• 대한조선학회논문집
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• 제56권4호
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• pp.373-382
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• 2019

This paper shows numerical results for the estimation of the propulsor efficiency of Pre-Swirl Duct for 176k bulk carrier as well as its design method. Reynolds averaged Navier-Stokes equations have been solved and the k-epsilon model applied for the turbulent closure. The propeller rotating motion is determined using a sliding mesh technique. The design process is divided into each part of Pre-Swirl Duct, duct and Pre-Swirl Stator. The design of duct was performed first because it is located further upstream than Pre-Swirl Stator. The distribution of velocity through the duct was analyzed and applied for the design of Pre-Swirl Stator. The design variables of duct include duct angle, diameter, and chord length. Diameter, chord length, equivalent angle are considered when designing the Pre-Swirl Stator. Furthermore, a variable pitch angle stator is applied for the final model of Pre-Swirl Duct. The largest reduction rate of the delivered power in model scale is 7.6%. Streamlines, axial and tangential velocities under the condition that the Pre-Swirl Duct is installed were reviewed to verify its performance.

• 설비공학논문집
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• 제1권4호
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• pp.265-275
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• 1989

An experimental study of decaying swirl air flow has been obtained by tangential inlet in a straight tube with Reynolds number range 20,000~40,000. The friction factor, swirl angle, velocity profiles and turbulent intensity are measured by using micro-manometer and hot-wire anemometer. It is found that the swirl flow behaviors depend on the swirl intensity along the test tube.

• 대한조선학회논문집
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• 제44권2호
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• pp.93-100
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• 2007

Post swirl stator is an energy saving device to recover rotational energy of the propeller. To optimize the performance of post swirl stator in container vessels, computational fluid dynamics using body force method was introduced. A commercial code Fluent was used in conjunction with body force distributed on the surface of actuator disk which is located in the propeller plane to optimize pitch angle of the post swirl stator blade. This study showed that CFD is an important tool to simulate flow behind ship with propeller, rudder and post swirl stator.

• 한국가시화정보학회지
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• 제1권1호
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• pp.82-91
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• 2003

The study of swirl flow has been of technical and scientific interest because it has an internal recirculation field and its tangential velocity is related to the curvature of the streamline. The fluid flow for ducts or elbows of an internal engine has been much studied through numerical methods and experiments, but studies about swirl flow has been insufficient. Using the PIV (Particle Image Velocimetry) method, this study found the time-mean velocity distribution, time-mean turbulent intensity, with swirl and without swirl flow for Re=10,000, 15,000, 20,000, and 25,000 along longitudinal sections and the results appear to be physically reasonable. In addition, axial velocity distribution is compared with that of Jeong's, Kodadadi's and Murakami's. It was found that the highest velocity of swirl and non-swirl flow occurs in the opposite position at the center of a round tube, $\phi$=45$^{\circ}$

• 한국가시화정보학회지
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• 제3권2호
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• pp.79-87
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• 2005

Two engines, one is conventional DOHC 4 valve and the other is narrow valve angle, were used to compare the characteristics of swirl motion generation in the cylinder. One intake port is deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake and compression stroke. The results show that the flow patterns of narrow valve engine are much more stable and well arranged compared with the normal engine over the entire intake and compression stroke except early intake stage, and very strong swirl motion is generated at the end of compression stage in this engine nevertheless using straight port which is unfavorable for swirl generating. In the normal engine, however, strong swirl motion induced during intake stroke is destroyed as the compression progresses.

• 한국자동차공학회논문집
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• 제8권6호
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• pp.9-21
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• 2000

In this study, the characteristics of high-pressure swirl injector have been studied using a commercial CFD code, STAR-CD and experiment to investigate the effect of the length of orifice and swirl port on the spray characteristics. Influences of swirl port angle and initial conditions have also been examined in terms of penetration depth and Sauter`s mean diameter. Computed results of the spray characteristics are compared with experimental results. The results show that the tangential velocity at the nozzle exit decreases, but the axial velocity increases as swirl port angle is increased. Hence, the static flow rate increases, but the initial spray angle decreases with increasing the swirl port angle. It is also shown that the values of the initial SMD used as input data for spray simulation influences the penetration depth and SMD. The spray pattern from the present numerical simulation agrees well with experimental result.

• Wind and Structures
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• 제11권4호
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• pp.291-302
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• 2008

Three-dimensional engineering simulations of momentum-driven tornado-like vortices are conducted to investigate the flow dynamics dependency on swirl ratio and the possible relation with real tornado Fujita scales. Numerical results are benchmarked against the laboratory experimental results of Baker (1981) for a fixed swirl ratio: S = 0.28. The simulations are then extended for higher swirl ratios up to S = 2 and the variation of the velocity and pressure flow fields are observed. The flow evolves from the formation of a laminar vortex at low swirl ratio to turbulent vortex breakdown, followed by the vortex touch down at higher swirls. The high swirl ratios results are further matched with full scale data from the Spencer, South Dakota F4 tornado of May 30, 1998 (Sarkar, et al. 2005) and approximate velocity and length scales are determined.

• 한국전산유체공학회지
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• 제11권2호
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• pp.40-48
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• 2006

In the present, The theoretical and numerical results of gas flow characteristics inside a swirl injector are presented. For this purpose a one-dimensional (theoretical) model and 2D/3D CFD models are proposed for use in the design of the injector. It was found that contradictory to the classical theory about the compressible flow, the swirl has a significant effect on the mass flow rate and the choking conditions. It was found that the one-dimensional model provides reasonably accurate results compared with the 2D/3D numerical results, and thus can be used at the initial stage of the swirl-injector design process.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.177-180
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• 2002

The study on the design of pre-swirl stator vanes is performed. The pre-swirl stator vanes is an energy-saving device to improve propulsive performance by providing pre-swirl to the propeller inflow. The theoretical background and the design conditions for pre-swirl stator vanes are presented. The flow characteristics around the pre-swirl stator vanes attached ship hull are analyzed through the experimental method. The technique to determine the optimum location, angle and the number of stator vane is investigated and applied it to 310,000 TBW VLCC The flow velocities are measured using 5-hole Pilot tubes at the condition with and without a propeller.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 춘계 학술대회논문집
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• pp.207-212
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• 2005

In this paper, we present the theoretical and numerical results of flow characteristics of a gas in a swirl injector. Proposed in this study are one-dimensional (theoretical) model and 2D/3D CFD models for use in the design of the injector. It was found that contrary to the classical theory about the compressible flow, the swirl gives a significant effect on the mass flow rate and the choking conditions. The one-dimensional model was found to Provide reasonably accurate results compared with the 2D/3D numerical results, so that it can be employed in th initial stage of the swirl-injector design process.