• Journal of computational fluids engineering
• /
• v.6 no.4
• /
• pp.35-42
• /
• 2001

In this study, numerical calculations are carried out in order to evaluate the performance of low-Re Reynolds stress model based on SSG model for a swirling turbulent flow in a pipe. The results are compared with those of k-ε model, GL model and the experimental data. The results show that low-Re Reynolds stress model and GL model give better results than k-ε model. In the region near the wall, low-Re Reynolds stress model improves the predictions. However, there is no large difference between the predictions with two Reynolds stress models.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.2
• /
• pp.185-197
• /
• 1999

Heat transfer and solidification of liquid silicon in von-$K{\acute{a}}rm{\acute{a}}n$ swirling flow is investigated. The moving boundary is fixed for all times by a coordinate transformation, and finite difference method Is used to obtain the instantaneous location of the solid-liquid Interface and the heat transfer from the surfaces of solid and liquid. For small Stefan number or low wall temperature, the transient heat transfer from the surface of solid(QS(t)) is much larger than that from the liquid side of solid-liquid interface(QL(t)) and QL(t) reaches its quasi-steady-state value much faster than QS(t).

• Journal of Advanced Marine Engineering and Technology
• /
• v.29 no.4
• /
• pp.417-425
• /
• 2005

An experimental study is performed on the turbulent swirling flow behind a crcular cylinder using 2-D PIV technique. The Reynolds numbers investigated are 10.000, 15,000. 20.000 and 25.000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the cylinder along the test tube. A comparison is included without swirling flow behind a circular and square cylinder. The recirculation zones are shown unsymmetric profiles.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.849-854
• /
• 2008

We have been developing a 1500N-thrust Swirling-Oxidizer-Flow-Type hybrid rocket engine. In order to put the engine into practical use, we conducted long duration burning experiments up to 25s to examine the influence of configuration change of fuel grain on the engine performance and designed an LOX vaporization nozzle to supply GOX for the 1500N-thrust engine. The experiment with a small hybrid rocket engine showed that combustion was stable and the engine performance was approximately constant during combustion. There was no essential problem to with increasing combustion time. The LOX vaporization nozzle designed had 30 rectangular channels with a depth of 0.5mm. During passing through the nozzle, the LOX increased in temperature and vaporized sufficiently.

• 한국연소학회:학술대회논문집
• /
• 2005.10a
• /
• pp.181-188
• /
• 2005

Large eddy simulation(LES) methodology used to model the isothermal swirling flows in a dump combustor and the turbulent premixed flame in a model gas turbine combustor. The LES solver was implemented on parallel computer consisting 16 processors. In isothermal flow simulation, the results was compared with that of ${\kappa}-{\varepsilon}$ model as well as experimental data, in order to verify the capability of LES code. To model the turbulent premixed flame in a gas turbine, the G-equation flamelet model was used. The results showd that LES and RANS well predicted the mean velocity field of a non-swirling flow. However, in swirling flow, LES showed a better performance in predicting the mean axial and azimuthal velocities, and the central recirculation zone than those of RANS. In a model gas turbine combustor, the operation condition of high pressure and temperature induced the different phenomena, such as flame length and flow-field information, comparing with the condition of ambient pressure and temperature. Finally, it was identified that the flame and heat release oscillations are related to the vortex shedding generated by swirl flow and pressure wave propagation.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.2
• /
• pp.440-452
• /
• 1990

Comprehensive numberical computations have been made for four turbulent swirling jets with and without recirculation to critically evaluate the accuracy and universality of several exising turbulence models as well as of the modified k-.epsilon. model proposed in the present study. A numerical scheme based on the full Navier-Stoke equations ha been developed and used for this purpose. Inlet conditions are given by experiments, whenever possible, to minimize the error due to incorrect initial conditions. The standard k-.epsilon. model performs well for the strongly swirling jets with recirculation while it underpredicts the influence of swirl for weakly swirling jets. Rodi's swirl correction and algebraic stress model do not exhibit universality for the swirling jets. The present modified k-.epsilon. model derived from algebraic stress model accounts for anisotropy and streamline curvature effect on turbulence. This model performs consistently better than others for all cases. It may be because these flows have a strong dependence of stresses on the local strain of the mean flow. The predictions of truculence intensities indicate that this model successfully reflect the curvature effect in swirling jets, i.e. the stabilizing and destabilizing effects of swirl on turbulence transport.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.3
• /
• pp.138-152
• /
• 1996

Many studies of heat transfer on the swirling flow or unswirled flow in a abrupt pipe expansion are widely carried out. The mechanism is not fully found evidently due to the instabilities of flow in a sudden change of the shape and appearance of turbulent shear layers in a recirculation region and secondary vortex near the corner. The purpose of this study is to obtain data through an experimental study of the swirling flow and heat transfer downstream of an abrupt expansion in a circular pipe with uniform heat flux. Experiments were carried out for the turbulent flow nd heat transfer downstream of an abrupt circular pipe expansion. The uniform heat flux condition was imposed to the downstream of the abrupt expansion by using an electrically heated pipe. Experimental data are presented for local heat transfer rates and local axial velocities in the tube downstream of an abrupt 3:1 & 2:1 expansion. Air was used as the working fluid in the upstream tube, the Reynolds number was varied from 60, 00 to 120, 000 and the swirl number range (based on the swirl chamber geometry, i.e. L/d ratio) in which the experiments were conducted were L/d=0, 8 and 16. Axial velocity increased rapidly at r/R=0.35 in the abrupt concentric expansion turbulent flow through the test tube in unswirled flow. It showed that with increasing axial distance the highest axial velocities move toward the tube wall in the case of the swirling flow abrupt expansion. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk temperatures ranging from 24.deg. C to 71.deg. C. In swirling flow, the wall temperature showed a greater increase at L/d=16 than any other L/d. The bulk temperature showed a minimum value at the pipe inlet, it also exhibited a linear increase with axial distance along the pipe. As swirl intensity increased, the location of peak Nu numbers was observed to shift from 4 to 1 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 2.2 to 8.8 times larger than fully developed tube flow values.

• 한국전산유체공학회:학술대회논문집
• /
• 2000.10a
• /
• pp.135-140
• /
• 2000

Numerical calculations are carried out in order to evaluate the performance of low-Re Reynolds stress model based on SSG model for a swirling turbulent flow in a pipe. The results are compared with those of $\kappa-\epsilon$ model and GL model, and the experimental data. The finite volume method is used for the discretization, and the power-law scheme is employed as a numerical scheme. The SIMPLE algorithm is used for velocity-Pressure correction in the governing equations.

• Journal of the Korean Society of Safety
• /
• v.8 no.3
• /
• pp.19-25
• /
• 1993

This paper deals with the experimental study of the turbulent characteristics in the swirling coaxial Jets. In this research, the experimental study has been carried out to investigate the effects of swirl number and equivalence ratio on the flow characteristics in nonreacting flow field of the model combustor which symplifys the continuous type combustor for the practical use. Author particularly Intends to find out the fuel-air mixing In the recirculation zone In order to make sure the effects of swirl number and equivalence ratio on the stabilization of flame.

• 한국가시화정보학회:학술대회논문집
• /
• 2004.11a
• /
• pp.5-9
• /
• 2004

An experimental study is performed turbulent swirling flow behind a crcular cylinder using 2-D PIV technique. The Reynolds number investigated is 15,000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the cylinder along the test tube.