• Coupled systems mechanics
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• v.13 no.3
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• pp.247-275
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• 2024

The paper studies the influence of the fluid flow velocity and flow direction in the initial state on the dispersion of the axisymmetric waves propagating in the inhomogeneously pre-stressed hollow cylinder containing this fluid. The corresponding eigenvalue problem is formulated within the scope of the three-dimensional linearized theory of elastic waves in bodies with initial stresses, and with linearized Euler equations for the inviscid compressible fluid. The discrete-analytical solution method is employed, and analytical expressions of the sought values are derived from the solution to the corresponding field equations by employing the discrete-analytical method. The dispersion equation is obtained using these expressions and boundary and related compatibility conditions. Numerical results related to the action of the fluid flow velocity and flow direction on the influence of the inhomogeneous initial stresses on the dispersion curves in the zeroth and first modes are presented and discussed. As a result of the analyses of the numerical results, it is established how the fluid flow velocity and flow direction act on the magnitude of the influence of the initial inhomogeneous stresses on the wave propagation velocity in the cylinder containing the fluid.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.12
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• pp.999-1006
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• 2014

Mindlin plate theory includes the shear deformation and rotatory inertia effects which cannot be negligible as exciting frequency increases. The statistical methods such as energy flow analysis(EFA) and statistical energy analysis(SEA) are very useful for estimation of structure-borne sound of various built-up structures. For the reliable vibrational analysis of built-up structures at high frequencies, the energy transfer relationship between out-of-plane waves and in-plane waves exist in Mindlin plates coupled at arbitrary angles must be derived. In this paper, the new wave transmission analysis is successfully performed for various energy analyses of Mindlin plates coupled at arbitrary angles.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.154-154
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• 2021

Since the development of Bubble Image Velocimetry (BIV) technique as the complementary technique of Particle Image Velocimetry (PIV), the application of digital imaging technique in the field of hydraulic and coastal engineering increased rapidly. BIV works very well in multi-phase flow (air-water) flows where the PIV technique doesn't. However, the velocity field obtained from BIV technique often resulted in a velocity vector on the outside of the flow (false velocity) since the Field of View (FOV) usually not only cover the air-water flow but also the area outside the flow. In this study, a simple technique of post processing velocity field was developed. This technique works based on the average of the pixel value in the interrogation area. An image of multi-phase flow of wave overtopping was obtained through physical experiment using BIV technique. The velocity calculation was performed based on the similar method in PIV. A velocity masking technique developed in this study then applied to remove the false velocity vector. Result from non-masking, manually removed and auto removed false velocity vector were presented. The masking technique show a similar result as manually removed velocity vector. This method could apply in a large number of velocity field which is could increase the velocity map post-processing time.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1667-1674
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• 2000

A new method is proposed to measure the flow rate in a pipe by multiple measurements of acoustic pressure using a microphone array. It is based on the realization that variation in flow velocity affects the change in wave number. The method minimizes measurement random errors and sensor mismatch errors thereby providing practically realizable flow rate measurement. One of the advantages of the method is that it does not obstruct the flow field and can provide the time-spatial mean flow rate. Numerical simulations and experiments were conducted to verify the utility of this method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.424-431
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• 1994

The characteristics of supersonic flow with condensation along a wavy wall of a small Smplitude in a channel is investigated experimentally and numerically. In the present study for the case of supersonic moist air flow, the dependency of location of reflection of oblique shock wave generated by the wavy wall, and the distributions of flow properties in the flow field, on the stagnation relative humidity and temperature is clarified by the plots of streamline, iso-Mach number and iso-flow properties of numerical result and the schlieren photographs of experiment. And. experimental and numerical results are in good agreement.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1990-1997
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• 1992

The characteristic of supersonic flow with condensation along a wavy wall of small amplitude in channel is investigated through the direct marching method of characteristics. The very complex problem that may appear where the overlapping of the same family characteristics occurs, can be satisfactorily solved by means of the modified method suggested by Zucrow. In the present study for the case of supersonic moist air flow, the dependency of location of formation and reflection of oblique shock wave generated by the wavy wall, and the distributions of flow properties, on the relative humidity and temperature at the entrance of wavy wall is clarified by plots of streamline, ios-Mach umber and ios-flow properties. Also, it is confirmed that the wavy wall plays an important key role in the formation of oblique shock wave, and that the effect of condensation on the flow field appears apparently.

• 한국가시화정보학회:학술대회논문집
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• 2001.12a
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• pp.1-5
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• 2001

A particle image velocimetry (PIV) was applied to a flow measurement in a transonic centrifugal impeller. A phase locked measurement technique every $20\%$ blade pitch enabled a reconstruction of a velocity field over one blade pitch. The measured velocity field at the inducer of impeller clearly showed a shock wave generated on the suction surface of a blade.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3033-3038
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• 2007

In this research, Rayleigh instability of gas-liquid flow in annular pipe is studied in film boiling using viscous potential flow. Viscous potential flow is a kind of approximation of gas-liquid interface considering velocity field as potential including viscosity. A dispersion relation is obtained including the effect of heat and mass transfer and viscosity. New expression for dispersion relation in film boiling and critical wave number is obtained. Viscosity and heat and mass transfer have a stabilizing effect on instability and its effect appears in maximum growth rate and critical wave number. And the existence of marginal stability region is shown.

• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.148-154
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• 2008

The Wells turbine rotor consists of several symmetric airfoil blades arranged around a central hub, and the stagger angle is 90 degrees. These characteristics simplify the total construction of OWC type wave energy converters. Although the Wells turbine is simple, the turbine produces a complicated flow field due to the peculiar arrangement of blades, which can rotate in the same direction irrespective of the oscillating airflow. In order to understand these flows, flow visualization is carried out with an oil-film method in the water tunnel. This research aims to analyze the mechanism of the 3-D flows around the turbine with the flow visualization. The flow visualization explained the influence of attack angle, the difference between fan-shaped and rectangular wings, and the sweep angle.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.2
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• pp.149-156
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• 2016

The hypersonic flow on the stagnation streamline of a blunt body is analyzed with quasi one-dimensional (1-D) Navier-Stokes equations approximated by adopting the local similarity to the two-dimensional (2-D)/axisymmetric Navier-Stokes equations. The governing equations are solved using the implicit finite volume method. The computational domain is confined from the stagnation point to the shock wave, and the shock fitting method is used to find the shock position. We propose a boundary condition at the shock, which employs the shock wave angle in the vicinity of the stagnation streamline using the shock shape correlation. As a result of numerical computation conducted for the hypersonic flow over a sphere, the proposed boundary condition is shown to improve the accuracy of the prediction of the shock standoff distance. The quasi 1-D Navier-Stokes code is efficient in computing time and is reliable for the flow analysis along the stagnation streamline and the prediction of heat flux at the stagnation point in the hypersonic blunt body flow.