• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.1
• /
• pp.17-25
• /
• 2019

An intake of Aircraft becomes S-shaped geometry due to spatial limitation or procuring survivability. But curvature of the S-shaped geometry makes secondary flow or flow separation which is the cause of non-uniform pressure distribution. In this study, boundary layer suction is applied to RAE M 2129 S-Duct by attaching sub duct. Design variable is suction location and angle. A mass flow rate drawn out by suction at the sub duct outlet is constant over every model. A grid dependency test was conducted to verify validity of computation. The comparison among the CFD (Computation Fluid Dynamics), ARA experimental result, and ARA computation result of non-dimensional pressure distribution on the Port side and Starboard Side confirmed the validity of CFD. In this study, Distortion Coefficient was used for evaluating aerodynamic performance of S-Duct. The analysis, which was about flow separation, vortex, mass flow rate distribution, and pressure distribution were also investigated. Maximum 26.14% reduction in Distortion Coefficient was verified.

• The KSFM Journal of Fluid Machinery
• /
• v.7 no.4 s.25
• /
• pp.40-46
• /
• 2004

This paper is concerned with the numerical analyses of an S-shaped duct for the inter-channel between compressor spools. For the compactness and lightweight of an engine, the length of the S-shaped duct is desired to be minimized. Shortening the S-shaped duct, however, flow separation is likely to occur. Numerical investigation using a three-dimensional Navier-Stokes flow solver was performed to determine the availability of the minimization of an S-shaped duct. Computations were performed introducing the experimental data as the inlet flow condition of the OGV in determining the minimum length of the S-shaped duct. Also, the leaning effect of the OGV which assists the flow to turn radially inward was studied adopting mixing-plane method to consider the rotor/OGV interaction.

• 유체기계공업학회:학술대회논문집
• /
• 2003.12a
• /
• pp.621-626
• /
• 2003

This paper is concerned with the numerical analyses of an S-shaped duct for the inter-channel between compressor spools. For the compactness and lightweight of an engine, the length of the S-shaped duct is desired to be minimized. Shortening the S-shaped duct however, flow separation is likely to occur. Numerical investigation using a three-dimensional Navier-Stokes flow solver has been performed to determine the availability of the minimization of an S-shaped duct. Computations are performed introducing the experimental data as the inlet flow condition of the OGV in determining the minimum length of the S-shaped duct. Also, the leaning effect of the OGV which assists the flow to turn radially inward are studied adopting mixing-plane method to consider the rotor/OGV interaction.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.2 no.2
• /
• pp.64-73
• /
• 1998

In twin spool aero-engine, there may be a S shaped annular duct between high pressure and low pressure spools. The flow passing this S shaped duct experiences the flow acceleration and deceleration due to the convex and concave surface of the duct as well as the increase of blockage according to the boundary layer growth along the surfaces. So, the high pressure compressor which is located behind the S shaped duct is influenced by the non-uniform flow field generated by the geometry of inlet duct. To study the influence of the S shaped duct on the centrifugal stage, performance tests were implemented for the compressor with straight cylindrical inlet duct and with S shaped inlet duct, respectively. The test results showed that the performance, such as pressure ratio and efficiency, of the compressor with S shaped duct was worse than that of the compressor with cylindrical duct. And the compressor with S shaped duct had reduced maximum flow rate around design speed. To investigate the cause of performance degradation, flow anlaysis was performed for the impeller in front of which is located S shaped annular duct. The result of CFD showed the strong acceleration of the flow in the axial direction around the inducer tip region which caused the increase of relative mach number and the decrease of incidence angle of the flow.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.05a
• /
• pp.295-298
• /
• 2009

Bent ducts add loss and decrease efficiency. Many researchers have been conducted the performances of bent ducts, but their shapes of inlet and outlet are same. However, in this investigation, the focus is on a bent duct which is annular at the inlet and circular at the outlet. The bent duct of these complex shapes has not been investigated, but has been used in many fields. The performance of such bent duct is investigated under inlet speed 54 m/s and Re = 238,000. Wall static pressure tappings are located surface of the bent duct to measure the static pressure and a probe is traversed at the inlet and outlet of the bent duct to measure the total pressure. As a result, it presents static pressure distribution on the bent duct surface, streamwise velocity profile at inlet and outlet of the bent duct and total pressure loss profile at outlet. In this investigation, the total pressure loss coefficient is 0.243.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.2
• /
• pp.109-117
• /
• 2015

Aircraft needs an inlet duct to supply the airflow to engine face. A fighter aircraft that requires low radar observability has to hide the engine face in the fuselage to reduce the Radar Cross Section(RCS). Therefore, the flow path of the inlet duct is changed into S-shape. The performance of the aircraft engine is known to be influenced by the shape and the centerline curvature of the S-Duct. In this study, CFD analysis of the RAE M 2129 S-Duct has been performed to investigate the influence of aspect ratio of inlet geometry. The performance of the S-Duct is evaluated in terms of the distortion coefficient. To simulate the flow under adverse pressure gradient better, $k-{\omega}SST$ turbulence model is employed. The computational results are validated with the ARA experimental data. The secondary flow and the flow separation are observed for all computational cases, while the semi-circular geometry has been found to produce the best results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.157-159
• /
• 2008

An numerical investigation of the flow characteristics inside a diffusing S-duct inlet with and without vortex generators(VGs) was conducted. The primary discussion herein focuses on development of secondary flow in the S-duct with and without VGs, pressure recovery and distortion at the exit are also discussed. Full three-dimensional Navier-Stokes equations are solved using finite volume method and $k-\varepsilon$ turbulence model is employed. In order to validate the credibility of the numerical methods, predicted results of surface pressure are compared with flight test for the S-duct inlet without VGs, and it shows fairly good agreement. The result shows that VGs alter the flow characteristics in the S-duct and are effective in reducing distortion and ineffective in improving pressure recovery.

• Advances in pediatric surgery
• /
• v.9 no.2
• /
• pp.81-88
• /
• 2003

Congenital dilatation of the common bile duct (choledochal cyst) is an uncommon disease. Although the etiology is unknown yet, various theories such as distal obstruction of the common bile duct, congenital weakness of the duct and anomalous union of the pancreaticobiliary duct have been offered to explain the occurrence of choledochal cyst. Thirty - six cases of choledochal cyst over 22 years were analyzed clinically and classified according to Todani's classification and Kimura's anomalous union of pancreaticobiliary duct type. Todani type 1 consisted with 22 cases which were subdivided into 19 cases of type Ia, 1 case of type Ib and 2 of type Ic. Type IVa consisted with 14 cases including one case of Caroli's disease. There were 25 type BP cases and 10 type PB cases and 1 normal pancreatobiliary junction. Serum alkaline phosphatase was increased significantly in almost all cases. Seven patients (19.4%) had associated congenital anomalies such as double gallbladder, left - sided gallbladder, common bile duct web, biliary atresia, accessory hepatic duct, heterotopic pancreas, cleft lip and 2 cases of intestinal malrotation. All patients underwent cyst excision and Roux - en - Y hepaticojejunostomy and cholecystectomy. There was one death due to methicillin resistant Staphylococcus aureus sepsis.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1595-1600
• /
• 2004

When a shock wave arrives at a duct, an impulsive wave is discharged from the duct exit and causes serious noise and vibration problems. In the current study, the characteristics of the impulsive wave discharged from a partial closed duct exit is numerically investigated using a CFD method. The Yee-Roe- Davis's total variation diminishing(TVD) scheme is used to solve the axisymmetric, unsteady, compressible Euler equations. With several partial closed duct exits, the Mach number of the incident shock wave $M_s$ and the distance L/D between the duct exit and a flat plate are varied in the range of $M_s$ = 1.01 ${\sim}$ 1.50 and L/D = 1.0 ${\sim}$ 4.0, respectively. The results obtained show that the magnitude of the impulsive wave impinging upon the flat plate strongly depends upon $M_s$, L/D and the partial closure of duct exit. The impulsive wave on the flat plate can be considerably alleviated by the partial closure of duct exit and, thus, the present method can be a passive control for the impulsive wave.

• International Journal of Aeronautical and Space Sciences
• /
• v.1 no.1
• /
• pp.36-47
• /
• 2000

Three-dimensional compressible turbulent flow fields within the passage of a diffusing S-duct have been simulated by solving the Navier-Stokes equations with SIMPLE scheme. The average inlet Mach number is 0.6 and the Reynolds number based on the inlet diameter is $1.76{\times}10^6$ The extended $k-{\varepsilon}$ turbulence model is applied to modeling the Reynolds stresses. Computed results of the flow in a circular diffusing S-duct provide an understanding of the flow structure within a typical engine inlet system. These are compared with experimental wall static-pressure, total-pressure fields, and secondary velocity profiles. Additionally, boundary layer thickness, skin friction values, and streamlines in the symmetric plane are presented. The computed results depict the interaction between the low energy flow by the flow separation and the high energy flow by the reversed duct curvature. The computed results obtained using the extended $k-{\varepsilon}$ turbulence model.