• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2005.04a
• /
• pp.489-496
• /
• 2005

In this paper, the feasibility of the high-performance damping device vibration suppression of stay cables has been investigated. The proposed damping system consists of a linear viscous damper and a scissor-jack-type toggle linkage. Since the mechanism of the scissor-jack-type toggle linkage amplifies the relative displacement of the linear viscous damper, it is expected that the capacity of the viscous damper used in the scissor-jack-damper energy dissipation system can be reduced without the loss of the control performance. Numerical simulation results demonstrate the efficacy of the damping system employing the scissor-jack-type toggle linkage. Therefore, the proposed damping system could be considered as one of the promising candidates for suppressing vibration of stay cable.

• Proceedings of the IEEK Conference
• /
• 2003.07c
• /
• pp.2713-2716
• /
• 2003

This paper presents a dynamic manipulability analysis method of the limb moving in viscous fluid. The key idea of the presented method is that the boundary of joint velocity can be converted to the velocity-dependant dynamic manipulability polytope through the coriolis, centrifugal and drag terms in dynamic equation. The velocity-dependant dynamic manipulability polytope is added to the inertial and restoring force manipulability polytope to get overall manipulability polytope of the limb moving in the fluid Each of the torque and velocity bounds arc considered in the infinite norm sense in joint space, and the drag force of a limb moving in fluid viscous is modeled as a quadratic form An analysis example with proposed analysis scheme is presented to validate the method.

• Advances in Computational Design
• /
• v.2 no.1
• /
• pp.71-87
• /
• 2017

This study focuses on the efficiency and applicability of dynamic relaxation methods in form-finding of membrane structures. Membrane structures have large deformations that require complex nonlinear analysis. The first step of analysis of these structures is the form-finding process including a geometrically nonlinear analysis. Several numerical methods for form-finding have been introduced such as the dynamic relaxation, force density method, particle spring systems and the updated reference strategy. In the present study, dynamic relaxation method (DRM) is investigated. The dynamic relaxation method is an iterative process that is used for the static equilibrium analysis of geometrically nonlinear problems. Five different examples are used in this paper. To achieve the grading of the different dynamic relaxation methods in form-finding of membrane structures, a performance index is introduced. The results indicate that viscous damping methods show better performance than kinetic damping in finding the shapes of membrane structures.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.311-318
• /
• 2001

A three-dimensional numerical analysis of the flow and heat transfer characteristic of wood-flour-filled polypropylene melt in an extrusion die was carried out Used for this analysis were Finite Concept Method based on FVM, unstructured grid and non-Newtonian fluid viscosity model. Temperature and flow fields are closely coupled through temperature dependent viscosity and viscous dissipation. With large Peclet, Nahme, Brinkman numbers, viscous heating caused high temperature belt near die housing, Changing taper plate thickness and examining some predefined parameters at die exit investigated the effect of taper plate on velocity and temperature uniformities. In the presence of taper plate, uniformity at die exit could be improved and there existed an optimum thickness to maximize it.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.518-523
• /
• 2001

Vortex methods were originally conceived as a tool to model the evolution of unsteady, incompressible, high Reynolds number flows of engineering interest. Recently various methods have been proposed for simulating the diffusion in vortex methods for two-dimensional incompressible flows. We test the diffusion schemes of vortex methods. In this paper we directly compare the particle strength exchange scheme with the vorticity redistribution scheme in tenus of their accuracy and computational efficiency. Comparisons between both viscous models described are presented for short-time runs of impulsively started flows past a circular cylinder for Reynolds number of 60. The particle strength exchange scheme has been shown more accurate and efficient than the vorticity redistribution scheme.

• 한국전산유체공학회:학술대회논문집
• /
• 2009.04a
• /
• pp.31-38
• /
• 2009

In the present study, viscous flow calculations of helicopter main rotor system in forward flight were made by using an unstructured hybrid mesh solver. Each rotating blade relative to the cartesian frame was simulated independently by adopting unstructured overset mesh technique. For the validation of the present method, calculations for the Caradonna-Tung non-lifting forward flight and the AH-1G main rotor system in forward flight were made. Additional computation was made for the UH-60A rotor in forward flight. Reasonable agreements were obtained between the present results and the experiment.

• 한국전산유체공학회:학술대회논문집
• /
• 2009.04a
• /
• pp.252-268
• /
• 2009

In the present study, a grid deformation technique has been incorporated into the unsteady compressible and incompressible viscous flow solvers on unstructured hybrid meshes. An algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was adopted for inviscid elements among several spring analogy methods due to its robustness. The present method was validated by comparing the results obtained from the grid deformation and the rigid motion of entire grids. Fish swimming motion of an NACA0012 airfoil and flapping wing motion of a generic fighter were simulated to demonstrate the robustness of the present grid deformation technique.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.19 no.2
• /
• pp.19-25
• /
• 1982

Several formulae have been proposed to estimate the viscous resistance of ships by wake surveys. Both the total head and the velocity should be measured. The integration of he total head loss shows over estimations of the resistance by about 10%. Therefore measurements of the velocity are required, which need much more works. A simple method is suggested in this paper to take accout of the velocity-defect from the measured total head. It gives reasonable estimations of the viscous resistance within the experimental accuracy. Experimental data of a low-drag body of revolution in the wind-tunnel and Series 60 model, CB=0.6 in the tank are used to verify the suggested formula.

• Journal of computational fluids engineering
• /
• v.13 no.3
• /
• pp.35-43
• /
• 2008

A methodology for the simulation of compressible high Reynolds number flow over rigid and moving bodies on a structured Cartesian grid is described in this paper. The approach is based on a modified version of the Brinkman Penalization method. To avoid oscillations in the vicinity of the body and to simulate shcok-containing flows, a Weighted Essentially Non-Oscillatory scheme is used to discretize the spatial flux derivatives. For high Reynolds number viscous flow, two turbulence models of the two-equation Menter's SST URANS model and a two-equation Detached Eddy Simulation are implemented. Some simple flow examples are given to assess the accuracy of the technique. Finally, a moving grid capability is demonstrated.

• Proceedings of the KSME Conference
• /
• 2001.06c
• /
• pp.59-63
• /
• 2001

A high-impulse, low-power, continuous-shot microthruster has been developed using low boiling temperature liquid-propellant with high viscous fluid-plug. The viscous friction force of the fluid-plug increases the blast pressure and the low boiling temperature liquid-propellant is intended to reduce input power consumption. The three-layer microthruster has been fabricated by surface micromachining as well as bulk micromachining in the size of $7{\times}13{\times}1.5mm^{3}$. A continuous output impulse bit of $6.4{\times}10^{-8}N{\cdot}sec$ has been obtained from the fabricated microthruster using perfluoro normal hexane (FC72) propellant and oil plug, resulting in about ten times increase of the impulse bit using one hundredth electrical input energy compared to the conventional continuous microthruster.