• International Journal of Fluid Machinery and Systems
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• v.2 no.3
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• pp.223-231
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• 2009

Experimental investigations were conducted for the internal flows of the axial flow stator and diagonal flow rotor. Corner separation near the hub surface and the suction surface of stator blade are mainly focused on. For the design flow rate, the values of the axial velocity and the total pressure at stator outlet decrease between near the suction surface and near the hub surface by the influence of corner wall. For the flow rate of 80-90% of the design flow rate, the corner separation of the stator between the suction surface and the hub surface is observed, which becomes widely spread for 80% of the design flow rate. At rotor outlet for 81% of the design flow rate, the low axial velocity region grows between near the suction surface of rotor and the casing surface because of the tip leakage flow of the rotor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.8
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• pp.1034-1045
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• 1997

For the improvement of the pump characteristics in the partial capacity range, it must be verified that the influence of the impeller design factor on the internal flows and the influence of the impeller internal flows on the pump characteristics. In this paper, in order to understand the influence of inlet angles on flow conditions and characteristics of a mixed flow pump, experiments were carried out for three kinds of impeller, which have the same outlet angle distributions and meridional section shapes. Results show that separation and stall in the partial capacity range can be controlled by the inlet angles. The relationship between the separation - stall at the impeller leading edge and the discharge flow conditions is clarified.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.170-177
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• 2020

A mixer with a new concept design has been adapted into water treatment plants. It reportedly cuts down the energy consumption of the mixer by the new mixer, which moves vertically and creates internal flows toward its bottom. However, no experimental observations have been made on the internal flow caused by a vertical impeller. In this study, a radiotracer experiment, radioactive particle tracking (RPT) technique, and particle image velocimetry (PIV) were carried out to visualize the flow in the mixer, and compared to each other. The results show that the flow patterns from these techniques are very similar to each other, and the performance of the mixer was good enough to mix the inner materials.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.2
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• pp.29-35
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• 2011

The behaviors of combustion-induced internal flows of SRM equipped with fin-slot grain and submerged nozzle are very complex and diverse. Cold air-flow tests for 2D and 3D scale models of SRM have been done in order to specify the visualization method to analyze particular internal flow patterns such as roll-torque inducing flow. Swirl flow induced by asymmetric vortical tubes also has been visualized through employing various light source and recording directions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1061-1069
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• 2010

In this study, a simplified axisymmetric model is proposed for the problem of compressible internal flow past a microgap. Using numerical and experimental methods, the phenomena of choked flows are observed; these flows are induced by the acceleration of subsonic flows past the narrow cross-section of an annular shape made by a microgap. The relation between mass flow rate and differential pressure is obtained, and by comparing the result with experimental results, the reliability of the numerical results is discussed. The generation of a supersonic jet flow and its diffraction are visualized by performing the numerical analysis of axisymmetric compressible Navier-Stokes equations. This investigation greatly extends the physical understanding of the axisymmetric compressible flow, which has a wide range of engineering applications, e.g., in the case of valves in automotive power systems.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.46-49
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• 2002

Three-dimensional flow characteristics in a liquid fuel ramjet combustor were investigated using the PIV method. The combustor has two rectangular inlets that loin a 90-degree angle each other. Three cases of test combustors are made in which those inlet angles are 30 degree, 45degree and 60 degree. The experiments were performed in a water tunnel test with the same Reynolds number as Mach 0.3 at the inlet. PIV software was developed to measure the characteristics of the flow field in the combustor. Accuracy of the developed PIV program was verified with a rotating disk experiment and standard data. The characteristics of the internal flows of the combustor are large swirling flows which appear symmetric with respect to the symmetric section. This is attributed to the fact that the flows introduced from the right and left intakes collide with each other, thus forming symmetrically large vortices. A large and complex three-dimensional recirculating flow was measured behind the intakes. An inlet angle of 30 degrees is the most suitable angle as a frame he]der in the performed experimental ranges.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.35-42
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• 1998

Time marching algorithms applied to compressible Navier-Stokes equation have a convergence problem at low Mach number. It is mainly due to the eigenvalue stiffness and pressure singularity as Mach number approaches to zero. Among the several methods to overcome the shortcomings of time marching scheme, time derivative preconditioning method have been used successfully. In this numerical analysis, we adopted a preconditioner of K.H. Chen and developed a two-dimensional, axisymmetric Navier-Stokes program. The steady state driven cavity flow and backward facing step flow problems were computed to confirm the accuracy and the robustness of preconditioned algorithm for low Mach number flows. And the transonic and supersonic flows insice the JPL axisymmetric nozzle internal flow is exampled to investigate the effects of preconditioning at high Mach number flow regime. Test results showed excellent agreement with the experimental data.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.11a
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• pp.69-83
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• 1995

A great number of experimental data indicating shock-induced separation(SIS) in internal or external supersonic flows were reviewed to make clear the mechanism of SIS and to present the criterion of turbulent boundary layer separation. The interesting conclusions were obtained for the considerably wide range of flow geometries that the incipient separation is almost independent of the flow geometries, and that it is relatively unaffected by changes in gas specific heat, and boundary layer Reynolds number, Furthermore, the pressure rise necessary to separate boundary layer in external flows was found to be applicable to SIS in overexpanded propulsion nozzles. This is due to the fact that the SIS phenomenon caused by the interaction between shock waves and turbulent boundary layers is processed through a supersonic deceleration. This is, the SIS in almost all of interacting flow fields is governed by the concept of free interaction, and criterion of SIS is only a Function of upstream Mach number.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.2
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• pp.91-107
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• 1992

A numerical formulation is developed to solve the linear three-dimensional hydrodynamic equations which describes wind induced flows in a homogeneous shelf sea. The hydmdynamic equations are at the outset separated into two systems. namely, an equation containing the gradient of sea surface elevation and the mean flow (external mode) and an equation describing the deviation from the mean flow (internal mode). The Galerkin method is then applied to the internal mode equation. The eigenvalues are determined from the eigenvalue problem involving the vertical eddy viscosity subject to a homogeneous boundary condition at the surface and a sheared boundary condition at the sea bed. The model is tested in a one-dimensional channel with uniform depth under a steady, uniform wind. The analytical velocity profile by Cooper and Pearce (1977) using a constant vertical eddy viscosity in channels of infinite and finite length is chosen as a benchmark solution. The model is also tested in a homogeneous, rectangular basin with constant depth under a steady, uniform wind field (the Heaps' Basin of the North Sea scale).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.42 no.1
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• pp.38-43
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• 2006

The 3-D modeling of ocean finite element method(OFEM) using $k-{\varepsilon}$ turbulent model and tetrahedron grids has been used to investigate the internal wave generation during the expansion of the deep water from the open sea to the shelf with a simple shape, which can be widely used in the fields of submarine development, ocean environment and meteorology, etc. In this paper, the detailed configuration of internal wave with its length and height and also the distribution of salinity and turbulent kinematic energy, etc. were derived. It is hoped that this OFEM method can be successfully applied to the numerical calculation of internal wave for and the oceanographic problems (tidal flows around underwater hill, plateau, Georges Bank, etc.) and ocean engineering problems(flow past artificial sea reefs) in future.