• Journal of computational fluids engineering
• /
• v.3 no.1
• /
• pp.22-29
• /
• 1998

Parallel implementation is conducted for a SIMPLER finite volume model. The present parallelism is based on domain decomposition and explicit message passing using MPI and SHMEM. Two parallel solvers to tridiagonal matrix equation are employed. The implementation is verified on the Cray T3E system for a benchmark problem of natural convection in a sidewall-heated cavity. The test results illustrate good scalability of the present parallel models. Performance issues are elaborated in view of convergence as well as conventional parallel overheads and single processor performance. The effectiveness of a localized matrix solution algorithm is demonstrated.

• 한국전산유체공학회:학술대회논문집
• /
• 1997.10a
• /
• pp.23-28
• /
• 1997

A parallel implementation is made of a two-dimensional finite volume model based on the SIMPLER. The solution domain is decomposed into several subdomains and the solution at each subdomain is acquired by parallel use of multiple processors. Communications between processors are accomplished by using the standard MPI and the Cray-specific SHMEM. The parallelization method for the overall solution procedure to the Navier-Stokes equations is described in detail, The parallel implementation is validated on the Cray T3E system for a benchmark problem of natural convection in a sidewall-heated cavity. The parallel performance is assessed and the issues encountered in achieving a high-performance parallel model are elaborated.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.4C
• /
• pp.379-383
• /
• 2003

A simpler nonparametric detector test statistic based on reference observation in addition to the rank statistics of regular observations is suggested in this letter. Using reference observations instead of sign statistics helps us a simpler detector structure especially for random signals buried in multiplicative noise.

• Communications for Statistical Applications and Methods
• /
• v.3 no.3
• /
• pp.75-81
• /
• 1996

Polynomial measurement error model(MEM) with one predictor is considered. It is briefly mentioned that Chan and Mak's generalized least squares estimator(GLSE) can be derived more easily if Hermite polynomial concept is applied. It is proved that GLSE derived using new procedure is equivalent to the estimator obtained from corrected score function. Finally, much simpler proof of the asymptotic behavior of GLSE than that of Chan and Mak is provided. Much simpler formula of asymptotic covariance matrix of GLSE is a part of that proof.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.6
• /
• pp.15-20
• /
• 2005

Two-dimensional incompressible Navier-Stokes flow solver is developed using SIMPLER method to study the unsteady viscous flow physics over two-dimensional ellipses. Unsteady viscous flows over various thickness-to-chord ratios of 0.6, 0.8, 1.0, and 1.2 elliptic cylinders are simulated at different Reynolds numbers of 200, 400, and 1,000. This study is focused on the understanding the effects of Reynolds number and elliptic cylinder thickness on the drag and lift forces. The present numerical solutions are compared with available experimental and numerical results and show a good agreement. Through this study, it is observed that the Reynolds number and the cylinder thickness affect not only the frequency of the force oscillations but also the mean values and the amplitudes of the total drag and lift forces significantly.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.12
• /
• pp.1-8
• /
• 2005

A parametric study has been accomplished to figure out the effects of the elliptic cylinder thickness, angle of attack, and Reynolds number on the lift and drag forces exerted on the elliptic cylinder. A two-dimensional incompressible Navier-Stokes flow solver is developed using SIMPLER method to analyze the unsteady viscous flow over elliptic cylinder. Thickness-to-chord ratios of 0.2, 0.4, and 0.6 elliptic cylinders are simulated at different Reynolds numbers of 400 and 600, and angles of attack of $10^{\circ}$, $20^{\circ}$, and $30^{\circ}$. Through this study, it is observed that the elliptic cylinder thickness, angle of attack, and Reynolds number affect significantly not only the time-mean values and the amplitudes of the drag and lift forces but also the frequencies of the force oscillations.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2747-2752
• /
• 2007

A numerical study has been performed on the flow past a two-staged orifice in a rectangular duct. The flow field including the recirculation region behind the orifice was investigated and the pressure drop was calculated. Water was used as a working fluid and the flow was treated as the turbulent flow, of which the Raynolds number was 6000. The main parameters for the pressure drop and the recirculation region were the orifice's inclined angle against the duct, the interval between two orifices, the shape of the orifice's hole having the same area, and the change of the hole position at the same interval. The variation of the flow field was investigated with each parameter. Consequently, it was found that the most dominant parameter influencing the drop of the pressure was the change of the hole position at the same interval between orifices. Especially when the interval between orifices was narrow and the relative position the holes was changed, its effect to the flow field was shown most drastically as a result of this study. The SIMPLER algorithm with FLUENT code was employed to analyze the flow field.

• East Asian mathematical journal
• /
• v.9 no.2
• /
• pp.275-282
• /
• 1993

• Journal of Mechanical Science and Technology
• /
• v.20 no.1
• /
• pp.167-175
• /
• 2006

A parametric study has been accomplished to figure out the effects of elliptic cylinder thickness, angle of attack, and Reynolds number on the unsteady lift and drag forces exerted on the elliptic cylinder. A two-dimensional incompressible Navier-Stokes flow solver is developed based on the SIMPLER method in the body-intrinsic coordinates system to analyze the unsteady viscous flow over elliptic cylinder. Thickness-to-chord ratios of 0.2, 0.4, and 0.6 elliptic cylinders are simulated at different Reynolds numbers of 400 and 600, and angles of attack of $10^{\circ},\;20^{\circ},\;and\;30^{\circ}$. Through this study, it is observed that the elliptic cylinder thickness, angle of attack, and Reynolds number are very important parameters to decide the lift and drag forces. All these parameters also affect significantly the frequencies of the unsteady force oscillations.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.33B no.11
• /
• pp.83-96
• /
• 1996

On PR-IV magnetic recording systems, the maximum likelihood sequence detection (MLSD) method is optimum. But it has the problem of the complexity of the structure. The three level detection (TLD) method can be used, which has simpler structure than MLSD, but requires almost twice of power to achieve the same probbility of error as MLSD does. Therefore a new detection method (error controlled detection: ECD) is proposed which has much simpler structure than MLSD and gives much better performance than TLD. The simulation resutls show that the performance of ECD is better than that of TLD by approximaterly 0.5~1.3dB both in linear and nonlinear channels.