressible, and fully compressible flow solvers were used for the purpose. In the present study, to understand the compressibility effect on cavity dynamics, both incompressible and fully compressible flow solvers were developed, respectively. Experiments were also carried out in a cavitation tunnel to compare with the computational results. The cavity shedding dynamics, re-entrant jet, transition from bounded shear layer vortices to Karman vortices, and pressure and velocity contours behind the two-dimensional wedge by the two developed solvers were compared at various cavitation numbers.

Nonlinear dynamics of a two dimensional airfoil with freeplay in an inviscid compressible flow

2000 ◽  
Vol 4 (2) ◽  
pp. 125-133 ◽  
Author(s):  
Zoran Dimitrijević ◽  
Guy Daniel Mortchéléwicz ◽  
Fabrice Poirion
Keyword(s):  
Nonlinear Dynamics ◽  
Compressible Flow ◽  
Two Dimensional ◽  
Inviscid Compressible Flow

Computational Simulations of Dynamic Compaction of Dry Sand

2012 ◽  
Vol 598 ◽  
pp. 516-519
Author(s):  
Yu Qing Ding ◽  
Wen Hui Tang ◽  
Xian Wen Ran ◽  
Xin Xu
Keyword(s):  
Computational Analysis ◽  
Dynamic Compaction ◽  
Back Surface ◽  
Computational Results ◽  
Two Dimensional ◽  
Computational Simulations ◽  
Plate Impact ◽  
Arrival Times ◽  
Dry Sand ◽  
Impact Experiments

The computational analysis of plate impact experiments on dry sand utilizing the Mie- Grüneisen (MG) equation of state and the P-α compaction model were investigated in this study. A number of two dimensional axial symmetric computations were performed by using the hydrocode AUTODYN. The computational results were compared with the particle velocity on the back surface of the rear plate measured by the VISAR system and the first shock-wave arrival times detected by piezoelectric pins in the samples respectively. It was found that the P-α compaction model was more accurately reproduce the experimental data than the MG EOS.

Numerical Simulation of Flows in a Pipe with an Aneurismal Sac (Effects of Aneurismal Models and Stents)

2008 ◽  
Vol 33-37 ◽  
pp. 1025-1030
Author(s):  
Gulbahar Wahap ◽  
Tatsuya Kobori ◽  
Yoko Takakura ◽  
Norio Arai ◽  
Yoshifumi Konishi ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Human Blood ◽  
Steady States ◽  
Computational Results ◽  
Two Dimensional ◽  
Blood Flows ◽  
Inflow Condition ◽  
Inflow Conditions ◽  
Two Dimensional Flows

Recently, the intravascular therapy using microcoils and stents to treat aneurysms has attracted researcher’s interest. In this study, in order to evaluate the effects of the stents, a numerical simulation of two-dimensional flows has been carried out for a pipe with a model of an aneurismal sac. Using aneurismal models with different inclined angles to the pipe, inflow conditions with steady states or pulsations have been applied in the range of Reynolds number in human blood flows. First, the computational results are compared with experiments under the steady inflow condition, which has shown the reliability of the numerical simulation. Furthermore, the mechanism of flows with an aneurismal model is discussed in the case with or without a stent, and consequently the effect of the stent is clarified.

Numerical Simulation of Cavitating Flow Around a Hydrofoil

2014 ◽  
Author(s):  
Tan Dung Tran ◽  
Bernd Nennemann ◽  
Thi Cong Vu ◽  
François Guibault
Keyword(s):  
Turbulence Models ◽  
Cavitating Flow ◽  
Navier Stokes ◽  
Naval Academy ◽  
Cavitating Flows ◽  
Compressibility Effect ◽  
Hybrid Meshes ◽  
Fortran Code ◽  
Cavitation Tunnel ◽  
Prediction Capability

The objective of this paper is to evaluate the applicability of different cavitation models and determine appropriate numerical parameters for cavitating flows around a hydrofoil. The simulations are performed for a NACA 66 foil at 6 degrees angle of attack, Reynolds number of 750 000 and for a cavitation number of 1.49 corresponding to the partial sheet cavitating regime. The incompressible, multiphase Reynolds-averaged Navier-Stokes (RANS) equations are solved by the CFD solver CFX with Kubota and Merkle cavitation models. As part of the work, the Merkle model is implemented into CFX by User Fortran code because this model has shown good cavitation prediction capability according to the literature. The effects of the k-ε and SST turbulence models on the cavitating flow dynamics are compared. Also, an investigation on structured and hybrid meshes with different mesh sizes and concentrations is carried out in order to better understand the mesh influence for this cavitation simulation. The local compressibility effect is considered by correcting the turbulent eddy viscosity inside the mixture vapor/liquid zones. The numerical results are validated by experiments conducted in a cavitation tunnel at the French Naval Academy.

Large-scale modes of turbulent channel flow: transport and structure

2001 ◽  
Vol 448 ◽  
pp. 53-80 ◽  
Author(s):  
Z. LIU ◽  
R. J. ADRIAN ◽  
T. J. HANRATTY
Keyword(s):  
Shear Stress ◽  
Kinetic Energy ◽  
Shear Layer ◽  
Turbulent Kinetic Energy ◽  
Large Scale ◽  
Reynolds Shear Stress ◽  
Reynolds Numbers ◽  
Upstream Region ◽  
Two Dimensional ◽  
Normal Plane

Turbulent flow in a rectangular channel is investigated to determine the scale and pattern of the eddies that contribute most to the total turbulent kinetic energy and the Reynolds shear stress. Instantaneous, two-dimensional particle image velocimeter measurements in the streamwise-wall-normal plane at Reynolds numbers Reh = 5378 and 29 935 are used to form two-point spatial correlation functions, from which the proper orthogonal modes are determined. Large-scale motions – having length scales of the order of the channel width and represented by a small set of low-order eigenmodes – contain a large fraction of the kinetic energy of the streamwise velocity component and a small fraction of the kinetic energy of the wall-normal velocities. Surprisingly, the set of large-scale modes that contains half of the total turbulent kinetic energy in the channel, also contains two-thirds to three-quarters of the total Reynolds shear stress in the outer region. Thus, it is the large-scale motions, rather than the main turbulent motions, that dominate turbulent transport in all parts of the channel except the buffer layer. Samples of the large-scale structures associated with the dominant eigenfunctions are found by projecting individual realizations onto the dominant modes. In the streamwise wall-normal plane their patterns often consist of an inclined region of second quadrant vectors separated from an upstream region of fourth quadrant vectors by a stagnation point/shear layer. The inclined Q4/shear layer/Q2 region of the largest motions extends beyond the centreline of the channel and lies under a region of fluid that rotates about the spanwise direction. This pattern is very similar to the signature of a hairpin vortex. Reynolds number similarity of the large structures is demonstrated, approximately, by comparing the two-dimensional correlation coefficients and the eigenvalues of the different modes at the two Reynolds numbers.

scholarly journals Resonance Vibration of Mistuned Bladed Discs in Stationary Operations

1997 ◽  
Author(s):  
Romuald Rządkowski
Keyword(s):  
Numerical Model ◽  
Compressible Flow ◽  
Two Dimensional ◽  
Rotating System ◽  
Response Level ◽  
Stationary Response ◽  
The Real ◽  
Disc Model ◽  
Real Geometry ◽  
Airfoil Blades

A numerical model for the calculation of resonance stationary response of mistuned bladed disc is presented. The bladed disc model includes all important effects on a rotating system of the real geometry. The excitation forces were calculated by a code on the basis of two-dimensional compressible flow (to M < 0.8) for thin airfoil blades. The calculations presented in this paper show that centrifugal stress, and the values of excitation forces, play an important role in considering the influence of mistuning on the response level.

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